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IV/1.2: Cisterns
IV/1.2.1: Definition
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The subarachnoid space is not uniform.
(Sub)arachniod cisterns are such flares in the subarachnoid space that form where the pia mater which closely follows the brain surface, separates widely from the arachnoid mater which follows the inner surface of the skull bones along with the dura mater.
IV/1.2.2: Supratentorial cisterns
Here belong the single (unpaired):
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1) cistern of the corpus callosum,
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2) cistern of amina terminalis,
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3) chiasmatic and
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4) infundibular cistern,
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5) cistern of the great cerebral vein (or quadrigeminal cistern or cistern of lamina tecti),
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6) velum interpositum cistern;
and the paired
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7) olfactory cistern,
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8) carotic cistern,
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9) cistern of the lateral cerebral fossa (Sylvian cistern),
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10) crural cistern,
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11) ambient cistern and
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12) interhemispheric cisterns.
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The carotic cistern locates immediately on top of the cavernous sinus and contains the intradural segment of the internal carotid artery (ICA) with its bifurcation, and the initial segment of the arteries that originate from the ICA (ophtalmic, superior hypophyseal, posterior communicating, anterior choroid, anterior and middle cerebral arteries).
The carotic cistern communicates with the chiasmatic cistern in the anterior and medial direction. The latter contains the optic chiasm with initial segments of the optic nerves and tracts, the hypophyseal stalk, and the continuation of the optic artery all the way to the optic canal. It is clinically important that the cistern forms a funnel and later a sheath, and escorts the optic nerve in the optic canal all the way to the optic papilla. This enables us to judge cerebrospinal fluid pressure by the status of the papilla during an eye fundus examination. The chiasmatic cistern continues backward and downward, and surrounds the tuber cinereum and the pituitary stalk, and often extends into the hypophyseal fossa through the sellar diaphragm. Some descriptions therefore mention a separate infundibular or pituitary cistern.
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The chiasmatic cistern continues upward in the cistern of lamina terminalis. Its posterior wall – which is also the anterior wall of the third cerebral ventricle – is consisted of the lamina terminalis and the upper part of the optic chiasm downwards. Here we can find the two anterior cerebral arteries with the anterior communicating artery between them, several perforating arteries that originate from the above vessels and the recurrent artery of Heubner .
The continuation of the cistern upwards and to the front is the cistern of the corpus callosum in the longitudinal cerebral fissure between the two hemispheres which is located under the falx cerebri and pipes the cerebrospinal fluid towards the splenium of corpus callosum and the quadrigeminal cistern rearwards. It is bilaterally bounded by the cingular gyrus and contains the pericallosal artery which is part of the anterior cerebral artery following the anterior communicating artery, and its branches.
The olfactory cistern starts in an anterior direction where the chiasmatic and carotic cisterns and the cistern of the lamina terminalis meet. This narrow subarachnoideal compartment contains the olfactory tract and bulb with their accompanying vessels.
If we proceed laterally from the carotic cistern, we reach the cistern of the lateral cerebral fossa (Sylvian cistern), that leads to the cerebral convexity between the touching surfaces of the frontal and temporal lobe. At the bottom of the cistern is the insula which is covered by the above lobe parts and the operculum of the parietal lobe. The trunk of the medial cerebral artery (M1 segment) and the larger arterial branches that originate from it, and form a loop around the insula (M2 or insular sebment) are also found here. The venous network is also very significant here.
In the backward direction, the carotic cistern contacts the more caudal crural cistern and the cranial ambient cistern. The crural cistern is adjacent medially with the interpeduncular cistern. It contains the anterior choroid artery, the medial posterior choroid artery, and the basal vein of Rosenthal. The ambient cistern is next to the crural and interpeduncular cisterns and goes round the midbrain from lateral. It is adjacent to the cerebellum downwards and the medial surface of the temporal lobe laterally. It contains the posterior cerebral artery after the posterior communicating artery, the continuation of the basal vein of Rosenthal, the superior cerebellar artery, and the trochlear nerve.
The cistern of the great cerebral vein (or quadrigeminal cistern or cistern of lamina tecti or Galen’s cistern) is located at the dorsal side of the midbrain. It is bounded by the two ambient cisterns anterolaterally, the velum interpositum cistern from the front, and the cistern of the corpus callosum from anterior-superior direction. The vermis of the cerebellum is found posteriorly and inferiorly. This cistern contains the four colliculi of the mesencephalon, the pineal body, the origin of the trochlear nerve, the posterior cerebral artery, and the medial posterior choroid artery. The two basal veins and the two internal cerebral veins unite here into the great cerebral vein (vein of Galen) which flows into the straight sinus that starts where the tentorial plates meet.
The velum interpositum cistern is actually a crease of the pia mater above the epithelial choroid lamina which makes the roof of the third ventricle. It reaches until the two foramina of Monro in the front, and is bounded laterally by the thalami. The splenium and trunk of the corpus callosum are located above the cistern. Its main structures are the medial posterior choroid artery and the two internal cerebral veins.
IV/1.2.3: Infratentorial cisterns
Here belong the single (unpaired):
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1) interpeduncular cistern,
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2) median pontine cistern,
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3) anterior medullary cistern,
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4) cisterna magna or cerebellomedullary cistern,
and the paired
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5) lateral pontine cistern,
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6) lateral medullary cistern,
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7) superior cerebellar cistern.
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The interpeduncular cistern is bounded by the posterior perforated substance which constitutes the bottom of the interpeduncular fossa, the two mamillarry bodies, and the two cerebral crura posterosuperiorly and laterally. A strong arachnoid membrane fold separates it from the chiasmatic cistern which is called Liliequist membrane after one of its descriptor. It communicates with the crural and ambient cisterns laterally, while it also touches the carotic cistern on the two sides of the chiasmatic cistern. Here we find the bifurcation of the basilary artery with the P1 segment of the two posterior cerebral arteries that origianate from this artery, and the initial segments of the two superior cerebellar arteries. Both oculomotor nerves run at the lateral-superior edge of the cistern, and between their origins are the posterior thalamoperforating arteries and the thalamogeniculate artery.
The median pontine cistern or prepontine cistern is separated from the above by a less remarkable arachnoid membrane septum called anterior pontomesencephalic membrane, and is bilaterally bounded by the lateral pontine cisterns. It contains the longest segment of the basilar artery trunk on the ventral surface of the pons with the origins of the two inferior anterior cerebellary arteries and the pontine arteries. Several descriptions mention the abducent nerve too.
Its caudal neighbour is the anterior medullary cistern (premedullary cistern), which communicates with the lateral medullary cisterns laterally and the (anterior) spinal cistern – laying in front of the spinal cord – caudally. Its main structures are the anterior spinal arteries that run on the ventral surface of the medulla oblongata.
The lateral medullary cistern (or lateral cerebellomedullary cistern or inferior cerebellopontine cistern) contains the two vertebral arteries, the origin of the inferior posterior cerebellar artery and the hypoglossal, glossopharyngeal, vagus and accessory nerves that leave the medulla in the preolivary and postoilvary sulci.
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