Device for evaluating cutaneous sensory detection

Abstract

An improved hand-held device for evaluating cutaneous sensory detection consisting of a plastic or similar material rod handle and a simple curve that enables function and versatility not possible without the curve. The curve helps prevent an attached monofilament used as the testing stimulus from being laid down upon itself, or being damaged when put in a case. It helps prevent the monofilament from being sheared off by another device's handle when several devices are grouped for a cutaneous sensory detection test. One embodiment adds a disk attachment at the end of the handle curve and extension. The disk is pre-embedded with a monofilament of a given diameter size, and length, enabling the monofilaments to be quickly and easily replaced or interchanged by an examiner without replacing an entire device, or disassembling a device. Alternative disks contain two or a plurality of filaments of preselected diameter size and length. An optional connector for the handle, with or without the disk attachment, permits more than one device to be used together. The connector enables two of a selected monofilament size and force to concurrently or sequentially apply the given force of application.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a division of application Ser. No. 11/975,750, Filed Oct. 19, 2007

FIELD OF INVENTION

The present invention relates to a testing device for the purpose of peripheral nerve evaluation, in particular it relates to an improved testing device, more specifically it relates to a device used for the purpose of testing patients for cutaneous sensory detection provided by the peripheral nervous system, and central nervous system, in human or animal subjects.

BACKGROUND OF INVENTION

IDS References and Publications

References Cited:

U.S. Patent Documents

	2,704,539	Mar. 22, 1955	Fisher
	3,074,395	Jan. 22, 1963	Kevorkian
	3,662,744	May 16, 1972	Low, et al
	3,933,148	Jan. 20, 1976	Wyler, et al
	4,313,446	Feb. 2, 1982	Kanatani
	4,823,806	Apr. 25, 1989	Bajada
	5,027,828	Jul. 2, 1991	Kovacevic, et al
	7/860,900	Mar. 31,1992	Weinstein, et al
	5,316,011	May 31, 1994	Weinstein, et al
	5,381,806	Jan. 17, 1995	Weinstein, et al
	5,492,132	Feb. 20, 1996	Weinstein, et al
	5,823,969	Oct. 20, 1998	Christy
	6,234,976 B1	May 22, 2001	Linden
	6,234,977	May 22, 2001	Christy
	6,387,055	May 14, 2002	Christy

Other Publications Cited:

Bell, J A: Sensibility testing, In Hunter, J M; Schneider, L H; Mackin, E J; and Bell, J A (eds), Rehabilitation of the Hand, Philadelphia, CV Mosby: 273-291, 1978.

Bell-Krotoski, J A: Light touch-deep pressure testing using Semmes-Weinstein Monofilaments, In Hunter et al (eds), Rehabilitation of the Hand, Philadelphia, C. V. Mosby, 1990.

Bell-Krotoski, J A: Pocket filaments and specifications for the Semmes-Weinstein Monofilaments, J Hand Ther, Hanley & Belfus, 3: 26-30, 1990.

Bell-Krotoski, J A; and Buford, W L, Jr.: The force/time relationship of clinically used sensory testing instruments, Hanley & Belfus, J Hand Ther, 1(2):76, 1988; Bell-Krotoski, J A; and Buford, W L., Jr.: The force/time relationship of clinically used sensory testing instruments: A revision and update, J of Hand Ther, 10(4): 297-309, 1997.

Bell-Krotoski, J A; and Tomancik, E: The repeatability of testing with Semmes-Weinstein Monofilaments; the American Society of Hand Therapists; J Hand Surg, 12A, No 1, pp. 155-161, January 1987.

Bell-Krotoski, J A; Fess, E E; Hiltz, D; and Figarola, J: Threshold detection and Semmes Weinstein Monofilaments: A comparative study, J Hand Ther, 8:155-162, 1995.

Semmes, J; Weinstein, S; Ghent, L; and Teuber, H L: Somatosensory Changes after Penetrating Wounds in Man, Harvard University Press for the Commonwealth fund, Cambridge, 60-61, 1960. (Listed Library of Congress)

Von Prince, K; and Butler, B: Measuring sensory function of the hand in peripheral nerve injuries, American J Occup Ther, 21:385-396, 1967.

Weinstein, S: Fifty years of somatosensory research: from the Semmes-Weinstein Monofilaments to the Weinstein Enhanced Sensory Test; J Hand Ther, Hanley & Belfus 6:11-22, 1993.

Discussion of Prior Art

Early Prior Art

Assessment of cutaneous sensory detection levels can allow mapping of abnormal nerve areas and provide information on the condition of peripheral nerves for the purpose of treatment or medical follow up, and is used in diagnosis of diseases and injuries. The sense of touch made possible by our nervous system is our lifeline with the world outside of our body. It provides us with the ability to discern objects. It helps protect skin and soft tissue from damage by providing quick recognition of light touch and deep pressure detection. Cutaneous sensory threshold detections is important in allowing us to “feel,” interpret objects, and protect ourselves from harmful objects in the environment such as objects with sharp edges and objects which could burn or otherwise cause a wound. Sensitive repeatable measurement and quantification of early abnormality is important for early treatment intervention aimed at restoring normal nerve function, or maintaining remaining nerve function. Detection of more advanced abnormality is important to help prevent injury and amputations. Quantification of nerve status in patients is considered by some as critical. Without special care and treatment, patients with peripheral nerve impairment who use hands and feet in daily life activities can have repetitive damage to skin and soft tissue resulting in injuries and amputations. In neurological and other examinations of patients with carpal tunnel or entrapment syndromes, work related injuries, repetitive stress syndromes, congenital neuropathies, and diseases such as diabetes and leprosy, it often becomes necessary to locate, outline, and map skin areas of change by testing cutaneous sensory detection in areas which are known to be innervated by specific nerves.

A cutaneous sensory detection threshold test is not new and has been around since the 1800's. In body areas suspected of nerve change the test was originally performed using horsehairs of increasing diameter. These were applied starting with the lightest until the subject detected a force of application, i.e. cutaneous sensory detection level was established. Devices using horsehair were apparently never patented. Horsehair has the disadvantage of absorbing humidity, thereby affecting the force of application delivered to a patient. In addition, horsehair is fragile, sometimes brittle, and had to be replaced frequently. Horsehair is no longer used in cutaneous sensibility testing.

