Collateral Trigone (Medial View)

Description

Collateral trigone anatomy comes into focus at the junction where the posterior horn of the lateral ventricle meets the inferior (temporal) horn, forming the atrium (trigone) in the posteroinferior cerebrum. From a medial perspective, the ventricular cavity is framed superiorly and posteriorly by the splenium region and tapetum of the corpus callosum, while the floor is shaped by the collateral eminence produced by the collateral sulcus in the parahippocampal and occipitotemporal region. Medial and slightly inferior to this atrial region, the calcar avis related to the calcarine sulcus may be appreciated as a neighboring contour within the posterior horn. Boundaries matter here. Clinically, the collateral trigone is a practical landmark when you need to orient within the atrium on cross sectional neuroimaging, because enlargement of the posterior and inferior horns in obstructive hydrocephalus or ex vacuo ventriculomegaly often changes the atrial proportions first and can distort the adjacent choroid plexus. Its relationship to the medial temporal lobe also provides context for approaches that traverse the temporal horn or atrium, where unintended violation of deep white matter (including callosal tapetal fibers) can complicate postoperative visual field outcomes. The fixed medial viewpoint supports rapid left right orientation and highlights the horn confluence without distracting surface gyri. Neuroanatomy lecturers can pair this illustration with coronal and sagittal MRI teaching slides to clarify the atrium, posterior horn, and inferior horn continuum, and radiology authors can reference it when describing ventricular caliber, intraventricular hemorrhage layering, or catheter tip positioning relative to the atrium. Neurosurgical education materials on temporal horn access, atrial lesions, and peritrigonal trajectories also benefit from the explicit spatial relationships in a single frame. Anatomical accuracy verified by SciePro's Medical Advisory Board.