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Acoustic Neuroma Explained – Symptoms, Treatments and Surgery

Acoustic Neuroma

Acoustic neuroma, also called as vestibular schwannoma, is an unusual cause of hearing loss. Usually, it is a noncancerous (benign) but gradual growth of tumor that progresses on the main nerve landing, i.e. eighth cranial nerve. The major function of this cranial nerve is to bridge connection between the inner ear and brain. This cranial nerve is also known as vestibulocochlear nerve and it has two different parts (cochlear nerve and vestibular nerve). Each part performs different roles in hearing; one performs the function of transmitting sound and the other functions to transmit balance or equilibrium information.

As these two parts play a significant role in hearing, growth of an acoustic neuroma tumor can interrupt the balance and hearing; this eventually causes loss of hearing, unsteadiness and ringing in the ear. Although, acoustic neuroma develops very slowly, but there are a few exceptions too. In some cases, it was shown to grow rapidly and became great enough to press on nearby other cranial nerves. Several researches on acoustic neuroma tumors suggest that these can be lethal, if they somehow develop enough to press on the cerebellum or stem of the brain.
small tumor of acoustic neuroma

Acoustic Neuroma Symptoms

As acoustic neuroma tends to develop gradually over a period of years, approximately 1-2 mm per year, it may not show any symptoms in the early stages. Most of the patients often fail to identify any symptoms in the initial periods and they often attribute the initial symptoms as normal changes due to aging. However, according to several studies, these tumors may not grow continually; in many cases, it was observed that the tumors were not developed for a long period. As a result, the symptoms may take a while to show up or properly diagnosed.

Usually, the initial symptom comes up with slow but sure loss of hearing in any one of the two ears. This hearing loss is often accompanied by two other symptoms: tinnitus (i.e. ringing in the ear) and pressure in the ear or fullness.

Usual Symptoms

  • Hearing loss
  • Problem with equilibrium
  • Tinnitus
  • Vertigo (a sensation as if everything is moving or spinning)
  • Unsteadiness

Relatively Rare Symptoms

  • Facial numbness, tingling, or pain
  • Temporary vision or sight loss
  • Changes of taste
  • Swallowing difficulty
  • Headache

Acoustic Neuroma Treatments

Several different treatment options are available for an acoustic neuroma patient. These options mainly depend on the size, shape, and position of the tumor, patient’s age, and overall physical condition of the patient. However, physicians often prefer from the following three acoustic neuroma treatment options.
  • Monitoring or observation
  • Surgery
  • Radiotherapy

Monitoring

As acoustic neuroma is cancerous and develops slowly, many researchers suggest that monitoring is the best option if the patient has a relatively small and slowly growing tumor. However, several other factors are also associated for preferring the monitoring as a best option. One of the major facts is that both surgery and radiotherapy are associated with several hazardous risks. The patient may not only loss hearing in the affected ear but also these two options can occasionally damage the facial nerve.

To help monitor the growth of the tumor, physicians often perform periodic MRI (magnetic resonance imaging) scans. Doctors usually suggest other necessary treatments depending on these scan reports. Other treatments are often considered if the tumor grows large or significantly arise serious symptoms.

Surgery

Microsurgery is another option for treating acoustic neuromas. This surgery may require removal of the whole or part of the tumor. Surgeons usually carried out this surgery under general anesthetic, and the tumors are removed via an incision created in the skull. Surgical options for removing the acoustic neuroma tumor often involve three main approaches.

Translabyrinthine

To remove the tumor of acoustic neuroma, this surgical approach involves creating an incision behind the ear. In this approach, surgeons usually remove the bone behind the ear, including some of the inner ear, before removing the tumor. Consequently, this surgical approach leads to complete loss of hearing in the affected ear though preserves the facial nerve than any other approaches.

Retrosigmoid

The retrosigmoid (also known as suboccipital craniotomy) is the most versatile surgical approach. To remove the tumor, this approach involves opening a portion of the occipital bone near the back of the ear. Surgeons often use the retrosigmoid approach to remove large tumors and restrict the possibility of hearing loss.

Middle fossa

The middle fossa is another main surgical approach for removing the tumor of acoustic neuroma. To get access near the tumor, this surgical approach involves removing a relatively little piece of bone above the ear canal. The middle fossa approach has the highest percentage of preserving hearing. However, this approach is mostly limited to the tumor of the internal auditory canal, a passageway or canal that carries nerves from inside the skull to the middle and inner ear. In addition, this surgical approach is often dangerous to the facial nerve and requires special training for the surgeons.

Radiotherapy

Radiotherapy is usually used in particular cases for acoustic neuromas; mainly for treating small tumors and after surgery on large tumors, if a small part of the tumor remains. This therapy is not recommended for large tumors of acoustic neuroma.

Radiotherapy is carried out under local anesthetic and delivers highly intensive and accurate doses of radiation to the acoustic neuroma. In addition, this therapy can be delivered in both single and multiple sessions (smaller daily doses for several weeks). The main benefit of this therapy is that it is very focused to the tumor and it provides the maximum amount of radiation doses without exposing or damaging the surrounding tissue. However, radiation therapy is not an ultimate treatment for acoustic neuromas; it only helps stop or slow the progress of a tumor.

Medical References

  1. Skull Base: Acoustic Neuroma - The Fully Endoscopic Removal of Acoustic Neuromas.
  2. Zhong Nan Da Xue Xue Bao Yi Xue Ban. 2013 Jul;38(7):695-8. doi: 10.3969/j. Protection of the superior petrosal vein in microneurosurgery for acoustic neuroma.
  3. Zhonghua Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 2013 Apr;48(4):270-3. A clinical analysis for sudden sensorineural hearing loss with acoustic neurinoma.

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