Perineural Tumor Spread in Head and Neck Cancers: Imaging Pearls and Pitfalls for the Skull Base Surgeon

Background/Purpose: Perineural spread (PNS) from head and neck cancers is a well-known disease entity, ranging from 27 to 82% depending on type of cancer. PNS is most commonly found in squamous cell carcinoma, followed by adenoid cystic carcinoma, lymphoma and rhabdomyosarcoma. Presence of PNS is a marker for poor outcomes, with increased risk for locoregional recurrence and reduced survival rates. CT and MRI are used as complementary methods to assess PNS, which often is difficult to diagnose due to the complex nature of cranial nerve anatomy throughout the skull base. While the cranial nerves may be more readily identified in normal situations, pathologic anatomy can be a challenge to interpret if the anatomic relationships are not well understood. Furthermore, PNS is often in areas that cannot be biopsied, thereby impeding histologic diagnosis. Thus, diagnosis is often made through imaging alone. The purpose of this abstract is to provide pearls and pitfalls for diagnosing PNS of head and neck cancers on imaging.

Methods: We performed a retrospective search of our radiology database using the Nuance mPower search engine for head and neck cases complicated by PNS from 2010 to 2018. Both CT and MRI images were reviewed.

Results: CT and MRI are used as complementary methods to assess PNS of head and neck cancers. Multiple imaging examples were used in this pictorial essay to illustrate pearls and pitfalls in diagnosing PNS.

Conclusion: PNS can be a subtle but critically important finding on imaging, as it directly influences management and prognosis. It is imperative for both the neuroradiologist and skull base surgeon to understand how to navigate the complexity of skull base imaging to diagnose PNS in patients with head and neck cancers.