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Anatomy – CNS Brain

Ventricles

C-shaped cavity within cerebral hemisphere

Body

Medial wall contains choroid fissure

C-shaped slit containing choroid plexus (mass of

capillaries, pia mater, ependyma)

Anterior horn

Foramen of monro connects to 3rd ventricle

3rd ventricle connects with 4th ventricle via foramen of

midbrain

Inferior horn

Posterior horn

CSF

Circulation:

Formed in choroidal epithelial cells (plexus) in lateral/3rd

/4th

ventricles

Lateral ventricles → 3rd

ventricle via interventricular

foramina

3rd

ventricle → 4th

ventricle via aqueduct

Some CSF passes into subarach space via median and

lateral aperatures

Most passes into interpeduncular/quadrigeminal cisterns

CSF from various subarach cisterns flows superiorly thru

sulci and fissures on medial and superolateral surfaces of

cerebral hemispheres

Absorbed in arachnoid granulations esp those that

protrude into superior sagittal sinus

Functions:

Protect brain by providing cushion effect

Buoyancy effect to prevent compression nerves/vessels

Blood supply of the brain

Circle of Willis

Posterior circulation

2 vertebrals (from subclavian) give off posterior and anterior

inferior cerebellar, then unite to form basilar at caudal border pons

Basilar ascends to superior border of pons giving off superior

cerebellar, which in turn divides into right/left posterior cerebrals

PCA each join MCA by post communicating artery

What areas vessels supply:

Vertebral As → cranial meninges and cerebellum

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Basilar → brainstem, cerebellum and cerebrum

Post cerebral → supplies inf aspect cerebrum and occipital lobe

Post communicating → optic tract, cerebral peduncle, int capsule, thalamus

Anterior circulation

L and R internal carotids (from common carotid) give rise to middle and anterior cerebral arteries

ACA linked by anterior communicating artery

What areas vessels supply:

Ant cerebral → supplies medial and sup surface and frontal poles except occipital lobes

Middle cerebral (continuation of ICA after origin ACA) → supplies lat surface of both hemispheres excluding ant

part of frontal lobe and occipital lobe, and temporal lobes, and basal ganglia but not thalamus

What motor and sensory areas lie in distribution of MCA:

Motor and sensory of opposite half of body except legs and perineum

Auditory and speech areas

Vertebral Artery

1 of 2 main arteries supplying the brain

+ supplies spinal cord, meninges, surrounding muscles/ bones

Origin - branch of 1st part of subclavian art

Course and relations

Cervical (1st) part

Extends from origin to transverse process C7, enters foramen in transverse process C6

Anterior relations: carotid sheath and common carotid, vertebral vein, inf thyroid artery, on left

side – thoracic duct

Posterior relations: transverse process C7, stellate ganglion, ventral rami C7,8

Vertebral (2nd

) part

Extends from transverse processes of C6 to C1 (runs thru foramina), emerges from transverse

process of atlas

Suboccipital (3rd

) part

Winds medially behind lateral mass of atlas, enters vertebral canal after piercing dura and

arachnoid, passes thru foramen magnum, then makes a sharp loop

Intracranial (4th) part

Ascends medially in front medulla, at lower border of pons vertebral arteries form basilar artery

Branches

Cervical branches – spinal and muscular

Cranial branches – meningeal, posterior spinal, medullary arteries

Middle Meningeal Artery

Does NOT supply the brain

Chief source of extradural haemorrhage

Origin

Branch of maxillary artery, arises in infratemporal fossa deep to ramus of mandible

Course and relations

In infratemporal fossa runs upwards and medially (deep to lat pterygoid, passes between 2 roots of

auricutotemporal nerve)

Enters middle cranial fossa thru foramen spinosum

In middle fossa has extradural course, running forward and laterally, dividing into ant/post branches

