FACIAL WEAKNESS (FACIAL NERVE [VII]) is a topic covered in the Harrison's Manual of Medicine.

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Look for hemifacial weakness that includes muscles of forehead and orbicularis oculi (see Fig. 187-2). If lesion is in middle ear portion, taste is lost over the anterior two-thirds of tongue and there may be hyperacusis; if lesion is at internal auditory meatus, there may be involvement of auditory and vestibular nerves; pontine lesions usually affect abducens (sixth cranial) nerve and often corticospinal tract. Peripheral nerve lesions with incomplete recovery may produce continuous contractions of affected musculature (facial myokymia); contraction of all facial muscles on attempts to move one group selectively (synkinesis); hemifacial spasms; or anomalous tears when facial muscles activated as in eating (crocodile tears).

FIGURE 187-2

The facial nerve. A, B, and C denote lesions of the facial nerve at the stylomastoid foramen, distal and proximal to the geniculate ganglion, respectively. Green lines indicate the parasympathetic fibers, red line indicates motor fibers, and purple lines indicate visceral afferent fibers (taste). (Adapted from MB Carpenter: Core Text of Neuroanatomy, 2nd ed. Baltimore, Williams & Wilkins, 1978.)

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