In the 1950's, Semmes and Weinstein replaced horsehairs used for cutaneous sensory testing with nylon monofilament of increasing diameters placed in straight length plastic Lucite rod handles The original Semmes-Weinstein device design uses a 6.35 mm square diameter clear plastic rod for a handle of a specified length into which a hole is drilled on one end of the rod to hold the nylon monofilament of the given size permanently attached at a 90-degree angle to the rod. Each monofilament is blunt cut to measures an exact 38 mm length from the point it leaves the rod handle. In order to assess the entire range of potential levels of cutaneous sensory detection—normal through abnormal levels—the lightest nylon monofilament size in the original complete set begin at 0.0635 mm and progressively increase in diameter to a diameter of 1.143 mm. In the original Semmes-Weinstein Set of devices, 20 monofilament sizes are available producing application force range from 0.0045 gm to 447. gm. Each stimulus used in the test is applied 3 times with one out of 3 “yes” responses considered positive to establish detection and recognition by a subject. The original instrument incorporating the nylon monofilament was never patented, but has become widely used in cutaneous sensory testing of patients, it is a valued testing device by many examiners for cutaneous sensory testing, and is still in use today. Semmes, J; Weinstein, S; Ghent, L; & Teuber, H L (1960) Somatosensory Changes after Penetrating Wounds in Man, Harvard University Press for the Commonwealth fund, 60-61.

Nylon has little humidity absorption, has an indefinite shelf life, and repeatable bend and recovery elastic physical properties making it ideal for the cutaneous sensory detection test. Nylon monofilament of increasing diameter size can provide a range of repeatable test stimuli application forces suitable for cutaneous sensory testing of individuals or groups of patients. When recorded for force of application recognized by the subject, full or abbreviated versions of the test produce detailed and specific maps of peripheral nerve abnormality. Cutaneous sensory detection threshold levels were consistently color coded for specific force recognition level in 1978, and provide information to the examiner, physician, patient, family, employer, and judge regarding the status and change in nerve function. Bell, J A (1978) Sensibility testing, In Hunter, J M; Schneider, L H; Mackin, E J; & Bell, J A (eds), Rehabilitation of the Hand, Philadelphia, C V Mosby: 273-291.

Accuracy of the monofilament test for cutaneous sensory detection threshold is dependent both upon the properties of material being used as a stimulus, and the proper application of the stimulus monofilament tip for testing of subjects. Nylon monofilament, or material with similar physical properties, is applied perpendicular to the skin surface of the subject until the monofilament bends and exerts its desired force of application for testing. The nylon monofilament bends when applied to the skin, achieves a peak force immediately in application, and holds peak force until lifted, when it again becomes straight, and application force becomes zero. The force of application applied by a device is important for test accuracy and validity.

A monofilament device has been shown to be more sensitive and accurate than other hand-held instrument devices that use rigid plastic or metal in probe type instruments, that are not force-controlled in application. In studies of hand-held cutaneous sensory test devices, unless force during application is controlled for, even the vibration of the examiner's hand has been shown to vary widely and can easily exceed the lighter application force needed for recognition of normal cutaneous threshold detection. Unseen vibration, which is not easily appreciated by an examiner's sight, will be detected by sensitive sensory end-organ receptors of the peripheral nerves in the skin of the patient being tested, and can change the results of the test. The elastic properties of nylon help absorb the vibration of the examiner's hand. Normal subjects are so sensitive they can feel light “puffs of air” on their skin. The control enabled by the elasticity of the monofilaments can help quantify differences even among normal subjects at this sensitive level of detection. Bell-Krotoski, J A; & Buford, W L (1988, 1997) The force/time relationship of clinically used sensory testing instruments, Hanley & Belfus, J Hand Ther, 1(2):76; A Revision and Update,” J of Hand Ther, 10(4): 297-309.

The 90 degree angle of the monofilament to the rod handle, has been determined optimal. The angle enables smooth positioning when the device is in use, and helps to place the monofilament in the perpendicular position to the skin area being tested, so that the stimulus application can be made in a smooth and consistent fashion. The distance from the monofilament the examiner holds the handle should be consistent, as can also make a difference on the amount of examiner hand vibration, and the repeatability of the stimulus. So long as the material is pure nylon, is extruded with controlled humidity in straight lengths on manufacture, diameter and length of the nylon monofilament are in specifications for size and force, the stimulus is applied at a consistent distance from the examiner's hand, the monofilament is correctly cut without sharp edges, and the device is used in a correct application protocol, the monofilament test stimulus is highly repeatable from test to test, among examiners, and clinic to clinic. This means the handle holding the monofilament can be changed in design so long as the other known critical specifications are met and will still produce consistent test stimuli. Bell-Krotoski, J A; & Tomancik, E (1987) The repeatability of testing with Semmes-Weinstein Monofilaments, J Hand Surg, 155-161.

Today the most frequently used variations of the monofilament cutaneous sensory detection test include a set of five or six devices with nylon monofilaments consisting of specified diameter sizes, or a single device of a given size monofilament. Those included or used are the sizes most needed for patient testing from the original Semmes-Weinstein set of 20 devices. Occasionally, examiners add additional monofilament sizes from the original set for specific needs in testing, such as for normative studies where lighter than normal threshold stimuli are needed to determine cutaneous sensory detection threshold in normal subjects. Bell-Krotoski, J A (1990) Light touch-deep pressure testing using Semmes-Weinstein Monofilaments, In Hunter et al (eds), Rehabilitation of the Hand, Philadelphia, C. V. Mosby.

Disadvantages of Early Art and Attempt to Redesign

Disadvantages of the many Semmes-Weinstein design type sets with reduced numbers of monofilament are the same as with the original set of 20 in that the monofilament can be damaged and need replacement. If only one monofilament is broken in any set of increasing monofilament diameters, an entire test set can be rendered incomplete, e.g. where monofilaments are used in a “hand and body,” “face,” or “foot” screen set, or in a nerve status “screening” or “normative testing” set requiring more than one monofilament size. Clinics doing testing often only have one set, or two sets available at any one time.

