Localization of the gustatory pathway in the human midbrain.

The localization of the secondary gustatory pathway in the human brainstem still remains uncertain. Here we report two patients with small vascular lesions in the unilateral midbrain tegmentum who presented with taste disturbance on the ipsilateral side of the tongue. In both cases, the dorsomedial mesencephalic tegmental region lateral to the oculomotor nucleus, including the central tegmental tract and the ventral part of the periaqueductal gray, was involved commonly in the lesions. The secondary gustatory pathway arising from the nucleus of the solitary tract appears to run rostrally, without crossing, to the ipsilateral thalamic nucleus through the dorsomedial part of the tegmental region at the rostral level of the midbrain.