Aetiology

• the causes of facial palsy may be classified in a number of ways:
  • depending on the type of the lesion it may be classified as :
    • unilateral upper motor neurone palsy:
      • vascular disease
      • tumour
    • unilateral lower motor neurone palsy:
      • pontine causes:
        • vascular
        • tumour
        • multiple sclerosis
      • posterior fossa causes:
        • acoustic neuroma
        • meningioma
  • depending on the site of the lesion it may be classified as: (1)
    • extracranial
      • traumatic
        • facial lacerations / blunt forces, newborn paralysis
      • neoplastic
        • parotid tumours, tumours of the external canal and middle ear, facial nerve neurinomas, metastatic lesions
    • intra-temporal
      • traumatic
        • fractures of petrous pyramid, penetrating injuries
      • neoplastic
        • glomus tumours, cholesteatoma, facial neurinomas, acoustic neurinomas, squamous cell carcinomas, metastatic cancer
      • infectious
        • herpes zoster oticus ( Ramsey-Hunt syndrome), acute otitis media, chronic otitis media, malignant otitis externa
      • idiopathic
        • Bell's palsy (2)
          • although traditionally defined as idiopathic it is thought to be associated with herpes simplex virus type 1
    • intracranial
      • neoplastic lesions, stroke (2)
  • many systemic diseases also may be associated with facial paralysis:
    • sarcoidosis
    • HIV infection
    • lyme disease
    • Guillain-Barré syndrome (2)
    • multiple sclerosis
  • some influenza vaccines also may cause facial nerve paralysis(2)

Reference:

1. Libreros-Jiménez HM, Manzo J, Rojas-Durán F, et al. On the cranial nerves. NeuroSci. 2024 Mar;5(1):8-38.
2. Glass GE, Tzafetta K; Bell's palsy: a summary of current evidence and referral algorithm. Fam Pract. 2014 Dec;31(6):631-42.