Peripheral Lesions

By using your knowledge of the anatomy of the facial nerve, the location of a lesion can be determined by the presence or absence of certain deficits.

A lesion in the facial canal proximal to the branching of the greater petrosal nerve and chorda tympani is characterized by the following:

  • Paralysis of all the muscles of facial expressionipsilateral to the lesion (LMN lesion of the branchial motor component of CN VII).

  • Loss of secretion from lacrimal gland and mucous membranes of nasal and oral pharynx ipsilateralto the lesion (lesion of the greater petrosal nerve, visceral motor component of CN VII).

  • Loss of secretion from submandibular and sublingual glands ipsilateral to the lesion (lesion of the chorda tympani, visceral motor component of CN VII).

  • Loss of taste from anterior 2/3 of tongueipsilateral to the lesion (lesion of the chorda tympani, special sensory component of CN VII).

  • Loss of general sensation from concha of external ear and small area of skin behind the ear (general sensory component of CN VII).

  • Deficits in hearing and/or vestibular functionsipsilateral to the lesion (associated with CN VIII).

  • Intact general sensation to the tongue (supplied by CN V3).

If the lesion was distal to the greater petrosal nerve but proximal to the chorda tympani the patient would present as above, except that secretory functions of the lacrimal, nasal, and palatine glands would be intact.

A lesion which affected the lingual nerve just distal to its junction with the chorda tympani would present as follows:

Loss of secretion from submandibular and sublingual glands ipsilateral to the lesion (visceral motor component of CN VII) Loss of taste from anterior 2/3 of tongue ipsilateral to the lesion (special sensory component of CN VII) Loss of general sensation from the tongue (general sensory component of CN V3).