It is a common mistake for the examiner to inadvertently place the original monofilament straight handle device on its side in a position that can damage the lighter monofilaments, or upside down on the monofilament, particularly when placed into its storage box. When opening boxed sets, persons not familiar with the monofilament design such as supervisors, custom inspectors, clinic visitors, etc., often do not know how to replace the monofilaments in correct orientation to prevent their damage. Persons curious about the device can and do unwittingly cause permanent damage, particularly to the lighter monofilaments. Many sets I have sent overseas have been received too damaged to be useful by their intended clinicians because they were opened in route and replaced incorrectly. Due to the high cost for replacement and potential damage of the monofilaments in transit, alternative ways had to be found. In research grants on peripheral nerve testing, bulk packaged monofilament material was obtained and sent overseas for placement into handles onsite within a country.

Pocket Monofilament Combined Handle Design

My earlier attempt to circumvent some of the recognized disadvantages of the original Semmes-Weinstein device resulted in the creation of a “pocket set” device design that put the then most commonly used monofilaments into one metal handle device with square metal rod arm interlocking extensions that could be expanded or collapsed for patient testing. Bell-Krotoski, J A (1990) Pocket filaments and specifications for the Semmes-Weinstein Monofilaments, J Hand Ther, Hanley & Belfus, January-March, 26-30. This design was published but never patented, and is no longer in use. The nylon monofilament material in this device was made in color during manufacture, for diameter size and application force for the monofilaments most frequently used in hand/foot/or body testing. The coding was made to correspond with consistent color-coding for cutaneous sensory detection levels I introduced in 1978, for mapping abnormal peripheral nerve areas. Bell, J A (1978) Sensibility testing, In Hunter, J M; Schneider, L H; Mackin, E J; & Bell, J A (eds), Rehabilitation of the Hand, Philadelphia, C V Mosby: 269-291. The addition of color for identification of monofilament diameter size insures correct recognition by the examiner of a given diameter size monofilament in a device, facilitates several monofilament sizes being able to be put into one handle, and is frequently used in various version of the monofilaments test today.

Disadvantages of the “pocket set” included that the 1.5875 mm and 2.38 mm square diameter handles in this thin metal multiple monofilament composite handle design, still leaves the monofilaments vulnerable while extended or collapsed during patient testing, in relation to the examiner holding the handle. Replacement of one monofilament requires replacement of the entire instrument device including handle, or part of the handle and its specified diameter size monofilament. Since handle parts are not uniform in design, replacement parts are not practical for replacement of only one. Additional monofilament sizes when needed are not available that are frequently used in the testing set as alternative, except individually.

Different Monofilament Stimulus Tip

Weinstein, et al, in U.S. Pat. No. 7,860,900, Mar. 31, 1992, introduced a specific treatment to the monofilament stimulus tip to produce a rounded tip for measuring itch sensitivity. Weinstein describes the inadvertent elicitation of pain rather than touch or pressure to be a problem in use of the original Semmes-Weinstein instrument. If the original Semmes-Weinstein monofilaments are applied to the eye or mucous membranes as described, and included in their testing, the monofilament test could produce pain. The modification of the monofilament tip to make it curved and rounded may have advantages over the original design, but creates a different device instrument.

The test stimulus has been changed when the stimulus tip is rounded. This means that information developed in normative studies and for patients with impairment, using the original blunt cut Semmes-Weinstein stimulus, does not directly apply to the device design with rounded tips and vice versa. Bell-Krotoski J A, Fess E E, Hiltz D, & Figarola J: Threshold Detection and Semmes Weinstein Monofilaments: A Comparative Study, J Hand Ther, 8:155-162, 1995.

If blunt cut as in the original design, and not containing sharp edges by incorrect cut on manufacture, the monofilaments in the original set of 20 monofilament diameter sizes rarely elicit a pain response in patients who are being tested for normal and abnormal peripheral nerve function of skin areas of the face, body, and extremities. Even hypersensitive patients tolerate the test well. In these patients and others with higher spinal cord, head trauma, or abnormality causing sensory changes to the head, body, and extremities, the test stimulus needs to be in the range of light touch to deep pressure for cutaneous sensory detection as provided by the original Semmes-Weinstein design. The original monofilament cutaneous sensory detection blunt cut monofilament device design remains valid and valuable in patient testing.

If patients with nerve abnormality do not feel the heaviest monofilament, they may still have residual pain response intact, but this is tested by a different type of device. Pain is produced at much higher force levels than produced by the monofilaments, and test devices specifically for pain require sharp tipped instruments that can reach higher force/pressure levels on the subject skin tissue such as the many pin or pinwheel type devices. Kavorkian, U.S. Pat. No. 3,074,395, 1963, invented a pinwheel algesimeter, and others such as Bajada, U.S. Pat. No. 4,823,806, Apr. 25, 1989, invented one of many variations of pin or pinwheel design instruments for testing pain detection of the sensory system. Disadvantages of these include that while these may be suitable for testing pain, as intended, since they are a relatively heavy stimulus, they lack the specificity, and the sensitivity needed for testing lighter levels of cutaneous sensory detection important for early detection of nerve abnormality, early intervention, and quantification of change.

Weinstein Combined Handle Design

Based on the criticisms of the original Semmes-Weinstein device design, and my described monofilament “pocket set,” Weinstein introduced a combined handle design incorporating the most used monofilament sizes into one handle for measuring itch or pressure sensation, Weinstein, et. al, U.S. Pat. No. 5,316,001, May 31, 1994. In trade this invention is referred to as the Weinstein Enhanced Sensory Test (WEST). Weinstein, S (1993) Fifty years of somatosensory research: from the Semmes-Weinstein Monofilaments to the Weinstein Enhanced Sensory Test; J Hand Ther, Hanley & Belfus 6:11-22. The WEST has monofilaments that rotate outward from one handle to be individually placed in the position for testing at 90 degrees from the device handle, and returned to an array arrangement with the other monofilaments. This device design has some advantage of making the test more convenient, and better protects the monofilaments if the instrument is dropped. The device design places the largest monofilament in the array of several on the forward end of the handle, the largest monofilament and handle thereby protecting the lighter monofilaments when in its stored position. In a later invention using the WEST, Weinstein, et al, in U.S. Pat. No. 5,381,806, Jan. 17, 1995, added a method of delivering pressure-induced sensations for itch sensitivity of the skin surface of a subject by dragging the monofilament distally and proximally across the skin surface. In a further improvement of the WEST device, Weinstein specifically obtained a patent for the monofilament tip treatment that makes it curved and rounded thus reportedly eliminating eliciting a pain response, and helping to prevent slippage and misapplication of a monofilament to the patient's skin, Weinstein, et al, U.S. Pat. No. 5,492,132, Feb. 20, 1996.

