Powerful yet simple monitoring Neurosign 400 is intended for neurosurgery, otology, and maxillofacial and general ENT surgery, allowing the surgeon to identify and locate delicate neural tissue with precision. With 4 channels, the Neurosign 400 provides greater monitoring capacity than the Neurosign 100 and offers surgeons increased precision for monitoring the facial nerve. Neurosign 400 has a proven track record of providing important information to the surgeon during a variety of surgical procedures.