• ANATOMY OF VENTRICULAR SYSTEM• CSF PHYSIOLOGY

ANATOMY OF VENTRICULAR SYSTEM

Ventricular System:

• The ventricular system is a set of structures containing cerebrospinal fluid in the brain. It is continuous with the central canal of the spinal cord.

Ventricular system

TWO LATERAL VENTRICLES

THIRD VENTRICLE

FOURTH VENTRICLE

Lateral ventricles

Frontal hornBodyTrigone (Atrium)Occipital hornTemporal horn

FRONTAL HORNBODY

TRIGONE ( ATRIUM)

OCCIPITAL HORN

TEMPORAL HORN

Frontal horn: It lies within the frontal lobe, running forwards and slightly outwards. It is triangular in shape with concave lateral walls.

Roof: Genu of Corpus callosum. Medial wall: Septum

pellucidum.Lateral wall: Head of caudate

nucleus.

Body: Extends from the foreman of monro to the trigone and its boundaries are:

• Roof: Body of corpus callosum

• Medial wall: Is biconcave • Superior concavity:

Caudate nucleus • Inferior concavity:

Thalamus

Trigone (atrium): • Contains the bulk of

choroid plexus (Glomus).

• Posterior part of the body of lateral ventricle at its junction with the temporal and occipital horns.

Posterior horn (occipital horn): This runs posteriorly from the trigone into the occipital lobe.

• Proximal roof and lateral wall formed by the splenium of corpus callosum.

• Medial wall by occipital cortex.

• In 90% of cases it is either vestigial or absent."

Temporal horn: Extends downwards, forwards and outwards from trigone lying within the temporal lobe, its boundaries are:

• Roof: Formed by white matter of temporal lobe and tail of caudate nucleus.

• Medial wall and floor: Hippocampus.

Body

Third Ventricle:

• It is a median cleft between the two thalami. It communicates anteriorly with the lateral ventricles through interventricular foramina of monro and posteriorly with the fourth ventricle through the cerebral aqueduct (of sylvius).

Its boundaries are,• Roof: Formed by a layer of piamater, the velum interpositum .• Floor: ventrodorsally formed by optic chiasma, infundibulum and mamillary

bodies.• Anteriorly : Lamina terminalis• Posteriorly : Pineal body, posterior commisure, pineal and suprapineal recess• Lateral- upper part- Medial surface of the anterior 2/3 of thalamus • Lower part: hypothalamus• Lowest part of III ventricle: Represents the optic and infundibular recess.• Lateral walls join each other across the cavity of third ventricle by a band of

gray matter inter thalamic adhesion or massa intermedia.

Cerebral Aqueduct (Aqueduct of sylvius):

• The cerebral aqueduct is a narrow channel about 1.8cms long, connects the third with the fourth ventricle.

• It is lined with ependyma and is surrounded by a layer of gray matter called the central gray.

• The direction of flow of CSF from third to fourth ventricle.

• There is no choroid plexus in the cerebral aqueduct.

Fourth Ventricle

The fourth ventricle is a tent or rhomboid shaped space situated ventral to cerebellum and dorsal to the pons and upper part of medulla.

Its boundaries are:• Roof: - Vermis and the superior cerebellar peduncle which forms the

lateral connection from the pons to the cerebellum. • Floor (rhomboid fossa): Posterior part of the pons and the cranial

part of medulla oblongata. • The foramen of magendie lies in the middle at the lower end of the

fourth ventricle and opens between the cerebellar tonsils into the cisterna magna.

• The lateral recess of ventricle contains the foramina of Luschka which open into the cisterns of cerebellopontine angles.

Cavum Septum Peliucidum (Fifth Ventricle) and Cavum Vergae (Sixth Ventricle):

• The cavum septum peliucidum and cavum verage lie between the frontal horns and bodies of lateral ventricles. These fluid filled structures are present in all premature infants

• The anterior fornix serves as an arbitary landmark dividing the cavum septum peliucidum anteriorly from the cavum vergae posteriorly.

CSF Physiology:

• The CSF is an ultrafiltrate of blood and clear, colourless fluid.

• The Glucose content is about half that of blood and there is only a trace of protein.

• Onlv a few cells are present and these are lymphocytes. The normal lymphocyte count is 3 cells/mm.

• The normal C.S.F pressure: 100-200mm of H20. • The total volume of CSF in the subarachnoid space

and within the ventricles: 130-150ml.• The rate of CSF formation ranges from 0.3-0.4ml/min

LU

Composition:

• Color - clear; Microscopy - Nil-5cell/cu.mm. (Lymphocytes)

• Biochemical: Glucose=50-80mg/100ml• Chlorides=720-750mg/100ml• Protein=20-40mg/ 100ml• Also contains urea, Na, K, Ca and bicarbonate.

Function:

• Acts as a cushion - by spreading impact injury.• Serves as reservoir and helps in regulation in

of contents of skull.• Carry nutrients to brain - plays an active part

in nourishment of nervous system.