Disadvantages of the WEST design include the fact that the more the monofilament is manipulated during use in the handle (rotated for use), the more likely it can be damaged, particularly if incorrectly approached by the examiner's hand rotating the selected test monofilament away from the others included on the handle. The monofilaments in the WEST design, affixed in a certain array arrangement of monofilament sizes in one handle, are not protected by the handle design when rotated in position for use. The handle has to be disassembled for repair or replacement of the monofilament. Since the monofilaments are lined up at various distances from the handle, there is no provision for the monofilament to be applied at the same distance from the examiner's hand during application of the device.

All versions of the WEST have a different monofilament stimulus tip than the original blunt cut design Semmes-Weinstein monofilaments which were never patented. Information developed in normative studies and for patients with impairment, using the original blunt cut Semmes-Weinstein stimulus, does not directly apply to the device design with rounded tips and vice versa. Bell-Krotoski J A, Fess E E, Hiltz D, & Figarola J: Threshold Detection and Semmes Weinstein Monofilaments: A Comparative Study, J Hand Ther, 8:155-162, 1995.

Later Variations

Christie, U.S. Pat. No. 5,823,969, Oct. 20, 1998, introduced a new hand-held device handle with nylon monofilament in pivoting head, where the monofilament incorporated into the head rotates from a channel in the pen handle to a 90 degree angle for testing, and then is rotated back to the channel in the pen for storage, thus protecting the monofilament when not used. An advantage is that the pen type devices, when in stored position, can be placed adjacent to each other in a case or small packet without damage, with several of specified sizes included.

Disadvantages of the Christie device include the fact that the more the monofilament is handled or manipulated in a handle, the more likely it is to be damaged. The head that rotates out of a channel with the monofilament and away from the handle during patient testing can become inadvertently damaged by the examiner's hand when rotating the monofilament into its test position. The monofilament in this device is fully protected only when stored in the channel in the handle, not while extended out of its handle 90 degrees, for patient testing. Replacement of the monofilament is accomplished by replacing the whole pen type device of a given size monofilament. The device heads with fixed given size monofilament are not designed to be routinely interchanged on other handles for other size monofilaments by the examiner.

Linden, U.S. Pat. No. 6,234,976 B1, May, 22, 2001, introduced a hand-held device handle design with a rotating head and nylon monofilament on the forward end of a device handle for measuring “protective sensation” (protective sensation being a previously described threshold detection level of many significant levels of cutaneous sensory function). Von Prince, K; & Butler, B (1968) Measuring sensory function of the hand in peripheral nerve injuries, American J Occup Ther, 21:385-396. The monofilament in this device is fully protected only when stored in its protective channel in the handle, not while extended out of its handle 90 degrees, perpendicular to the handle, for patient testing.

In recent years individual monofilaments, primarily intended to measure a level of “protective sensation” for testing of the diabetic foot, have become available in disposable flat paper holders. These are intended for one or limited-time patient screen testing, not for clinical testing where accuracy is paramount. Disadvantages include that the paper does not firmly secure a monofilament where it is attached. Another version can be found in small relatively flat plastic handles with the monofilament extending straight out from the handle. The paper or plastic versions (no patent found) do not incorporate the desired length of handle or 90 degree orientation of the monofilament with respect to the handle, considered by experts to help dampen the normal vibration of the examiner's hand in patient testing. No provision is made for applying the monofilament test stimulus at a given distance from the examiner's hand. On a practical level, without touching an area of the patient's hand during testing, the handles are too short to always positioning the monofilament perpendicular to the patient skin area tested, particularly when applying the monofilaments to the hand in clinical testing.

Other Related Art

Low et al, U.S. Pat. No. 3,662,774, May 16, 1972, provides a variation in a hand-held device design for cutaneous sensory testing. This device uses one single vertical handle and a single nylon monofilament that extends and retracts in the vertical handle to deliver a range of approximate forces of application. This device design does not allow the same control of the examiner's hand vibration, as do designs that hold the monofilament perpendicular to the handle. Further, the device handle constantly crimps the Nylon monofilament along its length during adjustments, causing early fatigue of the monofilament material and quickly causes mechanical damage to the monofilament where it is crimped. The monofilament is not replaceable except in another device, or by ordering another monofilament assembly if available separately. Christie, U.S. Pat. No. 6,234,977. May 22, 2001, introduced a similar retracting and extending monofilament design, which has the same criticisms.

Two-versus one-point stimulus testing is a common test variation in cutaneous sensibility testing. Conventionally, the test is performed with metal probe type devices. Several hand-held devices have been designed for testing one- and two-point discrimination of the hand in cutaneous sensory testing, e.g., Christie, U.S. Pat. No. 6,387,055, May 14, 2002. These devices while historically popular and advocated in clinical use by many, they lack force control, similar to other hand-held tests that have been found to lack sufficient control on their force of application needed to be a repeatable stimulus. Their force of application has been shown to vary widely from one application to another and one test to another. There is also no control on the force that can be added by the examiner. Applied force can vary as much as 30 grams from one application to another, and range from 2 grams to over several hundred grams. Two-point testing devices have been found additionally variable in that they consistently produce a heavier force when one point is applied versus when two points are applied, or vice versa, clearly showing the need for control on force applied.

