1. Meninges, Brain and
Spinal Cord
MBBS, Batch 17
Year I
Dr. Wai Wai Kyi

2. Meninges, brain and spinal cord (Lecture:10)
Objectives
The objective of the lecture is to discuss the brain and spinal cord: major divisions of the brain, meninges & CSF;external and internal features of spinal cord and relevance of lumbar puncture.
Learning Outcomes
At the end of the lecture, students should be able to:
Outline the major divisions of the brain.
Describe the different layers of meninges and its spaces.
Explain the different folds of dura mater.
Describe the flow of the CSF and its relevance to clinical conditions such as hydrocephalus.
Describe the formation and branches of circle of Willis.
Explain the dural venous sinuses.
Discuss the extent,meninges,internal structure and blood supply of spinal cord.
Outline the anatomical basis of lumbar puncture.

3. Meninges

4. Protection of the Brain
The brain is protected from injury by
The skull (Bone)
Meninges
Cerebrospinal fluid (Watery cushion)
Blood-brain barrier

5. Meninges
The brain and spinal cord are surrounded by three connective
tissue membranes, the meninges (singular, meninx).
■ Brain (cranial meninges)
■ Spinal cord (spinal meninges)
1. Dura mater (tough mother)- outermost, tough membrane
2. Arachnoid mater (spider mother) - spider web filamentous layer
3. Pia mater (gentle mother) - thin vascular layer adherent to contours of brain.
Pia + arachnoid = called
leptomeninges.
Arachnoid = Greek words
which mean spider-like.

6. Functions of the meninges
Cover and protect the CNS.
Protect blood vessels and enclose venous sinuses.
Contain cerebrospinal fluid (CSF).
Form partitions in the skull.

7. Dura mater ■ Outermost sheet, tough, strongest of the meninges.
■ Composed of two layers:
Endosteal layer, outer layer
Meningeal layer, inner layer
(Endosteal layer attached to inside of skull – fused to
periosteum, present in skull only; meningeal layer, true
external covering, extends downward and surrounds spinal
cord forms the dural sheath of the spinal cord in the vertebral
canal).
■ Dural sinuses
Two layers are fused except to enclose the dural venous sinuses
■ Meningeal layer of cranial dura gives rise to dural septa which divide the cranial cavity into compartments.

8. Cranial dural septa The inner layer of dura matter is folded and modified into: 1. Falx cerebri 2. Tentorium cerebelli 3. Falx cerebelli 4. Diaphragma selli The dural septa extend inward & limit excessive movement of the brain.

9. Falx cerebri
Sickle-like form that dips into the longitudinal fissure.
Separates 2 cerebral hemispheres above the corpus callosum.
Attached anteriorly to the crista galli (a sharp upward projection of ethmoid bone in the midline) and posteriorly to the internal occipital protruberance and along the roof of the cranium.
The broad post. part is connected with the upper surface of the tentorium cerebelli.
Upper border enclose the
superior saggital sinus,
lower margin is free and
concave and contains the
inferiorsagittal sinus

10. 2.Tentorium cerebelli ▪ Attachments: Free border is attached to
▪ Shape: tent- shaped
▪ It separates the temporal &
occipital lobes of the cerebral
hemispheres from the
cerebellum & infratentorial
brainstem.
▪ Attachments:
Free border is attached to
anterior clinoid processes.
Fixed border is attached to the
posterior clinoid processes,
petrous part of the temporal
bone & inner surface of the
occipital bone.
Tentorium
cerebelli
Intercavernous
circular sulcus

11. Ant. Clinoid process Free margin of tentorium cerebelli
Post. clinoid process
Free margin of
tentorium cerebelli
Tentorium cerebelli

13. Tentorium cerebelli ( Cont
Tentorium cerebelli ( Cont.) ▪ Free border is U-shaped, tentorial notch which lodges the midbrain. ▪ The falx cerebri and the falx cerebelli are attached to the upper and lower surfaces of the tentorium respectively. ▪ It encloses ○ Straight sinus - along the attachment to falx cerebri ○ Transverse sinuses - along its attachment to the occipital bone. ○ Superior petrosal sinuses- along its attachment to the petrous bone.
Superior petrosal
sinus

