The Neurosign 800 is intended to be used to monitor multiple cranial nerves and spinal nerve roots. It is used to monitor multiple cranial motor nerves; for example, during acoustic neuroma excision the Neurosign 800 can be used to monitor 4 branches of the facial nerve, together with the trigeminal, glossopharyngeal, vagus and accessory nerves. It is important to monitor the facial nerve thoroughly. Experience has shown that it is not always adequate to use 2 channels to monitor the nerve; in tumours where the nerve is stretched it can become very thin and played out, so that its fibres cover a large area. By using just 2 channels, only a proportion of those fibres are monitored, resulting in potential damage to part of the nerve. By using 4 channels, more of the nerve is covered. The additional channels also allow the user to monitor other important neural structures during the removal of acoustic neuromas and meningiomas. The trigeminal, glossopharygeal and accessory nerves are all easily monitored using needle electrodes; the vagus can be monitored using the laryngeal electrode (soon to be available in the USA). The Neurosign 800 can also be used in spinal procedures, to monitor the spinal nerve roots during the placement of pedicle screws, spinal instrumentation, the release of tethered cord, the removal of spinal tumours, especially in the cauda equina, and as an aid during scoliosis correction.