Acoustic neuroma

The most common tumour of the inner ear is the acoustic neuroma. Other names for this are cerebellar bridge angle tumour and vestibularis schwannoma. This is a neurinoma or schwannoma in the inner part of the auditory canal or a neurinoma in the cerebellar bridge angle.

A neurinoma or schwannoma is a benign and usually slowly growing tumour. It originates from the Schwann cells. These are the cells that form the envelope of the peripheral nerves, i.e. the nerve fibres that are not located in the spinal cord and brain.

This coating of nerve fibres is relevant for the support of the nerve cell and also for its myelination. Through myelination, the nerve fibre can conduct electrical signals faster, with less loss and thus over longer distances. But it is precisely these cells that can give rise to a tumour if they proliferate (grow) excessively. Depending on where such a tumour develops, it is called differently and causes different symptoms. However, a common feature of most acoustic neuroma is that, as their name suggests, their starting point is the auditory nerve (nervus vestibularis).

Function of the auditory nerve

The vestibular nerve lies for a large part of its course together with the cochlear nerve. Together they form the vestibulocochlear nerve, the eighth cranial nerve. The nervus vestibularis is the nerve that innervates the organ of equilibrium.

This means that it transports information from the vestibular organ to other structures in the brain in order to enable a connection of all stimuli that the human being perceives. The organ of equilibrium is located in the inner ear. It consists of three semicircular canals and two macular organs through which the organism can perceive and classify movements.

Since there are three archways that are almost perpendicular to each other, all three levels of space and movements in them can be perceived, such as turning the head. Through the macula organs, information about linear accelerations is passed on, such as the force of gravity, when braking and accelerating in vehicles and also when falling. Normally, an image of the position, location and movement of the body in space is formed from the electrical signals that reach the brain via the left and right vestibular nerves.

In case of failures and injuries, faulty or no information from the respective organ of balance reaches the brain and leads to wrong conclusions being drawn by the processing centres in the brain. The other part of the eighth cranial nerve is the cochlear nerve. This nerve innervates the cochlea. This is a bony, snail-shell-like structure that is responsible for hearing. If this nerve is injured, it is possible that information will no longer be transmitted to the brain.