14. 3.Falx cerebelli
Small sickle-shaped fold of dura mater
Continuation of falx cerebri, partly separating the two cerebellar hemispheres.
Base is attached to posterior part of inferior surface of tentorium cerebelli.
Apex reaches till foramen magnum
It’s post. fixed margin encloses occipital sinus.
Intercavernous
sinuses
Falx cerebelli
Occipital sinus

15. 4. Diaphragma sellae/ sellar diaphragm (Sella turcica is named for its
Circular fold of dura mater that forms the roof for the sella turcica of the sphenoid bone
A small opening in the center
allows passage of the stalk of the pituitary gland.
Anteriorly attached to tuberculum sellae.
Posteriorly to dorsum sellae
Laterally continues with dura mater of middle cranial fossa
It encloses the anterior and
posterior intercavernous sinuses.
(Sella turcica is named for its
resemblance of the Turkish
saddle with its anterior
tuberculum sellae, hypophysial
fossa and posterior dorsum
sellae).
Diaphragma sellae
Dorsum sellae

16. Dural arterial supply
Meningeal arteries supply the intracranial dura, ususlly arise
from the branches of external carotid artery.
1. Middle meningeal artery, branch of maxillary artery is the major blood supply to the dura mater. It enters the cranial cavity through the foramen spinosum and lies bet. the meningeal and endosteal layers of the dura. It then runs in a groove on the squamous part of the temporal bone.
The middle meningeal artery is commonly damaged in head injuries.
2. Meningeal branches of vertebral, ophthalmic, anterior ethmoidal, internal carotid, ascending pharyngeal, occipital accessory meningeal.
Dural venous drainage
Middle meningeal vein drains into the pterygoid venous plexus or
the sphenoparietal sinus. Meningeal veins course through the
dura.

17. Nerve supply
Trigeminal nerve, V1, V2 & V3
Upper three cervical nerves, cervical part of the sympathetic trunk
Vagus [X]

19. Arteri Supply to Dura Pterion Middle meningeal artery Maxillary artery
External carotid artery

20. Cranial Nerves – relation to dura

21. Cranial Nerves – relation to dura

22. Arachnoid mater
A delicate, impermeable membrane that covers the brain.
Located beneath the dura mater.
Subdural space, bet. meningeal duramater & arachnoid mater
Subarachnoid space (SAS), bet. arachnoid mater & pia mater
SAS surrounds each cranial nerve for a short distance at its foramen. Around the optic nerve the space reaches as far as the eyeball; the central retinal artery & vein cross it. Increased intracranial pressure may compress the vein causing odema of the optic disc, papilloedema.
Arachnoid villi
○ Projections from the arachnoid protrude through the dura
mater into the dural sinuses.
○ transport the one-way flow of CSF from the subarachnoid
space to the dural sinuses.
○ Aggregations of arachnoid villi are called arachnoid
granulation.

23. Emissary veins
Drain blood from the external surface of the skull into the dural sinuses.
Drain blood from the space within the bone of the skull (diploic space) into the dural sinuses.
Diploic veins
Dura mater
Cells of
Arachnoid
mater
Subarachnoid
space

25. Contains cerebral blood vessels and CSF.
Meningeal spaces
Subarachnoid space
Contains cerebral blood vessels and CSF.
Surrounds the entire brain & spinal cord.
Extends in the adult below the conus medullaris to the level of the 2nd sacral vertebra, the lumbar cistern.
The fine threads of tissue that spread across this space resemble a spider web (arachnoid= spidery).
Rupture of the vessels leads to subarachnoid hemorrhage
Condition may be due to trauma, congenital abnormalities
(aneurysms), high blood pressure.
Subdural space
Intracranially transmits superior cerebral veins to the superior sagittal sinus. Lacerations of these bridging veins results in subdural hemorrhage ( hematoma).
Spinal epidural space
Located bet. the dura & the vertebral periosteum.
Contains areolar tissue, venous plexuses and lymphatics.
Local anaesthetic can be injected into this space, epidural anaesthesia.

