CEREBRAL CIRCULATION AND CEREBROSPINAL FLUID [CSF] Sultan Ayoub Meo MBBS, PGC Med Ed, M.Phil, Ph.D...

CEREBRAL CIRCULATION AND CEREBROSPINAL

FLUID [CSF]

Sultan Ayoub Meo MBBS, PGC Med Ed, M.Phil, Ph.D

Professor, Department of PhysiologyCollege of Medicine, King Saud University

CEREBRAL CIRCULATIONThe Circle of Willis is

the joining area of several arteries at

the bottom (inferior) side of the brain. At the Circle of Willis, the internal carotid arteries branch into

smaller arteries that supply oxygenated blood over 80% of

the cerebrum.

CEREBRAL CIRCULATION


The Circle of Willis is a vital formation of arteries at

the base of the brain OR

Grouping of arteries near the base of the brain which

is called the Arterial Circle of Willis.

It is named after an English physician named

Thomas Willis, who discovered it and then published

his findings in his 1664, a seminal peace on the

inner workings of the brain entitled, Cerebri anatomi

(from the Latin for “Anatomy of the Brain”).

CEREBRAL CIRCULATIONThe brain receives its

blood supply from four main arteries: the two

internal carotid arteries and the two vertebral arteries.

The clinical consequences of

vascular disease in the cerebral circulation is

depend upon which vessels or combinations of vessels are involved.

CEREBRAL CIRCULATIONThe vertebral arteries unite to form Basilar artery

The basilar artery and the carotids form the circle of

Willis below the hypothalamus

The circle of Willis is origin of six large vessels

supplying the cerebral cortex

Substances injected into one carotid artery

distributed almost completely to the cerebral

hemisphere on that side. Normally no crossing over

occurs probably because the pressure is equal on

both sides

CEREBRAL CIRCULATIONThe arteries and arterioles supply blood to the

brain are highly specialized, include both vascular smooth muscle and endothelial cells that are

unlike vascular cells from the peripheral circulation or other vascular beds.

The vascular smooth muscle is highly responsive to changes in pressure, a process called myogenic

activity, that contributes to autoregulation of cerebral blood flow. The endothelial cells in the brain circulation are also highly specialized and

provide a barrier to fluid movement called the blood-brain barrier. When these normal cell

processes fail or altered such as in hypertension

CEREBRAL CIRCULATIONFainting: Temporary loss of consciousness,

weakness of muscles, and inability to stand up,

caused by sudden loss of blood flow to the brain.

Fainting is a relatively common symptom caused

by a variety of problems relating to changes in

blood pressure.

The American Heart Association reports that

fainting is responsible for 3% of all visits to

emergency rooms and 6% of all admissions to

hospitals.

CEREBRAL CIRCULATIONStroke: Stroke occurs when the blood supply to a

part of the brain is blocked resulting in the death of

an area within the brain.

If a large vessel is blocked the outcome may be

rapidly fatal or may lead to very severe disability.

If smaller blood vessels are blocked the outcome is

less severe and recovery may be good. The most

common types of disability are the loss of functions

of one side of the body and speech problems.

CEREBRAL CIRCULATIONPrincipal types of stroke:

Thrombotic: Stroke due to the blockage of an artery

leading to or in the brain by a blood clot.

Haemorrhagic: Stroke due to bleeding from a

ruptured blood vessel, usually a consequence of

hypertension.

Embolic: Stroke due to the formation of a blood clot in

a vessel away from the brain. The clot is carried in

the bloodstream until it lodges in an artery leading to

or in the brain.

The thrombotic and haemorrhagic forms are

common,

CEREBRAL CIRCULATIONTransient ischaemic attack: When blood supply to a

part of the brain is temporarily interrupted without

producing permanent damage.

Recovery may occurs within 24 hours.

Usually result from small blood clots or clumps from

plaques of atheroma which get carried into the

blood circulation producing transient blockages.

Occasionally these clots may get carried from the

heart or arteries leading to the brain (e.g. carotid

arteries), rather than from within the cerebral

circulation itself.


Dementia: This may result from repeated episodes

of small strokes which produce progressive

damage to the brain over a period of time.

The main clinical feature of dementia is a gradual

loss of memory and intellectual capacity.

Loss of motor function in the limbs and

incontinence can also occur.

CEREBROSPINAL FLUID

The cerebrospinal Fluid [CSF] is a

clear, colorless transparent, tissue fluid

present in the cerebral ventricles,

spinal canal, and subarachnoid spaces.

