Acoustic neuroma guide

28/08/2022

Icon editWhat is acoustic neuroma?

What is acoustic neuroma?Acoustic neuroma is a rare brain tumour. It is a benign (non-cancerous) growth that develops on the nerve that connects the inner ear to the brain. The tumour grows very slowly and usually does not spread to distant body parts. It is also widely called a vestibular schwannoma.

In most people, the cause of the acoustic tumours is unknown. However, a rare genetic disorder causes about 7 out of every 100 neuromas.

Acoustic neoplasms are occasional. Every year, between 1 and 20 people in a million worldwide are diagnosed with this condition. Neurinomas make up about 8 out of 100 brain tumours. It is more common in middle-aged adults and rare in children and in women than in men.

Icon microscopeDiagnostic tests

A small tumour may not cause any signs. Since it grows slowly, the symptoms usually develop very gradually. Common symptoms are:

  • Vertigo;
  • Loss of sensation (facial numbness), tingling or pain;
  • Headache and earache;
  • Visual problems;
  • Fatigue, lack of energy.

The disease is usually not difficult to diagnose, and the initial tests will depend on the symptoms caused by the disease. Doctors prescribe:

  • A hearing test (audiometry) is a hearing function test that measures how well a patient hears sounds and speech. This is usually the first one done to diagnose vestibular schwannomas. The doctor asks to listen to sounds and speech, and the hearing function is measured with the help of headphones connected to the device.
  • Magnetic resonance imaging (MRI scan) is the best imaging test. To obtain comprehensive images of the brain and the structures inside it a strong magnetic field and radio waves are used. For example, MRI with a contrast agent can see a 1-2 mm tumour.

Treatment methods

If the auditory nerve tumour is tiny, doctors may decide that the best treatment tactic is to observe and control it carefully. Such formations are not cancerous (malignant) and do not spread to other organs, so it is safe to follow them for some time. In addition, any treatment can have complications and side effects. Therefore, the risks and benefits of therapy should be balanced. Finally, the doctor decides on further monitoring of vestibular schwannoma based on the test results.

The primary method of treatment is surgery. Operation is designed to remove as much of the mass as possible while preserving essential nerves, especially those that control facial movement. The type of neuroma surgery will depend on:

  • Suitability for surgery: Factors such as age and general health determine the possibilities of different types of treatment.
  • The size and position of the acoustic neuroma will influence the type of surgical treatment offered.
  • The tests and scans help determine which type of treatment is best for each case.

Surgical approaches to remove the tumour of the auditory nerve comprise:

  • Retrosigmoid approach (also known as retromastoid approach or suboccipital approach). It implies an incision behind the ear and removal of the bone to expose the tumour. It can be used on tumours of any size, and patients with small tumours can retain their hearing.
  • Translabyrinthine approach. This method involves an incision behind the ear and removing the bone, including part of the structures of the inner ear, which gives the surgeon excellent access to the tumour. The disadvantage of the method is complete deafness, but many patients with acoustic neuromas have already lost their hearing at the time of the operation.
  • Access to the middle fossa (also known as the infratemporal approach). This technique is intended for small tumours in patients with good hearing. It is achieved by incision above the ear and removing the bone to access the formation.

The treatment team will determine the choice of the best approach. During surgery, surgeons use sophisticated monitoring techniques to minimize risk to the nerves in the area and the brain.

Icon plusNew treatment options

The development of new tumour treatment methods is aimed at preventing any neurological complications. Neurologists and electrophysiologists monitor for any changes in the activity of the facial and auditory nerves during treatment and changes in the brain.

  • Stereotactic radiosurgery is a new type of treatment for acoustic neuromas. Stereotactic radiosurgery involves delivering radiation to a well-defined area in the brain where the schwannoma is located. Stereotactic means to find a point using three-dimensional (3D) coordinates. In this case, we are talking about a tumour of the acoustic nerve in the brain. A metal frame (similar to a halo) is attached to the scalp, and a series of scans are taken to show the tumour's exact location. Stereotactic radiosurgery can be done with a conventional radiation therapy machine, a CyberKnife, or a technique known as the GammaKnife.
    • GammaKnife is not a surgical procedure per se. During this type of stereotactic radiosurgery, surgeons use highly focused radiation beams to kill tumour cells and stop their growth without damaging surrounding tissue.
    • CyberKnife treatment process starts with imaging via a CT scan. The CT scan is then imported into the CyberKnife treatment planning system. The neurosurgeon or otolaryngologist then teams up with a radiological oncologist and a radiological physicist to create a plan for adequately treating the vestibular schwannoma while avoiding surrounding essential structures.
  • Fractionated stereotactic radiotherapy is performed using a head ring and a beamformer system. First, the ring is fixed on the patient's head. Then, with the help of a linear accelerator, the photon beam is localized in the tumour, killing its cells. The direction of photons is based on computed tomography data.

Early intervention with the methods described can reduce the risk of hearing loss associated with a rapidly growing acoustic neuroma. In addition, new treatments provide 92 to 97% tumour control in patients with acoustic neuroma even after five years.

Icon chartStatistics and prognosis

As already noted, neuroma on the auditory nerve is a slowly growing tumour that does not spread to other organs. But the disease can cause certain complications:

  • Hearing loss is the most common complication, and its severity is difficult to predict. In addition, the percentage of hearing loss is different for each patient.
  • Hydrocephalus ("water in the brain") - the large neuroma makes it difficult to flow fluid in the brain. Pressure can build up inside the brain, leading to permanent brain damage if not detected and treated.
  • Damage is caused by pressure on other nerves in the brain or on the brainstem. Enlargement of a neuroma causes pressure on nearby brain structures. Prolonged pressure leads to irreversible consequences.

According to the observations, the treatment method for vestibular schwannoma depends on the size of the neuroma and the age and condition of the patient. However, it looks like this: 45.4% of patients undergo surgical treatment, and 54.6% undergo active observation.

An exciting observation was published in The New England Journal of Medicine on the results of the degree of hearing preservation for 5 years with different treatment methods. After the Gamma Knife for acoustic neuroma, the hearing preservation rate was 51%, fractional stereotaxic therapy showed a hearing preservation rate of 66%, and the CyberKnife treatment was 74%.

Statistics and prognosis

AiroMedical specialists work with leading ear, nose and throat surgeons, auditory surgeons (neurootologists), neurologists and neurosurgeons. To assess the patient's condition, neurooncologists, radiation therapy specialists (radiation oncologists), imaging (radiologists) and other doctors are involved. Therefore, the disease will be diagnosed early and successfully treated.

References:

  1. Patient: Acoustic Neuroma
  2. NHS: Acoustic neuroma (vestibular schwannoma)
  3. Medscape: Acoustic Neuroma Treatment & Management
  4. International Journal of Radiation Oncology, Biology, Physics: Fractionated stereotactic radiation therapy and single high-dose radiosurgery for acoustic neuroma: early results of a prospective clinical study
  5. National Library of Medicine: Multifactor Influences of Shared Decision-Making in Acoustic Neuroma Treatment