Interactive Guide to Physical Examination
Specific nerve roots are responsible for specific reflexes. Therefore, an abnormal reflex can help locate a pathologic lesion. Reflexes commonly tested (with their corresponding nerve roots) include: biceps reflex (C5,C6), triceps reflex (C6,C7), brachioradialis reflex (C5,C6), knee jerk reflex (L2,L3,L4), ankle reflex (S1) and plantar response (L5,S1). Cutaneous reflexes (a twitch in the muscle) can also be elicited by stroking the skin of the upper abdomen (T8,T9,T10) or lower abdomen (T10,T11, T12).
When evaluating reflexes, compare one side to the other and note the speed, force, and amplitude of the upward reflex response and downward component. Symmetrically diminished or absent reflexes may be normal.
Reflexes are graded on a zero to four point scale, with hyper-reflexia suggesting central nervous system disease. In contrast, reflexes may be diminished with sensory loss, spinal segment damage, peripheral nerve disease, or disease of the muscle or neuromuscular junction.
If you are having trouble eliciting reflexes, consider holding the reflex hammer a bit more loosely. Strike the area with more bouncing motion of the wrist so as not to dampen the reflex response. Lastly, strike a bit more forcefully. If you are still having difficulty, consider reinforcement to augment the response.
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Click on the video icon to view a demonstration of the examination of reflexes. |
