Neurosurgical management of perineural metastases: A case series and review of the literature

BACKGROUND: Perineural invasion (PNI) and spread are one of the grimmest prognostic factors associated with primary skin and head-and-neck cancers, yet remain an often confused, and underreported, phenomenon. Adding complexity to reaching a diagnosis and treating perineural spread (PNS) is the finding that patients may have no known primary tumor, history of skin cancer, and/or incidental PNI in the primary tumor. These delays in diagnosis and treatment are further compounded by an already slow disease process and often require multidisciplinary care with combinations of stereotactic radiosurgery, surgical resection, and novel treatments such as checkpoint inhibitors. METHODS: Six patients with metastatic cancer to the cranial nerves who underwent Gamma Knife radiosurgery (GKRS) treatment were chosen for retrospective analysis. This information included age, gender, any past surgeries (both stereotactic and regular surgery), dose of radiation and volume of the tumor treated in the GKRS, date of PNS, comorbidities, the patient follow-up, and pre- and post-GKRS imaging. The goal of the follow-up with radiographing imaging was to assess the efficacy of GKSS. RESULTS: The clinical course of six patients with PNS is presented. Patients followed variable courses with mixed outcomes: two patients remain living, one was lost to follow-up, and three expired with a median survival of 12 months from date of diagnosis. Patients at our institution are ideally followed for life. CONCLUSION: Given the morbidity and mortality of PNS of cancer, time is limited, and further understanding is required to improve outcomes. Here, we provide a case series of patients with PNS treated with stereotactic radiosurgery, discuss their clinical courses, and review the known literature.