Acoustic Neurinoma

In case of middle acoustic neurinoma, the hearing and important cranial nerves have to be monitored. An acoustic stimulus at the ear induces (if the stimulus is forwarded without interruption) so-called acoustic evoked potentials (AEPs) in the brain. They can be measured in nanovolt as small electric signals on the head surface. This enables a continuous control of the hearing function.

In the field of cranial nerve monitoring, facial nerve monitoring is one of the most common method used. Here the facial nerve is first stimulated for localisation (prior to entry into the resection area) and later for function control (after withdrawal from the resection area). Afterwards following muscle answer is recorded at the corresponding muscles, orbicular oculi and orbicular oris muscles.

It is recommended to perform continuous EMG monitoring without direct nerve stimulation. Thus spontaneous activity by mechanical manipulation of the nerve is established.