How is sensory examination done for multiple sclerosis (MS)?

Sensory examination involves the testing of the main parts of the body - face, trunk, arms, and legs - for the modalities of sensation. Sensitivity to touch is tested with a wisp of cotton. Sensitivity to pain is tested with a pinprick. Temperature sensitivity is examined by touching with warm and cold objects. Vibratory sense is tested by placing a vibrating tuning fork on bony prominences. Position sense is tested by having the patient close the eyes and identify upward or downward movements of the fingers and toes. Finally, certain combined sensory modalities are important to examine. Stereognosis is the ability to identify, with the eyes closed, common objects such as a coin and a key placed in the hand. Stereognosis requires both normal touch sensation and normal position sense in the hand. The ability to identify two simultaneous touches on the face and hand is called for in double simultaneous stimulation. Recognition of whether one or two points are touching the face, hand, or foot is called two-point discrimination.

Identifying numbers "written" on the palms of the hands is the object of the palm-writing test. Two typical patterns of sensory loss are seen in multiple sclerosis (MS). The first is decreased touch or pinprick sensitivity on the legs and trunk up to a particular level, which may be at the navel, at the bottom of the rib cage, up to the nipple line, or as high as the armpits or neck. The exact upper limit of the level pinpoints the lesion to a particular segment of the spinal cord.

The second typical finding is the loss of position sense and stereognosis in the hands. The hands may be normally strong but difficult to use effectively because the patient does not know where the fingers are or what is in the hand without looking. This is called the "useless hands syndrome" and indicates involvement of the cervical (neck) portion of the spinal cord. Frequently, however, the results of the sensory examination are normal in MS, even when the patient is in the midst of a sensory attack.