Blood Supply and Ventricular Systems Flashcards
CSF has higher concentrations of what ions as compared to blood?
Sodium
Chloride
Magnesium
CSF has lower concentrations of what ions as compared to blood?
Potassium
Calcium
Glucose
Protein
The ventricular system is a series of communicating cavities lined by _________ which is elaborated into complex vascular folds called _____ _______
Ependyma (glial cells); choroid plexuses
What produces CSF and where are the primary areas of production?
Choroid plexus
Primarily in lateral ventricles and 4th ventricle
What are the 4 interconnected ventricles that make up the ventricular system? Where are they located?
2 Lateral ventricles (one in each cerebral hemisphere) 3rd ventricle (between thalami) 4th ventricle (between cerebellum and pons)
Trace the path of CSF from lateral ventricles to the superior sagittal venous sinus
Lateral ventricles Interventricular foramina of monro 3rd ventricle Cerebral aqueduct 4th ventricle
From 4th ventricle either goes to central canal of spinal cord or via median and lateral aperatures to the subarachnoid space
From subarachnoid space to arachnoid granulations, then superior sagittal sinus
Condition characterized by increase in cerebral mass/size d/t presence of excessive CSF, affecting the ventricular system, subarachnoid space, or both
Hydrocephalus
Communicating hydrocephalus is also known as …
External hydrocephalus
[other types include supratentorial external hydrocephalus and infratentorial external hydrocephalus]
External hydrocephalus results in excess accumulation of CSF in the ______ space, _____ ventricular size, and compression of the CNS
Subarachnoid; normal
Supratentorial external hydrocephalus is most commonly associated with what condition?
Senile atrophy of the cortex (alzheimer’s disease)
Noncommunicating hydrocephalus is also known as …
Internal hydrocephalus — CSF produced in the ventricular system does NOT drain into the subarachnoid space, resulting in dilation of the ventricle(s) proximal to the obstruction
3 possibilities for internal hydrocephalus obstructions
Interventricular foramen = 3rd ventricle choroid plexus ependymoma
Cerebral aqueduct = midbrain astrocytoma
Median and lateral apertures = arnold-chiari malformation or dandy-walker cyst
Communicating hydrocephalus is a combination of infratentorial external hydrocephalus and internal hydrocephalus due to an obstruction where? What causes this obstruction?
Narrow space between tentorial notch and midbrain
Obstruction caused by adhesions or fibrosis in subarachnoid spaces from previous inflammation (meningitis), cerebral edema, or uncal herniation
With communicating hydrocephalus, CSF can move through the ventricular system into the infratentorial subarachnoid space, but cannot circulate over the cerebrum to be resorbed at the arachnoid villi near the superior sagittal sinus. What does this result in?
Hypertrophy of ventricles (internal hydrocephalus)
Accumulation of CSF in the infratentorial space (external hydrocephalus)
What is the primary sign/symptom of increased intracranial pressure in someone with hydrocephalus?
Papillaedema
Difference between infants/young children and adults with hydrocephalus
Infants cranial sutures are not fused, so they are able to compensate with enlargement of the cranium
Adults cranial sutures are fused, preventing head enlargement but increased risk of high intracranial pressure
2 other signs of hydrocephalus other than papilledema
Internal strabismus/abducens palsy
Mental retardation
What venous system receives drainage from the spinal cord and is located in the epidural space? Where does it drain to?
Internal venous plexus of Batson
Drains into intervertebral veins and then segmental veins
Deep venous drainage of cerebral hemispheres is partially due to the ______ v. which runs next to the parahippocampal gyrus, receives the thalamostriate and anterior septal veins, and drains into the great vein of Galen
Internal cerebral vein
Deep venous drainage of the cerebral hemispheres is partially due to the _________ v. which runs next to the cerebral peduncle, receives middle deep cerebral and anterior cerebral vv. and drains into the great v. of Galen
Basilar v. (Basal v. of Rosenthal)
Deep venous drainage of cerebral hemispheres is partially d/t the _____ v. which runs next to the posterior portion of the corpus callosum and receives the internal cerebral vein and basal vein of rosenthal, eventually draining into the straight sinus
Great cerebral v. (Great vein of Galen)
Effects of occlusion of great cerebral v. (Of Galen)
Usually fatal, as it drains the deep cerebrum
What condition concerning deep venous drainage of cerebral hemispheres may compress the pineal body and posterior commissure?
Great vein varix
Which venous sinus typically empties directly into the right transverse sinus?
Superior sagittal sinus
Thrombosis of superior sagittal sinus or right transverse sinus leads to what complications?
Cortical ischemia and/or necrosis
The straight sagittal sinus typically empties directly into what venous sinus?
Left transverse venous sinus
Thrombosis of straight sagittal sinus or left transverse sinus may lead to what complications?
