(AICA) The fifth (V) cranial nerve and the petrosal vein Superior cistern - It is situated dorsal to the midbrain. Thin, sheet-like extensions of the superior cistern that extend laterally about the midbrain, connecting it to the interpeduncular cistern. Ambient cistern may also refer to the combination of these extensions and the superior cistern. It is composed of a supratentorial and an infratentorial compartment. It contains: The great cerebral vein The posterior pericallosal arteries The third portion of the superior cerebellar arteries Perforating branches of the posterior cerebral and superior cerebellar arteries The third portion of the posterior cerebral arteries Its supratentorial portion contains: The basal vein The posterior cerebral artery Its infratentorial portion contains: The superior cerebellar artery The fourth (IV) nerve Crural cistern. It is situated around the ventrolateral aspect of the midbrain. It contains: The anterior choroidal artery The medial posterior choroidal artery The basal vein Carotid cistern. It is situated between the carotid artery and the ipsilateral optic nerve. It contains: The internal carotid artery The origin of the anterior choroidal artery The origin of the posterior communicating artery Insular/Sylvian cistern. It is situated in the fissure between the frontal and temporal lobes. It contains: The middle cerebral artery The middle cerebral veins The fronto-orbital veins Collaterals to the basal vein Cistern of lamina terminalis. It is situated just rostral to the third ventricle. It contains: The anterior cerebral arteries (A1 and proximal A2) The anterior communicating artery Heubner's artery The hypothalamic arteries The origin of the fronto-orbital arteries Lumbar cistern. It extends from the conus medullaris (L1-L2) to about the level of the second sacral vertebra. It contains the filum terminale and the nerve roots of the cauda equina. It is from the lumbar cistern that CSF is withdrawn during a lumbar puncture. It is of clinical significance that cerebral arteries, veins and cranial nerves must pass through the subarachnoid space, and these structures maintain their meningeal investment until around their point of exit from the skull. See also Subarachnoid hemorrhage References Nolte, J (2002) The Human Brain, 5th edition. , 87 Meninges