Dural Sinuses, Meninges, & Vasculature Flashcards
These are three dense regular CT layers that separate the soft tissue of the brain from the bones of the cranium.
Cranial Meninges
The Cranial Meninges enclose and protect _______ ______ that supply the brain, and contain and circulate _______.
Blood vessels
CSF
Parts of the Cranial Meninges form some of the _______ that drain blood from the brain.
Veins
From superficial to deep, the Cranial Meninges are…
Dura Mater
Arachnoid Mater
Pia Mater
Put the following layers correctly in order, from superficial to deep:
A. Pia Mater B. Arachnoid Mater C. Periosteal Dura Mater D. Scalp E. Cerebral Cortex F. Meningeal Dura Mater G. Subarachnoid Space H. Skull
1) D
2) H
3) C
4) F
5) B
6) G
7) A
8) E
The Dura Mater has two sub-layers, which are…
Periosteal Layer (Superficial; touching skull) Meningeal Layer (Deep; touching Arachnoid Mater)
This is the strongest of the meninges.
Dura Mater
In the Dura Mater, the meningeal layer is usually fused to the periosteal layer, except in specific areas where the two layers separate to form large, blood-filled spaces called…
Dural Venous Sinuses
These veins drain from the scalp to the Dural Venous Sinuses.
Emissary V.
These veins drain from the cerebral cortex to the Dural Venous Sinuses.
Bridging V.
The Arachnoid Mater lies immediately internal to the Dura Mater and is partially composed of a delicate web of collagen and elastic fibers called the…
Arachnoid Trabeculae
This is a “potential space” between the Arachnoid and the Dura Mater. It is not normally present, but can be present if something goes wrong.
Subdural Space
The Subarachnoid Space is immediately deep to the Arachnoid, and this spaces houses…
CSF
These exist in the Subarachnoid Space, and if there is an aneurysm it can cause bleeding into the space.
Cerebral As.
What are 2 reasons the Subdural Space could be present?
1) Bleeding from Bridging V. (pass through space to get to Dural Venous Sinus).
2) Following lumbar puncture, can create negative pressure and pull down the Arachnoid Mater causing the space.
This is the most fragile layer of the meninges, and it directly overlays the brain (follows all curves of brain).
Pia Mater
The Meningeal Layer of the Dura Mater extends as flat partitions (septa) deep into the cranial cavity at four locations, called…
Cranial Dura Septa
The Cranial Dural Septa are membranous partitions that separate specific parts of the brain and provide additional stabilization and support to the entire brain. These septa are…
Falx Cerebri
Tentorium Cerebelli
Falx Cerebelli
Diaphragma Sellae
Within the Cranial Dura Septa are Dural Venous Sinuses, such as…
Superior Sagittal Sinus Inferior Sagittal Sinus Straight Sinus Sigmoid Sinus Transverse Sinus
This Cranial Dural Septa is in the horizontal plane and separates the Cerebellum from the Cerebrum.
Tentorium Cerebelli
This Cranial Dural Septa is in the sagittal plane and separates the 2 hemispheres of the Cerebrum.
Falx Cerebri
This Cranial Dural Septa is near the Optic Chiasm right around the Pituitary Gland.
Diaphragma Sellae
This Cranial Dural Septa is in the sagittal plane and separates the 2 hemispheres of the Cerebellum.
Falx Cerebelli
What provides arterial supply to the meninges?
Middle Meningeal A.
- **External Carotid A. – Maxillary A. – Middle Meningeal A.
- **Supplies ONLY meninges, no brain tissue!
What branches does the Middle Meningeal A. give off?
Parietal (Posterior) Branch
Frontal (Anterior) Branch
What provides innervation to the meninges?
CN V(V1) -- More medial, does anterior and posterior CN V(V2) -- Anterior and lateral to area of V1 CN V(V3) -- Most lateral Cervical Spinal Nerves C2-C3 -- To posterior cranial fossa
This is caused as the result of the Middle Meningeal A. rupturing. This artery runs between the skull and the Dura Mater.
Epidural Hematoma
Why is an Epidural Hematoma often a clinical symptom of someone that gets hit in the side of the head?
The temple area (Pterion) is a very think and weak area of the skull. Directly deep to this, the Middle Meningeal A. runs. If this area is hit, the artery can be damaged and cause an Epidural Hematoma.
Why might people suffering from an Epidural Hematoma not know that something is wrong right away?
There is a period right after injury called the Lucid Interval. During this time the blood is slowly filling in the epidural space and the person will only have a headache and not realize anything is wrong. Eventually, so much blood will fill into the space and cause the brain to herniate somewhere it’s not supposed to.
