Magnetic resonance evidence of perineural metastasis.

Contiguous spread along perineural and endoneural spaces, that is, perineural tumor extension, in cutaneous squamous cell carcinoma is fairly common. Infrequently, these tumors spread and involve intracranial structures. One consequence of this complication is meningeal carcinomatosis which is underrecognized. Herein described is a patient with recurrent cutaneous squamous cell carcinoma with perineural invasion along the maxillary nerve that was subsequently shown by magnetic resonance imaging to the trigeminal root. The patient initially presented with a cavernous sinus syndrome but despite aggressive treatment, extensive meningeal carcinomatosis and cauda equina dysfunction developed. Awareness of perineural invasion and proper evaluation are crucial. Perineural spread intracranially worsens the prognosis and limits treatment options to palliation.