CSF FLOWNAME FROM TO

RIGHT AND LEFT INTERVENTRICULAR FORAMINA (MONRO)

LATERAL VENTRICLES THIRD VENTRICLE

CEREBRAL AQUEDUCT (SYLVIUS) THIRD VENTRICLE FOURTH VENTRICLE

MEDIAN APERTURE (MAGENDIE) FOURTH VENTRICLE SUBARACHNOID SPACE/

CISTERNA MAGNA

RIGHT AND LEFT LATERAL APERTURE (LUSCHKA)

FOURTH VENTRICLE SUBARACHNOID SPACE/CISTERN OF GREAT CEREBRAL VEIN

Hydrocephalus

• Hydrocephalus can be defined broadly as a disturbance of formation, flow, or absorption of cerebrospinal fluid (CSF) that leads to an increase in volume occupied by this fluid in the CNS

CLASSIFICATION AND CAUSATIVE FACTORS:I.Non Obstructive:

1. Overproduction1. Choroid plexus papilloma2. Villous hypertrophy of choroid

plexus

2. Increased CSF pulse pressure:3. High flow arterio venous

malformations 4. Jugular venous thrombosis5. Superior venacaval

obstruction6. Increased CSF mean

pressure

II. Non-Communicating (Obstructive):

1. Post-inflammatory (post infection)2. Congenital anomalies Aqueduct stenosis

Dandy walker cyst3. Post haemorrhagic4. Tumours

a) Anterior third ventricle: Intra-axial

TraumaColloid cyst, Arachnoid cystHypothalamic gliomaEpendymoma

EXTRA AXIALPituitary adenomaCraniopharyngiomaGiant aneurysmEctopic teratomaArachnoid cystDermoid

b) Posterior third ventricle PinealomaTeratomaCollicular/ Paracollicular cysts,

Vein of Galen aneurysm

III.Communicating (EVOH):

1. Infection2. Neoplastic3. Subarachnoid haemorrhage4. Congenital anomalies

Arnold chiari type II malformation Agenesis of arachnoid granulations

5. Dural venous thrombosis6. Normal pressure hydrocephalus

Criteria to diagnose hydrocephalus

• Prominent temporal horns are amongst the first indicators.

• Transverse diameter of third ventricle > 5mm is considered as abnormal.

• Ballooning of frontal horn with periventricular hypodensity is seen in obstructive hydrocephalus.

• Ventricular Size index may be used.

Common indexes

• Ventricular size index• Frontal horn ratio• Ventricular angle• Temporal horn ratio

• Ventricular size index RATIO OF TRANSVERSE DIAMETER OF FRONTAL HORNSRATIO OF TRANSVERSE DIAMETER OF SKULL AT INNER TABLE

NORMAL = 16-30%MILD = 30-29%MODERATE = 40-46%SEVERE = >47%

**Dated on 7-03-2001, Dr.Priya chudgar, KEM hospital, mumbai

Frontal horn ratio

Maximum width of frontal hornTransverse diameter of inner table of calvarium

at same level

Normal = 35%Atrophy = 45-50%Hydrocephalus = >45% often exceeds 55%

**Ventricular Enlargement,Hans tritthart. 2006, Part 2, 251-256, DOI: 10.1007/4-431-28576-8_39.**FRONTAL HORN RATIO, Mohammad Jamous, Sandeep Sood, Ravi Kumar, Steven HamPediatric Neurosurgery 2003;39:17-

21 (DOI: 10.1159/000070874)

Frontal horn index

Ventricular angle

• Formed by two frontal horns

• Third ventricle and frontal horns must be in seen in same slice.

• Normal and atrophy = 95-140 degrees• Obstructive = 60-95 degrees Hydrocephalus

Temporal horn ratio

• Draw two parallel line to the temporal horn.

• Normal =3.5mm• Abnormal>5mm

INDEXESOBSTRUCTIVE

HYDROCEPHALUS ATROPHY

ANGLE OF FRONTAL HORNS ACUTE OBTUSE

FHR WIDE(>55%) NARROW(45-50%)

TEMPORAL HORN RATIO WIDE NARROW

SULCI AND CISTERNS OBLITERATED WIDENED

CSF Space Measurements:• The transverse diameter of lateral ventricles measured at

their maximum diameter, between outer edges of bodies 3.5-4cms.

• Vertical diameter of third ventricle = 2.0cmsWidth of third ventricle - 4-8mm

• Aqueduct of Sylvius = 1.5mm

• Maximum height of the fourth ventricleAverage (normal) = 14.6mm AP diameter of IV ventricle Average (normal) = 8mm

Clinical manifestations

• Depends on• Age• Nature of lesion causing obstruction• Duration• Rate of raise in intracranial pressure

• Infants:• Macrocrania• Wide anterior fontanellae• Dilated scalp veins• “Setting sun” eye sign• Delayed milestones• Epilepsy and mental retardation.

Older children and adults

• Irritablity, lethargic, poor appetite and vomiting.

• Headache• “Cracked pot” sign or “macewen” sign• Tremor

TESTS:Transillumination testFundoscopy

PapillodemaChorioretinitis

Careful examination of skull and spineSize of anterior fontanallaeSkin lesionsCafé-au-lait spots