Giant intra/extracranial facial nerve schwannoma: A case report and review of the literature

• Giant facial nerve schwannoma with intra- and extracranial involvement. • CT and MRI identified tumor extent and guided surgical planning. • Combined subtemporal-mastoid approach enabled complete tumor excision. • WHO grade I schwannoma confirmed by pathology and immunohistochemistry. • Rehabilitation essential for facial nerve function recovery post-surgery. Facial nerve schwannomas (FNSs) are rare, benign neoplasms arising from Schwann cells. While most FNSs are confined to the temporal bone or internal auditory canal, giant schwannomas extending across both intracranial and extracranial segments of the facial nerve are exceptionally rare and pose significant diagnostic and surgical challenges. We report a 51-year-old woman with a 10-year history of progressive right-sided facial paralysis (House-Brackmann grade VI) and profound hearing loss. Imaging revealed a large, heterogeneous mass involving the right middle cranial fossa, external auditory canal, and mastoid, with destruction of adjacent bony structures. Electrophysiological studies confirmed severe facial nerve dysfunction. A combined subtemporal and mastoid approach enabled total tumor resection. Histopathology confirmed a WHO grade I schwannoma with strong S100, SOX10, and H3K27me3 positivity. This case highlights the importance of integrating advanced neuroimaging, electrophysiological studies, and meticulous surgical planning in the management of extensive FNSs. Early diagnosis and timely intervention contribute to favorable outcomes, although functional recovery may require prolonged rehabilitation.