Arachnoid Mater, Inferior View

Description

Viewed from the inferior aspect, the arachnoid mater spans the ventral surface of the brain and bridges over the basal cisterns that pool cerebrospinal fluid around the midline skull base. Anteriorly, the optic nerves converge at the optic chiasm, which sits superior to the hypophyseal region where the pituitary gland occupies the sella turcica. Posterior to the chiasm, the interpeduncular fossa and ventral midbrain lead into the pons and medulla, with cranial nerves emerging in sequence and coursing anterolaterally toward their foramina. Basal cistern anatomy matters when you are trying to localize subarachnoid hemorrhage or interpret why blood tracks into specific recesses on CT. The suprasellar cistern around the optic chiasm and pituitary stalk, along with the interpeduncular and prepontine cisterns anterior to the brainstem, are common early reservoirs for hemorrhage from a ruptured intracranial aneurysm, classically at the anterior communicating artery or posterior communicating artery. Clear relationships between the arachnoid membrane, cranial nerves, and basal vessels also anchor microsurgical planning for approaches that work through these CSF spaces, including pterional and subfrontal routes to the parasellar region. Neuroanatomy and neurosurgery teaching sessions use this perspective to connect the meninges to cranial nerve emergence patterns (III in the interpeduncular cistern, VI at the pontomedullary junction) and to reinforce why cisternal opening provides brain relaxation during aneurysm clipping. It also fits endocrine and ophthalmic content where the chiasm–pituitary corridor frames chiasmal compression, pituitary macroadenoma extension, and endoscopic endonasal surgical targets. Anatomical accuracy verified by SciePro's Medical Advisory Board.