cerebral circulation & CSF

Indicate The Correct Letter Shown in the MRI to the appropriate sign or symptom given below. Difficulty in swallowing the oral secretions? Patient is finding difficulty from sitting to standing posture? Alexia without Agraphia? Contralateral Leg Weakness? Patient is unable to clench his teeth?

Blood Supply to Brain About 18% -20% of the total blood volume in the body circulates in the brain(about 750ml), which accounts for about 2% of the body weight. The blood transports oxygen, nutrients, and other substances necessary for proper functioning of the brain tissues and carries away metabolites. Loss of consciousness occurs in less than 15 seconds after blood flow to the brain has stopped, and irreparable damage to the brain tissue occurs within 5 minutes. Cerebrovascular disease, or stroke, occurs as a result of vascular compromise or hemorrhage and is one of the most frequent sources of neurologic disability. Nearly half of the admissions to many busy neurologic services are because of strokes. Cerebrovascular disease is the third most common cause of death.

Blood Supply to Brain The brain is unusual in that it is only able to withstand very short periods of lack of blood supply (ischaemia). This is because neurons produce energy (ATP) almost entirely by oxidative metabolism of substrates including glucose and ketone bodies, with very limited capacity for anaerobic metabolism. Without oxygen, energy dependent processes cease leading to irreversible cellular injury if blood flow is not re-established rapidly (3 to8 minutes under most circumstances). Therefore, adequate cerebral blood flow must be maintained to ensure a constant delivery of oxygen and substrates and to remove the waste products of metabolism Cerebral blood flow (CBF) is dependent on a number of factors that can broadly be divided into: a. Those affecting cerebral perfusion pressure b. Those affecting the radius of cerebral blood vessels

Blood Supply of Brain & Applied aspects internal carotid circulation Vertebrobasilar circulation Circle of Willis ‘Stroke’ Venous drainage CSF

Internal carotid artery Arises from common carotid artery Enters skull through carotid canal of petrous bone & proceeds through cavernous sinus curving in an ‘S’ shape (carotid siphon) Supplies rostral 2/3rds of brain including main parts of basal nuclei & internal capsule

cerebral circulation

Internal carotid artery gives off several collateral branches before it divides into its two terminal branches: middle cerebral artery & anterior cerebral artery

ICA - collateral branches inferior & superior hypophyseal arteries & the ophthalmic artery come off the ica as soon as the artery has entered the skull posterior communicating & anterior choroidal arteries are the other named branches

Ophthalmic artery Ophthalmic artery: It passes into the orbit through the optic foramen. It supplies the structures of the orbit, frontal and ethmoidal sinuses, frontal part of the scalp and dorsum of the nose. Anterior choroidal artery: It supplies the optic tract, choroid plexus of the lateral ventricle, hippocampus and some of the deep structures of the hemisphere, including the internal capsule and globus pallidus.

Ophthalmic artery 1. ethmoidal arteries 2. ciliary arteries 3. optic nerve & ophthalmic artery 4. central retinal artery 5. retinal arteries 6. supratrochlear artery 7. supraorbital artery 8. dorsal nasal artery 9. anterior ciliary artery

Middle cerebral artery largest terminal branch of the ica runs between temporal & frontal lobes in lateral fissure many perforating branches (7-10 striate arteries) emerge from the initial segment of the mca and penetrate the anterior perforating space to supply: striatum, putamen, globus pallidus & internal capsule

middle cerebral striate arteries

middle cerebral artery MCA divides into several large arteries on the surface of the insula continues laterally to emerge on surface of hemisphere practically the whole lateral surface of the brain including motor & sensory areas of the cortex is supplied by branches of the mca

cortical distribution of MCA

functional distribution of MCA

anterior cerebral artery smaller than middle cerebral artery this terminal branch of the ica runs between the optic nerve and anterior perforating space to the region of the longitudinal fissure connected with the corresponding artery on the opposite side by the short anterior communicating artery

anterior cerebral artery perforating arteries to the hypothalamus and to other important structures in the basal parts of the brain arise from the proximal part of the ACA distal to the anterior communicating artery the two ACA’s ascend in the longitudinal fissure (where they curve upwards & backwards above the corpus callosum)

anterior cerebral artery although the two arteries lie close together during their course in the longitudinal fissure they are separated by the falx cerebri terminal ramifications of the aca supply most of the corpus callosum as well as the medial surfaces of the frontal & parietal lobes - including leg area in the paracentral lobule

cortical distribution of ACA

functional distribution of ACA

vertebrobasilar system two vertebral arteries (carrying about 1/3rd of cerebral blood) arise from first part of the subclavian arteries ascend through foramen transversarium of cervical vertebrae then enter skull through foramen magnum

vertebrobasilar system major branches of vertebral artery anterior spinal artery posterior inferior cerebellar artery bulbar branches +/- anterior inferior cerebellar artery both vertebral arteries unite at the pontomedullary junction to form the basilar artery

vertebrobasilar system basilar artery continues in midline of pons before it bifurcates into its two terminal posterior cerebral arteries at pontomesencephalic junction gives off: anterior inferior cerebellar artery internal auditory artery pontine arteries superior cerebellar artery

cortical distribution of PCA

functional distribution of PCA

the circle of Willis anterior & posterior communicating arteries help form an arterial circle ‘of Willis’ on the ventral aspect of the brain provides possibility of collateral circulation in event of occlusion in one of the major arteries proximal to the circle

the ‘circle of Willis’

regional blood supply

stroke - definition “sudden neurological deficit of vascular aetiology lasting more than 24 hours” compared with TIA (transient ischaemic attack) indicates a transient neurological deficit of vascular origin lasting less than 24 hours