26. Haemorrhage of the brain
Epidural hematoma (Artery) - middle meningeal artery rupture
Usually due to blow to the side of the head at the pterion (area
where skull is thinnest/easiest to fracture). Fracture may rupture the anterior branch of middle meningeal artery.
Subdural hematomas (Veins) – tears in bridging veins that cross the subdural space.
Meningitis- Inflammation of the (meninges) pia-arachnoid of the
brain spinal cord or both. .

27. (Bridging veins)

28. Pia mater It is a delicate highly vascular connective tissue layer.
Closely applied to the outer surface of the brain,and spinal cord, follows the contours of gyri & sulci the cortex.
Connected to arachnoid by trabeculae.
Carries the blood vessels into the brain.
Forms [with the ependymal
cells of the brain and the
blood vessels] the
choroid plexus.
Subarachnoid space
(The space that separates
the arachnoid and pia)
where the CSF flows.

29. CSF & Hydrocephalus

31. Cerebrospinal fluid and Hydrocephalus
Formation of CSF
Formed mainly in the choroid plexuses of the lateral, third, and
fourth ventricles.
(Choroid plexuses =vascular pia projecting into ventricles as a
fringe covered with ependymal covering)
There are 4 ventricles filled with CSF within the brain
2 lateral ventricles
(One in each hemisphere)
3rd ventricle
4th ventricle

32. Circulation CSF
Lateral ventricles communicate with the 3rd ventricle through
interventricular foramina (Foramen of Monro)
The 3rd ventricle is connected to the 4th ventricle through cerebral aqueduct (Aqueduct of Sylvius).
The 4th ventricle continues with the central canal of the spinal
cord. Leaves the fourth ventricle,
through the three openings,
the median aperture
(foramen of Magendie)
and the two lateral foramina,
(foramen of Luschka) &
enters the subarachnoid
space.

33. Circulation in the subarachnoid space
After leaving the ventricular system, the CSF moves down the
cisterns (cerebellomedullary and pontine cisterns) at the base of the brain, then upwards over the lateral surface of the cerebral hemispheres to reach the sup. saggital sinus.
Some of the cerebrospinal fluid moves inferiorly in the sub
arachnoid space around the spinal cord.

36. Absorption
The main sites for the absorption of the CSF are the arachnoid villi that project into the dural venous sinuses, especially the superior sagittal sinus
Arachnoid villi tend to be grouped together to form elevations
known as arachnoid granulations.

37. Hydrocephalus (Means excess water in the cranial vault).
A clinical disorder in which there is increase in the volume of the CSF. It may be due to:
Obstruction to circulation of the CSF which may be congenital of acquired:
a. Obstruction in some parts of ventricular system called
obstructive hydrocephalus.
b. Obstruction in free flow of CSF in the subarachnoid space
(blockage of arachnoidal villi) called communicating
hydrocephalus, resulting in dilation ofall ventricles. This
condition is sometimes called internal hydrocephalus
Senile atrophy of brain - compensatory phenomenon, sometimes called external hydrocephalus.
Increased formation of CSF
Impaired absorption of CSF eg. thrombosis of sup. sagittal sinus

39. Dural Venous Sinuses

40. Dural Venous Sinuses Unpaired sinuses Superior sagittal sinuses
Inferior sagittal sinuses
Straight sinus
Sinus confluens
Paired sinuses
Cavernous sinus
Superior petrosal sinuses
Inferior petrosal sinuses
Squamopetrosal sinus
Transverse sinuses
Sigmoid sinuses

41. Intracranial venous sinuses
Superior sag. sinus
Inferior sag. sinus
Great cerebral vein (Galen)
Straight sinus
Occipital Sinus-
Venous return
from the cerebellum

42. Intracranial venus sinuses
Straight Sinus - drains into the internal jugular via the transverse sinus.
Superior Sagittal Sinus (cut)
Transverse Sinus
Sigmoid Sinus (Drains into the Internal Jugular Vein)
Tentorium
Cerebelli

43. Intracranial venous sinuses
Confluence of Sinuses - Occipital region where the dural sinuses
come together:
Superior Sagittal Sinuses
Straight Sinus
Occipital Sinus

