Meninges, Venous Sinuses, & Cranial Circulation

Branches from the ophthalmic vein drain into the ophthalmic vein which drains into the cavernous sinus. The intercavernous sinus joins the cavernous sinus around the sella turcica. Blood drains from the cavernous sinus through several routes, two of which are shown. The first route shown is via the superior petrosal sinus which joins the transverse sinus to empty into the sigmoid sinus. The second route shown is via the inferior petrosal sinus. In addition to receiving blood from the cavernous sinus, the inferior petrosal sinus drains cerebellar veins, and veins from the internal ear and brainstem. The basilar sinus joins the two inferior petrosal sinuses. The inferior petrosal sinus drains into the jugular vein (like the sigmoid sinus). You may notice in gross lab that there will be a dominant transverse sinus which will receive the drainage from the superior sagittal sinus.

Branches from the ophthalmic vein drain into the __________ which drains into the __________. The __________ joins the cavernous sinus around the __________. Blood drains from the cavernous sinus through several routes. The first route shown is via the __________ which joins the transverse sinus to empty into the sigmoid sinus. The second route shown is via the _________. In addition to receiving blood from the cavernous sinus, the inferior petrosal sinus drains cerebellar veins, and veins from the internal ear and brainstem. The __________ joins the two inferior petrosal sinuses. The inferior petrosal sinus drains into the __________ (like the sigmoid sinus). You may notice in gross lab that there will be a dominant transverse sinus which will receive the drainage from the superior sagittal sinus.

Dural partitions are formed by the meningeal layer of the dura mater. The dural partitions project into the cranial cavity and partially subdivide the cranial cavity. They include the falx cerebri, tentorium cerebelli, falx cerebelli, and diaphragma sellae. The falx cerebri is a crescent-shaped downward projection of meningeal dura mater from the dura lining the calva that passes between the two cerebral hemispheres. The tentorium cerebelli is a horizontal projection of the meningeal dura mater that covers and separates the cerebellum in the posterior cranial fossa from the posterior parts of the cerebral hemispheres. The anterior and medial borders of the tentorium cerebelli are free, forming an oval opening in the midline (the tentorial notch), through which the midbrain passes. The falx cerebelli is a small sickle shaped fold of dura mater, projecting forwards into the posterior cerebellar notch as well as projecting into the vallecula of the cerebellum between the two cerebellar hemispheres. The final dural projection is the diaphragma sellae. This small horizontal shelf of meningeal dura mater covers the hypophyseal fossa in the sella turcica of the sphenoid bone. There is an opening in the center of the diaphragma sellae through which passes the infundibulum, connecting the pituitary gland with the base of the brain and any accompanying blood vessels.

Dural partitions are formed by the __________ layer of the dura mater. The dural partitions project into the cranial cavity and partially subdivide the cranial cavity. They include the falx cerebri, tentorium cerebelli, falx cerebelli, and diaphragma sellae. The __________ is a crescent-shaped downward projection of meningeal dura mater from the dura lining the calva that passes between the two cerebral hemispheres. The __________ is a horizontal projection of the meningeal dura mater that covers and separates the cerebellum in the posterior cranial fossa from the posterior parts of the cerebral hemispheres. The anterior and medial borders of the tentorium cerebelli are free, forming an oval opening in the midline (the tentorial notch), through which the midbrain passes. The __________ is a small sickle shaped fold of dura mater, projecting forwards into the posterior cerebellar notch as well as projecting into the vallecula of the cerebellum between the two cerebellar hemispheres. The final dural projection is the __________. This small horizontal shelf of meningeal dura mater covers the hypophyseal fossa in the __________ of the sphenoid bone. There is an opening in the center of the diaphragma sellae through which passes the __________, connecting the __________ with the base of the brain and any accompanying blood vessels.

Along the carotid artery, as you age, some people develop plaques/calcifications within their arteries. This is referred to as carotid stenosis. As the artery becomes more stenotic, it leads to a higher potential for blood clots and plaques breaking off into the brain and causing strokes. Carotid stenosis can be auscultated using the bell of your stethoscope. You will hear a bruit if carotid stenosis is present.

Explain what carotid stenosis is and how to check for it.