Kovacevic, et al, U.S., Pat. No. 5,027,828, Jul. 2, 1991, provides a computerized stimulus device for determining the sensory responses of the human skin primarily to evaluate the ability to discriminate one or two points of touch on the hand, but the device can be applied with only one point in contact with the skin for cutaneous sensory detection threshold testing. Force/pressure detection is recorded when the subject clicks a signaling device indicating recognition. Although computerized, this device is typically hand applied. This device is a different instrument from the devices that use monofilament. When applied, light contact is made, and the force is ramped up to the level at which the patient detects stimulation. The probes do not bend, but the device is said to have electronic sensors for determining displacement of force that helps dampen the vibration of the examiner's hand during application. Disadvantages of the device include that the test application probes are hand-applied, made of metal, and can conduct temperature. Rather than respond, “yes” to a specific threshold stimulus, as in the monofilament test, the patient must determine when they begin to detect a stimulus that is already in skin contact, and click a control. If they delay even a second to be sure they have actually felt a stimulus, a heavier threshold can be recorded.

Kanatani, U.S. Pat. No. 4,313,445, Feb. 2, 1982, introduced a hand held steel wire aesthesiometer as another variation in cutaneous sensibility testing. A steel wire in this device bends in a length along a horizontal plane rather than a vertical axis as do the monofilaments. There are other important differences in application of this instrument. Similar to the computerized metal instrument, when the device is applied, light contact is made, and the force is ramped up to the level at which a patient detects stimulation.

Disadvantages include that wire is malleable, and can become bent with repeated application, reducing the intended force of application. With the metal being relatively rigid, the vibration of the examiner's hand can be exaggerated in transmission to the subject rather than absorbed or dampened.

In other more loosely related instruments designs Fisher, U.S. Pat. No. 2,704,539, Mar. 22, 1955, provides hand-held design for a spring-loaded pin for sensory detection. Wyler, et al, U.S. Pat. No. 3,933,148, Jan. 20, 1976, provides a hand-held spring-loaded device design for determining skin reactive sensitivity on the basis of a persistent skin streak. Disadvantages include that springs are notoriously hard to calibrate exactly, and a needle or pin, as stated previously, produce too heavy stimulus force to apply the sensitive detection thresholds needed for cutaneous sensory testing.

Overall Disadvantages of Prior Art

It is a significant problem to the examiner when the device that needs to be used in a clinical test becomes damaged. An examiner may have only one damaged device of a needed size available in the set of several. Examiners may continue to use the damaged, less than accurate, set of devices, or not perform the needed exam. Clinicians are more likely to replace questionable monofilaments used as test stimuli if they are easily interchanged.

• • a) Monofilament is fragile: The monofilament in the original Semmes-Weinstein device handle design is most fragile where it leaves the rod. Here it can be inadvertently bent at a severe angle, potentially changing its force of application as the testing stimulus and accuracy when applied to the patient. A monofilament, particularly the lightest used for testing of normal subjects, can break or come out at the point where it leaves the rod handle.
  • b) Handle sides are often confused: In the original Semmes-Weinstein device design that uses the straight clear square plastic rod handle, the side into which a hole has been drilled for housing the monofilament looks exactly the same as the other sides of the device. The very small monofilament “hairs” can be easily damaged if the rod handle is inadvertently laid down upon the monofilament, or if the monofilament is laid down upon itself, particularly if a storage case is dropped and the monofilament devices fall out.
  • c) Adjacent handle damage to monofilament: In the Semmes-Weinstein original straight handle device design, if two or more devices are assembled together, or nested, the end of a neighboring adjacent rod handle can shear off the monofilament of another. This happens when two or more devices are grouped for using several different diameter monofilaments sizes together for the specific test.
  • d) Large box needed for protective storage: In the original Semmes-Weinstein device design the devices cannot be nested, thus they require a relatively large box container, which can be cumbersome, whereas clinicians prefer devices that can fit into a pocket. Large boxes cannot fit easily on or near a treatment table or area, and are more apt to be knocked off of the table when other therapy or testing equipment is used, thereby damaging the monofilament devices.
  • e) Unmet need for currently applying more than one device: It has been clearly demonstrated that hand-held instruments for performing the two-point discrimination version of cutaneous sensory tests do not adequately control force of application applied by the examiner. Yet many examiners maintain that a two-point stimulus application versus a one-point is superior to the monofilament cutaneous sensory threshold test. Thus there is a need for more than one repeatable stimulus force of application in cutaneous sensory testing, if for no other reason than to determine the difference in variations of the cutaneous sensory tests.
  • f) Unmet need for consistent holding of handle: When applying the original device design Semmes-Weinstein Monofilament to the subject, examiners hold the rod handles in inconsistent ways. Some choke up on the monofilament, some place their index finger on the opposite side of the handle directly over the monofilament, and some—correctly—hold the instrument by placing their index and other fingers at a given distance from the monofilament during every patient application.
  • g) Fixed monofilament in handle: The monofilament in the original straight handle Semmes-Weinstein device design is permanently fixed to the rod handle, thus if damaged, the whole unit device has to be replaced with an entirely new rod handle and monofilament. This is costly, and time consuming to reorder, as well as interruption to patient testing. Often clinicians only have one set available for testing. Replacement monofilaments are not available for the original device except by replacing the entire device containing a specific monofilament size. All the original Semmes-Weinstein design set of 20 devices and various reduced number of monofilament sets using the original Semmes-Weinstein design, share this in common. Other device designs assembling selected size monofilaments, with or without a single handle, share the same problem of not being easily interchangeable without replacing the entire device or being disassembled.
  • h) Unmet need for disposable or replaceable monofilament: That the monofilament in the original straight handle Semmes-Weinstein design is permanently fixed to the rod handle, makes the use of disposable monofilaments prohibitive in cost, as the device has to be replaced. While the monofilament can be cleaned, it is not usually sterilized between patient test applications. The device can be cleaned by dipping a monofilament tip in hydrogen peroxide, etc., but is not usually between patient test applications. Disposable devices are important for health safety in patients with resistive diseases such as TB and HIV.
  • i) Unmet need for other test stimulus variations: That the monofilament in the original straight handle Semmes-Weinstein device design is permanently fixed to the rod handle, limits alternative stimuli for cutaneous sensory testing, the monofilaments can apply.
  • j) Stimulus application needs to be repeatable for accuracy: Examiners need to assure that the monofilaments are applied perpendicularly to the skin area tested in order for the monofilaments to exert intended force of application or they will apply too little force. They can slip across the skin surface and be misapplied. The subject could be judged not to have detected the monofilament force of the specific cutaneous threshold when, instead, the examiner has misapplied the monofilament. If applied at an angle, they are likely to slip.

