Stuck in the Middle: Nervus Intermedius‐Related Neuropathologic Imaging Spectrum

The nervus intermedius is a complex nerve that traverses the cerebellopontine angle and is associated with a wide range of pathologies for which imaging plays a crucial diagnostic role. Cerebellopontine angle masses or neurovascular compression may directly involve the nervus intermedius. Alternatively, pathologies that involve branches of the nervus intermedius may present with symptoms referable to the nervus intermedius, including sinonasal tumors, perineural tumor spread, or viral reactivation such as in Ramsay Hunt syndrome. Overlapping innervation with branches of the trigeminal, glossopharyngeal, and vagus nerves can confound diagnosis and/or lead to mislocalization, which may result in delayed diagnosis or inappropriate therapy. This review article provides an in-depth overview of nervus intermedius anatomy and physiology, and the wide spectrum of pathologies that can involve the nervus intermedius or its branches, with an emphasis on clinical relevance.Learning Objective: To understand the normal anatomy and physiology of the nervus intermedius as well as the clinical relevance and imaging findings of the neuropathologic spectrum of disease referable to the nervus intermedius and its branches: the greater superficial petrosal nerve, the chorda tympani, and the sensory auricular branch.