A Case of Physiologic Enhancement of Scarpa's Ganglia Mimicking Bilateral Vestibular Schwannomas in a Patient With Atypical Meningioma With NF2 Mutation.

We followed a 36-year-old man with an atypical meningioma with somatic NF2 mutation and invasion into the bone, temporalis muscle, and pterygopalatine fossa, treated with surgical resection and adjuvant radiation therapy. His medical history included medulloblastoma treated with resection and adjuvant radiation therapy and a WHO Grade 1 meningioma treated with gross total resection. A brain MRI during routine follow-up revealed small enhancing foci in both internal auditory canals (IACs), which prompted concern for bilateral vestibular schwannomas and suspect NF2-related schwannomatosis (NF2-SWN). However, the lesions were symmetric, fundal, and nonnodular on high-resolution constructive interference in steady-state (CISS) imaging, with smooth vestibular nerve contours, long-term interval stability, and a lack of clinical symptoms, favoring physiologic enhancement of the vestibular ganglia (Scarpa's ganglia) rather than vestibular schwannomas. Recognition of these distinguishing features also helped avoid associating the IAC findings with the known NF2 mutation, which was determined to be somatic. While germline NF2 mutations (NF2-SWN) often lead to meningiomas and vestibular schwannomas, somatic NF2 mutations are common in sporadic meningiomas and should not suggest NF2-SWN. This case highlights the need to correlate small enhancing IAC foci with morphology on CISS MRI, symmetry, longitudinal stability, and NF2 pathology to avoid misdiagnosis of enhancing Scarpa's ganglia as vestibular schwannomas, as misdiagnosis can lead to increased patient anxiety and unnecessary follow-ups.