A schwannoma is a growth that develops from the protective sheath surrounding nerves, known as the nerve sheath. These growths originate from Schwann cells, which produce the myelin insulation necessary for nerves to transmit signals efficiently. Schwannomas are overwhelmingly benign, meaning they are non-cancerous growths that do not spread. They are typically slow-growing and may exist for years without causing noticeable symptoms.
Understanding Schwannomas: Origin and Common Locations
Schwannomas arise from the Schwann cells of the peripheral nervous system, which includes all nerves outside the brain and spinal cord, as well as cranial nerves. These growths can technically develop on any nerve in the body, ranging from those in the limbs and trunk to those in the head and spine. They are often categorized as peripheral schwannomas, which occur on nerves in the arms, legs, or torso, or cranial/spinal schwannomas.
The most frequent type is the vestibular schwannoma, sometimes called an acoustic neuroma, which accounts for about 60% of cases. This growth develops on the eighth cranial nerve (the vestibulocochlear nerve), which connects the inner ear to the brain. This nerve transmits both hearing and balance information, making this location prone to producing noticeable symptoms. Other locations include the nerves of the neck, the spinal nerve roots, and the facial nerve.
Identifying Symptoms Based on Tumor Site
The specific problems caused by a schwannoma depend entirely on the location of the growth and the function of the nerve it is compressing. Because the growths are slow-moving, symptoms often start subtly and worsen gradually as the mass increases in size.
A vestibular schwannoma often presents with progressive, one-sided hearing loss, which can be accompanied by tinnitus (a persistent ringing or buzzing sound). As the growth enlarges, it can also disrupt balance, leading to unsteadiness, dizziness, or vertigo.
For schwannomas occurring on peripheral nerves in the limbs or trunk, the symptoms are primarily sensory and motor. Patients may notice a palpable, sometimes tender lump under the skin, particularly if the nerve is close to the surface. Pressure on the nerve can cause sharp, aching, or burning pain that may radiate along the nerve’s path. This compression can also lead to numbness, a pins-and-needles sensation, or muscle weakness in the area supplied by the affected nerve.
Confirming the Diagnosis
Diagnosis begins with a detailed neurological and physical examination, where a doctor assesses the patient’s symptoms and neurological function. If a schwannoma is suspected, imaging tests are the primary tools used to confirm its presence, size, and location. Magnetic Resonance Imaging (MRI) is the most effective imaging technique, providing high-resolution views of the nerves and surrounding soft tissues. The use of a contrast dye during the MRI helps the growth stand out clearly.
For vestibular schwannomas, specialized tests like audiometry are routinely performed to measure the extent of hearing loss. Other neurophysiological studies, such as a nerve conduction study or an electromyogram (EMG), may be used to assess how well a peripheral nerve is transmitting electrical signals. A tissue biopsy is occasionally necessary to rule out other types of growths, but it is often avoided when imaging is conclusive, due to the risk of irritating or damaging the involved nerve.
Management and Treatment Options
The approach to managing a schwannoma is highly personalized and depends on factors like the tumor’s size, its rate of growth, the patient’s age, and the severity of symptoms. For small, slow-growing growths that are not causing significant symptoms, doctors often recommend an initial strategy of observation, often called “watchful waiting.” This involves regular monitoring with follow-up MRI scans every six to twelve months to track any changes in size. This strategy allows the patient to avoid unnecessary intervention while still ensuring early detection of problematic growth.
If the schwannoma is large, rapidly growing, or causing severe symptoms or progressive neurological deficits, more active treatment is required. Surgical removal is a common option, with the goal of excising the entire growth while preserving the function of the involved nerve. Complete removal can sometimes carry the risk of nerve damage, which could result in permanent hearing loss for vestibular schwannomas or functional deficits for peripheral ones.
The third treatment method is radiation therapy, specifically stereotactic radiosurgery. This non-invasive technique delivers a highly concentrated, precise beam of radiation directly to the growth over one or a few sessions. The radiation is intended to stop the growth from enlarging further, rather than immediately shrinking it. Stereotactic radiosurgery is frequently used for smaller growths in difficult-to-reach locations, such as vestibular schwannomas, or for individuals who cannot undergo traditional surgery.