Sensory: Exam Demonstration

Upper extremity pain and temperature

The pain and temperature pathway can be tested either by a "painful" stimulus, e.g. pinprick, or by heat/cold discrimination.  The demonstration shows (1) cold sensation tested by using the end of the tuning fork, which at room temperature is colder than skin, and (2) pain sensation tested by a pinprick stimulus.   In both examples, a proximal stimulus is compared to a distal stimulus.  

This tests the spinothalamic system, which carries pain and temperature sensation. Remember that the spinothalamic fibers cross the midline near their point of entry into the spinal cord, and ascend in the lateral spinothalamic tract contralateral to the stimulus.  As in all sensory testing, asymmetry is important as an indication of a unilateral lesion, and proximal areas should be compared to distal areas. 

A loss of sensation in a DERMATOME distribution suggests a lesion in the corresponding dorsal root (e.g. the C6 dermatome would include the thumb; the C7 dermatome would include the middle finger). A loss of sensation can also be localized to specific peripheral nerves (e.g. distribution of the median nerve to the thumb and first three fingers).

Clck the play button to watch the video

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