CEREBROSPINAL FLUID

CEREBROSPINAL FLUID [FORMATION]

CSF is largely formed by the choroid plexus of the lateral ventricle and remainder in the third and

fourth ventricles.

About 30% of the CSF is also formed from the ependymal cells lining the ventricles and other brain

capillaries.

The choroid plexus of the ventricles actively secrete cerebrospinal fluid.

The choroid plexuses are highly vascular tufts covered by ependyma.

FORMATION & CIRCULATION OF CSF

MECHANISM OF FORMATION OF CSFCSF is formed primarily by secretion and also by

filtration from the net works of capillaries and

ependymal cells in the ventricles called choroid

plexus.

Various components of the choroid plexus from a

blood-cerebrospinal fluid barrier that permits

certain substances to enter the fluid, but prohibits

others.

Such a barrier protects the brain and spinal cord

from harmful substances.

MECHANISM OF FORMATION OF CSF

The entire cerebral cavity enclosing the brain and spinal cord has a capacity of about 1600 to 1700

milliliters

About 150 milliliters of this capacity is occupied by cerebrospinal fluid and the remainder by the

brain and cord.

MECHANISM OF FORMATION OF CSFRate of formation:

About 20-25 ml/hour

550 ml/day in adults. Turns over 3.7 times a day

Total quantity: 150 ml:

30-40 ml within the ventricles

About 110-120 ml in the subarachnoid space [of which 75-80 ml in spinal part and 25-30 ml in the

cranial part].

MECHANISM OF FORMATIONCSF is formed at a rate of about 550 milliliters each

day,. About two thirds or more of this fluid originates as secretion from the choroid plexuses in

the four ventricles, mainly in the two lateral ventricles.

Additional small amount of fluid is secreted by the ependymal surfaces of all the ventricles and by the

arachnoidal membranes

Small quantity comes from the brain itself through the perivascular spaces that surround the blood

vessels passing through the brain.

MECHANISM OF FORMATIONSecretion by the Choroid Plexus. The choroid plexus, is a cauliflower-like growth of blood vessels covered by a thin layer of epithelial cells. Secretion of fluid by the choroid plexus depends mainly on active transport of sodium ions through the epithelial cells lining the outside of the plexus. The sodium ions in turn pull along large amounts of chloride ions because the positive charge of the sodium ion attracts the chloride ion's negative charge. The two of these together increase the quantity of osmotically active sodium chloride in the cerebrospinal fluid, which then causes almost immediate osmosis of water through the membrane, thus providing the fluid secretion.

MECHANISM OF FORMATION

Less important transport processes move small amount of glucose into the cerebrospinal fluid and both potassium and

bicarbonate ions out of the cerebrospinal fluid into the capillaries.

The resulting characteristics of the CSF are: Osmotic pressure approximately equal to that of plasma sodium

ion concentrationApproximately equal to that of plasma chloride ion

About 15 per cent greater than in plasma potassium ion approximately 40 per cent less glucose

ABSORPTION OF CSF THROUGH ARACHNOID VILLI

The arachnoidal villi are fingerlike inward projections of the arachnoidal membrane through the walls into

venous sinuses.

villi form arachnoidal granulations can protruding into the sinuses.

The endothelial cells covering the villi have vesicular passages directly through the bodies of the cells large

enough to allow relatively free flow of (1) cerebrospinal fluid, (2) dissolved protein molecules, and (3) even

particles as large as red and white blood cells into the venous blood.

COMPOSITION OF CSF

Proteins = 20-40 mg/100 mlGlucose = 50-65 mg/100 mlCholesterol = 0.2 mg/100 mlNa+ = 147 meq/Kg H2OCa+ = 2.3 meq/kg H2OUrea = 12.0 mg/100 mlCreatinine = 1.5 mg/100 mlLactic acid = 18.0 mg/100 ml

CHARACTERISTICS OF CSF

Nature:Colour = Clear, transparent fluidSpecific gravity = 1.004-1.007Reaction = Alkaline and does not

coagulateCells = 0-3/ cmmPressure = 60-150 mm of H2O

The pressure of CSF is increased in standing, coughing, sneezing, crying, compression of internal Jugular vein (Queckenstedt’s sign

CIRCULATION OF CSF

Circulation: CSF is mainly formed in choroid pleaxus of the lateral ventricle.

CSF passes from the lateral ventricle to the third ventricle through the interventricular foramen

(foramen of Monro). From third ventricle it passes to the fourth ventricle

through the cerebrol aqueduct. The circulation is aided by the arterial pulsations of the chroid plexuses.