No. 1 - dura mater 2 - arachnoid mater 3 - superior sagittal sinus

Is dura matter present in this image?

Yes. 1 - inner dura 2 - outer dura

Is dura matter present in this image?

The pia mater covers the brain. Between the pia mater and the arachnoid mater is the subarachnoid space. Within the subarachnoid space are cerebral arteries and veins and cerebral spinal fluid. The meningial layer of the dura mater lies in direct contact with the arachnoid mater. The meningial layer of the dura mater forms the dural partitions as well as the dural sinuses. Bridging veins connect the cerebral veins to the dural sinuses. Arachnoid granulations drain CSF from the subarachnoid space.

The __________ mater covers the brain. Between the pia mater and the arachnoid mater is the __________. Within the subarachnoid space are __________. The __________ layer of the dura mater lies in direct contact with the arachnoid mater. The __________ layer of the dura mater forms the dural partitions as well as the dural sinuses. __________ connect the cerebral veins (found in the subarachnoid space) to the dural sinuses. __________ drain CSF from the subarachnoid space.

The arachnoid mater is a thin, avascular membrane that lines, but is not adherent to, the inner surface of the dura mater. From its inner surface thin processes or trabeculae extend downward, cross the subarachnoid space, and become continuous with the pia mater.

The __________ mater is a thin, avascular membrane that lines, but is not adherent to, the inner surface of the dura mater. From its inner surface thin processes or trabeculae extend downward, cross the subarachnoid space, and become continuous with the pia mater.

The pia mater is a thin, delicate membrane that closely invests the surface of the brain. It follows the contours of the brain, entering the grooves and fissures on its surface, and is closely applied to the roots of the cranial nerves at their origins.

The __________ mater is a thin, delicate membrane that closely invests the surface of the brain. It follows the contours of the brain, entering the grooves and fissures on its surface, and is closely applied to the roots of the cranial nerves at their origins.

The brain, as well as the spinal cord, is surrounded by three layers of membranes called the meninges. They consist of a tough outer layer referred to as the dura mater, a delicate middle layer referred to as the arachnoid mater, and an inner layer firmly attached to the surface of the brain referred to as the pia mater.

The brain, as well as the spinal cord, is surrounded by three layers of membranes called the __________. They consist of a tough outer layer referred to as the __________ mater, a delicate middle layer referred to as the __________ mater, and an inner layer firmly attached to the surface of the brain referred to as the __________ mater.

The cranial dura mater is a thick, tough, outer covering of the brain. It consists of an outer periosteal layer and an inner meningeal layer: ▪ The outer endosteal/periosteal layer is firmly attached to the skull, is the periosteum of the cranial cavity, contains the meningeal arteries, and is continuous with the periosteum on the outer surface of the skull at the foramen magnum and other intracranial foramina. ▪ The inner meningeal layer is in close contact with the arachnoid mater and is continuous with the spinal dura mater through the foramen magnum. The two layers of dura separate from each other at numerous locations to form two unique types of structures: 1) dural partitions, which project inward and incompletely separate parts of the brain 2) intracranial venous structures (dural sinuses)

The cranial __________ mater is a thick, tough, outer covering of the brain. It consists of an outer __________ layer and an inner __________ layer: ▪ The outer endosteal/periosteal layer is firmly attached to the __________, is the periosteum of the cranial cavity, contains the meningeal arteries, and is continuous with the periosteum on the outer surface of the skull at the foramen magnum and other intracranial foramina. ▪ The inner meningeal layer is in close contact with the __________ and is continuous with the spinal dura mater through the foramen magnum. The two layers of dura separate from each other at numerous locations to form two unique types of structures: 1) __________, which project inward and incompletely separate parts of the brain 2) __________

The scalp is drained through superficial veins. The superficial veins connect to emissary veins which drain through the osteum, joining with diploic veins. Emissary veins then drain into the dural sinuses. Because the veins of the head are valveless, infections of the scalp can spread to the diploic portion of the cranial vault as well as the dural sinuses via emissary veins.

The scalp is drained through __________ veins. These __________ veins connect to __________ veins which drain through the osteum, joining with __________ veins. Emissary veins then drain into the __________. Because the veins of the head are __________less, infections of the scalp can spread to the diploic portion of the cranial vault as well as the dural sinuses via __________ veins.