stroke - categorized as cerebral infarction (80%) signifying ischaemic brain damage due to occlusion of a vessel cerebral haemorrhage primary pathology involves vascular rupture & extravasation of blood into surrounding tissue or compartments

stroke artery territory mca occluson aca occlusion stroke syndrome contralateral hemiplegia, hemianaesthesia, homonymous hemianopia, aphasia, inattention, cortical sensory loss hemiparesis chiefly in the leg

stroke artery territory internal carotid artery occlusion pca occlusion stroke syndrome mixture of aca & mca syndromes (may be asymptomatic) homonymous hemianopia, disconnection syndromes, hemianaesthesia, amnesia, midbrain & thalamic syndromes

stroke artery territory vertebrobasilar thrombosis (basilar occlusion) ventral pontine infarction stroke syndrome quadriparesis, bulbar paralysis, impaired gaze, coma quadriparesis, absent horizontal (but retained vertical) gaze, normal conscious state (‘locked in’ syndrome)

stroke artery territory lateral medullary syndrome (vertebral, pica or aica) stroke syndrome ipsilateral ataxia (icp), Horner’s syndrome, dysphagia & dysarthria (CN 9 & 10), vertigo, nausea & Nystagmus (vest. nuclei), ipsilateral facial anaesthesia (CN 5), contralateral pain & temperature loss (spinothalamic tract)

stroke artery territory medial medullary syndrome stroke syndrome ipsilateral paralysis of tongue (CN 12), contralateral hemiparesis (corticospinal tract), contralateral impairment of touch & position sense (medial lemniscus)

lateral medullary syndrome

Weber syndrome

venous drainage superior sagittal sinus --> right transverse sinus (confluence of sinuses) --> right sigmoid sinus inferior sagittal sinus --> straight sinus --> left transverse sinus (confluence of sinuses) --> left sigmoid sinus the sigmoid sinuses --> (become) internal jugular veins at jugular foramen

cavernous sinus located lateral aspect sphenoid receives blood from pituitary gland, orbit through ophthalmic veins & middle cerebral veins cavernous sinus --> superior & inferior petrosal sinuses

cavernous sinus superior petrosal sinus --> junction transverse & sigmoid sinuses inferior petrosal sinus --> internal jugular vein emissary veins link CS with facial & scalp veins

cerebrospinal fluid circulation clear & colorless water-like fluid formed by choroid plexus mainly in lateral ventricles (& to lesser degree in 3rd & 4th ventricles) formation of CSF complex includes both passive filtration & active secretary mechanisms

CSF circulation CSF produced in lateral ventricles enters third ventricle through interventricular foramen flows through cerebral aqueduct into fourth ventricle from fourth ventricle it reaches the subarachnoid space

CSF circulation CSF enters subarachnoid space via three openings: median aperture (posterior medullary velum) two lateral apertures (lateral recesses of fourth ventricle)

CSF circulation collections of microscopic arachnoid villi form macroscopic elevations (arachnoid granulations) that protrude into the lateral expansions of the superior sagittal sinus through openings in the dura flow of CSF is fairly rapid

CSF circulation total volume of CSF in the ventricular system & subarachnoid space is only about 125 ml but it is estimated that about four times that amount (~500 ml) is formed during a 24 hr period a small amount of CSF seeps down around the spinal cord

A 65-year-old man has loss of pain and temperature sensation on the right side of the face and on the left side of the body. Examination shows partial paralysis of the soft palate, larynx, and pharynx, and ataxia, all on the right. The most likely cause of these findings is thrombosis to which of the following arteries? Basilar Right posterior inferior cerebellar Left posterior inferior cerebellar Right superior cerebellar Left superior cerebellar A 59-year-old male suffered a stroke and later presented with a spastic paralysis. Which of the following structures was affected by the stroke that accounts for the spasticity? Ventral horn cells Corpus callosum Postcentral gyrus Internal capsule Substantia nigra

A 81-year-old woman had a cerebrovascular accident month ago A 81-year-old woman had a cerebrovascular accident month ago. Her past medical history is remarkable. She initially presented with slurred speech and right hemiparesis. The hemiparesis resolved, but her speech is still agrammatic and nonfluent, and she has difficulty finding words and completing sentences. Her comprehension is intact, and she appears frustrated when she attempts to speak. The remainder of the neurologic examination is normal. Which of the following best describes her deficit? Apraxia Ataxia Broca’s aphasia Wernicke’s aphasia A 77-year-old right-handed man with a history of atrial fibrillation and diabetes mellitus is brought to the emergency department by his family. His son describes that when his father awoke that morning, he was unable to use words or sentences that made any sense. On examination, the patient has spontaneous, fluent speech, with normal grammatical constructs and prosody. However, the majority of what he says is meaningless. He is unable to follow commands, except to close his eyes. When asked to identify objects, he uses inappropriate substitutions of words. He also fails to repeat words and is unable to read. A lesion of which of the following areas would most likely account for his language deficits? Inferior frontal gyrus Crus cerebri Prefrontal cortex Superior temporal gyrus

A 3-month-old infant was admitted to the pediatric ward because of a large head. The infant stayed quietly in bed most of the day. The circumference of the head was 44 cm (normal value for this age is about 40 cm). The fontanelles protruded, and the cranial sutures were separated. The skull could be transilluminated with a flashlight. Magnetic resonance imaging showed enlarged lateral, third, and fourth ventricles. The closure of the vertebrae was defective in the lower back (spina bifida). Treatment was surgical implantation of a catheter into the lateral ventricle with drainage into the peritoneum. Is this a communicating or Non-communicating type of hydrocephalus? Communicating; because the CSF drainage is impaired within the subarachnoid space or at the level of the arachnoid villi Noncommunicating; the fluid communication between the ventricular system and the subarachnoid space is impaired None of above