New Device

Objects and Advantages of New Device

Accordingly, several objects and advantages of my invention are . . .

• • a) (Monofilament is better protected from damage) to provide a handle design in the my new device that can reduce the risk of monofilament damage during use in a simple device design, and at the same time make the instrument more functional and versatile.
  • b) (Monofilament side of handle is made obvious) to provide a handle design in my new device in which the handle side where the monofilament is attached is clearly obvious.
  • c) (Monofilament protection from adjacent handle damage enabled) to provide an improved handle design in my new device where several monofilaments can be safely assembled together, reassembled, and disassembled for various cutaneous sensory tests.
  • d) (Small box or case is enabled) to provide an improved handle design in the new device where several monofilaments desired for a specific test can be safely assembled, and nested storage in a small box or case.
  • e) (Option for application of two or more devices is enabled) to provide a means for attaching two or more devices for concurrent stimulation with preselected force of application.
  • f) (Consistent holding of handle enabled) to provide, in the preferred embodiment, a mark or rest for the examiner's index finger, on the side opposite the monofilament, at a given distance from the monofilament to enable consistency in examiner holding and applying the device.
  • g) (Replaceable monofilament members enabled) to provide monofilament replacement disks in the new device where a damaged monofilament can be quickly and easily replaced.
  • h) (Disposable or replaceable monofilament members enabled) to provide economical monofilament replacement disks in the new device where an unclean monofilament can be quickly and easily replaced.
  • i) (Option for other test stimulus variations enabled) to provide alternative monofilament replacement disks in my new device that can be interchanged with other discs for additional or alternative stimuli.
  • j) (Repeatable stimulus application enhanced) to minimize slippage and twisting of the monofilament during application to the patient in the new device by assuring correct application of the monofilament stimulus.

Further objects and advantages of my new device will become apparent from consideration of the drawings and ensuing description.

Summary of Invention

What is needed to improve cutaneous sensory threshold testing but not available in previous art is a versatile handle for a visible monofilament stimulus whereby several diameter sizes can be grouped safely together and be readily available for clinical testing by an examiner in a small box or packet, with replacement monofilaments on hand and readily interchangeable as needed to assure a test is accurate, safe, and more versatile for clinical use in patients, or research into variations of optimal sensory test design. Weinstein and others have created usable instrument devices with several types of handles for testing cutaneous sensory detection threshold in prior use, but it is proposed that the best solution is to resolve the disadvantages of the original device and create a simple but improved device handle design that can help protect the monofilament test stimulus with as few moving parts as possible, and provide for the versatility needed when the device is used in patient testing.

My new device design for cutaneous sensory detection testing includes a functional handle, and means for replaceable monofilament, whereby several devices of same or different diameter sizes can be safely grouped together and be readily available for clinical testing by the examiner in a small box or packet. Replacement monofilaments can be on hand and readily interchangeable during testing as needed to assure the test is both accurate and safe for clinical use in patients. The addition of the curve and extension to the handle better protects the monofilament where it is attached to the handle. If inadvertently laid down incorrectly the handle falls on its side or back, not on the monofilament. If dropped, the device lands on its back or side rather than the side to which the monofilament is secured. The curve and extension in handle design helps prevent the handle from being laid down on the monofilament, and the monofilament from being laid down upon itself and damaged. The curve serves the purpose of letting the examiner immediately recognize the correct orientation of the handle. The curve and extension in handle design prevents one device when grouped or nested together from shearing off its neighbor monofilament, with or without a replaceable disk attachment. The replaceable disk serves as an additional cushion and shield for the monofilament, and fits into the handle curve and extension of a neighboring device when assembled. Monofilament devices in the new design can be secured in the smaller box or case for coat-pocket, tabletop, or other form of display, and are safer if the box is dropped.

List of Names

Prior Art:

7. Straight rod handle device design (prior art)

9. Monofilament member (prior art)

11. Point monofilament member exits from straight rod handle and is most vulnerable to damage (prior art)

13 Monofilament end of straight rod handle that can damage a neighboring monofilament when assembled together (prior art)

New device:

15. Device handle

17. Functional curve

19. Handle curve extension

21. Monofilament member

23. Monofilament stimulus tip end

25. Monofilament embedded in handle end

27. Hole in handle for monofilament

29. Mark or rest for examiner index finger to consistently hold the device.

31. Adapter connector for two handles

33. Disk attachment with monofilament for replacement or interchange

35. Example of alternative disk attachment for two point testing

37. Example of alternative disk attachment for three point testing

39. Alternative attachment means of clip for the disk replacements or interchange

41. Hole for clip attachment to hold disks

BRIEF DESCRIPTION OF THE DRAWINGS

a) Prior Art:

FIG. 1A shows in prior art a Semmes-Weinstein monofilament style rod handle device design, monofilament, and its point of exit from the straight handle rod where it is most vulnerable to damage.

FIG. 1B shows in prior art a view of what happens when the handle is laid down on the fixed monofilament and damaged.

FIG. 1C shows in prior art how the end of an adjacent handle can shear off and damage a neighboring monofilament by hyperflexion of the monofilament at its attachment where it exits the rod.

b) New Device:

FIG. 2A shows my new device handle incorporating a functional protective curve, and extension containing nylon monofilament in one embodiment, and the preferred embodiment of a mark or rest on the handle opposite the side of the monofilament for consistent placement of the examiner's index finger on the handle, at a distance from the monofilament.

FIG. 2B shows several of the new devices nested together without injury to the monofilament using the new handle design, one curve abuts another handle curve, not the monofilament.

FIG. 3A shows two new device handles and optional connector attachment in one embodiment, for two or more device handles to be secured together during patient testing.

FIG. 3B shows a close up of one embodiment of the connector attachment for two handles.

