pontomedullary groove pon·to·med·ul·lar·y groove (pŏn'tō-měd'l-ěr'ē, -mə-dŭl'ə-rē)
n.
The transverse groove on the ventral aspect of the brainstem that demarcates the pons from the medulla oblongata and from which emerge the sixth, seventh, and eighth cranial nerves.