Module Exam 6: Cerebral Circulation Flashcards
Posterior Circulation is from the
Basilar Artery
Anterior Circulation is from the
Internal Carotid Artery
Joins the two Anterior Cerebral Arteries
Anterior Communicating Artery
Joins the Internal Carotid Artery with the Basilar circulation
Posterior Communicating Artery
Normally communicating arteries have little _____ unless occlusion in one artery occurs.
Blood flow
Circle of Willis variants: the complete circle is seen in only ______ of individuals.
20-25%
Circle of Willis variants: one or both _______ are hypoplastic in ____.
Posterior Communicating Artery. 34%.
Circle of Willis variants: The _____________ may be absent or hypoplastic in _____.
Precommunicating segment of ACA (A1). 25%.
Circle of Willis variants: bilateral hypoplastic ___ segments in ___.
P1. 11%.
________ drain into dural venous sinuses which eventually empty into the _____.
Cerebral veins. IJV.
Dural venous sinuses
Superio sagittal sinus, Inferior sagittal sinus, Transverse sinus, Sigmoid sinus, Cavernous sinus & Straight sinus “SITS CS”
Major cerebral veins
Basal vein of Rosenthal, Internal cerebral vein & Great cerebral vein of Galen “BIG”
In 1981, Lumbar puncture was introduced by
Quincke
In 1912, he made the first correlations between disease processes and the cellular and chemical changes in the CSF.
Mestrezat
In 1937, they published their classic monograph on the CSF changes in all types of disease.
Merritt & Fremont-Smith
In 1950s, this technique were introduced
Membrane filtration
Their studies provide the basis of our knowledge of CSF formation, circulation and absorption. Pappenheimer, Ames, Fishman & Davson.
Dandy & Weed
Total CSF volume in the adult is
150mL
Total CSF volume in the subarachnoid space is
30mL
About how many volume of CSF fluid is produce per day
500 mL
Helps to preserve a stable chemical environment for neurons and their myelinated fibers. Act as a mechanical support and it removes the wast products of cerebral metabolism.
CSF
CSF provides ______ for the brain and SC. Provides ______ to the brain.
Water jacket. Buoyancy.
Waste products removed by CSF
CO2, Lactase & Hydrogen ion
Average rate of CSF formation is
21-22mL/h (0.35mL/min)
The CSF is therefore renewed _______ daily.
4x or 5x
Main sites of CSF formation
Choroid plexuses
Choroid plexuses are located in the
Floor of lateral, third and fourth ventricles
In CSF formation, The thin walled vessels of the plexuses allow _______ of substances from the blood plasma into the extracellular space surrounding choroid cells.
Passive diffusion
In CSF formation, Electrolytes equilibrate with the CSF at all points in the _______ and _________. The same is true of ______. The transport of sodium is accomplished by the action of a _________ exchange pump at the apical surface of the choroid plexus cells.
Ventricular & Subarachnoid spaces. Glucose. Sodium potassium ion exchange.
In CSF formation, it is also known that the penetration of certain drugs and metabolites is in direct relation to their ________. Ionized compound such as _______ & ___, being relatively insoluble in lipids, enter the CSF slowly unless facilitated by a membrane transport system.
Lipid solubility. Hexoses & AAs.
Is a collective term for all barriers lying between the plasma and the neuropil.
Blood Brain Barrier
BBB is formed by the tight junction, _________, of capillary endothelial cells.
Zonula occludens
Physiologically, the system of barriers enables the regulation of the ______ of brain tissue and CSF and the ____ & _______.
Osmolarity. ICP & volume.
Is permeable to water soluble substances but not to lipo-soluble substances such as anesthetics, psycho active drugs and analgesics.
Blood CSF barrier
Is generally permeable to liposoluble substances (of molecular weight less than ______) but not to water soluble substances.
Blood Brain Barrier. 500 daltons.
Specialized areas without BBB
Vascular organ of the lamina terminalis, Median eminence, Area postrema, Pineal body, Posterior pituitary & Subfornicial organ “VMAPPS”
The fluid filled cerebral ventricles constitute the
Inner CSF space
CSF circulation: 1. two lateral ventricles communicate with the ________ through the intraventricular __________.
Third ventricle. Foramen of Monro.
CSF circulation: 2. Fluid passes from the third ventricle through the _________ into the _______.
Aqueduct of Sylvius/Cerebral Aqueduct. 4th ventricle.
CSF circulation: 3. Through the single midline foramen (________) and paired lateral foramina (________) into the subarachnoid space (outer CSF space)
Magendie. Luschka.
Cerebromedullary
Cisterna magna
From the conus medullaris to about the 2nd sacral vertebra; contains the filum terminale and nerve roots of the cauda equina.
Lumbar cistern
CSF circulation: the pressure is highest in the _______ & diminishes successively along the ________ pathways.
Ventricles. Subarachnoid.
CSF circulation: help drive the fluid from the ventricular system.
Arterial pulsations of the choroid plexuses
CSF absorption: absorption of the CSF is through the _______. Microscopic excrescences of arachnoid membrane that penetrate the ______ and protrude into the ________ and other venous structures form the ___________.
Arachnoid villi. Dura. Superior Sagittal Sinus. Pacchionian granulation or bodies.
CSF absorption: the arachnoid villi are present at the ____ of the brain and around the ________ and have thought to act as functional valves that permit unidirectional bulk flow of CSF into the vascular lumen.
Base. SC roots.
