ABSTRACT

Bell’s palsy is a lower motor neuron weakness of the facial nerve the aetiology of which is unknown. A viral cause is favoured based upon the isolation of herpes simplex virus-1 genome from the facial nerve endoneurial fluid of sufferers. The facial nerve innervates the muscles of facial expression and the stapedius muscle, which dampens sound waves in the inner ear. The nervus intermedius is the branch of the facial nerve containing sensory and parasympathetic fibres. A patient who has weakness affecting the lower face on one side, but sparing the upper face, have an upper motor neurone lesion affecting the supranuclear connections of the facial nerve and nucleus. Bell’s palsy is an isolated lower motor neurone weakness of the facial nerve, acute at onset and unilateral. Typically individuals experience pain around or behind the ear followed by evolution of unilateral upper and lower facial muscle weakness for a few hours up to a couple of days.