Sensory function assessment. A pilot comparison study of touch pressure threshold with texture and tactile discrimination.

The purpose of this study was to determine if a correlation exists between touch-pressure threshold testing and sensory discrimination function, specifically tactile gnosis for texture and object recognition. Twenty-nine patients diagnosed with carpal tunnel syndrome (CTS), as confirmed by electromyography or nerve conduction velocity tests, were administered three sensibility tests: the Semmes-Weinstein monofilament test, a texture discrimination test, and an object identification test. Norms were established for texture and object recognition tests using 100 subjects (50 females and 50 males) with normal touch-pressure thresholds as assessed by the Semmes-Weinstein monofilament test. The CTS patients were grouped into three categories of sensibility as determined by their performance on the Semmes-Weinstein monofilament test: normal, diminished light touch, and diminished protective sensation. Through an independent t test statistical procedure, each of the three categories mean response times for identification of textures of objects were compared with the normed response times. Accurate responses were given for identification of all textures and objects. No significant difference (p < .05) was noted in mean response times of the CTS patients with normal touch-pressure thresholds. A significant difference (p < .05) in response times by those CTS patients with diminished light touch was detected in identification in four out of six objects. Subjects with diminished protective sensation had significantly longer response times (p < .05) for identification of the textures of cork, coarse and fine sandpaper, and rubber. Significantly longer response times were recorded by the same subjects for identification of such objects as a screw and a button, and for the shapes of a square, triangle, and oval.