44. Cranial dural venous sinuses
Located bet. the 2 layers of a dural fold (meningeal & endosteal layers of the dura mater).
Lined by endothelium and have no valves.
Drain into internal jugular veins.
They receive cerebral, diploic, meningeal tributaries and through skull foramina communicates via valveless emissary veins with extracranial vessels.
Cutaneous sepsis may thereby cause infective thrombosis of an intracranial sinus

45. Cranial intravenous sinuses:
1 sphenoparietal
2 cavernous
3 inferior petrosal
4 transverse
5 sigmoid
6 superior petrosal
7 straight
8 superior sagittal

46. Cavernous sinus
A large collection of thin-walled veins lies on either side of the body of the sphenoid bone, lateral to the sella turcica.
Intercavernous sinuses – connect the 2 cavernous sinuses thro’ the sella turcica.

47. Cavernous sinus The cavernous sinus drains by two channels, the superior and inferior, ultimately into the internal jugular vein. Relations Medial - Body of sphenoid bone with sphenoid sinuses Lateral wall - Each cavernous sinus (one for each hemisphere of the brain) contains the following: 1. Occulomotor nerve 2. Trochlear nerve 3. Ophthalmic, division of v nerve 4. Maxillary nerve, division of v nerve Structures passes through the cavernous sinus Internal carotid artery with its surrounding sympathetic plexus. inferolateral to it is abducent nerve Anterior end - optic canal -optic nerve and ophthalmic artery Posterior end - apex of petrous part of temporal bone - trigeminal cave- trigeminal ganglion

48. This complex web of veins contains no valves.
The cavernous sinuses receive venous blood from the facial veins (via the superior and inferior ophthalmic veins), sphenoparietal sinus, central vein of retina, middle cerebral veins and is connected to the basiler plexus of veins posteriorly.
The cavernous sinus drains by two channels, the superior and inferior petrosal sinuses, ultimately drain into the internal jugular vein.
This complex web of veins contains
no valves.
Anterior facial vein, ophthalmic vein & the cavernous sinus are in direct communication. Infections of the face including the nose, ethmoidal sinusitis and orbits can lead to cavernous sinus thrombosis which is a life- threatening condition.
Cavernous
venous sinus
Facial
vein

50. Clinical anatomy
Cavernous sinus thrombosis
Pituitary adenoma
Ophthalmoplegia-compression of 3,4,6th cranial nerves
Carotid cavernous fistula
Dangerous area of face- through facial vein and superior ophthalmic vein
Spread infection from / to dural venous sinuses

51. Brain

52. Brain
The brain can be divided into three main parts. The forebrain, midbrain and hindbrain. The midbrain and hindbrain are collectively know as the brain stem.
Forebrain (Prosencephalon)
Telencephalon (cerebrum)
Diencephalon (thalamus, hypothalamus, pineal body).
Midbrain (Mesencephalon)
Hindbrain
Rhombencephalon
Pons
Cerebellum.
Metencephalon
Medulla oblongata.

53. The brain
Composed of three parts:
Cerebrum
Cerebellum
Brainstem
The cerebrum is
divided into four lobes:
Frontal
Parietal
Temporal
Occipital

54. Imaginary lines
A little anterior to the occipital pole the inferolateral border shows a slight indentation called the preoccipital notch.
The first imaginary line connects the upper end of the parieto-occipital sulcus to the preoccipital notch.
The second imaginary line is a backward continuation of the posterior ramus of the lateral sulcus to meet the first line.
Central sulcus
Lateral sulcus

55. Four lobes Each cerebral hemisphere is divided into 4 lobes named
according to the cranial bones under which they lie.
▪ Frontal lobe
▪ Parietal lobe
▪ Temporal lobe
▪ Occipital lobe
▪ Insula -
Considered to
be the fifth
lobe.

