The Meninges

THE MENINGES

20-35 days of gestation

34-48 days of

gestation

45- 60 days of gestation

DEVELOPMENT - developed from the cells of the neural crest & mesenchyme (mesoderm) forming the primitive meninges - differentiate into ectomeninx (outer more compact layer) & endomeninx (inner more reticulated layer) - ectomeninx becomes more compact and with spaces (future sinuses) dura mater (pachymeninx); endomeninx becomes more reticulated with development of spaces (future SAS & cisterns) arachnoid & pia mater (leptomeninges) - by the end of the first trimester, the meninges cover over the entire brain & spinal cord

MENINGES • Protect the underlying brain and spinal cord • Serve as support framework for important arteries, veins, and sinuses • Enclose a fluid-filled cavity, the subarachnoid space, which is vital to the survival and normal function of the brain and spinal cord * Brain loses about 97% of its weight when suspended in CSF e.g. 1400 g in air will weigh only about 45-50 g in fluid*

Mening es

DURA MATER

BLOOD & NERVE SUPPLY

CRANIAL FOSSA

BLOOD SUPPLY

FORAMEN

NERVE SUPPLY

ANTERIOR

- ethmoidal aa -ascending pharyngeal aa.

- ethmoidal f. - ant. foramen lacerum

- ethmoidal n. -superior cervical - brs maxillary & ganglia mandibular n.

MIDDLE

-middle meningeal a - acc. meningeal a. - lacrimal a.

POSTERIOR

SPINAL

f. spinosum f. ovale sup. orbital fissure

A N S

- brs of maxillary -superior cervical & ganglia mandibular n.

- meningeal br of asc. pharyngeal a. - br of occipital & vertebral aa.

- condylar canal -Sensory br. From -superior cervical (inconstant) dorsal root of ganglia C1, - mastoid f. C2 & C 3 - vagus n - tentorial n

-aa. of vertebral, intercostal & lumbosacral

- Intervertebral -recurrent br of -superior cervical f. the spinal nerve ganglia

Dural Infolding & Sinuses •

Dural Infolding – – – –

•

Falx cerebri - SSS,Straight S Falx cerebelli – Occipital sinus Tentorium cerebelli – Transverse sinus Diaphragma sellae – Intercavernous sinuses

Dural Sinuses –

Unpaired: • Superior Sagittal Sinus, • Inferior Sagittal sinus • Straight sinus, • Occipital sinus Paired: • Transverse sinus • Cavernous sinuses • Sigmoid sinuses • Petrosal sinuses • Sphenoparietal sinuses

Dural Infolding & Sinuses

Dural Infolding & Sinuses

(Smallest of the dural infolding)

Cavernous sinuses - ant. & post. intercavernous sinuses Tentorial notch

COMPARTMENTS & HERNIATION SYNDROMES FALX CEREBRI

5-UPWARD HERNIATION

ARACHNOID VILLI or arachnoid granulation or pacchionian bodies

Arachnoid cap cells

Meningotheliomatous (syncytial) meningioma

Transitional meningioma

Fibroblastic meningioma (fibrous)

Epidural Hematoma Subdural Hematoma Subdural Hygroma

PIA MATER • Pia + arachnoid constitute the leptomeninges • Very closely adherent to the brain surfaces • Vessels penetrate the brain and bring along with it a small envelope of pial cell processes and extracellular space known as the perivascular spaces (Virchow-Robin spaces) • The spinal cord is anchored by 3 pial structures: denticulate ligaments, filum terminale internum, filum terminale externum

Contains CSF, vessels, cranial nerve roots Cisternal puncture

Subarachnoid hemorrhage Meningitis

CSF Findings in Various CNS Disorders DISORDER

PRESSURE

APPEARANCE

GLUCOSE

PROTEIN

Acute Pyogenic

increased

cloudy/turbid

decreased

increased

Inc. PMNs

Chronic TB, Fungal, Part.Tx M

increased

Clear or cloudy

decreased

increased

inc. lymphos

Acute Viral

Normal or Mildly inc.

normal

Mildly increased

SAH increased Traumatic tap

normal

Clear, colorless Bloody, does not clot, super-natant xantho. Bloody, clots spontaneously, No xantho.

CELLS

Inc. lymphos Plenty of rbcs

normal

increased

normal

4 mg inc. per Same as 5000 peripheral count rbc