The structures inside and beside the cavernous sinus and their relative positions can be recalled with the following mnemonic: O TOM CAT Consider a coronal view of the cavernous sinus. 'O TOM' are the first letters of components of the lateral wall of cavernous sinus considered vertically, from the top to the bottom. CA are the first letters of the structures located within the sinus. CA continues virtually at the level of the T of 'O TOM'. So that the T represents the point of conjunction of the two words. Mnemonic O: oculomotor nerve T: trochlear nerve O: ophthalmic branch of trigeminal nerve M: maxillary branch of trigeminal nerve C: internal carotid artery A: abducens nerve T: trochlear nerve Remember two things: 1) The mandibular branch of the trigeminal nerve is not associated with the cavernous sinus since it has descended vertically through the foramen ovale underneath the trigeminal ganglion (Gasser ganglion), which is anatomically posteriorly to the cavernous sinus 2) The maxillary branch of the trigeminal nerve is external but immediately adjacent to the lateral wall of the cavernous sinus, which becomes important in the differential diagnosis of lesions of the cavernous sinus - lesions of this nerve tends to distort the sinus rather than occupy it

The structures inside and beside the cavernous sinus and their relative positions can be recalled with the following mnemonic: __________ Consider a coronal view of the cavernous sinus. 'O TOM' are the first letters of components of the lateral wall of cavernous sinus considered vertically, from the top to the bottom. CA are the first letters of the structures located within the sinus. CA continues virtually at the level of the T of 'O TOM'. So that the T represents the point of conjunction of the two words. Mnemonic O: __________ T: __________ O: __________ M: __________ C: __________ A: __________ T: __________ Remember two things: 1) The mandibular branch of the trigeminal nerve is not associated with the cavernous sinus since it has descended vertically through the foramen ovale underneath the trigeminal ganglion (Gasser ganglion), which is anatomically posteriorly to the cavernous sinus 2) The maxillary branch of the trigeminal nerve is external but immediately adjacent to the lateral wall of the cavernous sinus, which becomes important in the differential diagnosis of lesions of the cavernous sinus - lesions of this nerve tends to distort the sinus rather than occupy it

The superior sagittal sinus is in the superior border of the falx cerebri. It begins anteriorly at the foramen cecum, where it may receive a small emissary vein from the nasal cavity, and ends posteriorly in the confluence of sinuses, usually bending to the right to empty into the right transverse sinus.The superior sagittal sinus usually receives cerebral veins from the superior surface of the cerebral hemispheres, diploic and emissary veins, and veins from the falx cerebri. The inferior sagittal sinus is in the inferior margin of the falx cerebri. It receives a few cerebral veins and veins from the falx cerebri, and ends posteriorly at the anterior edge of the tentorium cerebelli. The straight sinus continues posteriorly along the junction of the falx cerebri and the tentorium cerebelli and ends in the confluence of sinuses, usually bending to the left to empty into the left transverse sinus. The straight sinus usually receives blood from the inferior sagittal sinus, cerebral veins (from the posterior part of the cerebral hemispheres), the great cerebral vein (draining deep areas of the cerebral hemispheres), superior cerebellar veins, and veins from the falx cerebri. The superior sagittal and straight sinuses, and the occipital sinus (in the falx cerebelli) empty into the confluence of sinuses, which is a dilated space at the internal occipital protuberance and is drained by the right and left transverse sinuses. The paired transverse sinuses extend in horizontal directions from the confluence of sinuses where the tentorium cerebelli joins the lateral and posterior walls of the cranial cavity. The right transverse sinus usually receives blood from the superior sagittal sinus and the left transverse sinus usually receives blood from the straight sinus. The transverse sinuses also receive blood from the superior petrosal sinus, veins from the inferior parts of the cerebral hemispheres and the cerebellum, and diploic and emissary veins. As the transverse sinuses leave the surface of the occipital bone, they become the sigmoid sinuses, which turn inferiorly, grooving the parietal, temporal, and occipital bones, before ending at the beginning of the internal jugular veins. The sigmoid sinuses also receive blood from cerebral, cerebellar, diploic, and emissary veins.

