Subtle Manifestation of Lower Cavernous Sinus Syndrome as the Initial and Sole Presentation of Pterygopalatine Squamous Cell Carcinoma Invasion from the Skull Base: A Case Report.

We present a case highlighting the critical role of early recognition of partial cavernous sinus syndrome (CSS), as diagnostic delay can lead to irreversible tumor progression. A 50-year-old woman presented with subtle binocular diplopia and facial tingling sensation for 1 month. Neurological examination revealed isolated right abducens nerve (VI) palsy and paresthesia at territories of right ophthalmic (V1) and maxillary (V2) nerves. Partial CSS was suspected. Brain magnetic resonance image (MRI) revealed a contrast-enhancing mass involving the pterygopalatine fossa, sphenoid, and maxillary sinuses extending into the cavernous sinus. Fiberscope biopsy confirmed nonkeratinizing squamous cell carcinoma (SCC). After consultation with otolaryngologist, concurrent chemoradiation as the initial treatment modality was suggested. We describe an uncommon etiology of CSS by pterygopalatine SCC invasion, presenting initially as subtle cranial nerve palsies. Involvement of lower anatomical structures in cavernous sinus and "mandibular sparing" can be a hint of invasive lesion from pterygopalatine fossa. This case emphasizes the importance of high clinical suspicion for partial CSS, as early recognition can have great impact on patient's prognosis.