Meninges, Ventricles and CSFNeuroanatomy block-Anatomy-Lecture 19

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01 Describe the cerebral meninges & list the main dural folds.

02 Describe the spinal meninges & locate the level of the termination of each of them.

03 Describe the importance of the subarachnoid space.

04 List the Ventricular system of the CNS and locate the site of each of them.

05 Describe the formation, circulation, drainage, andfunctions of the CSF.

06 Know some clinical point about the CSF.

Color guide ● Only in boys slides in Green● Only in girls slides in Purple● important in Red● Notes in Grey

At the end of the lecture, students should be able to:

Objectives

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MeningesThe brain and spinal cord are invested by three concentric membranes:

Pia Mater The innermost layer.

Dura MaterThe outermost layer.

Arachnoid MaterThe middle layer.

Dura MaterThe cranial dura is a two layered tough, fibrous thick membrane that surrounds the brain.

Formed of two layers

periosteal :attached to the skull. meningeal :is folded forming the dural folds : Two large reflection of dura extend into the cranial cavity:

Sensory innervation of the dura mater: is mostly from : meningeal branches of the: trigeminal and vagus nerves & C1 to C3.

Falx cerebri:-It is a vertical sickle shaped sheet of dura, in the midline.-Extends from the cranial roof into the great longitudinal fissure between the two cerebral hemispheres. -It has an attached border adherent to the skull and a free border lies above the corpus callosum.

Tentorium cerebelli:-A horizontal shelf of dura, lies between the posterior part of the cerebral hemispheres and the cerebellum. -It has a free border that encircles the midbrain. -Its superior surface in the middle line it is continuous above with the falx cerebri, separated by straight sinus.

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Arachnoid Mater & Pia MaterArachnoid Mater

- It is a soft, translucent membrane loosely envelops the brain.

- It is separated from the dura by a narrow subdural space.

Pia Mater - It is the innermost, thin, delicate & highly vascular

membrane that is closely adherent to the gyri and fitted into the sulci.

Between the pia and arachnoid mater lies the subarachnoid space which contains; fibrous trabeculae, main blood vessels and CSF.

Subarachnoid SpaceThe subarachnoid space is varied in depth forming; subarachnoid cisterns.

01Cisterna magna, or

cerebllomedullary cistern:

● lies between the inferior surface of thecerebellum and the back of the medulla.

● At this cistern CSF flows out of the fourth ventricle via the 2 lateral aperture and median aperture.

02 Interpeduncular cistern:● Is located at the base of the brain, where the arachnoid

spans between the two cerebral peduncles of midbrain.● It contains the optic chiasma & circulus arteriosus of

Wills .

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Spinal Meninges

● Spinal cord terminates at level L1-L2. ● The dura and arachnoid and, subarachnoid space, continue caudally to S2. ● Pia extends downwards forming the filum terminale which pierces the arachnoid and dural

sacs and passes through the sacral hiatus (11) to be attached to the back of the coccyx.● The spinal cord, is invested by three meningeal coverings:

Meningeal coverings

Dura Mater Pia mater

-The innermost covering, is a delicate fibrous membrane

closely envelops the cord and nerve roots.

-It is attached through the arachnoid to the dura by the

denticulate ligament.

-is a translucent membrane lies between the pia and dura, -Between arachnoid and pia lies the subarachnoid space

contains CSF.

-The outer covering; is a thick, tough fibrous membrane.

-It envelopes the cord loosely. -It is separated from

arachnoid mater by the subdural space, and from the

bony wall of the vertebral canal by the epidural space.

Arachnoid Mater

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Ventricular System1. Interconnecting channels within the CNS. 2. In the spinal cord; represented by the central canal. 3. Within the brain; a system of ventricles is found. 4. The central canal of the spinal cord is continuous upwards to the fourth ventricle. 5. On each side of the fourth ventricle laterally, lateral recess extend to open into lateral aperture (2 foramen of Luschka),

central defect in its roof (1 foramen of Magendie).6. The fourth ventricle is continuous up with the cerebral aqueduct, that opens in the third ventricle. 7. The third ventricle is continuous with the lateral ventricle through the interventricular foramen (foramen of Monro).

lateral recess

● Present in the ventricular system, together with the cranial and spinal subarachnoid spaces.● It is colourless clear fluid containing little protein and few cells. It is about 150 ml.● It acts as a cushion for the brain from sudden movements of the head.● It’s circulates in the subarachnoid space.

