Exam #1: Meninges, Ventricles, and CSF Flashcards
What three layers of the meningies?
Dura mater
Arachnoid mater
Pia mater
What are the two layers of the dura mater? What are the major differences between the two layers?
Periosteal
- Forms connective tissue sheaths around the cranial nerves
- Has a rich vascular supply
Meningeal
- No vascular supply
- In intimate contact with the arachnoid mater
How does the periosteal dura adhere to the skull?
Sharpie’s Fibers
Where does the meningeal artery lay in relation to the two layers of the dura?
The middle meningeal artery supplies the outer/periosteal layer with blood
Which layer of the dura dives into the fissures of the brain? What is the consequence?
- Meningeal layer dives into the fissures of the brain (not the sulci)
- Separation between the periosteal & meningeal layers forms the dural venous sinuses
What is the epidural space?
Potential interface between the bone & the periosteal dura
*****I.e. an epidural bleed is between the periosteal dura & bone
What is the subdural space?
Space between the meningeal dura & the arachnoid mater
What type of bleed is associated with an epidural & subdural hematoma?
Epidural= arterial Subdural= venous
What happens when there is a tear in the superior sagital sinus?
- Epidural hematoma
- “Lens shaped”
- Crosses both hemispheres
In a subdural hematoma, what prevents blood from crossing hemispheres?
Falx cerebri
What is the shape of a subdural hematoma?
“Sickle shaped”
What is the falx cerebri?
Reflection of the meningeal layer of the dura on itself that separates the right & left cerebral hemispheres
What are the attachments of the falx cerebri?
- Crista galli
- Tentorium cerebelli that extends to the internal occipital protuberence
What does the tentorium cerebelli separate?
This is a horizontal reflection of the meningeal layer of the dura that separates the cerebellum & occipital lobes of the cerebrum
What does the falx cerebelli separate?
Small reflection of the meningeal layer of the dura that separates the cerebellar hemispheres
What is the tentorial notch?
Anterior opening between the free edge of the tentorium cerebelli and the clivus for the passage of the brainstem
*****Note that this is also called the tentorial incisure
Where are the dural venous sinuses?
In the space between the periosteal & meningeal dura
What is the superior sagittal sinus?
This is the largest dural venous sinus that is contained within the falx cerebri; it ends in the confluence of sinuses posteriorly
Review the anatomy of the dural venous sinuses.
N/A
Clinically, what is important to remember about the sinues?
Sinuses do NOT have valves; thus, it is easy for them to transmit infection
How does the arachnoid mater appear on the brain? What is important to remember about the arachnoid mater?
Clear cling wrap
**Does NOT enter the sulci
What are the arachnoid trabeculae?
Delicate strands of connective tissue that loosely connect the two innermost layers of the meninges – the arachnoid mater and the pia mater.
What is the subarachnoid space?
Space between the arachnoid mater & the pia mater; note that arachnoid trabeculae are found within this space
*****This is the space occupied by CSF
What are the subarachnoid cisterns?
The arachnoid mater does not closely follow the contours of the brain; thus, there are places where a space is created between the pia mater & overlying arachoid mater–these spaces are called “subarachnoid cisterns”
What is the interpeduncular cistern?
This is the subarachnoid cistern between the two cerebral peduncles
What CN emergnes from the interpeduncular cistern?
CN III
What are the arachnoid villi? What is their function?
Specialized evaingations of the arachnoid mater that extend into the lumen of the dura; these help to expunge excess CSF from the brain & dump it into the sinuses
What structure produces CSF?
Choroid plexus
What layer of the meninges is closest to the brain?
Pia mater
What are the ventricles of the brain?
Spaces in the brain that generate CSF
How many ventricles are there?
- 2x lateral
- 3rd
- 4th
Describe the flow of CSF.
Lateral ventricles Interventricular foramen of monro 3rd ventricles Cerebral aqueduct 4th ventricle
What are the different parts of the lateral ventricle?
1) Body
2) Four horns
What forms the walls of the 3rd ventricle?
Thalamus
What is the narrowest part of the ventricular system?
Cerebral aqueduct
Where is the 4th ventricle?
Between cerebellum posteriorly & pons/ rostural medualla anteriorly
What is the lateral apeture or foramen of Luschka?
Lateral opening of the 4th ventricle that open into the subarachnoid space
What is the median aperture/ foramen of magendie?
This the middle opening of the 4th ventricle that opens into the subarachnoid space
What is the function of CSF?
- Support
- Control of ECF
- Provides route for neuroactive hormones
Should you see RBC in CSF?
NO
**Indication of a hemorrhage somewhere
What supplies blood to the choroid plexus?
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Describe how blood is filtered in the choroid plexus to leave CSF.
Pressure through tight junctions that function as filter–>CSF= plasma
What is the blood brain barrier?
Anatomical & physiologic complex that controls movement of substances from general extracellular fluid
- Tight junctions at many levels
Where is the TRUE blood brain barrier?
Pia mater that contains perivascular glia (astrocytes) that limit the movement of substances
What should the physician suspect when a patient complains of fever accompanied by photophobia?
Meningitis or encephalitis (infection of the meninges vs. brain parenchyma)
Why is stiff neck an important sign of meningitis?
Patients want to limit movement of the neck to prevent movement of the meninges
What is first line treatment for suspected meningitis?
Antibiotics–meningitis confirmed with lumbar puncture (elevated protein & WBC) should be empirically treated with broad-spectrum antibiotics
