The sensory examination requires an alert and cooperative patient. Sensory testing includes light touch, pinprick, pro-prioception, and vibration. Start by testing for light touch using a wisp of cotton or tissue on the major dermatomes of the extremities and trunk. Observe for dermatomal losses or a distal-to-proximal gradient. The same areas are then tested for superficial pain with a pin. Temperature is mediated by the same pathway as pain, so any deficits of pain sensation should have a corresponding deficit in temperature sensation. Vibration is tested by placing a 128-cycles/sec tuning fork on the bony prominences of the extremities and asking the patient to identify when it stops vibrating. Comparisons are made side to side. If there is a question of myelopathy, a vibration level may be noted as the tuning fork is moved up the spinous processes. Position is best tested using the great toe and distal phalanx of the thumb or another finger. The digit is grasped on the sides and moved up and down. Even a very slight movement of a finger should be detected. Proprioception, vibration, and light touch are functions of the dorsal column, and pain, temperature, crude touch, and pressure are functions of the spinothalamic tract.
Stereognosis, graphesthesia, and touch localization are integrated cortical sensations and are difficult to test if primary sensations are impaired. To test stereognosis, several small familiar objects are placed in the patient's hand and the patient is asked to identify them. To test graphesthesia, the examiner writes numbers on the patient's palm and asks the patient to identify them.
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