Article
Do not forget bilateral facial nerve palsy
I refer to the above matter. I read with interest the article entitled ‘Facial palsy: aetiology, diagnosis and management’ by Dr McKernon and colleagues (Dent Update 2019; 46: 565–572). I believe it will benefit your readers if information regarding bilateral occurrence of facial nerve paralysis is also included. Bilateral facial nerve palsy is defined as a paralysis that affects the opposite side within 30 days of the onset of the first side.1
There is no doubt that bilateral facial nerve palsy is a rare phenomenon, if compared to unilateral nerve involvement. It is reported to have an incidence of 1 per 5 million population, occurring in 0.3% to 2.0% of facial palsy cases. Like unilateral peripheral facial palsy, it occurs in both paediatric and adult patients and the aetiology can be either congenital or acquired. However, bilateral facial nerve palsy is idiopathic in only 23% of cases, and an underlying systemic pathology or medical condition, which can be congenital, neurological, infectious, neoplastic, traumatic, or metabolic is often demonstrable.2,3
Most of the causes of bilateral facial nerve palsy are identical to those listed in Table 3 by Dr McKernon and colleagues. However, some other additional uncommon causes include post influenza, infectious mononucleosis, acute (lymphoblastic) leukaemia, acute porphyria, sarcoidosis and Parkinson's disease.4 Besides syphilis and poliomyelitis (both of which are not common in this millennium), more recent reports describe clostridium tetani bacilli, chikungunya virus and leptospira as the causes of bilateral facial nerve palsy.5,6,7 Two other unusual presentations of bilateral facial nerve palsy are those that result from adalimumab therapy, and as the first presentation of lung cancer.8,9