The superior sagittal sinus is in the superior border of the __________. It begins anteriorly at the foramen cecum, where it may receive a small emissary vein from the nasal cavity, and ends posteriorly in the __________, usually bending to the right to empty into the _________. The superior sagittal sinus usually receives cerebral veins from the superior surface of the cerebral hemispheres, diploic and emissary veins, and veins from the falx cerebri. The inferior sagittal sinus is in the inferior margin of the __________. It receives a few cerebral veins and veins from the falx cerebri, and ends posteriorly at the anterior edge of the __________. The __________ continues posteriorly along the junction of the falx cerebri and the tentorium cerebelli and ends in the confluence of sinuses, usually bending to the left to empty into the __________. The straight sinus usually receives blood from the inferior sagittal sinus, cerebral veins (from the posterior part of the cerebral hemispheres), the great cerebral vein (draining deep areas of the cerebral hemispheres), superior cerebellar veins, and veins from the falx cerebri. The superior sagittal and straight sinuses, and the occipital sinus (in the falx cerebelli) empty into the __________, which is a dilated space at the internal occipital protuberance and is drained by the right and left transverse sinuses. The paired transverse sinuses extend in horizontal directions from the confluence of sinuses where the __________ joins the lateral and posterior walls of the cranial cavity. The right transverse sinus usually receives blood from the __________ and the left transverse sinus usually receives blood from the _________. The transverse sinuses also receive blood from the _________, veins from the inferior parts of the cerebral hemispheres and the cerebellum, and diploic and emissary veins. As the transverse sinuses leave the surface of the occipital bone, they become the __________, which turn inferiorly, grooving the parietal, temporal, and occipital bones, before ending at the beginning of the __________. The sigmoid sinuses also receive blood from cerebral, cerebellar, diploic, and emissary veins.

The two main arteries that supply the cranial circulation are the vertebral arteries and the carotid arteries. The vertebral arteries come from the subclavian artery bilaterally. The left common carotid artery comes directly off of the aorta, while the right common carotid artery comes off of the braciocephalic trunk (which comes off of the aorta). The vertebral arteries enter the skull via foramen magnum. To do so, they turn at a sharp angle between the transverse foramina of C1 and the foramen magnum. The internal carotid arteries enter the skull via the carotid canal. Once through the carotid canal, the internal carotid enters the cavernous sinus. All of these arteries eventually end up at the Circle of Willis. This structure perfuses the brain via several arteries that branch from it.

The two main arteries that supply the cranial circulation are the __________ arteries and the __________ arteries. Where do these arteries come from? Where do these arteries enter the skull? Where do all of these arteries eventually end up at?

There are two "potential spaces" formed around the meninges: -the epidural space which lies between the periosteal portion of the dura mater and the bone of the cranium -the subdural space which lies between the meningeal portion of the dura mater and the arachnoid mater Two "real spaces" exist between specific meninges: -sinuses are formed by space between the endosteal and meningeal layers of the dura mater -there is also a "real space" formed between the arachnoid mater and the pia mater. The subarachnoid space contains cerebral spinal fluid (CSF) and blood vessels. The CSF returns to the venous system through arachnoid villi . These project as clumps ( arachnoid granulations ) into the superior sagittal sinus, which is a dural venous sinus

There are two "potential spaces" formed around the meninges: -the __________ space which lies between the periosteal portion of the dura mater and the bone of the cranium -the __________ space which lies between the meningeal portion of the dura mater and the arachnoid mater Two "real spaces" exist between specific meninges: -__________ are formed by space between the endosteal/periosteal and meningeal layers of the __________ mater -there is also a "real space" formed between the arachnoid mater and the pia mater. The subarachnoid space contains __________ and __________. The CSF returns to the venous system through arachnoid villi . These project as clumps ( arachnoid granulations ) into the superior sagittal sinus, which is a dural venous sinus

Mnemonic: SEDMD ASPC 1 - endosteal/periosteal layer of dura mater 2 - meningeal layer of dura mater 3 - dural partition 4 - scalp 5 - dura mater 6 - cranial vault 7 - arachnoid mater 8 - subarachnoid space 9 - blood vessels and CSF 10 - pia mater 11 - cerebrum

Utilize the mnemonic to remember these layers.

