Painful Trigeminal Neuropathy as a Rare but Important Presenting Complication of Metastasis of Head and Neck Cancer: A Case Report and Review

Neoplastic perineural involvement of cranial nerves represents an uncommon but important feature of metastatic involvement of squamous cell carcinoma of the head and neck. Tumor cells invade all nerve compartments, possibly causing ischemia and subsequent degradation of the nerve. Invasion is guided by targeted proliferation in the context of secreted neurotropins and growth factors. Patients often present insidiously with symptoms of isolated cranial neuropathies and atypical facial pain. The most frequently affected nerve is cranial nerve V (CN V), followed by cranial nerve VII (CN VII), due to the widespread anatomic connections between the skin and subcranial structures. The following case reports highlight the different presentations and the associated diagnostic challenges of perineural involvement by squamous cell carcinoma of the head and neck. We will review the proposed biology underlying perineural tumor metastasis, the anatomical basis for cranial nerve involvement, and current treatment options. Prognosis is poor in cases of extensive disease highlighting the importance of early recognition and detection.