Head and Facial Examination

It is important to examine the face and head carefully as most of the alternate causes for peripheral facial weakness arise from involvement of the facial nerve in its extracranial course.

The commonest cause of peripheral facial weakness is Bells palsy but a careful history and examination must be performed to exclude other rarer causes.

Ear, nose and throat

Examine for signs of ipsilateral vesicular rash in/behind the ear, on lateral neck, on the tongue, buccal mucosa, tongue or palate, which may indicate Ramsey Hunt Syndrome.

Examine the ear for evidence of otitis media, cholesteatoma, or malignant otitis externa (spread of infection from the ear canal eroding into the skull base, most commonly seen in immunocompromised and elderly diabetics). The mastoid may also appear inflamed as a consequence of chronic ear infection. Any evidence of the above requires urgent ENT referral.
Careful examination of the parotid gland may reveal swelling, suggesting parotitis or tumour, compressing the facial nerve as it passes between the deep and superficial lobes of the gland.

Cranial nerves

Altered sensation, such as heaviness or numbness, is commonly described by patients with facial weakness and is thought to be due to reduced muscle tone. Formal sensory testing of the trigeminal nerve should prove to be normal.

Strictly speaking, Bells palsy is an isolated facial nerve paresis, but there is some evidence that other cranial nerves, particularly trigeminal, glossopharyngeal and hypoglossal may, very occasionally, be involved [9].

If any cranial nerve deficits are identified in addition to the facial nerve, it must not be classified as Bells Palsy, and the patient should undergo further investigation.

Trauma

Post traumatic facial nerve paralysis is most commonly caused by fracture of the temporal bone and may be immediate or delayed [10].

If delayed, the weakness appears, on average, 4-5 days after the injury and is caused by oedema, delayed arterial spasm or external compression by haematoma.

History of concerning trauma is an indication for imaging and discussion with ENT/neurosurgery.

Learning bite

Important differential diagnosis for a facial palsy, other than Bells Palsy, include:

• (Central) UMN causes, such as a stroke, SDH, or tumour
• (Peripheral) LMN causes
  • Infective – acute otitis media, cholesteatoma, malignant otitis externa, Lyme Disease, viral infection (including HSV-1, CMV, and EBV)
  • Parotid pathology parotitis, malignancy
  • Trauma or iatrogenic
  • Neurological (Multiple Sclerosis , Guillain-Barr syndrome, Diabetic neuropathy, Myopathy etc)
  • Vascular Vertebrobasilar insufficiency