Figure 14-114.

Nerve Sheath Tumors.

A, Inner surface of the cranial vault, cranial nerves, dog. These tumors are usually lobulated, well-defined, tan, solitary to multiple masses that arise from the coverings of a cranial or spinal nerve (arrows). In the central nervous system, the trigeminal nerve is usually affected, and the masseter and temporalis muscles innervated by it may atrophy. Tumors compress the nerves, causing wallerian degeneration. B, Brain from dog in A. Peripheral nerve sheath tumors (arrows).

(A and B courtesy Dr. J.F. Zachary, College of Veterinary Medicine, University of Illinois.)