Venous drainage of the brain begins internally as networks of small venous channels lead to larger cerebral veins, cerebellar veins, and veins draining the brainstem, which eventually empty into dural venous sinuses. The dural venous sinuses are endothelial-lined spaces between the outer periosteal and the inner meningeal layers of the dura mater, and eventually lead to the internal jugular veins.

Venous drainage of the brain begins internally as networks of small venous channels lead to larger cerebral veins, cerebellar veins, and veins draining the brainstem, which eventually empty into __________ . The dural venous sinuses are endothelial-lined spaces between the outer __________ and the inner __________ layers of the __________ mater, and eventually lead to the ____________.

Venous drainage of the cranium can be divided into two parts: 1. Drainage of the subarachnoid space which contains __________ (in the cerebrum), __________ (in the cerebellum) and __________ (which coats the entire brain). 2. Drainage of the scalp and diploic portion of the cranial vault bone. The _________ portion of the cranial vault is cancellous flat bone, containing red bone marrow. It is __________.

Venous drainage of the cranium can be divided into two parts: 1. Drainage of the subarachnoid space which contains cerebral veins (in the cerebrum), cerebellar veins (in the cerebellum) and cerebral spinal fluid (which coats the entire brain). 2. Drainage of the scalp and diploic portion of the cranial vault bone. The diploic portion of the cranial vault is cancellous flat bone, containing red bone marrow. It is hematopoetic.

Very important to know: Running through the cavernous sinus are: The internal carotid artery (along with the sympathetic plexus). and CN's III, IV, V1, V2, and VI. These nerves innervate the eye and eye adnexa. The cavernous sinus drains cerebral and ophthalmic veins, sphenoparietal sinuses, and emissary veins from pterygoid plexus of veins. The spread of infection into the cavernous sinus can result in many clinically significant issues including abnormal blood flow to the brain (internal carotid artery) and abnormal eye movements. CN VI and the internal carotid a. run within the cavernous sinus. III, IV, V1, and V2 form the wall of the cavernous sinus. The floor of the cavernous sinus contains the foramen lacerum, foramen ovale, and foramen rotundum.

Very important to know: Running through the cavernous sinus are: The internal carotid artery (along with the sympathetic plexus). and CN's III, IV, V1, V2, and VI. These nerves innervate the ________________________________. The __________ drains cerebral and ophthalmic veins, sphenoparietal sinuses, and emissary veins from pterygoid plexus of veins. The spread of infection into the cavernous sinus can result in many clinically significant issues including abnormal blood flow to __________ (internal carotid artery) and abnormal __________. __________ and __________ run within the cavernous sinus. CNs __________ form the wall of the cavernous sinus. The floor of the cavernous sinus contains the foramen ___________, foramen __________, and foramen __________.

The vertebral arteries enter the skull via foramen magnum. To do so, they turn at a sharp angle between the transverse foramina of C1 and the foramen magnum. Doing HVLA on an extended neck could put a lot of strain and torsion on those arteries. This can cause a stroke and even kill a patient.

Why should you not do high velocity low amplitude (HVLA) on an extended spine?

Cavernous sinus tumors are the most common cause of cavernous sinus syndrome. Tumors may be primary or may arise from either local spread or as metastases. The danger triangle of the face consists of the area from the corners of the mouth to the bridge of the nose, including the nose and maxilla. A patient may present with a sore that will not heal within the danger triangle, and then will eventually present with eye deficits. Upon eye examination, you will uncover deficits due to the nerves that run through the cavernous sinus. Understand that the eyes are the windows to the soul. You can tell a lot about a patient from an eye exam alone.

__________ are the most common cause of cavernous sinus syndrome. Tumors may be primary or may arise from either local spread or as metastases. The danger triangle of the face consists of the area from __________, including the nose and maxilla. A patient may present with a sore that will not heal within the danger triangle, and then will eventually present with __________ deficits. Upon eye examination, you will uncover deficits due to the __________. Understand that the __________ are the windows to the soul. You can tell a lot about a patient from an __________ exam alone.