Acoustic Neuroma or Schwannoma is diagnosed through acoustic neuroma MRI or radiology and may require acoustic neuroma surgery. More details at Meri Sehat.

Acoustic Neuroma

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ZAKA CLINIC GULBERG LAHORE

Saad Ullah Siddiqui

Overview

Acoustic neuroma is also known as acoustic schwannoma or vestibular schwannoma. It is a rare noncancerous tumor, which is located in the ear and develops in the main nerve that connects the ear with the brain<a href="#accordion">[1]</a>. These nerves have a vital impact on the patient&rsquo;s hearing abilities and balance and; hence, acoustic neuroma can cause unsteadiness or hearing loss<a href="#accordion">[2]</a>.

&nbsp;

Acoustic neuromas are slow-growing tumors that are formed near or along the branches of the vestibulocochlear nerve. This nerve is responsible for maintaining equilibrium and sending sensory sound information to the brain. However, it is not responsible for any motor functions<a href="#accordion">[3]</a>.

The disease affects only 6% of the total cases of intracranial tumors. Some figures suggest that it occurs in 2 out of 10,000 people, whereas other figures suggest that the incidence is 0.3-1 per 100,000 people annually<a href="#accordion">[4]</a>.&nbsp;

In Pakistan, the treatment is not widely available, due to the rare nature of the disease. Resources like the trans labyrinthine approach for acoustic neuroma are offered by only one or two practitioners in the entire country.&nbsp;

<div>&nbsp;</div>

There are two main types of acoustic neuroma:

&nbsp;

<ul>
	<li>
	<h5>Unilateral Acoustic Neuroma</h5>
	</li>
</ul>

It is also known as sporadic acoustic neuroma. It has a sudden onset and can happen at any age, but most commonly occurs in people between the ages of 30 and 60. Also, only one side of the body is affected. This type of acoustic neuroma is not due to genetic factors.

&nbsp;

<ul>
	<li>
	<h5>Bilateral Acoustic Neuroma</h5>
	</li>
</ul>

These types of neuromas occur due to the genetic disorder NF 2, which is why it is also known as neurofibromatosis type 2. The disease is caused due to a chromosomal genetic mutation and causes the growth of noncancerous tumor cells concentrated in the nervous system.&nbsp;

<div>&nbsp;</div>

Signs And Symptoms

Acoustic neuroma is often confused as a sign of aging. The symptoms take a long time to develop to a point where they are easily identifiable. They include:

&nbsp;

<ul>
	<li>Ringing in the ear</li>
	<li>Gradual hear loss</li>
	<li>Ear cavity feeling full</li>
	<li>Poor balance</li>
	<li>Vertigo</li>
	<li>Confusion</li>
	<li>Clumsiness</li>
	<li>Headaches</li>
	<li>Blurred vision</li>
	<li>Pain or numbness in one side of the face</li>
	<li>Ataxia</li>
	<li>Trouble swallowing</li>
</ul>

<div>&nbsp;</div>

Causes

The name vestibulocochlear schwannoma or acoustic schwannoma comes from the Schwann cells that insulate the nerve fibers. The tumor develops around Schwann cells. These cells aid in improving the conduction of action potential along the pathway while the main vestibulocochlear nerve connects the ear directly to the brain<a href="#accordion">[5]</a>.&nbsp;

&nbsp;

Similar to most tumors, there is no exact known cause of the abnormal cell growth, however, two factors are believed to play a role in the disease:

<ol>
	<li>The first is neurofibromatosis type 2 or NF2, which is a hereditary disease characterized by the growth of tumors alongside the nerves<a href="#accordion">[6]</a>. These tumors are noncancerous<a href="#accordion">[7]</a>. 5% of the cases of acoustic neuroma are due to NF2.&nbsp;</li>
	<li>If we consider the disease on a cellular level, it is due to the inability of a gene to suppress the growth of Schwann cells that multiply and form the tumor.&nbsp;</li>
</ol>

&nbsp;

Radiation exposure is also a commonly believed cause of acoustic neuroma, but it is yet to be proven as a robust factor<a href="#accordion">[8]</a>.