ICP & CSF pressure is measured by
Lumbar puncture
Normal ICP
8mmHg or 110 mmH2O
1 mmHg is equal to _____ mmH2O
13.7
The inhalation and retention of ____ raises the blood PCO2 and correspondingly decreases the ____ to the CSF.
CO2. pH.
Acts as a potent cerebral vasodilator, causing an increase in cerebral blood flow and leading to intracranial hypertension.
CO2
Reduces PCO2. It increases the pH and teh cerebral vascular resistance and thereby decreases CSF pressure.
Hyperventilation
This maneuver of lowering the _________ content os utilized in the treatment of acutely raised ICP.
Arterial CO2
Exerts an almost immediate effect on CSF pressure by increasing the volume of blood in the cerebral veins, venules and dural sinuses.
Increased venous pressure
Cause the rise of ICP that is transmitted to the lumbar subarachnoid space. This is the basis of the _________.
Jugular vein compression. Queckenstedt test.
Also causes an increase intra-thoracic pressure, which is transmitted to the jugular and them to the cerebral and spinal veins.
Vasalva maneuver
The ICP rises in ________, when central and jugular venous pressures become elevated.
Heart failure
Elevates ICP by obstructing the SVC
Mediastinal tumors
The intact cranium and vertebral canal, together with the relatively inelastic dura, form a rigid container, such that an increase of any of its contents: brain, blood & CSF. will elevate the ICP. Furthermore, an increase in the volume of any one of these three components must be at the expense of the other two.
Monro-Kellie Doctrine
CPP stands for
Cerebral Perfusion Pressure
MAP stands for
Mean Arterial Pressure
ICP stands for
Intracranial Pressure
Formula for CPP
CPP= MAP-ICP
Cause of Increased ICP: A _________ mass.
Extra/cerebral
Cause of Increased ICP: Generalized __________.
Brain swelling
Cause of Increased ICP: An increase in _______.
Venous pressure
Cause of Increased ICP: _______ of the flow and absorption of CSF.
Obstruction
Cause of Increased ICP: Any process that _______ the volume of CSF.
Expand
After several day or longer, may result in periodic visual obscurations.
Papilledema
If papilledema is protracted, _________ & ________ may follow.
Optic atrophy & Blindness
Clinical features of Increased ICP
Headache, Ocular palsies, N & V, Drowsiness & Papilledema “HOND P”
A condition in which there is ventricular enlargement under tension as a result of an obstruction to the flow CSF at some point in its ventricular pathway: aqueduct of sylvius, medullary foramens of exit (Magendia & Luschka) & Basal subarachnoid space.
Hydrocephalus
In hydrocephalus, because of the obstruction, ____ accumulates within the ________ under increasing pressure, enlarging them and expanding the hemispheres.
CSF. Ventricles.
Clinical s/sx of Hydrocephalus
Headache, Drowsy/Stuporous, Bilateral babinski signs are the rule & Vomiting “HD BV”
Early in the process of acute hydrocephalus, the pupils are normal in size and eyes may rove horizontally; as the ventricles continue to enlarge, the pupils become ______, the eyes then cease roving and assume an _________, or there may be bilateral _______ and limitation of _______ gaze.
Miotic. Orthotopic. Abducens palsies. Upward.
In advanced stages of hydrocephalus, which are associated with ______, there is increased tone in the _______ and _____ posturing.
Coma. Lower limbs. Extensor.
There is frontal bossing and the skull tends to be brachiocephalic. With marked enlargement of the skull, the face looks relatively small and pinched and the skin over the cranial bones is tight and thin, revealing prominent distended veins.m
Congenital Hydrocephalus
The infant is fretful, feeds poorly and may vomit frequently. The infant appear languid, uninterested in his surroundings and unable to sustain activity. Later it is noticed that the ________ are retracted and the eyes tend to turn _____; there is paralysis of _____ gaze and the sclerae above the irises are visible _________ sign.
Chronic hydrocephalus. Upper eyelid. Down. Upward setting-sun sign.
Causes of Chronic Hydrocephalus: intraventricular ______ in premature infants.
Hemorrhages
Causes of Chronic Hydrocephalus: fetal and neonatal ________.
Infections
Causes of Chronic Hydrocephalus: ________ malformation.
Type II Chiari
Causes of Chronic Hydrocephalus: Aqueductal ______ & ______.
Atresis & Stenosis.
Causes of Chronic Hydrocephalus: the _______ syndrome.
Dandy-Walker Syndrome
Patient may complain of bifrontal or bioccipital headaches. S/sx are predominantly those of a _________ disorder of mentation or of gait. Slowness of mental response, inattentiveness, distractibility, perseveration and inability to plan activity or to sustain any type of complex cognitive function.
Occult Hydrocephalus. Frontal lobe.
In Occult Hydrocephalus: _______ may be slightly impaired.
Memory
In Occult Hydrocephalus: ____ deteriorates early in the course of hydrocephalus.
Gait
In Occult Hydrocephalus: A _______ & _______ of the hands and feet are variably present; _______ are sometimes extensor. There may be sphincter _______.
Suck & Grasp reflexes. Plantar reflex. Incontinence.
Slowness of mental response
Abulia
May involve meningitis, ventriculitis, myelitis & encephalitis.
CNS infection
Infection of gray and white matter of the brain
Encephalitis
Infection of the SC
Myelitis
Infection of ventricular system
Ventriculitis
Infection of leptomeninges & CSF spaces
Meningitis
Symptoms are fever, severe headache & backache, photophobia & phonophobia, N & V, impairment of consciousness, stiff neck and hyper extended posture with opisthotonus.
Meningitis
