CEREBRAL CIRCULATION AND CEREBROSPINAL FLUID [CSF] Sultan Ayoub Meo MBBS, PGC Med Ed, M.Phil, Ph.D Professor, Department of Physiology College of Medicine, King Saud University

CEREBRAL CIRCULATION The 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 CIRCULATION The 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 CIRCULATION The 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 CIRCULATION The 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 CIRCULATION Fainting: 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 CIRCULATION Stroke: 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 CIRCULATION Principal 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 CIRCULATION Transient 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.

CEREBRAL CIRCULATION 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.

CEREBRAL CIRCULATION

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 CSF CSF 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 CSF Rate of formation: About ml/hour 550 ml/day in adults. Turns over 3.7 times a day Total quantity: 150 ml: ml within the ventricles About ml in the subarachnoid space [of which ml in spinal part and ml in the cranial part].

MECHANISM OF FORMATION CSF 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 FORMATION Secretion 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.sodium chloride

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 concentration Approximately 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 ml Glucose=50-65 mg/100 ml Cholesterol=0.2 mg/100 ml Na+= 147 meq/Kg H2O Ca+=2.3 meq/kg H2O Urea=12.0 mg/100 ml Creatinine=1.5 mg/100 ml Lactic acid=18.0 mg/100 ml

CHARACTERISTICS OF CSF Nature: Colour = Clear, transparent fluid Specific gravity = Reaction = Alkaline and does not coagulate Cells = 0-3/ cmm Pressure = 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 CSF Lateral 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 absorber A mechanical buffer Act as cushion between the brain and cranium Act as a reservoir and regulates the contents of the cranium Serves as a medium for nutritional exchange in CNS Transport hormones and hormone releasing factors Removes the metabolic waste products through absorption

CSF AND INFLAMMATION Increased 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 INFLAMMATION Increased 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 ( 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-Barr é 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 GLUCOSE Low 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, encephalitis Inflammatory conditions:Sarcoidosis, neuro syphilis, SLE Infiltrstive conditions:Leukamia, lymphoma, carcinomatous - meningitis Administration of drugs in CSF (Therapeutic aim) Antibiotics:(In case of meningitis) Antimitotics Diagnostic aim: Myelography, Cisternography Anaesthetics 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 cerebri Suspected spinal cord mass or intracranial mass lesion (based on lateralizing neurological findings or papilledema) Uncontrolled bleeding diathesis Spinal 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-gauge 3. Manometer 4. Three-way stopcock 5. Sterile drapes 6. 1% lidocaine without epinephrine in a 5-cc syringe with a 22 and 25-gauge needles 7. Material for skin sterilization 8. Adhesive dressing 9. 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

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 PUNCTURE Find 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

HYDROCEPHALUSL Hydrocephalus" 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