CRANIAL MENINGES

Rajasri Manimaran

Group 2

Protection of the Brain

• The Skull

• Cranial meninges

• Cerebrospinal fluid

• Blood brain barrier

THE MENINGES

1. Dura Mater - Composed of two layers:a) Periosteal – outer layer, attaches to

bone.

b) Meningeal – inner layer, closer to brain.

Cranial Meninges - 3 layer protective membrane

Two layers fused, except to enclose the dural sinuses

3. Pia Mater - delicate, follows convolutions.

2. Arachnoid Layer - ‘spider’ web like.

Coronal section of the upper part of the head

Endosteal

layer

Meningeal

layer

They are closely

united except

along certain

lines; they are

separated to

form venous

sinuses

Superior sagittal sinus

(Dural venous sinus)Dura mater

Subdural

space

Sagittal section showing the duramater

1) Falx cerebri

2) Tentorium

cerebelli

3) Falx

cerebelli

4) Diaphragma sellae

DURAL NERVE SUPPLY

Branches of the trigeminal, vagus, and first three cervical nerves and branches from the sympathetic system pass to the dura.

The dura is sensitive to stretching, which produces the sensation of headache.

DURAL BLOOD SUPPLY

The middle meningeal artery supplies most of the blood for the dura mater, though the meningeal branches of the posterior and anterior ethmoidalartery also contribute.

ARACHNOID MATER

Subdural spacePotential space between dura and arachnoid

mater.

Cranial Meningeal Spaces Epidural space

Potential space superior to dura.

Subarachnoid spaceFilled with CSF

Contains the blood vessels supplying brain.

SUBARACNOID SPACE Relatively narrow

over the surface of cerebral hemisphere, but sometimes becomes much wider in areas at the base of the brain, the widest space is called subarachnoid cisterns.

Median sagittal section to show the subarachnoid cisterns

& circulation of CSF

Superior

cistern

Interpeduncular

cistern

Cerebellomedullary

cistern

Chiasmatic

cistern

Pontine

cistern

PIA MATER

Pia mater functions to cover and protect the central nervous system (CNS), to protect the blood vessels and enclose the venous sinuses near the CNS, to contain the cerebrospinal fluid (CSF) and to form partitions with the skull.

The CSF, pia mater, and other layers of the meninges work together as a protection device for the brain, with the CSF often referred to as the fourth layer of the meninges.

PATHOLOGYThere are three types of hemorrhage involving the

meninges: An epidural hematoma arise after an accident or

spontaneously A subdural hematoma is a hematoma (collection

of blood) located in a separation of the arachnoid from the dura mater. The small veins that connect the dura mater and the arachnoid are torn, usually during an accident, and blood leaks into this area

A subarachnoid hemorrhage is acute bleeding under the arachnoid; it may occur spontaneously or as a result of trauma.

Other medical conditions that affect the meninges include meningitis (usually from fungal, bacterial, or viral infection) and meningiomas that arise from the meninges, or from meningealcarcinomatoses (tumors) that form elsewhere in the body and metastasize to the meninges.

CRANIAL VENOUS SINUSES

The dural venous sinuses (also called dural sinuses, cerebral sinuses, or cranial sinuses) are venous channels found between layers of dura mater in the brain.

They receive blood from internal and external veins of the brain, receive cerebrospinal fluid (CSF) from the subarachnoid space, and ultimately empty into the internal jugular vein.

Name Drains to

Inferior sagittal sinus Straight sinus

Superior sagittal sinusTypically becomes right transverse

sinus or confluence of sinuses

Straight sinusTypically becomes left transverse sinus

or confluence of sinuses

Occipital sinus Confluence of sinuses

Confluence of sinuses Right and Left transverse sinuses

Sphenoparietal sinuses Cavernous sinuses

Cavernous sinuses Superior and inferior petrosal sinuses

Superior petrosal sinus Transverse sinuses

Transverse sinuses Sigmoid sinus

Inferior petrosal sinus Sigmoid sinus

Sigmoid sinuses Internal jugular vein

ARTERIES TO SPECIFIC BRAIN AREASCorpus striatum Middle & lateral

striate

Anterior &

Middle cerebral

arteryInternal capsule

Thalamus PComA, basilar, PCA

Midbrain PCA, supCerebellarA, basilar

Pons Basilar, Ant, inf, supCerebellarA,

Medulla

oblongata

Vertebral, ASA,PSA,PICA, basilar

Cerebellum supCerebellar, AICA,PICA

BLOOD SUPPLY OF THE BRAIN

VERTEBRAL

Basilar

Posterior cerebral artery

INTERNAL CAROTID

Middle cerebral

Anterior cerebral

Anterior communicating artery

Posterior communicating artery

CIRCLE OF WILLIS

Subarachnoid hemorrhage

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Aneurysm

SYMPTOMS

Headache (sudden onset, greater severity)