58. Circle of Willis (circulus arteriosus)
Location
Lies in the interpeduncular fossa at the base of brain around optic chiasma, tuber cinereum and
mamillary bodies.
Formation
It is formed by the anastomosis bet.
two internal carotid arteries & two
vertebral arteries.
Anterior part
Anterior cerebral arteries (Rt & Lt)
Anterior communicating artery
Posterior part:
Basilar artery
Posterior cerebral arteries (Rt & Lt)
Lateral part
Internal carotid artery (Rt & Lt)
Posterior communicating arteries (Rt & Lt)

60. Branches of the circle of Willis

61. Distribution of central arteries
Central arteries, arise from the arterial circle and proximal portion of the principal arteries, penetrate the substance of the brain and supply the deep structures.
Branches of the circle of Willis : central arteries
6 groups
▪ Anteromedial group
▪ Posteromedial group
▪ 2 Anterolateral groups
▪ 2 Posterolateral groups

62. Spinal Cord

63. The meninges of spinal cord
Spinal dura mater
Spinal arachnoid mater
Spinal pia mater

64. Spinal dura mater Spinal dural sheath, a single layer which
is the continuation of the meningeal layer
of cranial dura.
Does not have a endosteal layer
No dural venous sinuses
No dural septa.
Supplied by spinal brs of segmental arteries (cranial dura - middle meningeal artery).
Epidural space - space between the dura and the periosteum, especilly large the level of S2 vertebra. Local anaesthetic can be injected, epidural anaesthesia.
Subarachnoid space -space bet. arachnoid mater and pia mater
extends to S2 vertebra.
Contains cerebrospinal fluid (CSF) & blood vessels

65. Spinal dura mater ( Cont.)
The dura extends for a short distance along the cranial & spinal nerves. In spinal nerves it extends along the nerve roots up to the dorsal root ganglion & in trigeminal nerve it extends up to trigeminal ganglion.

66. Spinal arachnoid mater
A thin, delicate, tubular membrane loosely investing
spinal cord.
Above, it is continuous with cerebral arachnoid mater.
Spinal pia mater
A delicate vascular membrane that closely invests the spinal cord
Denticulate ligament:
Consists of two lateral flattened bands of pial tissue attached to the spinal dura with 21 teeth; help to fix position of spinal cord.

67. Spinal pia mater Filum terminale
An extension of pia beyond conus medullaris, descends through the cauda equina to be attached to the coccyx.

68. Blood-Brain Barrier
Consists of
Continuous endothelium of capillary walls, endothelial cells
joined by tight junctions.
Thick basal lamina around each capillary.
Regulated by foot processes of astrocytes, stimulate tight
junction formation between endothelial cells.
Absent at vomiting center (brainstem) and hypothalamus, where it is necessary to monitor the chemical composition of the blood.
Most bloodborne substances cannot readily enter the brain
Relatively impermeable (Capillary endothelium is joined by tight
junctions)
Barrier is selective
a. Facilitated diffusion of particular substance- Glucose and
others
b. Cannot prevent fat-soluble molecules from diffuses into brain.

71. Spinal cord (External features)
It is the lower elongated cylindrical part of the CNS and connect with the brain above.
It occupies upper 2/3rd of the vertebral canal.
It extends from the foraman magnum of the occipital bone
Terminates at the level of the L1- L2 intervertebral disc as
the conus medullaris
In neonates, the spinal cord extends approximately to vertebra L3, but can reach as low as vertebra L4.
It is about 45 cm in length.
From here a prolongation of pia mater, the filum terminale descends to be attached to the back of the coccyx.

72. Spinal cord
Anterolateral sulcus
Posterolateral sulcus

73. Spinal cord (External features) Cont.
It has six external longitudinal fissures and sulci. They are a deep anterior median fissure, a shallow posterior median sulcus, a pair of anterolateral sulcus and a pair of posterolateral sulcus lying lateral to them.
The anterolateral sulcus and posterolateral sulcus marks the sites of attachment for the anterior and posterior roots of each pair of spinal nerves.

74. Spinal cord enlargements
Two enlargements - cervical
and lumbar (lumbosacral) –
which mark the regions of the
cord that innervate the upper
and lower limbs respectively.
Cervical enlargements (C4-T1) corresponding to origin of the brachial plexus.
Lumbrosacral enlargement (L2-S3) corresponding to origins of the lumbar and lumbrosacral plexi.