Ischemia and/or necrosis of deep cerebrum — usually fatal
The blood brain barrier is composed of what 4 structures?
Endothelial cell layer (w/ tight junctions)
Basement membrane
Pericyte
Foot processes of astrocytes and oligodendrocytes
3 locations where BBB is absent
Pineal body
Area postrema
Median eminence of the hypothalamus
What 2 arteries pierce the dura and run in the subarachnoid space before giving off the cerebral arteries that supply blood to the brain?
Internal carotid a.
Vertebral aa.
The cerebral arteries run in the ________ space. Branches penetrate into the brain parenchyma and are surrounded by ___________ space (perivascular space) and __________ mater
Subarachnoid; virchow-robin; pia
Anterior cerebral circulation comes from the internal carotid aa. what are its main branches?
Ophthalmic a.
Anterior choroidal a.
Anterior cerebral a.
Middle cerebral a.
One of the branches of the internal carotid a. supplying anterior circulation to the brain is the anterior choroidal a. What structures does it specifically supply?
Choroid plexus of the lateral ventricle Internal capsule Basal ganglia Thalamus Rostral midbrain
Which branch of the internal carotid artery is prone to thrombosis d/t its long course in the subarachnoid space?
Anterior choroidal a.
The anterior choroidal a. is also frequently a cause of vascular insufficiency to _____ ____ and ______ brain structures in elderly
Globus pallidus; hippocampus
The anterior cerebral artery runs next to what 2 cranial nerves?
Olfactory n.
Optic n.
What artery supplies the anterior 2/3 of the medial side and superolateral portion of the hemisphere, as well as the paracentral lobule region which does sensation+motor to the LEs?
Anterior cerebral a.
Main branches of anterior cerebral a.
Recurrent artery of Heubner
Anterior communicating a.
2 cortical branches:
Anterior pericallosal a.
Callosomarginal a.
Occlusion of the anterior cerebral a. has what effects?
Contralateral paresis and/or paresthesia of the leg and foot
[due to its supply of paracentral lobule region]
What is meant by “watershed areas” of the brain?
Areas where both the middle cerebral and anterior cerebral aa. both supply
These areas are more susceptible to ischemia because they require dual blood supply
The medial and lateral striate/thalamostriate aa. are branches of the _____ a. that supply the internal capsule, corpus striatum, and thalamus
Middle cerebral
The ______ a. is a branch of the middle cerebral a. that supplies primary motor and somesthetic cortices
Central
Frontal branches of the middle cerebral artery supply what structures?
Premotor and prefrontal cortices
Broca’s area (usually dominant in left hemisphere)
Parietal branches of middle cerebral a. supply what structure(s)?
Association cortex
Temporal branches of middle cerebral a. supply what structure(s)?
Primary auditory cortex (assists in localization of sound)
The angular a. branch of middle cerebral supplies what structure(s)?
Supramarginal and angular regions
Wernicke’s area (usually dominant in left hemisphere)
Occlusion of the frontal branches of the middle cerebral artery could have what unique result?
Broca’s aphasia (expressive aphasia — difficulty putting words together to form complete sentences)
Occlusion of the angular a. branch of middle cerebral a. could have what unique complication?
Wernicke’s aphasia (comprehension aphasia — inability to grasp meaning of spoken words)
Result of occlusion of central a. (Branch of middle cerebral)
Contralateral spastic paralysis and/or paresthesia of the head and upper 1/2 of body
Result of occlusion of parietal branches of middle cerebral a.
Variety of interpretive disorders including body neglect, agnosia, and apraxia
Result of occlusion of temporal branches of middle cerebral a.
Difficulty localizing sounds
What 2 arteries supply primary posterior circulation to the brain
Vertebral a.
Basilar a.
3 branches of vertebral a. supplying posterior circulation to the brain
Anterior spinal a.
Posterior spinal aa.
Posterior inferior cerebellar a.
4 branches of basilar a. supplying posterior circulation to the brain
Anterior inferior cerebellar a.
Labyrinthine a.
Superior cerebellar a.
Posterior cerebral a.
Primary blood supply to the spinal cord comes from what 2 arteries?
Anterior spinal a.
Posterior spinal aa. (x2)
The anterior spinal a. runs deep to the anteromedian sulcus and supplies what structures?
Most of the central gray matter
Anteromedial portion of white matter
The posterior spinal arteries (x2) are branches of the vertebral a. or PICA and course in the posterolateral sulci on each side. What structures do they supply?
Dorsal roots and about 75% of the posterior columns
Also supply peripheral margins of the cord along with radicular aa.
Spinal cord trauma may interrupt blood to the spinal cord, especially in areas supplied by 2 arterial supplies. This most frequently occurs adjacent to what areas of the spinal cord?
