At the Crossroads

A middle-aged former smoker developed progressive facial pain associated with an unusual combination of involvement of the ipsilateral cranial nerves (CNs) in the cavernous sinus (III, IV, VI, V1, V2) and branches of the ipsilateral facial nerve. Her presentation was initially steroid responsive, though the diplopia and facial pain continued to progress. MRI showed contrast enhancement of the cavernous sinus, and on further review, involvement of the ipsilateral frontal and vidian nerve was appreciated. The vidian nerve likely served as a conduit for facial nerve involvement. Workup was initially unrevealing, and for two years, the diagnosis remained idiopathic cavernous sinus inflammation (Tolosa-Hunt syndrome). After the pain became uncontrollable with IV steroids and narcotics, a left frontal biopsy which yielded the diagnosis of squamous cell carcinoma (SCC) infiltrating multiple CNs. Neither dermatologic nor otolaryngologic evaluation revealed an obvious primary, thus this is presumed to be primary intracranial SCC. Intracranial SCC with unknown primary origin is a rare condition that presents insidiously with multiple cranial nerve involvement and facial pain without systemic manifestations. The rarity of this diagnosis, initially subtle clinical findings and equivocal imaging studies can delay appropriate diagnosis and treatment of such cases (Bourque et al, 2017)[1]. Histopathologic evidence of neural involvement portends a poor prognosis (Erkan et al, 2017)[2]. We believe this to be an extraordinary case of primary intracranial involvement with a unique pattern of cranial nerve abnormalities.