Pontine stroke presenting as isolated facial nerve palsy mimicking Bell's palsy: a case report

Abstract

IntroductionIsolated facial nerve palsy usually manifests as Bell's palsy. Lacunar infarct involving the lower pons is a rare cause of solitary infranuclear facial paralysis. The present unusual case is one in which the patient appeared to have Bell's palsy but turned out to have a pontine infarct.Case presentationA 47-year-old Asian Indian man with a medical history of hypertension presented to our institution with nausea, vomiting, generalized weakness, facial droop, and slurred speech of 14 hours' duration. His physical examination revealed that he was conscious, lethargic, and had mildly slurred speech. His blood pressure was 216/142 mmHg. His neurologic examination showed that he had loss of left-sided forehead creases, inability to close his left eye, left facial muscle weakness, rightward deviation of the angle of the mouth on smiling, and loss of the left nasolabial fold. Afferent corneal reflexes were present bilaterally. MRI of the head was initially read as negative for acute stroke. Bell's palsy appeared less likely because of the acuity of his presentation, encephalopathy-like imaging, and hypertension. The MRI was re-evaluated with a neurologist's assistance, which revealed a tiny 4 mm infarct involving the left dorsal aspect of the pons. The final diagnosis was isolated facial nerve palsy due to lacunar infarct of dorsal pons and hypertensive encephalopathy.ConclusionThe facial nerve has a predominant motor component which supplies all muscles concerned with unilateral facial expression. Anatomic knowledge is crucial for clinical localization. Bell's palsy accounts for around 72% of facial palsies. Other causes such as tumors and pontine infarcts can also present as facial palsy. Isolated dorsal infarct presenting as isolated facial palsy is very rare. Our case emphasizes that isolated facial palsy should not always be attributed to Bell's palsy. It can be a presentation of a rare dorsal pontine infarct as observed in our patient.

Microangiopathic Occlusion of a Perforating Prepontine Long Circumferential Artery Presenting with Lower Motor Neuron Facial Weakness: Clinical and Radiological Correlation

“…Pontine infarcts represent around 7% of all ischemic events, and isolated pontine strokes contribute to around 15% of all posterior circulation infarcts [1,2].…”

“…The pathophysiology behind such an uncommon condition is linked to focal microangiopathic occlusion of the perforating branches of the prepontine circumferential group [2][3][4][5]. Radiologically, these types of strokes tend to be overlooked by radiologists, as demonstrated in this short series where all 5 cases were initially reported negative for a tegmental pontine stroke [2,3,4]. …”

“…Pontine infarcts account for 7% of all ischemic strokes [1,2]. Within this group, the microangiopathic variant affecting the pontine tegmental location, specifically the area involving the infranuclear portion of the VII cranial nerve, is very atypical.…”

“…Our primary goal is to describe a perforating prepontine long circumferential artery occlusion affecting the CN VII nucleus. To our knowledge, there are only a handful of cases previously accounted [2][3][4][5].…”

“…Of note, these lesions appear to be radiologically misdiagnosed, despite showing as punctuate ≤5mm in size enhancing lesions on MRI diffusion weighted imaging (DWI) [2][3][4]. Additionally, it seems male gender, hypertension, and hyperlipidemia are all associated risk factors [2,4,5].…”