Acoustic neurinoma, also known as vestibular schwannoma, is a benign form of brain tumour originating from Schwann cells with symptoms that include unilateral sensorineural hearing loss.
Acoustic neurinoma, also referred to as vestibular schwannoma due to its location, is a non-cancerous tumor that forms on the vestibulo-cochlear nerve, more precisely the eighth cranial nerve. It primarily affects Schwann cells, which play a crucial role in forming myelin – a substance that envelops nerves, facilitating the transmission of electrical stimuli.
The presence of this tumor can lead to significant issues, primarily due to its location, as it exerts pressure on the auditory nerve and neighboring structures, resulting in debilitating disorders.
Given its specific location, acoustic neurinoma triggers symptoms related to auditory functions. These symptoms can vary in intensity, contingent on the tumor's size and growth. In its early stages, it often manifests as hearing disorders, including gradual one-sided hearing loss, tinnitus, vertigo and difficulties in maintaining balance.
As the tumor expands, it may compress other nerves and tissues, giving rise to problems like impaired coordination of movements, weakness in facial muscles on one side, headaches, facial paresis, and even hydrocephalus – the blockage of cerebrospinal fluid circulation.
The diagnosis of acoustic neurinoma is not simple and immediate. This is due to the tumor's slow growth rate, which typically advances at an average pace of 1-2 millimeters per year without a distinct pattern.
During the initial phase, the symptoms of the condition may be mistaken for other disorders, such as labyrinthitis or Ménière's disease, among others. To pinpoint and confirm the presence of an acoustic neurinoma, a combination of diagnostic tools are neccessary, including but not limited to, an MRI scan, a CT scan and an audiometric examination to quantify the hearing loss and check the functionality of the facial muscles.
The causes of vestibular schwannoma are still not completely clear. Experts agree that there is a genetic component, but the genes responsible have not yet been identified. Only for a small percentage of patients acoustic neuroma can be traced back to neurofibromatosis type 2, a rare hereditary disease caused by a mutation in chromosome 22. This disease causes the development of benign tumours on nerves, frequently on spinal and cranial nerves. If the neurinoma of the acoustic nerve is caused by neurofibromatosis type 2, the acoustic-type symptoms are bilateral, i.e. they occur on both sides.
There are different therapeutic procedures for acoustic neurinoma. In cases where the tumor is very small and not causing distressing symptoms, or when it is a non-expansive neurinoma characterized by a slow growth rate, direct intervention may not be necessary. Instead, patients are placed under regular surveillance through periodic examinations to monitor the disease's progression.
On the other hand, if intervention is warranted, tumor removal can be achieved through surgical procedures or radiotherapy. The choice between these options is determined by a comprehensive evaluation, considering factors such as the patient's age, overall health, tumor size, location, and hearing function.
Surgical removal is typically conducted under general anesthesia. A craniotomy is performed, involving an incision in the cranial box, to access and remove the tumor. The feasibility of complete removal depends on the tumor's size and location. In cases where total removal is not achievable, radiosurgery may be considered as a subsequent treatmen
An alternative treatment method is stereotactic radiotherapy, which involves focused radiation to target the tumor. This approach is primarily employed when the acoustic neurinoma is located in areas that are difficult to reach or when the patient's condition prohibits traditional surgery. Stereotactic radiotherapy is typically performed under local anesthesia.
Both procedures involve risks and complications, especially related to injury to cranial nerves close to the auditory nerve or preservation of hearing function.