• Clinical science

Facial nerve palsy

Summary

Facial (nerve) palsy is a neurological condition in which function of the facial nerve (cranial nerve VII) is partially or completely lost. It is often idiopathic but in some cases, specific causes such as trauma, infections, or metabolic disorders can be identified. Two major types are distinguished: central facial palsy (lesion occurs between cortex and nuclei in the brainstem) and peripheral facial palsy (lesion occurs between nuclei in the brainstem and peripheral organs). Central facial palsy manifests with impairment of the lower contralateral mimic musculature. In contrast, peripheral facial palsy leads to impairment of the ipsilateral mimic muscles and also affects the eyelids and forehead. Additionally, peripheral facial palsy can cause various sensory and autonomic disorders (depending on the exact location of the lesion). Diagnosis can usually be made clinically while patient history often helps in evaluating the underlying etiology. Idiopathic facial nerve palsy is treated with oral glucocorticoids and, in severe cases, antivirals. Treatment of the other types depends on the underlying cause. Most cases of idiopathic facial palsy heal completely within 3 weeks.

Etiology

References:[2][3][4][5]

Pathophysiology

  • The muscles responsible for eyelid and forehead movements are innervated by fibers from both sides
  • The lower facial muscles are only innervated by fibers from the contralateral hemisphere (via ipsilateral nuclei and the ipsilateral peripheral nerve), so they are paralyzed in both central and peripheral facial palsy.

References:[6]

Clinical features

Motor signs in central and peripheral facial palsy [6]

Central (signs are contralateral to the lesion) Peripheral (signs are ipsilateral to the lesion)
Inability to frown
  • No
  • Yes
Inability to close the eyelids completely
  • No
  • Yes
Mouth drooping
  • Yes

Additional signs of peripheral facial palsy

  • Sensory disturbances
  • Dry mouth (as a result of decreased saliva production)
  • Ocular features
  • Synkinetic involuntary movements of the facial muscles; (e.g., facial spasms while closing the eyes)

In central facial palsy, paralysis is contralateral to the lesion, and eyelid and forehead muscles are not affected!

Diagnostics

  • Ask about symptom onset and duration, recent infections, and outdoor trips
  • Ask patient to perform facial movements ; (e.g., frown, whistle, inflate cheeks, smile, show teeth/grimace, close eyes tightly, blink) and observe inabilities and asymmetries of the face.
  • Additional studies to investigate for potential causes (e.g., serology for Lyme disease)
  • Nerve conduction studies: can be performed to assess recovery prognosis [8]

References:[6][9]

Treatment

References:[9][11]

Prognosis

  • Idiopathic facial palsy: complete recovery in ∼ 85% of cases (within 3 weeks)
  • Misdirected regrowth of nerve fibers can lead to persistent disorders (e.g., synkinesias)

References:[12][13]

last updated 09/23/2020
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