From the fourth ventricle (CSF) passes to the sub arachnoid space around the brain and spinal cord

through the foramen of magendie and foramina of luschka.

CIRCULATION OF CSFLateral ventricle

Foramen of Monro [Interventricular foramen]

Third ventricle:

Subarachnoid space of Brain and Spinal cord

Fourth ventricle:

Cerebral aqueduct

Foramen of megendie and formen of luschka

CIRCULATION OF CSF

Circulation: CSF slowly moves cerebromedullary cistern and pontine cisterns

and flows superiorly through the interval in the tentorium cerebelli to reach the inferior

surface of the cerebrum. It moves superiority over the lateral aspect of each cerebrol

hemisphere.

FUNCTIONS OF CSF

A shock absorberA mechanical bufferAct as cushion between the brain and craniumAct as a reservoir and regulates the contents of the craniumServes as a medium for nutritional exchange in CNSTransport hormones and hormone releasing factorsRemoves the metabolic waste products through absorption

CSF AND INFLAMMATIONIncreased inflammatory cells [pleocytosis] may be caused by infectious and noninfectious

processes.

Polymorphonuclear pleocytosis indicates acute suppurative meningitis.

Mononuclear cells are seen in viral infections (meningoencephalitis, aseptic meningitis),

syphilis, neuroborreliosis, tuberculous meningitis, multiple sclerosis, brain abscess and brain

tumors.

CSF AND PROTEINS

Increased protein: CSF protein may rise to 500 mg/dl in bacterial meningitis.

A more moderate increase (150-200 mg/dl) occurs in inflammatory diseases of meninges (meningitis,

encephalitis), intracranial tumors, subarachnoid hemorrhage, and cerebral infarction.

A more severe increase occurs in the Guillain-Barré syndrome and acoustic and spinal schwannoma.

CSF AND PROTEINS

Multiple sclerosis: CSF protein is normal or mildly increased.

Increased IgG in CSF, but not in serum [IgG/albumin index normally 10:1].

90% of MS patients have oligoclonal IgG bands in the CSF.

Oligoclonal bands occur in the CSF only not in the serum.

The CSF in MS often contains myelin fragments and myelin basic protein (MBP).

MBP can be detected by radioimmunoassay. MBP is not specific for MS. It can appear in any condition

causing brain necrosis, including infarcts.

CSF & LOW GLUCOSELow glucose in CSF:

This condition is seen in suppurative tuberculosis

Fungal infections

Sarcoidosis

Meningeal dissemination of tumors.

Glucose is consumed by leukocytes and tumor cells.

BLOOD IN CSF

Blood: Blood may be spilled into the CSF by accidental puncture of a leptomeningeal vein

during entry of the LP needle.

Such blood stains the fluid that is drawn initially and clears gradually. If it does not clear, blood

indicates subarachnoid hemorrhage.

Erythrocytes from subarachnoid hemorrhage are cleared in 3 to 7 days. A few neutrophils and

mononuclear cells may also be present as a result of meningeal irritation.

Leukemia Cells in CSF

CSF AND XZNTHOCHROMIA

Xanthochromia [blonde color] of the CSF following subarachnoid hemorrhage is due to oxyhemoglobin which appears in 4 to 6 hours

and bilirubin which appears in two days.

Xanthochromia may also be seen with hemorrhagic infarcts, brain tumors, and

jaundice.

CSF AND TUMOUR CELLS

Tumor cells indicate dissemination of metastatic or primary brain tumors in the subarachnoid

space.

The most common among the latter is medulloblastoma.

They can be best detected by cytological examination.

A mononuclear inflammatory reaction is often seen in addition to the tumor cells.

INDICATIONS OF CSF EXAMINATION

Infections: meningitis, encephalitisInflammatory conditions: Sarcoidosis, neuro syphilis, SLEInfiltrstive conditions:Leukamia, lymphoma, carcinomatous - meningitisAdministration of drugs in CSF (Therapeutic aim)Antibiotics: (In case of meningitis)AntimitoticsDiagnostic aim: Myelography, CisternographyAnaesthetics are also given through the lumbar Puncture.

CONTRA-INDICATIONS FOR LP

Local skin infections over proposed puncture site (absolute contraindication)Raised intracranial pressure (ICP); exception is pseudotumor cerebriSuspected spinal cord mass or intracranial mass lesion (based on lateralizing neurological findings or papilledema)Uncontrolled bleeding diathesisSpinal column deformities (may require fluoroscopic assistance)Lack of patient cooperation

LUMBAR PUNCTURE

A lumbar puncture also called a spinal tap is a procedure where a sample of

cerebrospinal fluid is taken for examination.

