Magnetic Resonance Evidence of Perineural Metastasis

Abstract

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.

Perineural Invasion of Cutaneous Malignancies

“…The remaining group suffers from sensory or motor complaints and may have a poorer prognosis 8,9,22,29,30 . Involved nerves often appear normal on gross inspection because axial spread typically surpasses concentric growth 31–33 . Early PNI confined to small nerves in the reticular dermis is rarely suspected until demonstrated histologically 19 .…”

“…Because the trigeminal and facial nerves course through relatively small foramina in the cranium, they are more likely to be affected by nerve enlargement and have identifiable radiologic evidence 3 . Bony erosion is best demonstrated on plain films or contrast‐enhanced CT, while thin‐section, pre‐ and postcontrast MRI is useful for the demonstration of enlarged nerve trunks, intracranial or intraorbital tumor extension via nerves, muscle atrophy, and bony involvement 2,17,20,33,46 . Intravenous administration of gadolinium diethylenetriamine pentaacetic acid (Gd‐DTPA) enhances the visualization of affected nerves, allowing the course of the nerve to be traced through the foramina and into the brainstem 33,51 .…”

Leptomeningeal Metastasis

“…41 Direct extension can also occur from more distant tumors in the presence of perineural involvement where tumor cells track along the nerve to the subarachnoid space. 44,45 Iatrogenic Another proposed mechanism of leptomeningeal dissemination is iatrogenic spread into the CSF during surgery for parenchymal metastases. 46,47 In many situations, a parenchymal brain metastasis is diagnosed and treated, and leptomeningeal metastasis subsequently develops.…”

47 Diagnosis and Treatment of Cutaneous Malignancies

“…46,51,52,53 Larger diameter lesions also have an increased likelihood of recurrence and metastasis. Anatomical site appears to play an important role in behavior for SCC.…”