FIG. 4A shows the new device in the preferred embodiment, adding to the new handle a replacement disk fitted to the terminal end of the handle curve and extension, the disk having been pre-embedded with the monofilament of preselected diameter size.

FIG. 4B shows two examples of a variety of possible alternative replacement disks to enable two or more concurrent monofilament member test stimuli.

FIG. 4C shows the new device with embodiment incorporating an alternative means for securing the replaceable disk at the terminal end of the handle curve, the disks sliding into and out of position, and secured with a clip, the clip fitting into a hole drilled into the plastic handle at the terminal end of its curve and extension.

FIG. 4D shows a close up of an example of the alternative clip embodiment to secure the disk at the terminal end of the handle curve.

FIG. 4E shows that when several of my new device handles are assembled together with disk attachments, the disks abut an adjacent handle curve and extension, not the monofilament, and the handles can be safely nested together without damage to the monofilament.

DETAILED DESCRIPTION OF DRAWINGS

The preferred embodiment of my new device can best be seen by viewing FIG. 4A.

a) Prior Art:

FIG. 1A shows a prior art Semmes-Weinstein monofilament style device straight rod handle design 7 attached monofilament 9 and its point of exit from the straight handle rod 11 where the monofilament is most vulnerable to damage on a forward monofilament end of the handle 13.

FIG. 1B shows in prior art a view of what happens when the forward monofilament end of the handle 13 is inadvertently laid down on the fixed monofilament 9 and damaged.

FIG. 1C shows in prior art how the forward end of an adjacent handle 13 can damage a neighboring monofilament 9 when several devices are assembled together for test or case.

b) New Device:

FIG. 2A shows my new device handle 15 incorporating a functional curve 17 and an extension 19 of the handle to help protect a monofilament 21 having on one end a stimulating tip 23 and, in one embodiment, the other end 25 embedded in the handle curve extension 19. The monofilament is glued into a hole 27 in the handle securing the monofilament in a perpendicular orientation to the length of the handle. This drawing illustrates how the curve addition to the handle helps to protect the monofilament where it is attached to the handle. When laid down or dropped the new device handle is more likely to fall on the handle side without the monofilament test stimulus, not on the monofilament where it exits the handle. The curve 17 serves the purpose of letting the examiner immediately recognize the correct orientation of the handle. Also shown is the preferred embodiment of an identifying mark 29 that helps to further improve recognition of the correct orientation of the monofilament. It also provides a specific point for the examiner's index finger to contact the handle and hold the device on the first end of the handle for application at a consistent distance from the monofilament on the forward second end. Not only does the mark help protect the monofilament from damage from the hand of a novice examiner, it serves to help insure smooth application with minimal vibration of the examiner's hand, and improves the repeatability of the of the monofilament stimulus application.

The new device includes any of the known monofilament diameter sizes, or new diameter sizes, and lengths for the monofilament member. Nylon has been determined optional for its elastic properties, but other suitable materials may become available as determined in instrument testing, and the monofilament in this device is not limited to nylon. Today the most frequently used diameters for force of application in testing are those diameters sizes that at 38 mm in length from the point they leave the handle produce forces in the order of 0.68 mg, 200 mg, 2 gm, 4 gm, 10 gm, and 300 gms. The monofilaments are bent against skin surface to deliver stimulus force/pressure (force per unit area) to the subject.

In the most frequently used test protocol, each monofilament of a given diameter size used in the test is applied, first in an area that the subject can detect the monofilament as a reference. Then with the subject's eyes averted, the area of suspected abnormality is tested by the examiner applying the monofilament in a perpendicular fashion to the skin in 1.5 seconds, bending the monofilament, holding the monofilament for 1.5 seconds, and then lifting in 1.5 seconds, in a smooth application. If the patient responds with a “yes” or other affirmative response, the cutaneous sensory detection threshold is recorded as being that level. If a subject does not respond in an area, then progressively heaver monofilaments are tried until either the subject detects one, or it is established the subject does not respond to any of the monofilaments used in a test set. Other protocols are possible, particularly additional protocols for one and two point discrimination testing.

FIG. 2B shows my new device handle 15 with several devices nested together where the new device handle design with the handle curve 17 and extension 19 protects the given size monofilament 21 from another adjacent handle. The curve and extension prevent one device when grouped or nested from being sheared off by its neighbor monofilament device handle. The curve and extension device handle design allows the monofilament devices to be secured together in a small box or case. Screen and monitoring sets today for testing patients require only five or six monofilament diameter sizes. These devices can be assembled adjacently in a small box for coat-pocket, tabletop, or other form of display and availability. With the original straight rod design, boxes containing monofilament devices were frequently were knocked off of an examination table. The lid would break or just open, and the monofilaments would then be scattered over the floor in many orientations, damaging several that had to be replaced. The devices while nested can be secured in the case with Velcro or other means for safely securing them in the box in the event it is dropped, and the lid opens.

FIG. 3A shows the new device handle 15 and in one embodiment an optional adaptor connector attachment 31 for two or more devices to be used together for two-point testing. For two-point discrimination testing, 5 and 10 grams of force levels have been suggested as an optimal starting point for controlled force of application. The monofilament 21 in my new device can be cut off at lengths to apply these relatively heavy gram force levels. The elastic properties of the monofilament enables the monofilament to provide the same force of application for more than one device, thus providing force control that is missing in two-point testing devices.

FIG. 3B shows a close up of the connector attachment 31. The connector in the example can hold two device handles together for concurrent application of two of the given size monofilament as is needed for two-point discrimination testing. Other variations in the connector attachment can allow connection of more than two handles, if needed.

FIG. 4A shows my new device in the preferred embodiment, with replacement disk 33. The disks are pre-embedded with the monofilament 21, of a given size, and attached to the terminal end of the handle 15 extension 19 and curve 17 and by an attachment means. The disks in this embodiment are adhesive backed on their flat side to fit and attach onto the end of the curve extension. These disks and monofilaments can be sealed in packages and made available in clean or sterile packages. Even if the device is made as in claim 1, the disk can be used to quickly replace a damaged monofilament. If the disks of devices become dislodged, they can be secured again on the forward end of the curve extension 19 by self-stick adhesive backed tape available for this purpose from the group of available adhesives and sticky backed tapes.

