Lateral Groove Of The Midbrain Of The Brainstem, Lateral View

Description

Lateral mesencephalic sulcus (the lateral groove of the midbrain) forms a shallow longitudinal furrow along the lateral surface of the mesencephalon, separating the crus cerebri (basis pedunculi) anteriorly from the tegmentum posteromedially. In this fixed lateral view, the convex cerebral peduncle lies ventral and slightly superior, while the tegmental contour sits more dorsal and medial, creating a distinct boundary line that runs roughly parallel to the long axis of the brainstem. Superiorly, the groove approaches the diencephalic junction, and inferiorly it tapers toward the pontomesencephalic region. A narrow landmark. For neuroanatomy teaching and clinical localization, this groove helps orient the viewer to what is “peduncular” versus “tegmental,” a distinction that maps directly onto major tract and nuclei territories even when those deeper structures are not exposed. Lesions centered in the crus cerebri classically produce contralateral motor weakness from corticospinal and corticobulbar involvement, while tegmental infarcts can present with mixed cranial nerve and cerebellothalamic findings, as in midbrain syndromes such as Weber or Benedikt patterns. The lateral perspective supports bedside correlation by anchoring the midbrain surface anatomy to adjacent cisternal corridors where the trochlear nerve courses around the brainstem and where neurosurgical approaches work along the ambient cistern. Neuroanatomy courses, neuroradiology atlases, and operative anatomy chapters often need a single, consistent surface landmark to label the mesencephalon on lateral brainstem plates, and this illustration fits that role for print and digital layouts. It also pairs well with teaching material on brainstem stroke topography and cranial nerve relationships at the pontomesencephalic junction. Anatomical accuracy verified by SciePro's Medical Advisory Board.