Pathology of the peripheral nervous system.

In this review, the first four papers deal with an important chapter in peripheral nerve surgery: cranial nerve reconstruction after injury occurring during skull base surgery. The last paper discusses the problem of peripheral nerves affected by a ganglion cyst. Damage to a cranial nerve is no longer considered to be an absolutely irreparable event. The first two studies are related to facial nerve management during the surgical treatment of vestibular schwannomas. The most common mechanisms responsible for facial nerve injury during tumor removal and the technical means to avoid them are cited. The importance of intraoperative neurophysiologic monitoring to save the facial nerve is stressed. A comparison between microsurgery and radiosurgery results in the conclusion that for vestibular schwannomas, the first choice of treatment is microsurgery. These two large and exceptional series show that by using a refined technique it is possible to obtain both total tumor removal and preservation of the facial nerve in most of the vestibular schwannomas. In the minority of patients in whom the facial nerve is severed, there are several therapeutic options to re-establish facial nerve function. After facial nerve reconstruction, performed immediately during the same tumor operation, a satisfactory reinnervation was obtained in 74% of the cases. After facial nerve reanimation, using as donor nerve the hypoglossus and performed 1 week after the tumor operation, a satisfactory reinnervation was obtained in 96% of the cases. The other two papers deal with the intraoperative transection of the trochlear and abducens nerve during surgery for skull base tumors. These two cranial nerves, owing to their simply organized motor nerve system (they are purely motor nerves and supply one muscle each), show quite a good expectation of functional recovery. The behavior of ganglion cysts involving peripheral nerves is the topic of the last paper reviewed. These cysts are benign lesions that can cause permanent neurologic deficits of the involved nerve. The etiology, clinical presentation, surgical techniques, and recurrence rate are reported. In the present series, the outcomes after ganglion cyst excision are not as favorable as those reported in other series. Before surgery, patients must be informed about the possibility of residual motor deficits and recurrences.