Supplies – trigeminal ganglion, tympanic cavity, orbit

Surface Marking

Pt 1: at midpt of zygomatic arch = entry artery into skull = pt division artery

Pt 2: ∼ 2 cm above pt 1

Pt 3: centre of pterion

Pt 4: midpt btw nasion & inion

Pt 5: at lambda sinus

Joining pt 1& 2 - stem of artery

Joining pt 2, 3, & 4 - ant branch

Joining pt 2 & 5 - post branch

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Venous Drainage

Superior Sagittal Sinus

In upper convex margin of falx cerebri

Begins anteriorly at crista galli by union of meningeal veins, runs

upwards & backwards, becoming progressively larger, ends near

internal occipital protuberance by deviating to one side (usually to

right – continues as right transverse sinus)

Communicates with 2 or 3 small, irregularly-shaped venous lacunae

on each side

Arachnoid villi & granulations project into lacunae

Tributaries

receives bld from

1. diploic & meningeal veins via lacunae

2. emissary veins

3. sup cerebral veins

Drainage - into confluence of sinuses & hence into transverse

sinuses & occipital sinus, as well as straight sinus

Surface Anatomy - from above root of nose, over vault of skull

in median plane, to external occipital protuberance

Clinical Notes - thrombosis caused by spread of infection from

nose, scalp & diploe

Meninges

Dura

Outer endosteal (periosteal)

Inner meningeal (fibrous) – into folds for tentorium

cerebelli and falx cerebri

Outside both – middle meningeal vessels, site

extradural bleed

Between layers – venous sinuses and Meckels cave

Under both – subdural bleed (venous, slow)

Blood supply – middle meningeal artery, meningeal branches of vertebral, ophthalmic, anterior ethmoidal, interal

carotid, accessory meningeal

Nerve supply in cranial fossae

Anterior – anterior ethmoidal (Va)

Middle – nervus spinosus (Vc), middle meningeal (Vb)

Posterior – meningeal branches of glossopharyngeal (IX)

and vagus (X)

Foramen magnum – C1-3

Supratentorial – meningeal branches from Va

Meningeal layer sends 4 folds internally, divide cranial cavity into

many freely communicating compartments

Falx Cerebri (in median longitudinal fissure between

hemispheres)

Upper convex border contains sup sagittal sinus

Lower concave border contains inf sagittal sinus

Tentorium Cerebelli (tent shaped, roof of posterior

cranial fossa, separates occipital lobe and cerebellum)

Falx Cerebelli (small sickle-shaped fold below tentorium

cerebelli)

Diaphragma Sellae (small circular horizontal fold forms

roof of pituitary fossa)

Arachnoid Lines inside of dura

Forms villi to drain CSF into blood

Several villi give off arachnoid granulation, mostly in sup sagittal

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Pia

Follows contour of brain

Forms denticulate ligament in spine and filum terminale

Subarachnoid space

Between arachnoid and pia

For circulation of CSF

Larger areas are cisterns (cisterna magna, pontine, interpeduncular, chiasmatic – filled via foramen of Magendie

from 4th

ventricle

Cavernous sinus

Location

Plexus of veins

Lies alongside body of sphenoid bone in middle cranial fossa

Extends from apex of orbit to apex of petrous temporal bone 2cm long, 1cm wide

Borders

Lies in space between periosteum of body of sphenoid and inner layer of dura

Dura forms upper part of medial wall, roof and lateral wall

Roof continuous with diaphragma sellae

Anteriorly roof joins anterior and middle clinoid processes

Relations

Medial - Fibrous lateral wall of sella turcica

Lateral - Temporal lobe of brain

Contents

Internal carotid artery

Abducent nerve

Plus structures that are embedded in lateral wall

Oculomotor, Trochlear, Ophthalmic, Maxillary nerves

Draining into it

Superior and inferior ophthalmic veins

Superficial middle cerebral vein

Sphenoparietal sinus

Draining out of it

Superior and inferior petrosal sinuses

Communications

Pterygoid plexus via emissary veins (foramen ovale and foramen lacerum)

Danger area of face

Upper lip, nose, medial part of cheek

Cavernous sinus thrombosis

Thrombosis in cavernous sinus

Usually due to spread of infection from sinuses, ears, teeth or middle third of face

Symptoms include loss of vision, proptosis, headaches, paralysis of cranial nerves

Spinal Cord

Cylinder, flattened front to back

Extends from foramen magnum to cona medularis (L3 in neonates, L1 by 20 years)

