Subarachnoid cisterns are CSF-filled spaces within subarachnoid space between arachnoid mater and pia mater. There is marked difference in the shape of the brain and internal contour of the skull, so the subarachnoid space is deep in several places especially around the base of skull thus called subarachnoid cisterns.
They contain more CSF than the ventricles.
They are named according to the surrounding structures and are as follows:
- Cisterna magna (cerebellomedullary cistern)
- Pontine cistern (prepontine cistern)
- Interpeduncular cistern
- Quadrigeminal cistern (cistern of great cerebral vein or the superior cistern)
- Cistern of velum interpositum
- Ambient cisterns
- Suprasellar cisterns
- Pericallosal cistern
- Cisterna Magna lies behind the medulla and below the cerebellar hemispheres.
- Receives CSF from the median aperture of the 4th ventricle.
- It is continuous inferiorly through the foramen magnum with the spinal subarachnoid space and superiorly behind the cerebellum for a variable distance.
- Cisterna Magna contains the vertebral artery and its posterior inferior cerebellar branch in its lateral part on each side.
- The Pontine cistern is located between the pons and the clivus.
- It receives CSF from lateral apertures of the 4th ventricle.
- This continuous above with the interpeduncular cistern and below with the cisterna magna.
- The contents of pontine cistern are the basilar artery and its pontine & labyrinthine branches.
- Interpeduncular cistern lies between the cerebral peduncles of midbrain and the dorsum sellae.
- It continues above with the suprasellar cisterns, below with the pontine cistern & laterally with the ambient cisterns.
- Posterior part of the circle of Willis lies in the interpeduncular cistern.
- Quadrigeminal cistern lies posterior to the quadrigeminal plate of the midbrain.
- It is bounded above by the splenium of corpus callosum, below by the cerebellar vermis and limited posteriorly by the tentorium & falx.
- The venous confluence of the internal cerebral vein and the basal veins (to form great cerebral vein of Galen) lies in this cistern.
- Great cerebral vein joins with inferior sagittal sinus to form straight sinus.
- It contains:
- Posterior choroidal arteries
- Superior cerebellar arteries
- Trochlear nerve
- Posterior cerebral arteries
CISTERN OF VELUM INTERPOSITUM:
- The space that lies between the layers of tela choroidea as it passes beneath the splenium of the corpus callosum and the fornix.
- It continues posteriorly with the quadrigeminal plate cistern through a narrow slit under the splenium called transverse fissure.
- On axial sections, it has triangular shape.
- It contains the internal cerebral veins.
- It lies on each side of the midbrain.
- It extends between the interpeduncular cistern anteriorly & the quadrigeminal cistern posteriorly.
- The lateral extensions of the superior part of ambient cisterns around the posterior part of the thalamus are called ambient wing cisterns.
- The anterior part of each ambient cistern contains posterior cerebral artery and the basal veins.
- Suprasellar cistern lies between the anterior part of the floor of 3rd ventricle above and the diaphragma sellae below.
- It is continuous with interpeduncular cistern posteriorly.
- Extends laterally into the Sylvian cistern at the lower end of Sylvian fissure.
- The optic nerve passes to the optic chiasma in the anterior part of this cistern,
- It contains anterior part of the circle of Willis.
- Pericallosal cistern lies on the superior surface of the corpus callosum.
- This continues inferiorly with suprasellar cistern through cistern of lamina terminalis and posteriorly with the quadrigeminal cistern below the splenium.
- It contains branches of the anterior cerebral artery.