Acoustic neuroma symptoms and causes

Symptoms and causes of Acoustic neuroma

Acoustic neuroma, also known as vestibular schwannoma, is a slow-growing, benign tumor that develops on the vestibulocochlear nerve, which controls hearing and balance. As it enlarges, the tumor can compress surrounding structures, leading to progressive hearing loss, balance disturbances, and neurological symptoms. While typically noncancerous, untreated acoustic neuromas can significantly affect quality of life and, in severe cases, cause life-threatening complications due to brainstem compression.

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Symptoms of acoustic neuroma

Symptoms

Gradual Hearing Loss

Acoustic neuromas typically cause unilateral (one-sided) hearing loss, meaning it affects only the ear on the side where the tumor is growing. The hearing loss is usually progressive, meaning it worsens over time rather than occurring suddenly. In some cases, it may begin as difficulty understanding speech in noisy environments before progressing to noticeable hearing impairment. While sudden hearing loss can sometimes occur, most patients experience a gradual decline in auditory function.

Tinnitus (Ringing in the Ear)

Many patients with acoustic neuroma experience tinnitus, a persistent ringing, buzzing, or hissing sound in the affected ear. Unlike pulsatile tinnitus, which is linked to blood flow, tinnitus caused by an acoustic neuroma is often constant and does not synchronize with the heartbeat. It may worsen in quiet environments or when lying down and can significantly affect concentration, sleep, and overall mental well-being.

Balance Issues and Dizziness

Since the vestibulocochlear nerve plays a crucial role in maintaining balance and spatial awareness, the presence of a tumor can cause frequent dizziness, vertigo, and instability. Patients may feel as though they are swaying, tilting, or experiencing the sensation of movement even when they are standing still. These balance disturbances may become more pronounced in low-light conditions or when walking on uneven surfaces, increasing the risk of falls and injuries.

Ear Fullness or Pressure

A sensation of fullness, congestion, or pressure in the affected ear is another common symptom of acoustic neuroma. This may feel similar to having water trapped in the ear or like a mild ear infection that does not improve over time. The sensation can fluctuate but tends to worsen as the tumor grows and begins pressing against inner ear structures.

Facial Numbness or Weakness

As the acoustic neuroma expands, it can begin compressing the facial nerve (cranial nerve VII), which controls facial movement and sensation. This can result in numbness, tingling, or weakness on one side of the face. Some individuals experience a sensation similar to a mild “pins and needles” feeling that progresses over time. In more advanced cases, the tumor can lead to facial twitching or muscle paralysis, affecting expressions and basic facial movements such as blinking or smiling.

Headaches

When the tumor grows large enough to increase intracranial pressure, it can trigger persistent headaches that may range from mild and intermittent to severe and debilitating. These headaches may be accompanied by nausea, visual disturbances, or a feeling of tightness in the skull. If the tumor causes significant pressure on the brainstem, the headaches may become more intense and frequent, potentially interfering with daily activities.

Cognitive Impairments (Rare Cases)

In cases where an acoustic neuroma grows exceptionally large, it can begin compressing brainstem structures, leading to cognitive changes such as memory issues, trouble concentrating, or slowed mental processing. While this is uncommon, it is a sign of a severe and advanced tumor that may require urgent medical intervention to prevent life-threatening complications.

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Dr. Zachary Barnard

Neurosurgeon

Tumor growth, genetic mutations, radiation exposure, and other risk factors

Causes of Acoustic Neuromas

Primary causes

Genetic Mutations

In most cases, acoustic neuromas arise due to mutations in the Schwann cells that wrap around the vestibulocochlear nerve. These cells, which normally provide insulation and support to nerve fibers, begin growing uncontrollably, forming a benign but progressively enlarging mass. While these mutations are often spontaneous, they can also be linked to specific genetic disorders, particularly Neurofibromatosis Type 2 (NF2).

Sporadic Growth

The majority of acoustic neuroma cases occur randomly without a known family history or genetic predisposition. Unlike some cancers, these tumors are not caused by lifestyle factors such as diet, smoking, or environmental toxins. Instead, they appear to develop due to errors in cell growth regulation, leading to the gradual accumulation of Schwann cells into a solid tumor.

Vestibulocochlear Nerve Overgrowth

Normally, the vestibulocochlear nerve transmits auditory and balance-related signals from the inner ear to the brain. However, when the Schwann cells covering this nerve begin to multiply excessively, they form a slow-growing mass that interferes with normal nerve function. This disruption leads to the hearing loss, balance problems, and tinnitus commonly associated with acoustic neuroma.

Potential risk factors

Neurofibromatosis Type 2 (NF2)

NF2 is a rare genetic disorder that significantly increases the risk of developing bilateral acoustic neuromas, meaning tumors on both vestibulocochlear nerves. Individuals with NF2 often develop tumors at a younger age and may experience more severe symptoms than those with sporadic cases. Regular screening and genetic counseling are recommended for individuals with a family history of NF2.

Radiation Exposure

High-dose radiation to the head and neck region, particularly during childhood, has been associated with an increased risk of developing vestibular schwannomas. This risk is particularly relevant for individuals who received radiation therapy for conditions such as brain tumors, leukemia, or severe acne treatments in the past.

Prolonged Loud Noise Exposure

Although acoustic neuromas are not directly caused by loud noise, prolonged exposure to high-decibel environments (such as concerts, construction sites, or industrial work) can lead to sensorineural hearing damage, which may exacerbate symptoms in individuals who already have a tumor. While not a primary cause, protecting hearing with earplugs or noise-canceling headphones may help reduce complications.

Hormonal or Environmental Triggers

Some researchers believe that hormonal imbalances or environmental stressors may influence tumor growth, though no definitive link has been established. There is ongoing research into whether hormonal fluctuations, exposure to certain chemicals, or chronic inflammation might play a role in the development or progression of vestibular schwannomas.

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