What Is It?
A schwannoma is a benign tumor of Schwann cells, the cells that insulate nerve cells in the peripheral nervous system. They occur on peripheral nerves, not in the brain or spinal cord itself. Normally, Schwann cells aid in the conduction of normal electrical impulses along nerve fibers. This tumor is the result of abnormal growth of these cells.
Schwannomas can occur anywhere along peripheral nerve fibers. They create a bulge on the nerve and can slowly grow. In the intracranial compartment (in the head), the most common location for these tumors is on the vestibulocochlear nerve (also called cranial nerve VIII). This nerve brings sensory information back to the brain from the inner ear. It has both cochlear fibers which carry hearing information and vestibular fibers which carry information about balance. These tumors almost always occur on the vestibular portion of the nerve. This specific type of schwannoma is referred to either as an Acoustic Neuroma or a Vestibular Schwannoma
While most of these tumors occur sporadically without a known cause, some familial genetic disorders can give rise to frequent growth of this type of tumor, most notably neurofibromatosis. The great majority of these tumors are benign, but rarely malignant types have been described.
What Types of Symptoms Are Typical?
Symptoms vary considerably depending on which nerve is affected. Generally, the normal function of the nerve will be compromised. So in a peripheral nerve that serves motor and sensory function, it would not be uncommon to have numbness or tingling as well as muscle weakness in the distribution of that nerve. Pain is also possible.
In the case of an acoustic neuroma (vestibular schwannoma), the typical first symptoms include tinnitus (ringing in the ear) and hearing loss in one ear, due to damage to the adjacent cochlear nerve. While there are many causes of hearing loss in both ears, there are only a handful of causes that can cause monaural hearing loss. In addition, as the tumor gets larger, other symptoms can occur including facial weakness, headache and others.
How Is The Diagnosis Typically Made?
The diagnosis of schwannoma varies depending on its location. Typically, symptoms or a mass will lead to a neurological evaluation and some sort of imaging study to identify the mass. In the case of intracranial tumors, such as an acoustic neuroma, a head CT scan
or MRI scan
is usually performed.
Definitive diagnosis usually requires a tissue sample so that a pathologist can analyze the tumor and differentiate it from other tumors that can occur on nerves.
What Are Some Common Treatments?
Again, treatments vary considerably depending on the location. Small, asymptomatic tumors will sometimes just be watched until they enlarge or begin causing symptoms. However, most tumors will eventually require surgical treatment. Because the great majority of these tumors are benign, the goal of surgery is to remove it in its entirety, which gives the best chance of a complete cure. The surgical approach varies depending on the location of the tumor. The specific treatment plan of each patient should be discussed with that patient's treating physician(s).
In the case of acoustic neuroma, there are various approaches to this complex area, some of which aim at preserving hearing and some of which loose the hearing in that ear completely. One of the most common complications of these procedures is damage to the facial nerve, which runs right alongside the vestibular nerve. If it is damaged at the time of operation, it can lead to temporary or permanent facial muscle weakness in some cases.
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This site is not intended to offer medical advice. Every patient is different, and only your personal physician can help to counsel you about what is best for your situation. What we offer is general reference information about various disorders and treatments for your education.