These tumors are typically benign and arise from the nerve sheath (covering) of cranial nerves along-side the cerebellum and brainstem. The most common schwannoma arises from the 8th cranial nerve (the vestibulo-cochlear nerve) or the 5th cranial nerve (the trigeminal nerve).

In some instances, schwannomas are related to a genetic syndrome called Neurofibromatosis. Bilateral vestibular schwannomas are associated with NF-2.

Symptoms
Vestibular (acoustic) schwannomas arise from the inferior vestibular nerve in the internal auditory canal and initially cause hearing loss and tinnitus (ringing in the ear). As they enlarge into the cerebello-pontine angle, they can compress the brainstem and other cranial nerves, resulting in loss of balance and coordination, vertigo, facial numbness, facial weakness and difficulty swallowing.

Diagnosis
MRI with contrast focused on the internal Auditory canal is important in making the diagnosis. Hearing function needs to be assessed by an audiogram to determine the degree and type of hearing loss.

Schwannomas are typically diagnosed by an MRI with gadolinium or a CT scan of the brain. A focused MRI of the internal auditory canals is typically best for visualizing a vestibular schwannoma. Other tests may also be needed such as angiography (typically now performed as a CT angiogram or an MR angiogram) or an audiogram

Treatment for vestibular (acoustic) schwannomas is by surgical removal through a retro-sigmoid craniotomy or other skull base approach or by radiosurgery. For tumors under 2.5 cm, either surgery or radiosurgery are reasonable treatment options. For tumors over 2.5 cm, surgical removal is generally recommended.

Treatment for trigeminal schwannomas is typically by surgical removal through a retro-sigmoid craniotomy or other skull base approach, depending upon the location.

In some patients with a vestibular or trigeminal schwannoma in whom only a sub-total tumor removal is possible, radiosurgery or stereotactic radiotherapy may be effectively used to control further tumor growth.

Radiation may be used as the first treatment option, particularly in cases where the tumor is not causing mass effect or as an adjuvant treatment after surgery for large acoustic neuromas from which there is a small residual lesion. Radiation is utilized to prevent further growth of the tumor and is usually indicated when tumors are small. This method may preserve hearing. Two types of radiation are commonly used: Gamma Knife radiosurgery and fractionated stereotactic radiotherapy. Radiosurgery or radiotherapy can also be used as supplementary treatment for patients who had surgery with partial resection of the tumor.