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  • Situation

    During parotid gland surgery or surgery at the cerebellopontine angle (e.g. acoustic neuroma - a tumour on the acoustic nerve) as well as in severe facial injuries or during surgical tumour resection, e.g. in the maxillary area, there is a risk of injuring one of the numerous motor nerves, such as N. facialis. 

    The nerve branches out from the brain stem into the two facial halves, innervating them throughout with its sensor and motor fibres. In parotid surgery, it runs across the operation site and is therefore particularly at risk. An injury of the N. facialis (facial paresis) results in the paralysis of facial muscles and disrupted sensation. The affected patients also suffer from the visible consequences of impaired facial movement. 


  • Monitoring of motor cranial nerves

    This is where intraoperative neuromonitoring comes into its own to ensure that the nerves are protected during surgery. The nerve at the operation site is electrically stimulated by dedicated simulation probes. The impulses triggered travel to the target muscles where they are picked up as motor unit action potential (MUAP) by electromyography (EMG) electrodes. The signals are processed by the neuromonitor and, with modern systems, converted into a signal waveform and into acoustic signals for the surgeon.

    Even the slightest irritation through pressure, strain or heat (HF surgical instrument) results in spontaneous activity in the innervated target muscles and becomes visible and audible to the surgeon. Thus, even the smallest neural branches can be located and their function tested so that they can be kept out of harm's way.

  • Sensory Monitoring of the Auditory Nerve and the Brain Stem

    When operating on the ear and the auditory nerve, measuring acoustic evoked potentials (AEP) helps the surgeon to identify impaired function. Pre-defined clicking sounds are played to patients via earphones. The action potentials thus triggered are picked up from the skull via needle electrodes. The AEP measurements provide an insight into the functionality of the auditory nerve (N. vestibulocochlearis) and the brain stem.

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