Clinical approach to brainstem lesions.

The brainstem consists of the midbrain, pons, and medulla. The cerebellum is attached to the dorsal surface of the pons and upper medulla. The brainstem contains 9 of the 12 cranial nerves and is crossed by ascending, descending, and cerebellar pathways and their nuclei as well as the reticular formation. Numerous and rare crossed brainstem syndromes have been described in recent years, many of them without clinical significance. The aim of this article is to provide a brief clinical description of some conditions affecting the brainstem.