Abstract: Intracranial fluid pressure is measured as a function of a characteristic or characteristics of an eardrum. Either or both of the displacement of the eardrum when the stapedius muscle is stimulated or the aural acoustic compliance of the eardrum is measured and provided the cochlear aqueduct is open this will give an indication of intracranial fluid pressure without surgery. Acoustic compliance is measured under conditions of tympanometry but the tympanometry facility is disabled during displacement measurement. The data obtained by the method of the invention may be compared with reference data obtained from the same patient or in clinical trials to provide a real-time record of intracranial fluid pressure changes. Preferably eardrum displacement is used as a baseline measure and acoustic compliance measurement records short-term variation, the two records being combined by computer. Reference data may be input to the computer to update the information displayed.

Abstract: Low volume flow measurement apparatus developed for hearing dysfunction diagnosis but also suited to other applications comprises means (10) defining a cavity operably communicable with the variable volume, a D.C. microphone (15) responsive to ambient pressure changes in the cavity due to variations in said volume, and a reference diaphragm (17) operably connected with the cavity and moveable under servo-control responsive to the microphone to maintain the cavity pressure constant. The cavity will normally have a vent valve (18) and in non-hearing application may be coupled with the subject volume by a plunger seal. For hearing diagnosis the apparatus is suitably carried by a helmet (21) or harness with a headphone on the opposite side for sound stimulus application, the helmet itself being at one end of a boom (22) with a counterweight (23).