Abstract: An improved pressure sensory threshold testing instrument comprised of a filamentous testing element (132) mounted on a head member (102) that is pivotally attached to a handle member (100) with a nonelectrical power assist pivot mechanism. The power assist pivot mechanism aids in actively biasing the head member (102) into either an open, testing position or a closed, storage position. The power assist mechanism and geometry resist accidental opening that could expose and damage the filament. The design facilitates one-handed operation with no change in grasp needed throughout the whole process of retrieval, testing, and storage. This singular grasp allows for increased ease and efficiency of the testing procedure. The configuration speeds the testing process while protecting the filament more securely in an instrument that is portable in a pocket. The design also minimizes the potentially threatening appearance of this type of medical testing device.