Isolated Abducens Nerve Palsy in the Setting of Isolated Sphenoid Sinusitis: A Case Report

Abstract

The cranial nerves (CNs) are responsible for multiple functions, including extraocular mobility, facial sensation and movement, hearing, mastication, tongue movement and sensation, and swallowing. Beyond these vital roles, they can also demonstrate importance in their diagnostic value. Isolated or combined palsies provide insights into potential localizations and various underlying etiologies, including stroke, tumor, and infections that may guide further neurological evaluation. CN VI, the abducens nerve, singularly innervates the lateral rectus muscle, which is responsible for the abduction of the eyes. Despite its long anatomic trajectory, making it susceptible to intracranial injury, an isolated abducens nerve palsy is extremely rare. The most common clinical presentation includes headache, diplopia, and the inability to abduct the afflicted eye. This case report introduces a 71-year-old female with a medical history of malignancy and pancytopenia who presented to the emergency room with complaints of ear pain and swelling and subsequently developed diplopia secondary to unilateral CN VI palsy. Magnetic resonance imaging (MRI) revealed isolated sphenoid sinusitis for which she was clinically asymptomatic. She was treated with a regimen of ampicillin-sulbactam, an oral anti-inflammatory agent, and a tapered course of methylprednisolone with a rapid and complete resolution of the abducens nerve palsy and sinusitis. Acute isolated diplopia is an unusual neurologic condition prompting the need for rapid and thorough investigation. Although exceedingly rare and infrequently cited in the literature, isolated abducens nerve palsies secondary to sphenoid sinusitis should be entertained in the differential diagnosis of this presentation.

Identifying the Risk Factors for Orbital Complications in Isolated Sphenoid Rhinosinusitis

“…Regarding the orbital complications secondary to isolated sphenoid rhinosinusitis, previous case reports have demonstrated cavernous sinus thrombophlebitis and optic neuritis [10][11][12][13][14]18,19]. The sixth cranial nerve (abducens nerve) and optic nerve were consequently affected, which resulted in ophthalmologic symptoms including diplopia, extraocular motility limitation, orbital pain, and visual impairment.…”

“…Furthermore, isolated sphenoid rhinosinusitis may have devastating consequences such as orbital complications due to its anatomical contiguity with vital structures including the cranial nerves and cavernous sinus [10][11][12][13][14]. For the orbital complications secondary to isolated sphenoid rhinosinusitis, previous case reports have demonstrated cavernous sinus thrombophlebitis and optic neuritis [10][11][12][13][14].…”

“…Furthermore, isolated sphenoid rhinosinusitis may have devastating consequences such as orbital complications due to its anatomical contiguity with vital structures including the cranial nerves and cavernous sinus [10][11][12][13][14]. For the orbital complications secondary to isolated sphenoid rhinosinusitis, previous case reports have demonstrated cavernous sinus thrombophlebitis and optic neuritis [10][11][12][13][14]. The sixth cranial nerve (abducens nerve) and optic nerve were consequently affected, which resulted in ophthalmologic symptoms including diplopia, extraocular motility limitation, orbital pain, and visual impairment.…”