Isolated facial nerve palsy of peripheral type caused by an intrinsic brain stem tumor

Abstract

Key words: Bell's palsy, brainstem glioma, magnetic reso- nance imaging Introduction Facial palsy of the peripheral type is generally seen in the pain clinic and is often treated with a stellate gang- lion block. The most common cause of peripheral facial nerve palsy is Bell's palsy, although its etiology remains controversial. The diagnosis of Bell's palsy is usually made by exclusion of other conditions such as herpes zoster oticus (Ramsay Hunt syndrome), trauma (including skull base fracture and surgery), otitis media, and neoplasm [1]. Isolated peripheral facial nerve palsy of neoplastic origin is uncommon. We herein describe a case of peripheral facial nerve palsy which was initially diag- nosed as Bell's palsy but was later found to be caused by an intrinsic brain stem tumor. Case report A 9-year-old boy presented to the Pediatric Depart- ment of our University Hospital in August 1990 with left facial weakness. His mother noticed the hyperemic conjunctiva and lacrimation of his left eye at the end of June. Consultation with the ophthalmologist revealed no abnormality in his left eye and the hyperemia im- proved with conservative therapy. In July, facial asym- metry became obvious. He was diagnosed as having Bell's palsy by a pediatrician in August and was referred to. our pain clinic. Address correspondence to: K. Kodama Received for publication on May 31, 1993; accepted on January 6, 1994 Upon examination, the patient had a left facial nerve palsy of the peripheral type (score of the facial paresis was 24/40), however, no other neurological deficits were seen. An audiogram failed to reveal a hearing abnormality. Although repeated stellate ganglion block was given, his facial palsy progressed slowly over a 2- month period, suggesting an etiology other than Bell's palsy. Magnetic resonance imaging (MRI) in September demonstrated a tumor in the left pons and brachium pontis extending into the left cerebellopontine angle (Fig. 1). The lesion was seen as a hypointense and hyperintense area on T1- and T2-weighted images, re- spectively. He was admitted to the Neurosurgical De- partment on September 29. The positive neurological findings on admission were Bruns' nystagmus, absence of left corneal reflex, decreased gag reflex, and mild trunkal ataxia, in addition to left facial nerve palsy. He underwent a wide suboccipital decompressive craniec- tomy, and biopsy of the tumor indicated low-grade glioma. In spite of postoperative radiation (60 Gy) and chemotherapy including Ranimustine and tumor necro- sis factor, he died due to tumor progression 17 months from the time of his initial symptom. Discussion Eighty percent of peripheral facial nerve palsy cases represent idiopathic or Bell's palsy, of which approxi- mately 20% can be demonstrated to have a specific etiology [2]. Peripheral facial nerve palsy with neoplas- tic origin is uncommon, and is estimated to be the cause in approximately 5% of all cases [3]. The diagnosis of Bell's palsy is unjustified unless an accurate history is taken along with a careful examina- tion of the ear and central nervous system (CNS). The differential diagnosis of neoplastic facial palsy is vast