Schwannoma (Trigeminal & Acoustic)
Minimally invasive keyhole & endoscopic surgery is now possible for most symptomatic schwannomas.
Schwannomas are relatively common benign skull base tumors that arise from the nerve sheath (covering) of cranial nerves along-side the cerebellum and brainstem. The two most common are the vestibular schwannoma (aka acoustic neuroma) of the 8th cranial nerve and the trigeminal schwannoma of the 5th cranial nerve.
Vestibular Schwannomas are the most common and typically cause hearing loss and ringing in the ears (tinnitus); as they enlarge they may also cause imbalance and incoordination as well as facial weakness. Trigeminal schwannomas are less common and typically case facial numbness, tingling or facial pain.
The optimal treatment for the majority of symptomatic vestibular and trigeminal schwannomas is maximal safe surgical removal. For patients with smaller vestibular schwannomas focused radiation therapy (radiosurgery) may be a reasonable option instead of surgery.
Fortunately, for patients requiring schwannoma surgery, most large acoustic neuromas can be removed through a retromastoid (behind the ear) keyhole craniotomy while most trigeminal schwannomas can be removed through either a retromastoid approach or an endoscopic endonasal approach.
At Pacific Brain Tumor Center, our neurosurgeons Drs. Daniel Kelly, Garni Barkhoudarian and Walavan Sivakumar have a large experience treating such skull base tumors with keyhole and endoscopic approaches. By incorporating leading-edge technology and instrumentation with proven surgical experience, our specialists strive to make schwannoma surgery safer, less invasive and more effective.
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 of Acoustic and Trigeminal Schwannomas
Vestibular (acoustic) schwannomas arise from one of the vestibular nerves 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.
Trigeminal schwannomas are less common than vestibular schwannomas. They generally arise in Meckel’s cave in the skull base and the pre-pontine space. These tumors typically cause facial pain (trigeminal neuralgia) or facial numbness. As they enlarge, they can grow farther into the cavernous sinus or into the brainstem, causing double vision, loss of coordination and other symptoms of brainstem compression.
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 audiograms.
Treatment for vestibular (acoustic) schwannomas is by surgical removal through a keyhole retrosigmoid 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 retrosigmoid 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. Chemotherapy is generally not used for treating schwannomas.