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Aetiology

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

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  • The aetiology of Bell's palsy was previously stated as unknown.
  • However there is increasing evidence to suggest that the main cause of Bell's palsy is latent herpes viruses (herpes simplex virus type 1 and herpes zoster virus), which are reactivated from cranial nerve ganglia (1,2).
    • herpes simplex virus type 1 ( HSV-1) is probably the cause of most cases of Bell's palsy (3)
      • research has found elevated HSV-1 titers in affected individuals (2)
      • it is thought to be due to virus reactivation from latency in the geniculate ganglion rather than primary infection (3)
    • herpes zoster virus has traditionally been associated with Ramsay Hunt syndrome (typical cutaneous vesicles and cochleovestibular dysfunction)
      • however vesiculation may not necessarily appear (zoster sine herpete) or may be delayed in up to half of patients
      • preherpetic neuralgia (dermatomal pain and dysaesthesia before vesiculation) may be the only clinical indicator that herpes zoster virus is involved
      • almost a third of facial palsies previously diagnosed as idiopathic are thought to be due to zoster sine herpete
  • In most patients, the condition occurs in isolation. Less commonly, it may be associated with:
    • diabetes mellitus
    • a viral polyneuropathy with inflammatory demyelination
    • severe hypertension
    • last trimester of pregnancy
    • dental anaesthesia
    • the common cold

Reference:


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