7th Cranial Nerve – Facial nerve lesions – Bell’s Palsy

Definition:

Facial hemiparesis as a result of a lesion to the facial nerve: cranial nerve VII.

Examination:

Although the true aetiology of facial nerve palsy also known as Bell’s palsy is not fully understood a number of well postulated theories may be considered; these include:

  • Viral infection such as HSV-I (Herpes Simplex Type-) being reactivated
  • Herpes zoster oticus
  • Demyelinating polyneuropathy
  • Diabetes mellitus
  • Advanced hypertension
  • HIV infection
  • Malignancies, tumours and other space occupying lesions
  • Supranuclear and nuclear lesions
  • Trauma e.g: temporal bone fracture
  • Acute and chronic otitis media
  • Neurosarcoidosis
  • Moebius syndrome

Examination:

The patient often presents with ptosis in the facial muscles affecting one side of the face, both the upper and lower parts may be affected depending whether the lesion is affecting the upper or lower motor neurons of the facial nerve.

Some patients may experience pain around the ear a few days prior to the onset of symptoms.

The patient is unable to frown or raise their eyebrow on the affected side, there is reduced lacrimation, dribbling due to sagging of the mouth, hyperacusis, reduced corneal reflex due to motor component paralysis (sensation to the cornea from trigeminal nerve remains intact) and inability to blow up the cheeks or whistle. Taste on the anterior two-thirds of the tongue may also be negatively affected.