CSF is mainly used to diagnose meningitis [an infection of the meninges].

It is also used to diagnose some other conditions of the brain and spinal cord.

PRECAUTIONS FOR LUMBAR PUNCTURE

Asked to sign a consent form

Ask about taking any medicines

Are allergic to any medicines

Have / had any bleeding problems

Ask about medications such as aspirin or warfarin

Ask the female patient might be pregnant

Empty the bladder before the procedure

LUMBAR PUNCTURE

1. Material for sterile technique [gloves and mask are necessary]2. Spinal Needle, 20 and 22-gauge3. Manometer4. Three-way stopcock5. Sterile drapes6. 1% lidocaine without epinephrine in a 5-cc syringe with a 22 and 25-gauge needles7. Material for skin sterilization8. Adhesive dressing9. Sponges - 10 X 10 cm

LUMBAR PUNCTURE [Complications]

Post lumbar puncture headache occurs in 10% to 30% of patients within 1 to 3 days and lasts 2 to 7 days.

The pain is relieved by lying flat.

Treatment consists of bed rest and fluid with simple analgesics.

LUMBAR PUNCTURE [Complications]Headache following a lumbar puncture is a common and often debilitating syndrome. Continued leakage of cerebrospinal fluid from a puncture site decreases intracranial pressure, which leads to traction on pain-sensitive intracranial structures. The headache is characteristically postural, often associated with nausea and optic, vestibular, or otic symptoms. Although usually self-limited after a few days, severe postural pain can incapacitate the patient. Management is mainly symptomatic, but definitive treatment with the epidural blood patching technique is safe and effective when done by an expert operator.

LUMBAR PUNCTURE

Patient usually lie on a bed on side with knees pulled up against the chest.

It may also done with sitting up and leaning forward on some pillows. Sterilize the area. push a needle through the skin and tissues

between two vertebra into the space around the spinal cord which is filled with CSF.

CSF leaks back through the needle and is collected in a sterile container.

As soon as the required amount of fluid is collected the needle is taken out and a plaster is

put over the site of needle entry.

LUMBAR PUNCTURE

Sent the sample to lab to be examined under the microscope to look for bacteria.

It is also 'cultured' for any bacterial growth

The fluid can also be tested for protein, sugar and other chemicals if necessary. Sometimes also measure the pressure of

the fluid. This is done by attaching a special tube to the needle which can

measure the pressure of the fluid coming out.

LUMBAR PUNCTURE

CEREBROSPINAL FLUID

LUMBAR PUNCTURE

LUMBAR PUNCTURE

Place the patient in the lateral decubitus position lying on the edge of the bed and facing away from

operator. Place the patient in a knee-chest position with the

neck flexed. The patient's head should rest on a pillow, so that the entire cranio-spinal axis is parallel to the bed. Sitting position is the second choice because there

may be a greater risk of herniation and CSF pressure cannot be measured

LUMBAR PUNCTUREFind the posterior iliac crest and palpate the L4

spinous process, and mark the spot with a fingernail.

Prepare the skin by starting at the puncture site.

Anesthetize the skin using the 1% lidocaine in the 5 mL syringe with the 25-gauge needle. Change to 22-gauge needle before anesthetizing between the

spinous process.

Insert in the midline with the needle parallel to the floor and the point directed toward the patient's

umbilicus

LUMBAR PUNCTURE

Advance slowly about 2 cm or until a "pop'' (piercing a membrane of the dura) is heard.

Then withdraw the stylet in every 2- to 3-mm advance of the needle to check for CSF return.

If the needle meets the bone or if blood returns (hitting the venous plexus anterior to the spinal

canal), withdraw to the skin and redirect the needle.

If CSF return cannot be obtained, try one disk space down

HYDROCEPHALUSLHydrocephalus" means excess water in the cranial

vault.

This condition is frequently divided into communicating hydrocephalus and noncommunicating hydrocephalus.

In communicating hydrocephalus fluid flows readily from the ventricular system into the

subarachnoid space,

in noncommunicating hydrocephalus fluid flow out of one or more of the ventricles is blocked.

HYDROCEPHALUSL

CEREBRAL CIRCULATION AND CEREBROSPINAL FLUID [CSF] Sultan Ayoub Meo MBBS, PGC Med Ed, M.Phil, Ph.D...

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