The enlargements — at C2, T1-4, and L1
What artery arises from the left inferior intercostal or superior lumbar artery and contributes to the anterior spinal a., serving as the major supply to the inferior 2/3 of the spinal cord?
Great anterior artery of Adamkiewicz
The great anterior artery of Adamkiewicz can be compromised secondary to thoracolumbar fracture or surgical repair of AAAs. What does this result in?
Ischemic necrosis of the spinal cord (partial or complete transection)
What causes central cord syndrome?
Disruption of blood flow to the anterior spinal a.
[d/t thrombosis or hyperextension of the neck, leading to ischemia of the central region of the spinal cord]
Signs/symptoms of central cord syndrome
Central necrosis and cavitation of spinal cord —> development of a syrinx
Sensory and motor deficits to UE > LE
Distal musculature > proximal musculature
PICA is a branch of the vertebral a. What are the 3 main structures it supplies?
Posterior inferior portion of cerebellum
Posterolateral aspect of the medulla
Choroid plexus of the fourth ventricle
What happens with occlusion of PICA?
Lateral medullar syndrome/wallenberg syndrome
The anterior inferior cerebellar artery is located in the ______ sulcus, next to cranial nerves ____, ____, and _____, as well as the ______ of the cerebellum
Pontobulbar; VI, VII, VIII; flocculus
What structures does the anterior inferior cerebellar artery supply?
Anterior inferior portion of cerebellum
Superior and middle cerebellar peduncles
Part of brainstem
The superior cerebellar a. is located posterior to CN _____, and supplies what 3 structures?
CN III
Supplies:
Superior lateral portion of cerebellum
Deep cerebellar nuclei
Part of pons and midbrain
The ______ a. arises as a branch of either basilar a. or AICA and is the main artery to the inner ear
Labyrinthine
Pontine aa. are branches of the _____ a. that supply the medial and lateral aspects of the pons. Branches distribute to regions of the brainstem in a pie wedge pattern, often een with necrosis in some brainstem lesions
Basilar
Penetrating branches of the posterior cerebral a. supply what structures?
Internal capsule
Thalamus
Choroid plexus of lateral ventricle
Upper midbrain
Temporal branches of the posterior cerebral artery supply what structure(s)?
Inferior temporal cortex
The parieto-occipital a. (branch of the posterior cerebral a.) supplies what structure(s)?
Primary visual cortex
What branch of the posterior cerebral a. anastomoses with the anterior pericallosal artery of the anterior cerebral a.?
Posterior pericallosal a.
What are the branches of the posterior cerebral a.?
Penetrating branches Temporal branches Parieto-occipital a. Calcarine a. Posterior pericallosal a.
Posterior cerebral a. occlusion may occur d/t what 2 primary causes?
Thrombosis
Compression d/t uncal herniation
Results of PCA occlusion
Ischemic necrosis of the primary visual cortex —> contralateral homonymous hemianopsia with macular sparing
What is falx herniation?
Falx cerebri partially separates the cerebral hemispheres
Falx herniation may occur if a unilateral space-occupying lesion is present causing herniation of ____ _____ which pushes beneath the free edge of the falx cerebri
Cingulate gyrus
Clinical symptoms of falx herniation
Headache
Contralateral leg weakness
[or may not present clinical deficits]
Early clinical sign of acute uncal (tentorial) herniation
CN III compression —> oculomotor nerve palsy
What happens when there is midbrain involvement in uncal (tentorial) herniation?
Contralateral hemiparesis and respiratory compromise
Kernohan’s notch = uncal herniation causes pressure on ipsilateral brainstem causing contralateral limb weakness; increased pressure pushes brainstem into tentorium cerebelli causing ipsilateral limb weakness
What type of herniation is acute and rapidly fatal d/t compression upon the medulla leading to respiratory arrest?
Tonsilar herniation = cerebellar tonsils herniate through the foramen magnum
What is the clinical course of progression with an epidural hematoma?
Traumatic history —> initially unconscious —> rapid recovery —> few hours pass —> neurologic symptoms
What causes subdural hematoma?
Head trauma causes cerebral veins to rupture as they cross the subdural space
Veins are vulnerable to sheer forces between movement of brain vs. dura. Ruptured veins causes slow accumulation of blood in subdural space
Compare clinical progression of subdural hematoma vs. epidural hematoma
Subdural hematoma has same symptoms as epidural hematoma (lethargy, seizures, or headaches) but onset is more insidious — delayed d/t slower pooling of blood
Primary causes of subdural hematoma in children vs. elderly
Children = associated with skull fracture
Elderly = associated with fragile blood vessels
Presence of erythrocytes in the CSF may indicate what?
Subarachnoid hemorrhage
To sample CSF, where is lumbar puncture performed?
L4-L5
[spinal cord ends ~L2]
