What is acoustic neuroma?

Acoustic neuroma, also known as vestibular schwannoma, is a benign form of brain tumor originating from Schwannn cells with symptoms including single-sided sensorineural hearing loss.

Symptoms of acoustic neuroma

The acoustic neuroma is a benign tumor that develops on the vestibular-cochlear nerve (more precisely eighth cranial nerve) and that affects the Schwann cells. These cells form myelin, a substance that lines the nerves and facilitates the passage of electrical stimuli.

This tumor, also called vestibular schwannoma due to its localization, although benign in nature, compresses the acoustic nerve and surrounding structures , causing disabling disorders.

Due to its location, acoustic neuroma gives symptoms related to auditory function, more or less intense depending on the development and growth of the neoplasm. At an early stage it comes to hearing disturbances , such as progressive unilateral hearing loss , tinnitus , dizziness and difficulty maintaining balance .

As the tumor grows it can compress other nerves and other tissues, causing problems with coordination of movements , unilateral weakness of the facial muscles, headaches, paresis of the face and hydrocephalus , which is the blockage of the circulation of the cerebrospinal fluid.

Diagnosis and causes of acoustic neuroma

The diagnosis of acoustic neuroma is not simple and immediate. Symptoms , in fact, occur gradually, at the rate of tumor growth, which occurs slowly (on average 1-2 millimeters per year) and without a precise progression.

In the initial phase, the first signs of the disease can be confused with those of other disorders, such as labyrinthitis or Ménière’s disease , for example.

Indispensable diagnostic tests are magnetic resonance and CT , both with contrast medium . L ‘ audiometric examination and some neurological tests are also needed to quantify the hearing loss and test the functionality of the facial muscles.

The causes of vestibular schwannoma are still not fully understood . Experts agree that there is a genetic component, but the responsible genes have not yet been identified. In only a small percentage of patients, acoustic neuroma can be traced to neurofibromatosis type 2, a rare inherited disease caused by a mutation of chromosome 22. This pathology causes the development of benign tumors on the nerves, frequently on the spinal and cranial ones. If the acoustic neuroma is caused by neurofibromatosis 2, the acoustic symptoms are bilateral, that is, they occur on both sides. 

Surgery and post-operation

The therapeutic procedures of acoustic neuroma are different. If the tumor is very small and does not give annoying symptoms or if it is a non-expansive neuroma, which has a very slow growth, no action is taken immediately, but the patient is monitored with periodic examinations to evaluate the evolution of the disease.

The removal of the tumor , on the other hand, can be done by surgery or by radiotherapy . These two options are evaluated by specialists based on many factors, such as the patient’s age and general condition, the size and location of the tumor, hearing function.

The surgery takes place under general anesthesia . An incision is made in the skull (craniotomy) and the tumor is removed. Total removal may not be possible depending on the size and location of the tumor. In this case, radiosurgery is subsequently intervened.

The other therapeutic option is stereotaxic radiation therapy . It consists of irradiating the tumor with a focused beam. This approach is mainly used when the acoustic neuroma is localized in areas that are difficult to reach with traditional surgery or when patients’ conditions do not allow them to undergo a proper surgery. It is performed under local anesthesia.

Both procedures involve risks and complications, especially related to injury to the cranial nerves near the auditory nerve or to the preservation of hearing function.

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