Other Cranial Nerve Schwannomas
Overview
Schwannomas are benign nerve sheath tumors that can sometimes grow to a substantial size. Cranial nerve (CN) schwannomas involve the nerves of the head & neck region, specifically ones that are responsible for sensation and movement of the face (CN V and CN VII), hearing and balance (CN VIII), sensation and movement of the back of the throat (CN IX and CN X), vocal cord movement (CN X), or shoulders and neck muscle movement (XI). CN VIII schwannomas, the most common of which are vestibular schwannomas are discussed elsewhere here (link to vestibular schwannomas page). One of the only known risk factors for these tumors is a rare genetic disorder known as neurofibromatosis type 2 (NF2).
Symptoms
The signs and symptoms of cranial nerve schwannomas depend on what nerve is affected and at what location. CN V schwannomas (also known as Trigeminal Schwannomas or Neuromas) involve either the nerve ganglion or the nerve root. Symptoms include trigeminal neuralgia, chronic burning facial pain, eye muscle deficits, facial muscle weakness, hearing loss, or loss of corneal reflux leading to corneal abrasions. Facial nerve schwannomas (CN VII) and neuromas often present with symptoms of facial weakness/paralysis that can be subtle or obvious for many years, sometimes with twitching. Other symptoms include temporary facial palsy mimicking a Bell's palsy and/or hearing loss. Other schwannomas involve the so called lower cranial nerve schwannomas listed above, including glossopharyngeal (CN IX), vagal (CN X), and spinal accessory (XI). Symptoms include hoarseness, hearing loss, palate weakness, diminished gag reflex, or diminished pharyngeal sensation. All of the above tumors if located within the cerebropontine angle (CPA) region can cause disequilibrium, hydrocephalus, and brain stem compression.
Diagnosis
Diagnosis of any of the cranial nerve schwannomas is typically by history, physical exam findings, and imaging. Imaging routinely involves a dedicated skull base MRI with and without contrast, and occasionally a CT scan as an adjunct.
Treatment
Treatment options are usually tailored to the needs of the patient. Options include observation with serial imaging, stereotactic radiation (such as Gamma Knife or CyberKnife), or surgical resection. A patient's preferences, age, overall physical health, and the size of the tumor are all factors in determining the treatment modality.