<div>&nbsp;</div>

Diagnosis

Diagnosis begins with a physical examination of the ear. It is difficult to diagnose the disease during the early stages because the signs are easily overlooked and the symptoms can be mistaken for anything, including signs of aging. The doctor may further go for some of the tests for a complete diagnosis<a href="#accordion">[9][10]</a>:

&nbsp;

<ul>
	<li>Hearing Test: Also known as audiometry, it is used to assess the patient&rsquo;s hearing ability. A hearing specialist or an audiologist plays the sound at various levels with different tones and the patient is asked to point out the type of sound they are hearing. They are able to listen to the sound from one ear at a time to fully assess the functioning of each ear. The tones are repeated at very low and faint levels, which are barely audible but are able to vibrate the eardrum.</li>
</ul>

&nbsp;

<ul>
	<li>ABR Testing: Once it is noticed that the patient&rsquo;s hearing is progressively worsening and that too abnormally, then further testing is carried out. This includes auditory brainstem response (also known as brainstem auditory evoked response). The test is not as sensitive as an MRI, but it is a better option in terms of cost. However, due to decreased instances of false negatives, ABR testing is not used as commonly anymore.</li>
</ul>

&nbsp;

<ul>
	<li>MRI: A gadolinium enhanced T1 MRI is the ideal diagnostic tool for acoustic neuroma. However, the ever-increasing costs of MRIs mean the diagnosis itself gets very costly, making it a less utilized option in low-income countries.</li>
</ul>

<div>&nbsp;</div>

Treatment

The treatment of acoustic neuroma depends on the severity of the problem, including the growth of the tumor itself, the symptoms that the patient is experiencing, and their overall health. Factors like age and any other possible underlying issues are also important to consider when formulating a treatment plan.&nbsp;

&nbsp;

<ul>
	<li>Monitoring: Small acoustic neuromas or in conditions where the neuroma is not too discomforting and have no visible symptoms, monitoring is preferred. Acoustic neuromas are very slow in terms of growth and show no signs initially. In patients who are not the ideal candidates for aggressive treatments, it is better to opt for monitoring and regular imaging.&nbsp;</li>
</ul>

&nbsp;

<ul>
	<li>Surgery: Acoustic neuroma surgery is performed if the issue gets too severe. Surgery is considered when the tumor is large and constantly growing and exerting its effects on the patient. The main target of acoustic neuroma surgery is to remove the tumor&nbsp;while ensuring that the facial nerve stays undisturbed in order to prevent facial paralysis. The surgeon removes the tumor partially to avoid any other complications. There are effectively 3 approaches that are used to remove the tumor during surgery:</li>
</ul>

&nbsp;

<ol>
	<li>Retrosigmoid</li>
	<li>Middle fossa</li>
	<li>Translabyrinthine</li>
</ol>

&nbsp;

<ul>
	<li>Radiation Therapy: Over the years, scientific advancements have made it possible for radiation therapy to have a 3-dimensional focus. The therapy involves multiple sessions with the administration of smaller doses. The main idea here is to aim accurately at the tumor cells so that the surrounding cells are not impacted. This leads to a halt in the tumor growth. It is a non-invasive treatment option; the effects of radiation therapy are seen over time, taking as long as weeks, months, or even years depending on the severity of the patient&rsquo;s acoustic neuroma<a href="#accordion">[11]</a>.</li>
</ul>

<div>&nbsp;</div>

Complications due to acoustic neuroma include<a href="#accordion">[12]</a>:

&nbsp;

<ul>
	<li>Hearing Loss: This is both a symptom as well as a complication. This is because when surgery is performed to remove the tumor, it is very common for patients to lose their hearing in the affected ear. CROS hearing aid or bone anchored hearing aid devices are suggested as they direct the sound over to the deaf ear.</li>
</ul>

&nbsp;

<ul>
	<li>Tinnitus: After the treatment, it is common for the patients to still experience tinnitus ( hearing sounds that come from inside your body, rather than from an outside source). It improves in many patients but normally it stays the same in 10% of the patients.&nbsp;</li>
</ul>

&nbsp;

<ul>
	<li>Facial Paralysis: This complication arises especially in case of complete removal of the tumor. The patient experiences temporary paralysis of the facial muscles that are responsible for the movement of the eyelid. This condition stays for 6-12 months.</li>
</ul>