This is caused by the rupture of Bridging Vs., which go from the cortex to the Dural Venous Sinus. Can present with nausea, vomiting, headache.
Subdural Hematoma
***Occurs in subdural space, which is between Arachnoid and Dura Mater
In what cases are Subdural Hematomas most common?
1) Older people with an acceleration and sudden deceleration injury (i.e., car crash)
2) Shaken baby syndrome
***Bridging Vs. are weak in babies and the elderly!
This is what we consider when we hear it’s the “worst headache of my life”.
Subarachnoid Hemorrhage
What causes a Subarachnoid Hemorrhage?
Aneurysm of a Cerebral A. – The Subarachnoid Space is not prepared for blood, only CSF. This causes problems.
Subarachnoid Hemorrhages are most common in who?
People with hypertension
Postmenopausal women
This presents as a convex lens shape on imaging. The Dura Mater is tightly adhered to suture lines, which is why it has an abrupt stop in the corners (Slide 36).
Epidural Hematoma
This presents as a “crescent” shape. It is below the Dura Mater and has no suture lines to adhere so the lines don’t stop as abruptly.
Subdural Hematoma
This presents as a “spiderweb” near the center of the brain in imaging. Blood pools near the Circle of Willis.
Subarachnoid Hemorrhage
This Dural Venous Sinus drains down and becomes the Internal Jugular V.
Sigmoid Sinus
T/F. Dural Venous Sinuses are groups of veins within the head.
False. They are NOT veins. Look similar but are not veins.
The Superior Ophthalmic V., Inferior Ophthalmic V, and the Facial V. are all on the front of the face. What can occur with these veins if there is an infection near them on the face?
The Facial V. can continue to spread the infection downward or these 3 veins can cause the infection to spread backwards into the Cavernous Sinus.
This helps with drainage from the Cavernous Sinus to the Sigmoid Sinus.
Superior Petrosal Sinus
This helps with drainage from the Basilar Plexus to the Sigmoid Sinus.
Inferior Petrosal Sinus
What is the purpose of the Superior Petrosal Sinus and the Inferior Petrosal Sinus?
To help drain the Cavernous Sinus
What artery lies within the Cavernous Sinus?
Internal Carotid A.
What cranial nerves are within the Cavernous Sinus?
CN III (Oculomotor) CN IV (Trochlear) CN V - V1 (Ophthalmic) CN V - V2 (Maxillary) CN VI - Abducens
What can happen to the cranial nerves if there is infection or thrombosis within the Cavernous Sinus?
They can be compressed and this can cause problems and deficiencies with the functions of these nerves.
What sinuses lie directly below the Cavernous Sinus?
Sphenoid Sinuses
Explain the path of the Internal Carotid A.
Cervical part enters through the external opening of the Carotid Canal, then it becomes the Petrous part. The Petrous part then bends basically 90 degrees anteromedially and becomes the Cavernous part. This part of the ICA is within the Cavernous Sinus. The ICA bends again and moves superiorly and becomes the Cerebral part. The Cerebral part is what will eventually give off the Cerebral As. within the Circle of Willis (that can cause Subarachnoid Hemorrhages).
This is a clear, colorless liquid that circulates in the ventricles and Subarachnoid Space. It bathes the exposed surfaces of the CNS and completely surrounds it.
CSF
What functions does the CSF perform?
Buoyancy
Protection
Environmental stability
CSF is produced by secretion of a fluid from the ________ ________ that originate from the blood plasma.
Ependymal cells
Ependymal cells make up the ________ _______ in each ventricle.
Choroid Plexus
CSF is similar to blood plasma but it has greater amounts of ________, _________, and _________ but less _________.
Sodium
Hydrogen
Calcium
Potassium
What are the main components that protect the brain?
Meninges
Dural Venous Septa
CSF
These are what transfer CSF from the Subarachnoid Space into the Dural Venous Sinuses.
Arachnoid Granulations
Once the CSF drains into the Dural Venous Sinuses, it drains where?
To Internal Jugular V. into the venous system.
When there is blood in the Subarachnoid Space (like in Subarachnoid Hemorrhage from Cerebral A. aneurysm), what does this do to the Arachnoid Granulations?
Arachnoid Granulations can’t filter blood, only CSF. The blood will damage the Granulations and cause them to fibrose. This causes a clog in the system and a buildup of CSF within the ventricles. The ventricles will enlarge and the brain will shrink, which is called Hydrocephalus.
