Blood Flow & CSF

Question 1

Blood-brain Barrier

Answer 1

endothelial cells of capillary walls are tightly packed to inhibit movements of large molecules into the tissues (brain)

• Protects from pathogens & internal chemicals (hormones)

Makes it hard to develop drugs for the brain/NS

Question 2

Major Blood supply to the brain (2)

- where do they enter

Answer 2

1. Internal Carotids
   - enters skull through carotid canal, curves around cavernous sinus & penetrates dura before dividing into branches
2. Vertebral arteries
   - ascend from subclavians, through foramen @ 6th vertebrae, through foramen magnum & meets to form basilar artery

Question 3

Circle of Willis

• what is it
• which arteries
• purpose

Answer 3

hexagon of vessels that surround the optic chiasm & pituitary gland including…

1. anterior and posterior communicating
2. anterior and posterior cerebral

Purpose: provide collateral circulation so if one is occluded blood can still get to that region from the opposite side

**common site for aneurism

Question 4

Major Branches of Internal Carotids (2)

• what area they supply
• presentation/defects of infarcts

Answer 4

1. Anterior cerebral - medial aspects of cortex, internal capsule & some basal ganglia
   - contralateral hemiplegia and somatosensory loss (mainly in LE), some loss of motivation and cognitive function
2. Middle cerebral - major artery to lateral cortex, lenticulostriate which supplies caudate, putamen and anterior limb of internal capsule
   - contralateral hemiplegia and somatosensory loss (mainly in UE and head), aphasia (speech), sensory association, cognition, working memoryy and major multisystem dysfunction
   * *lenticulostriate common site of occlusion

Question 5

Basilar Artery

• what does it form
• Major branches (3)

Answer 5

forms the two vertebral arteries when it bifurcates at teh base of the pons

1. Posterior cerebral - midbrain, thalamus, temporal and occipital lobe (visual cortex and memory)
   - hemianopsia
2. Superior cerebellar - middle and superior peduncles, medial and lateral lemniscus, spinal trigeminal nucleus and spinothalamic tract
   - contralateral loss of pain and temp (and lots more)
3. Pontine (paramedian) - pontine nuclei, CN nuclei, corticobulbar and corticospinal tracts in pontine area
   - ipsilateral loss of motor function, ipisilateral CN deficits

Question 6

Major Branches of Vertebral Artery (3)

Answer 6

1. Anterior spinal artery - pyramids, medial lemniscus of medulla, MLF, CN XII and inferior olive
2. PICA - lots
3. Posterior spinal artery - fasciculus gracilis & cuneatus, some of CN X, spinal trigeminal nucleus

Question 7

Common place of Vertebral Artery Compromise

Answer 7

as they pass through the transverse foramina of C6 to the foramen magnum

–> commonly due to neck positioning and posture, extension or rotation

Question 8

Two reasons for compromised blood flow to the brain

Answer 8

1. Ischemia - insufficient blood flow due to plaques or clot
2. Hemorrhage - rupture of blood vessel and bleeding into the cranial cavity

Question 9

Venous Drainage

• how does it work
• general path

Answer 9

Low pressure system, less risk to CNS

General path: Veins –> venous sinuses –> jugular vein

• sinuses drain deoxygenated blood and CSF from brain and scalp
• why CNS is susceptible to infections

Question 10

Confluence of Sinuses

Answer 10

near occipital pole where superior and straight sinuses connect to transverse, which becomes sigmoid and drains into the internal jugular vein

Question 11

Function of CSF

Answer 11

provide mechanicsl and chemical support for the brain that carries away metabolites and toxins

Question 12

Flow of CSF

Answer 12

Formed in choroid plexus in lateral ventricle –> 3rd ventricle –> cerebral aqueduct –> 4th ventricle –> central canal of SC or up and around the brain

ALL eventually ends up at arachnoid granulations and drains into the superior sagittal sinus

Question 13

Hydrocephalus

• what is it
• communicating vs. non-communicating

Answer 13

production of CSF continues even when flow is obstructed

Communicating - thickening of arachnoid space from prior insult or infection w/ reduced absorption
- spinal canal may enlarge of pressure increases

Non-communicating - blockage of cerebral aqueduct causing dilation of ventricles and increased pressure
- gyri flatten against skull causing head to enlarge in children

Question 14

The MCA supplies which of the following areas of the brain?

Answer 14

lateral motor strip
lateral sensory strip
temporal
frontal & parietal lobes
Broca & Wernicke's areas

Question 15

Clinical Presentation of anterior spinal artery:

Answer 15

weakness & loss of discriminative touch on LEFT side of body

Tongue deviated to the RIGHT

Question 16

Clinical Presentation of PICA

Answer 16

Wallenberg’s syndrome

lack of coordination in speech and disturbance of articulation

Question 17

What does the cerebral aqueduct connect?

Answer 17

the 3rd & 4th ventricles

Question 18

Clinical presentation of MCA

Answer 18

issues comprehending spoken language

contralateral hemiplegia and sensation loss in UE and head

Question 19

The anterior cerebral artery and middle cerebral artery arise from which artery?

Answer 19

Internal carotic

Question 20

Clinical Presentation of posterior cerebral artery

Answer 20

Hemianopsia
cortical blindness
Weber’s syndrome

Question 21

Clinical Presentation of R cerebral artery

Answer 21

loss of motor and sensation in LEFT leg