Cerebrospinal Fluid

It is produced by the (1) choroid plexus, which is located in the lateral, third & fourth ventricles.

From (2) lateral ventricle it flows: through the (3) interventricular foramen or foramen of monro into the (4) 3rd ventricle and, by way of the (5) cerebral aqueduct (aqueduct of sylvius), into the (6) 4th ventricle.

It leaves the ventricular system through the three apertures of the 4th ventricle ( 7) median foramen of Magendie & (8) 2 lateral foramina of Luschka, to enters the subarachnoid space.

Reabsorbed finally into the venous system along (9) arachnoid villi, and arachnoid granulation (larger than villi) that project into the dural venous sinuses , mainly (10)superior sagittal sinus.

1

2

3

45

6

7

foramina of Luschka8

7

01

02

03

04

109 Arachnoid villi

Clinical point

The obstruction of the flow of CSF leads to a rise in fluid pressure causing swelling of the ventricles (hydrocephalus).

Causes

Congenital Acquired

( Arnold-Chiarimalformation).

Stenosis of the cerebral aqueduct by tumor of pineal

region.

Obstruction of the interventricular foramina

secondary to tumors, hemorrhages or infectious such

as meningitis

Hydrocephalus shunt

Decompression of the dilated ventricles is achieved by inserting a shunt connecting the ventricles to the jugular vein or the abdominal peritoneum.

Cerebrospinal Fluid flow diseases

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Practice Q1: The subarachnoid space terminates at:

A. Coccyx

B. L1-L2

C. S2

D. S1

Q2: The CSF is about:

A.50 ml

B. 150 ml

C. 250ml

D. 300 ml

Q3: cerebrospinal fluid is produced by:

A. 3rd ventricle

B. Choroid plexus

C. Lateral ventricle

D. 4th ventricle

Q4: which layer of dura mater that form falx cerebri and tentorium cerebelli ?

A. meningeal layer

B. pia mater layer

C. periosteal layer

D. subarachnoid layer

Q5: the CSF flows through foramen of monro (interventricular foramen) from (...) to (...)

A. Cerebral aqueduct , 3rd ventricle

B. 4th ventricle , central canal

C. 3rd ventricle, lateral ventricle

D. Lateral ventricle, 3rd ventricle

Q6: which one of these does not supply the dura mater ?

A. Facial

B. vagus

C. C1-C3

D. Trigeminal

Q7: the Cisterna magna is between ?

A. posterior surface of the cerebellum and the back of the medulla

B. cerebrum and the back of the medulla

C. at the base of the brain between the two cerebral peduncles of midbrain

D. inferior surface of the cerebellum and the back of the medulla

Q8 : hydrocephalus shunt is connecting the ventricles to

A. Carotid artery

B. jugular vein

C. Abdominal peritoneum

D. B & C

Answers: Q1(C) Q2(B) Q3(B) Q4(A) Q5(D) Q6(A) Q7(D) Q8(D) 9

Girls team :

● Ajeed Al Rashoud● Taif Alotaibi● Noura Al Turki● Amirah Al-Zahrani● Alhanouf Al-haluli● Sara Al-Abdulkarem● Renad Al Haqbani● Nouf Al Humaidhi● Jude Al Khalifah● Nouf Al Hussaini● Rahaf Al Shabri● Danah Al Halees● Rema Al Mutawa● Amirah Al Dakhilallah● Maha Al Nahdi ● Razan Al zohaifi ● Ghalia Alnufaei

Boys team:

● Mohammed Al-huqbani (legend)- LR

● Salman Alagla● Ziyad Al-jofan● Ali Aldawood● Khalid Nagshabandi● Omar Alammari● Sameh nuser● Abdullah Basamh (ily) -lecture reviewer

● Alwaleed Alsaleh● Mohaned Makkawi● Abdullah Alghamdi

Team leaders

● Ateen Almutairi● Abdulrahman Shadid

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