Acoustic Neuroma – Symptoms and Causes
Overview
An acoustic neuroma is a non-cancerous growth that forms on the vestibular nerve, which connects the inner ear to the brain. This nerve plays a key role in controlling both hearing and balance.
Also known as vestibular schwannoma, this tumor develops from Schwann cells that wrap around the nerve.
Most acoustic neuromas grow slowly over time. In rare cases, they may grow rapidly and become large enough to press against the brain, potentially affecting essential functions.
As the tumor grows, it can cause symptoms like:
- Hearing loss
- Ringing in the ear (tinnitus)
- Balance problems
When a patient is diagnosed with an acoustic neuroma, doctors typically consider three main treatment options:
- Monitoring the tumor with regular imaging
- Radiation therapy to stop tumor growth
- Surgery to remove the tumor
The best treatment approach depends on factors like tumor size, growth rate, and the patient’s overall health.
Signs and Symptoms
Acoustic neuromas often develop slowly. Their symptoms can be hard to notice at first and may take years to appear. These tumors can affect your hearing and balance nerves.
They might also press against nearby nerves that control facial movement and feeling. In some cases, blood vessels or brain structures are affected.
Symptoms typically become more obvious as the tumor grows larger.
Common signs include:
- Gradual hearing loss on one side, happening over months or years (rarely, it can happen suddenly)
- Ringing in the ear (tinnitus) on the affected side
- Balance problems or unsteadiness when walking
- Dizziness that comes and goes
- Numbness in the face and, in rare cases, facial muscle weakness
In very rare situations, these tumors can grow large enough to press on the brainstem, which can be life-threatening.
When to Visit Your Doctor
Make an appointment with a healthcare provider if you notice:
- Hearing loss in one ear
- Ringing sounds in your ear
- Problems with balance or dizziness
Finding an acoustic neuroma early can help prevent it from growing to a size that causes more serious problems, like complete hearing loss.
Causes
Acoustic neuromas sometimes develop due to issues with a gene on chromosome 22. This gene normally creates a protein that controls the growth of Schwann cells, which cover our nerves.
Scientists haven’t identified what damages this gene in most cases. Many acoustic neuromas appear without any clear cause.
In people with a rare condition called neurofibromatosis type 2, this gene change is inherited. These individuals typically develop tumors on the hearing and balance nerves on both sides of the head, called bilateral vestibular schwannomas.
The genetic connection explains why some people develop these tumors, but for most patients with acoustic neuromas, the exact trigger remains unknown.
Risk Factors
NF2 Genetic Condition
The primary confirmed risk factor for acoustic neuromas is having a parent with the genetic disorder called neurofibromatosis type 2 (NF2). This rare condition accounts for approximately 5% of all acoustic neuroma cases.
People with NF2 typically develop noncancerous tumors on the balance nerves on both sides of the head. These individuals may also grow tumors on other nerve tissues throughout the body.
NF2 follows an autosomal dominant inheritance pattern, meaning:
- Only one parent needs to have the gene to pass it to a child
- Each child of an affected parent has a 50% chance of inheriting the condition
- The gene can be passed down through generations
Most acoustic neuromas (about 95%) occur in people without NF2 and appear to develop spontaneously without clear risk factors.
Complications
Acoustic neuromas can lead to several lasting issues. Permanent hearing loss in the affected ear is common. People may also experience numbness or weakness in their face.
Balance difficulties often occur, making it hard to walk steadily. Persistent ringing in the ear, called tinnitus, can be distressing for many patients.
When tumors grow large, they can press against the brainstem. This pressure might block the normal flow of cerebrospinal fluid between the brain and spinal cord.
As a result, this blockage can cause fluid buildup in the head (hydrocephalus), which increases pressure inside the skull.