Nausea and vomitting

Loss or impairment of consciousness (may progress to coma and death)

Confusion and irritability

Meningial irritation and nuchal rigidity (stiff neck)

Focal neurological deficits (may indicate site of lesions).

DIFFERENTIAL DIAGNOSIS

Meningitis

Migraine

Intracerebral hemorrhage

Ischemic stroke

Grade Signs and symptoms Survival

1Asymptomatic or minimal headache and

slight neck stiffness70%

2

Moderate to severe headache; neck

stiffness; no neurologic deficit

except cranial nerve plasy

60%

3 Drowsy; minimal neurologic deficit 50%

4

Stuporous; moderate to severe

hemiparesis; possibly early decerebrate

rigidity and vegetative disturbances

20%

5 Deep coma; decerebrate rigidity; moribund 10%

Hunt and Hess classification

TREATMENT

Stabilizing patient.

Prevention of rebleeding by obliterating the bleeding source.

prevention of a phenomenon known as vasospasm and,

prevention and treatment of complications.

PREVENTING RE-BLEEDING

Up to 14% of SAH patients may experience re-bleeding within 2 hours of the initial hemorrhage

Re-bleeding was more common in those with a systolic blood pressure >160mm Hg

Anti-fibrinolytic therapy may reduce re-bleeding but has not been shown to improve outcomes

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SURGICAL AND ENDOVASCULARMANAGEMENT OF SAH

Surgery – clip aneurysm baseEndovascular – coilingShould be performed within 2 days of

hemorrhage.

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Clipping

LEFT IMAGE ARROW -ANGIO WITH LARGE ANEURYSM

RIGHT IMAGE ARROW – ANGIO SHOWING ANEURYSM POST CLIPPING

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Angio Image Courtsey: The University of Texas Health Science Center at San Antonio – Department of Neurosurgery

SURGICAL AND ENDOVASCULARMANAGEMENT OF SAH

Combined morbidity and mortality was significantly greater in surgically treated patients than in those treated with endovascular techniques (30.9% vs. 23.5%; absolute risk reduction 7.4%)

During the short follow-up period, the re-bleeding rate for coiling was 2.9% versus 0.9% for surgery

There have been no randomized comparisons of coiling versus clipping for unruptured aneurysms

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Coiling

COIL SYSTEM EMBOLIZATION: IMMEDIATE RESULT 1

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Angio showing large ICA aneurysmSame aneurysm - Post GDC Coiling

Angio Image Courtsey: The University of Texas Health Science Center at San Antonio – Department of Neurosurgery

PREVENTING VASOSPASM

The use of calcium channel blockers, thought to be able to prevent the spasm of blood vessels by preventing calcium from entering smooth muscle cells, has been proposed for the prevention of vasospasm.

The oral calcium channel blocker nimodipine improves outcome if administered between the fourth and twenty-first day after the hemorrhage.

PREVENTING OTHER COMPLICATIONS

If medication don’t help, then angiography may be attempted to identify the sites of vasospasms and administer vasodilator medication (drugs that relax the blood vessel wall) directly into the artery.

Angioplasty (opening the constricted area with a balloon) may also be performed.

SUMMARY AND CONCLUSIONS

The current standard of practice calls for microsurgical clipping or endovascular coiling of the aneurysm neck whenever possible

Treatment morbidity is determined by numerous factors, including patient, aneurysm, and institutional factors

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SUMMARY AND CONCLUSIONS

Favorable outcomes are more likely in institutions that treat high volumes of patients with SAH, in institutions that offer endovascular services, and in selected patients whose aneurysms are coiled rather than clipped

Optimal treatment requires availability of both experienced cerebrovascular surgeons and endovascular surgeons working in a collaborative effort to evaluate each case of SAH

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