The sensory examination (Fig 218-1) is the least reliable part of the neurologic examination. It is also very time-consuming to test systematically touch, pain, temperature, position, and vibratory sensations. Situations where a careful sensory examination is needed include:
FIG. 218-1. Nerve root origin of various reflexes. (From Haymaker W, Woodhall B: Peripheral Nerve Injuries: Principles of Diagnosis. Philadelphia: WB Saunders, 1945, p. 16. Used by permission.)
1. Pain syndrome, especially on the trunk, looking for a dermatomal pattern as in preeruptive herpes zoster, or in the leg, looking for discogenic radiculopathy.
2. Localized atrophy or weakness.
3. Numbness, pins and needles, tingling, coldness or pain in any part.
4. Trophic changes, especially painless ulcers, blisters, and joint lesions, should lead to careful testing for loss of pain sense.
5. Presence of ataxia should always lead to careful evaluation of position and vibratory sense.
6. Visual inattention suggesting a non-dominant parietal lobe lesion.
7. Recurrent paroxysms of pain, suggesting a thalamic syndrome.
8. Spinal cord trauma or other causes of a sensory level or dissociated sensory loss.
9. Perianal sensation in suspected spinal cord dysfunction.
10. Following trauma to an extremity with motor or sensory complaints.
11. Following stroke with finding of a hemiparesis or hemianopia.
If sensory abnormalities exist related to the median, ulnar, or peroneal nerves, examination for Iinel's sign should be performed, if feasible, over the carpal ligament, the ulnar groove, and distal to the head of the fibula, respectively.
Two-point discrimination has utility, particularly for peripheral nerve lesions. There is normal variation when regions are compared. In the tongue, normal two-point discrimination is 1 mm, while the finger tip is 2 to 6 mm, the forearm and chest are 40 mm, and the thigh and upper arm are 75 mm.
Patients will on occasion attempt to influence the examiner to make a diagnosis that does not exist. A few counter maneuvers may be helpful to determine if lesions are real (Table. 218-6).
TABLE 218-6 Methods to Overcome Voluntary Patient Movements and Feigned Deficits
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