75. Spinal nerves The spinal cord gives off 31 pairs of spinal nerves.
8 cervical, 12 thoracic, 5 lumbar, 5 sacral, & 1 coccygeal
Each nerve is attached to the spinal cord by 2 roots, ventral
( motor) & dorsal ( sensory ), the ventral & dorsal nerve unites to
form the nerve trunk, each dorsal root bears a ganglion, the cells
of which give rise to peripheral & central nerve fibers.
The part of spinal cord that gives off one pair of spinal nerve is called a segment of spinal cord; 31 segments (31 pairs of spinal nerves)
Cauda equina
Collection of nerve roots L2 to S5 nerve roots below the lower
end of the spinal cord (resemble horse’s tail).

76. Vertebral relationship of the spinal cprd
From foramen magnum to:
Up to 3 months of foetal life - the spinal cord is as long as the vertebral column
The vertebral column elongates more rapidly than the spinal cord during further foetal development.
24 weeks - S2
Birth – L2/L3
Adult - L1 / L2 junction

77. Cross section of spinal cord

78. Gray matter
In transverse section of the cord
An H- shaped mass and is surrounded by white matter which contains the long ascending and descending tracts.
Right & left halves of spinal cord are connected across the midline by the grey commisure, which is traversed by the central canal.
It has:
Dorsal (Posterior) horns- contain somatic and visceral sensory nuclei
Ventral (Anterior) horns- contain somatic motor nuclei
Lateral horns- are in thoracic and lumbar segments only; contain visceral motor nuclei
Dorsal root ganglia- contain cell bodies of sensory neurons;
Pseudounipolar neurons

79. Blood supply to spinal cord
Arterial supply
Posterior spinal arteries
2 branches -from vertebral arteries
Anterior Spinal artery
1 branch - from vertebral arteries
Spinal arteries are reinforced by radicular
arteries
Radicular arteries
Are branches from segmental arteries:
Ascending cervical a.
Deep cervical a.
Posterior Intercostal a.
Lumbar a.
Sacral a.
Artery of Adamkiewicz (T8 –L3)

80. Anterior spinal arteries supply 2/3 anterior aspect of spinal cord
Posterior spinal arteries supply 1/3 posterior aspect of spinal cord

81. Spinal veins
Spinal veins form plexuses anteriorly and posteriorly
On each side the spinal veins are double, straddling the posterior nerve roots
All of them drain into
vertebral veins in the neck,
azygos veins in the thorax,
lumbar veins in the lumbar region,
lateral sacral veins in the sacral region through intervertebral foramina.

82. Cisterns
In certain locations, the subarachnoid is large and are called
cisterns.
The clinically used cisterns are:
Lumbar cistern
Cisterna magna/cerebellomedullary cistern
Lumbar puncture (spinal tap)
The clinical procedure for obtaining CSF from the lumbar cistern is called lumbar puncture. This is done by inserting special needle thro’ the intervertebral space bet. L3 & L4 posteriorly until it enters the lumbar cistern.
It may be used for diagnosis (meningitis, encephalitis,
subarachnoid haemorrhage) and/or for therapeutics (introduction of antibiotics, spinal anaesthesia). .

83. Lumbar puncture Layers that the spinal needle traverse are: 1. Skin 2
Lumbar puncture Layers that the spinal needle traverse are: 1. Skin 2. Superficial fascia 3. Supraspinous ligamen 4. Interspinous ligament 5. Ligamentum flavum 6. Epidural space containing the internal vertebral venous plexus 7. Dura mater 8. Arachnoid 9.Subarachnoid space containing cerebrospinal fluid. The best intervertebral space is between L3/L4 or L4/L5, usually lower levels in children.

84. Ligament flavum is a strong, elastic, yellow membrane covering the interlaminar space
Interspinal ligaments join the inferior and superior borders of adjacent spinous processes.
Supraspinal ligament connects spinous processes

85. Performed with the patient in the lateral recumbent position.
A line connecting the posterior superior iliac crest will intersect the midline at approx. the L4 spinous process.
Spinal needles entering the subarachnoid space at this point are well below the termination of the spinal cord.

86. ?
THANK YOU