Cavernous sinus syndrome secondary to trigeminal nerve invasion by cutaneous squamous cell carcinoma: A case report and brief review

• This article shows the spectrum of differential diagnosis of unilateral cavernous sinus syndrome with perineural infiltration of skin tumors in the head, especially when there is facial pain included in the clinical syndrome, which infers a high suspicion of trigeminal nerve involvement. • Perineural invasion is correlated with head-and-neck cutaneous squamous cell carcinoma in approximately 2,5 to 14% of cases. • Cutaneous squamous cell carcinoma neurotrophism correlates with interference of the neoplasm in the neural growth factor, a neurotrophin with a crucial role in neuronal development. • Cemiplimab, a monoclonal antibody against PD-1 receptors, is also emerging as a therapeutic alternative in the context of cavernous sinus syndrome with a worse prognosis and metastatic spread without surgical proposal. Cutaneous squamous cell carcinoma (cSCC) has a broad clinical spectrum, especially when it affects the head and neck. Given the possible presentations, there is perineural dissemination, with an unfavorable prognosis and involvement of less differentiated tumor cells. A possible outcome is cavernous sinus syndrome (CSS), which encompasses the cavernous sinus, an anatomical structure that includes the oculomotor, trochlear, abducens nerves and the V1 and V2 branches of the trigeminal nerve. We present a 62-year-old white man who manifested unilateral progressive ptosis, binocular diplopia and supraorbital pain in the right eye. The relevant history of skin neoplasms on the head raised the diagnostic hypothesis. Neuroimaging evaluation demonstrated nerve infiltration of the trigeminal nerve with tumor expansion at the level of the ipsilateral cavernous sinus. The concomitance between cSCC and CSS correlates with the participation of the neural growth factor and the overexpression of programmed cell death protein 1 (PD-1), with dermatological and neurological manifestations. In this context, the standard treatment used is cemiplimab, an immunotherapy used in unresectable and metastatic tumors and recently emerging as neoadjuvant therapy in surgical cases. The present report illustrates the association of such entities with the use of the described monoclonal antibody.