Neuro-ophthalmological approach to facial nerve palsy

Facial nerve palsy is associated with significant morbidity and can have different etiologies. The most common causes are Bell's palsy, Ramsay-Hunt syndrome and trauma, including surgical trauma. Incidence varies between 17 and 35 cases per 100,000. Initial evaluation should include accurate clinical history, followed by a comprehensive investigation of the head and neck, including ophthalmological, otological, oral and neurological examination, to exclude secondary causes. Routine laboratory testing and diagnostic imaging is not indicated in patients with new-onset Bell's palsy, but should be performed in patients with risk factors, atypical cases or in any case without resolution within 4 months. Many factors are involved in determining the appropriate treatment of these patients: the underlying cause, expected duration of nerve dysfunction, anatomical manifestations, severity of symptoms and objective clinical findings. Systemic steroids should be offered to patients with new-onset Bell's palsy to increase the chance of facial nerve recovery and reduce synkinesis. Ophthalmologists play a pivotal role in the multidisciplinary team involved in the evaluation and rehabilitation of these patients. In the acute phase, the main priority should be to ensure adequate corneal protection. Treatment depends on the degree of nerve lesion and on the risk of the corneal damage based on the amount of lagophthalmos, the quality of Bell's phenomenon, the presence or absence of corneal sensitivity and the degree of lid retraction. The main therapy is intensive lubrication. Other treatments include: taping the eyelid overnight, botulinum toxin injection, tarsorrhaphy, eyelid weight implants, scleral contact lenses and palpebral spring. Once the cornea is protected, longer term planning for eyelid and facial rehabilitation may take place. Spontaneous complete recovery of Bell's palsy occurs in up to 70% of cases. Long-term complications include aberrant regeneration with synkinesis. FNP after acoustic neuroma surgery remains the most common indication for FN rehabilitation.