Anterior and posterior median fissures

Cervical enlargement - C5-T1

Lumbosacral enlargement - L2-S3

Nerve roots

Roots formed from a series of rootlets

Anterior and posterior roots unite in the intervertebral foramen

Cervical nerve roots are horizontal, thoracic roots slope down, lumbar roots are vertical and form the

Internal structure

Grey matter

Central H-shaped mass enclosed in white matter divided into anterior, lateral and posterior horns

Central canal is a continuation of the 4th ventricle

Two halves almost separated by anterior median fissure a

Grey commissure connect right and left halves

Lateral horns between T1 and L2 contain preganglionic sympathetic cell bodies

anterior root and then the white rami to enter the sympathetic trunk

Cells lie in functional groups or laminae designated by roman numerals I

White matter

Ascending pathways

Divided into posterior, lateral and anterior columns

Lateral and anterior columns

Fibres entering cord form

or descends for 1 or 2 segments before synapsing.

Fibres then

90% then synapse with the brainstem reticular formation

Anterolateral tracts comp

Pain, Temperature,

Tracts to cerebellum for muscular coordination Posterior columns

Fibres from lo

Both tracts synapse in medulla (gracile/

lemniscus, pass to

Light (discriminative) touch

Vibration

Proprioception (position sense)

Bladder and rectum fullness

Descending pathways

Lateral corticospinal tract

Fibres decussate lower medulla, run in

98% of fibres synapse with interneurons then anter

Efferent pathways

Skeletal muscle control

Spinal nerves

Cell bodies

Project

Extends from foramen magnum to cona medularis (L3 in neonates, L1 by 20 years)

Roots formed from a series of rootlets

Anterior and posterior roots unite in the intervertebral foramen

Cervical nerve roots are horizontal, thoracic roots slope down, lumbar roots are vertical and form the

shaped mass enclosed in white matter divided into anterior, lateral and posterior horns

Central canal is a continuation of the 4th ventricle

Two halves almost separated by anterior median fissure and posterior median sulcus and septum

Grey commissure connect right and left halves

Lateral horns between T1 and L2 contain preganglionic sympathetic cell bodies

anterior root and then the white rami to enter the sympathetic trunk

Cells lie in functional groups or laminae designated by roman numerals I-X

Ascending pathways

Divided into posterior, lateral and anterior columns

Lateral and anterior columns

Fibres entering cord form dorsolateral tract that runs at tip of

or descends for 1 or 2 segments before synapsing.

Fibres then decussate to enter anterolateral tract (anterior to the denticulate ligament)

90% then synapse with the brainstem reticular formation

Anterolateral tracts composed of

Lateral spinothalamic (pain, temperature)

Ventral spinothalamic (crude touch, pressure)

Pain, Temperature, Crude touch, itch, tickle

Tracts to cerebellum for muscular coordination Posterior columns

Fibres from lower body carried medially in gracile tract, upper body lat in cuneate tract

Both tracts synapse in medulla (gracile/cuneate nuclei) then

lemniscus, pass to thalamus, synapse again then pass to cortex

Light (discriminative) touch

Vibration

Proprioception (position sense)

Bladder and rectum fullness

Descending pathways

Lateral corticospinal tract

Fibres decussate lower medulla, run in lateral white column behind attachment denticulate lig

98% of fibres synapse with interneurons then anterior horn cells

Efferent pathways

Skeletal muscle control

Spinal nerves

Direct corticospinal pathway

Upper motor neurons

Cell bodies in cortex, fibres thru int capsule/brainstem to ant horn cells in

Lower motor neurons

Cell bodies in ant horn of cord, axons end as motor endplates on

Indirect corticospinal fibres

Project to other cell bodies/nuclei so indirect (extrapyramidal) route to ant

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Cervical nerve roots are horizontal, thoracic roots slope down, lumbar roots are vertical and form the cauda equina

shaped mass enclosed in white matter divided into anterior, lateral and posterior horns

nd posterior median sulcus and septum

Lateral horns between T1 and L2 contain preganglionic sympathetic cell bodies - fibres pass into the

X

p of posterior horn and ascends

anterolateral tract (anterior to the denticulate ligament)

