The blink reflex may be helpful in revealing the presence of a subtle trigeminal or facial nerve lesion. Ipsilateral trigeminal nerve lesions lead to responses that are either lost or have a prolonged latency bilaterally. A unilateral facial nerve lesion, by contrast, leads to a delayed or absent response on the affected side regardless of which side is stimulated.
The blink reflex may be abnormal with polyneuropathies, thereby indicating the extent of the disorder. Abnormalities may also occur with tumors in the cerebellopontine angle involving either or both nerves or the brain stem and with brain stem lesions involving the central pathways subserving the reflex, such as in multiple sclerosis, sometimes in the absence of clinical evidence of brain stem involvement.
Figure 24-24 Arrangements for eliciting the blink refle>(From Aminoff MJ: Electromyography in Clinical Practice, 3rd ed. New York, Churchill Livingstone, 1998.)
Figure 24-25 The blink reflex elicited by electrical stimulation of the right supraorbital nerve in a normal adult. Two separate responses are shown. The R1 component of the response is present only on the side that is stimulated, wherease R2 is present bilaterally. (From Aminoff MJ: Electromyography in Clinical Practice, 3rd ed. New York, Churchill Livingstone, 1998.)
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