Replacement monofilaments are made available in disks pre-embedded with monofilaments in the variety of sizes and test kits required in cutaneous sensory detection threshold testing of light touch to deep pressure. Replacement monofilaments made available in disks pre-embedded with monofilaments can be disposable if needed, in the variety of sizes required in cutaneous sensory testing. Replacement disks can be made available with two or a plurality of controlled force of application monofilament stimulations. The replacement disks can be sealed and made available in clean or sterile packages. The elastic properties of the nylon or similar material can provide controlled force of application for replacement disks of more than one stimulus not attainable in other conventional instruments used for this purpose.

FIG. 4B shows two alternative disk replacements with variation in monofilament stimulus of two 35 or three 37 stimuli. Other alternatives are made possible by the controlled force of application provided by the nylon or similar elastic material that is not attainable in the design of other rigid probe conventional instruments used for this purpose.

FIG. 4C shows the new device handle 15 and an alternative means for securing the disk at the end the curve extension when the disks need to be interchanged. A connector clip 39 is mounted to the second end of the handle at the terminal end of the extension 19 and curve 17 and secured through a hole 41, in the handle at the end of the curve extension 19 allowing the disk to slide into and out of position on the handle. Interchanging disks are necessary for placing types of monofilament stimuli on one handle, without wasting handles or usable disks. One could also use more than one handle with pre-embedded disks with the desired monofilament stimuli.

FIG. 4D shows close up of alternative clip embodiment 39. The clip goes through the hole that has been drilled for this purpose in the second end of the handle. The disks can slide in and out of the clip indefinitely.

FIG. 4E shows the new device handle 15 and replacement disks can be nested when performing a test on a subject, or included in a storage case, without injury from adjacent monofilaments. On the monofilament 21 second end of the handle extension 19 curve 17 and of the handle the disk 33 also helps prevent one monofilament from being damaged by a neighboring handle. The disk 33 additionally helps keep the handle from being laid down on the monofilament. In the preferred embodiment, the disk 33 is made of hard silicone rubber, and can serve as a buffer against the other device handles, and give the embedded monofilament a slight flexibility where it leaves to handle, decreasing the stress on the monofilament at this vulnerable point.

CONCLUSION, RAMIFICATIOSN, AND SCOPE OF THE INVENTION

The diameter width of rod handle in my design can be varied, but if smaller than 6.35 mm diameter does not serve to protect the monofilament as well as the preferred embodiment. While a square rod helps keep the handle from rotating; round rod handle can be used in an alternative. Round, oval, or any other shape diameter material can be used for the handle equally as well as the square in the embodiment in examples shown, so long as the curve and extension are included with the handle, and attachments are made to correspond with the alternative diameter shape.

Handle material can be made of Lucite or any other synthetic material but is not limited to these. Other rigid or relative rigid synthetic materials can be used for handles in claims 1 and 2 of the current device.

Disk material can be made of clear rubber silicone, Lucite plastic, or any other synthetic material but is not limited to these. Other rigid or relative rigid synthetic materials can be used for disks in the current device.

While the cutaneous sensory test is aimed at testing peripheral nerve function, its use is not limited to testing peripheral nerves of subjects. It can also be used in patients with higher and more central nervous system abnormality such as stroke and spinal cord injuries, as well as for those with congenital absence of nerve function, diseases and trauma.

The reader will see that the new device provides a highly reliable, lightweight, economical device to be used by persons who do cutaneous sensory detection testing. With respect to various embodiments, certain aspects of this invention have been described in detail. It will be apparent that other modifications can be made within the scope of this invention, and my invention should not be determined by, or limited to, the embodiments in the drawings and claims illustrated. It is not intended to limit my invention to the exact details shown above except as examples of embodiments, and insofar as they are defined in the claims.

If the curve addition to the original straight Semmes-Weinstein design handle is considered obvious, at the time of the current application, the curve better protecting the monofilament, allowing the handle rods to be nested, and options for more than one concurrent stimulus have not been previously incorporated into any device design for clear plastic rod handles by any manufacturer, or patent, thus does not seem to have been obvious to them.

Claims

1. A device for testing human or animal cutaneous sensory detection comprised of whereby the monofilament testing device is improved, better protected from damage to said monofilament member, more functional, and thereby more practical for use.

a) a handle of plastic or similar material having a first end and a second end, said first end to be held by an examiner, said second end bent into a continuous curve with an extension and a means to hold a monofilament member test stimulus in a position perpendicular to the length of said handle

b) a handle means for securing said monofilament member of a selected force of application for test application

c) a first protective means provided by the curve and the extension of said handle for improving protection of said monofilament member from damage when said device is used

d) a second protective means provided by said curve and said extension of said handle for protecting said monofilament member whereby two or a plurality of said device can be nested together without injury to said monofilament member

e) an optional connection attachment to said handle thereby providing a means for connecting said device to another

f) a connection means for providing said monofilament member to be individually, concurrently, or sequentially applied

g) a mark or finger rest in the preferred embodiment, on said handle on the side opposite said monofilament member at a given distance from said monofilament member for an index finger of said examiner to be placed on said handle

h) a consistent means for improving controlled application of said monofilament member and further protecting said monofilament member from damage in use and application from the hand of said examiner

2. As in claim 1 and further including: whereby said monofilament testing device is simple in design but more versatile in that said monofilament member of predetermined size, shape, number, and force of application can be replaced or interchanged, and applied individually, concurrently, and sequentially with repeatable force of application.

a) a monofilament replacement object into which one said monofilament member or the plurality thereof has been secured, and means for said monofilament member to be attached to the handle and interchanged during testing of cutaneous sensory detection

b) a monofilament replacement object, in the preferred embodiment, a disk, having a circumference and two sides, said disk flat on one side by which said disk has a means for being attached to the terminal end of said curve of said handle, and can be attached to and detached from said curve at said second end, said disk on its other side thereof having a center into which one said monofilament member or said plurality thereof has been secured

c) a buffer protective means provided by said disk addition to said curve and said extension of said handle for protecting said monofilament member whereby a plurality of said device can be nested together without injury to said monofilament member