&nbsp;

<ul>
	<li>Death: It&rsquo;s probable due to brain related complications. If the acoustic neuroma is left untreated and left to grow, it can attach itself to the nerves and get intertwined with the blood vessels, thereby restricting blood supply to the brain. This disturbance in the blood supply leads to death.</li>
</ul>

<div>&nbsp;</div>

The following are the risk factors of acoustic neuroma<a href="#accordion">[13]</a>:

<ul>
	<li>Exposure to leisure noise (loud music) and occupation related noise</li>
	<li>Benign tumor of the thyroid (parathyroid neuroma)</li>
	<li>Low-level radiation exposure during early age</li>
</ul>

<div>&nbsp;</div>

Acoustic neuroma is a rare disease which cannot be prevented. However, it takes years to grow and goes unnoticed unless the symptoms are highly severe and discomforting.

&nbsp;

Research done by the scientists in Massachusetts Eye and Ear showed that the use of mifepristone, helps stop the growth and development of vestibular schwannoma. Up till now, there are no FDA-approved drugs for acoustic neuroma and the research on the drugs have been difficult due to the nature and location of the problem<a href="#accordion">[14]</a>.

&nbsp;

Key Points

<ul>
	<li>Acoustic neuroma is a rare disease that is characterized by the formation of a tumor on the Schwann cells. These cells cover the nerve fibers that go from the ear to the brain.</li>
	<li>There are two&nbsp;types of acoustic neuroma: (1) unilateral, which affects only one ear, and (2) bilateral acoustic neuroma, which happens due to NF2 and affects both ears.</li>
	<li>While there is no known fundamental cause of acoustic neuroma, people with the genetic disease neurofibromatosis 2 tend to develop acoustic neuroma in many cases.&nbsp;</li>
	<li>About 5% of the total cases of acoustic neuroma are related to patients that have NF2.</li>
	<li>Acoustic neuroma affects the hearing and balance of the person. Other symptoms are headaches, blurred vision, ringing in the ear, vertigo, confusion, and ataxia.</li>
	<li>There are no robust drugs that are targeted toward the tumor itself. The treatment is highly dependent on the patient and their age. In cases of older patients who cannot take on an aggressive treatment approach, monitoring is preferred.&nbsp;</li>
	<li>Surgical removal of the tumor does not always mean that the tumor can be completely removed. This is because the facial nerve responsible for the movement of the eyelid may get damaged. This is combated by removing the tumor partially to halt the growth.</li>
	<li>Research suggests that mifepristone may be one of the first drugs successful in stopping the growth of acoustic neuroma.</li>
</ul>

<div>&nbsp;</div>

[1] Acoustic neuroma (Vestibular Schwannoma). Johns Hopkins Medicine.

[2] Acoustic neuroma. Mayo Clinic

[3] Valeii K. Vestibulocochlear nerve: Anatomy, function, and treatment. Verywell Health.

[4] Lin D, Hegarty JL, Fischbein NJ, Jackler RK. The Prevalence of “Incidental” Acoustic Neuroma. Arch Otolaryngol Head Neck Surg. 2005;131(3):241–244. doi:10.1001/archotol.131.3.241 5.	University TAK. Acoustic neuromas. AKUH

[5] University TAK. Acoustic neuromas. AKUH.

[6] Acoustic Neuroma. Cedars Sinai.

[7] NHS choices. Acoustic Neuroma.

[8] UC San Diego Health. UC Health - UC San Diego. Acoustic Neuroma.

[9] Acoustic neuroma. Mayo Clinic.

[10] Timothy C. Hain MD. Diagnosis of acoustic neuroma using tests. Acoustic Neuroma Diagnostic tests

[11] Acoustic neuroma. NORD (National Organization for Rare Disorders).

[12] Risks & complications of acoustic neuroma surgery. The Center of Acoustic Neuroma Dallas.

[13] Chen M, Fan Z, Zheng X, Cao F, Wang L. Risk factors of acoustic neuroma: Systematic Review and meta-analysis. Yonsei Medical Journal. 2016;57(3):776. doi:10.3349/ymj.2016.57.3.776