schwannomen

Schwannomas, also known as neurilemmomas, are benign tumors that arise from Schwann cells, which form the myelin sheath around peripheral nerves. They are typically well circumscribed and slow growing, and most cases are solitary. Schwannomas can develop along any nerve but are most commonly found on cranial and spinal nerves. The vestibular nerve (cranial nerve VIII) is a frequent site for intracranial schwannomas.

Clinical features depend on location. Vestibular schwannomas commonly present with progressive unilateral sensorineural hearing loss, tinnitus, and balance problems. Spinal schwannomas may cause localized radicular pain, numbness, weakness, or signs of nerve root compression. Large tumors can compress nearby neural structures and cause additional deficits.

Histologically, schwannomas are composed of Schwann cells and show characteristic patterns known as Antoni A and Antoni B areas. The tumor cells typically stain positive for S-100 protein. Radiologic imaging, particularly MRI with contrast, usually reveals a well defined, enhancing mass that displaces adjacent nerves and structures; cystic changes can occur in larger lesions.

Genetically, most schwannomas are sporadic, but multiple schwannomas may occur in association with neurofibromatosis type 2 (NF2), a genetic disorder caused by mutations in the NF2 gene encoding the merlin (schwannomin) protein. A related condition called schwannomatosis involves multiple nonvestibular schwannomas without NF2 involvement.

Management depends on symptoms, size, and growth. Small, asymptomatic tumors may be observed with periodic imaging. Symptomatic or enlarging tumors are often treated with microsurgical excision or radiotherapy, such as stereotactic radiosurgery. The prognosis is generally favorable after complete resection, but surgical risks include facial nerve dysfunction and, when the tumor is near the auditory nerve, hearing loss. Recurrence is uncommon in sporadic cases.