90% then synapse with the brainstem reticular formation

act, upper body lat in cuneate tract

cuneate nuclei) then decussate to form medial

cortex

umn behind attachment denticulate lig

em to ant horn cells in cord

as motor endplates on muscles

ct (extrapyramidal) route to ant horn

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Blood supply

Anterior spinal artery

Lies on the anterior medial fissure

Formed at foramen magnum from union two ant spinal arteries from vertebral artery above foramen

Runs the whole length of the cord

Supplies anterior cord including lateral grey and white columns

Posterior spinal arteries

Arises from the vertebral or posterior inferior cerebellar arteries above the foramen magnum

Runs behind the posterior nerve rootlets

Runs the whole length of the cord

Supplies posterior cord including grey and white columns on its own side

Radicular arteries

Derived from various parent vessels depending on the level

Vertebral

Costocervical

Posterior intercostal

Lumbar

Lateral sacral

Very variable but may form dominant supply

Large feeder vessels typical from lower intercostals of upper lumbar branch of aorta

Form anastomoses between ant/post spinal arteries – anastomosing arteries run under pia and close to

lateral corticospinal and anterolateral columns.

Spinal cord injury

Hemisection (Brown-Sequard syndrome) Ipsilateral paralysis and loss of light touch

Contralateral loss of pain and temperature sensation

Central cord syndrome (sudden hyperextension of C-spine)

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Flaccid paralysis of upper limbs(anterior horn cell damage)

Loss of pain and temperature sensation (damage to deeply placed cervical anterolateral tracts)

Spasticity of lower limbs if lumbar fibres of lateral corticospinal tract are involved.

Anterior spinal artery syndrome Loss of motor and sensory function except light touch and vibration

Anastomoses may lead to ‘sacral sparing’

Myotomes

Upper limb

Shoulder Abduction, lateral rotation C5

Adduction, medial rotation C6/7/8

Elbow Flexion C5/6

Extension C7/8

Wrist Flexion/extension C6/7

Hand Long flexor and extensors C7/8

Intrinsic muscles T1

Lower limb

Hip Flexion L2/3

Extension L4/5

Knee Extension L3/4

Flexion L5/S1

Ankle Dorsiflexion L4/5

Plantarflexion S1/2

CNS radiology

Lobes (frontal, parietal, temporal, occipital)

Lateral ventricles (anterior and posterior horns)

Choroid plexus

Pineal gland

Thalamus

Internal capsule, basal ganglia, caudate, globus pallidus, putamen, sylvian fissure/lateral sulcus

Cerebellum (right and left hemispheres united by central vermis)

Pons

4th

ventricles and pre-pontine cistern

Right and left temporal lobes in middle cranial fossa

Mastoid, sphenoid and ethmoid sinuses

Base of skull:

Bones (occipital, temporal, sphenoid, nasal)

Air spaces (mastoid air cells, sphenoid sinus, ethmoid, nasal cavity)

Intracranial (4th ventricle, cerebellum, vermis, temporal lobes, pons)

A. Orbit

B. Sphenoid Sinus

C. Temporal Lobe

D. External Auditory Canal

E. Mastoid Air Cells

F. Cerebellar Hemisphere

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A. Frontal Lobe

B. Frontal Bone (Superior Surface of Orbital Part)

C. Dorsum Sellae

D. Basilar Artery

E. Temporal Lobe

F. Mastoid Air Cells

G. Cerebellar Hemisphere

A. Frontal Lobe

B. Sylvian Fissure

C. Temporal Lobe

D. Suprasellar Cistern

E. Midbrain

F. Fourth Ventricle

G. Cerebellar Hemisphere

A. Falx Cerebri

B. Frontal Lobe

C. Anterior Horn of Lateral Ventricle

D. Third Ventricle

E. Quadrigeminal Plate Cistern

F. Cerebellum

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A. Anterior Horn of the Lateral Ventricle

B. Caudate Nucleus

C. Anterior Limb of the Internal Capsule

D. Putamen and Globus Pallidus

E. Posterior Limb of the Internal Capsule

F. Third Ventricle

G. Quadrigeminal Plate Cistern

H. Cerebellar Vermis

I. Occipital Lobe

Cranial Nerves

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