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.