Blood Supply to the Brain Flashcards
1
Q
What 2 arteries is the blood supply to the brain derived from?
How do these arteries enter the skull?
A
Internal carotid artery:
- this is a branch of the common carotid artery
- it enters the skull via the carotid canal
Vertebral artery:
- this is a branch of the subclavian artery
- it enters the skull via the foramen magnum
2
Q
What is the difference in how the subclavian artery arises on the right and left sides?
A
- the left subclavian artery (and common carotid) arise directly from the arch of the aorta
- on the right side, the brachiocephalic trunk arises from the arch of the aorta
- this then divides into the right subclavian and common carotid arteries
3
Q
Where does the vertebral artery originate from?
How does it enter the cranium and what does it fuse once it is there?
A
- it is the first branch of the subclavian artery
- it enters the transverse foramen of C6 and ascends through the transverse foramina of higher vertebrae
- it enters the cranium via foramen magnum
- at the level of the pontomedullary junction, the 2 vertebral arteries fuse to form the basilar artery
4
Q
Where does the posterior cerebral artery arise from?
A
the posterior cerebral artery arises from the basilar artery as it bifurcates
5
Q
Where do the anterior and middle cerebral arteries arise from?
A
- the internal carotid artery terminates by dividing into the anterior and middle cerebral arteries
- the ACA is a smaller branch than the MCA
6
Q
What is the role of the anterior and posterior communicating arteries?
A
they connect the cerebral arteries
Anterior communicating artery:
- connects the left and right anterior cerebral arteries
Posterior communicating artery:
- connects the middle cerebral artery with the posterior cerebral artery on each side
7
Q
What are the 3 cerebellar arteries and where do they arise from?
A
Posterior inferior cerebellar artery (PICA):
- this is a branch of the vertebral artery
Anterior inferior cerebellar artery (AICA):
- this arises at the point where the 2 vertebral arteries fuse to form the basilar artery
Superior cerebellar artery:
- this arises from the basilar artery as it bifurcates at the level of the pontomesencephalic junction
8
Q
Where does the middle cerebral artery arise from?
How does it travel in the brain and which regions does it supply?
A
- it is the larger of the 2 terminal branches of the internal carotid artery
- the other branch is the anterior cerebral artery
- it passes laterally to supply blood to the lateral convexity of the cerebral hemisphere, including parts of the temporal, parietal, frontal and occipital lobes
9
Q
What are the branches of the middle cerebral artery?
A
- lenticulostriate branches
- orbitofrontal artery
- pre-central (pre-Rolandic) and central (Rolandic) branches
- anterior & posterior parietal arteries
- angular artery
- anterior, middle & posterior temporal arteries
10
Q
What is the role of the lenticulostriate branches of the MCA?
A
- these are a group of small arteries that supply the putamen, caudate nucleus and anterior limb of the internal capsule
- they are the first branches of the MCA
11
Q
What is supplied by the orbitofrontal artery of the MCA?
A
- it supplies part of the frontal lobe
- it supplies the orbital gyri and the inferior frontal gyrus
12
Q
What is supplied by the pre-central (pre-Rolandic) and central (Rolandic) arteries?
A
- these arteries supply different regions of the frontal lobe
- the Rolandic branch runs alongside the central sulcus
13
Q
What is supplied by the angular artery?
A
- this supplies the angular gyrus
- this is part of the inferior parietal lobule that has a role in language and number processing, memory and reasoning
14
Q
How can the middle cerebral artery be divided?
A
It can be divided into 4 anatomical segments (M1-M4)
- M1 - horizontal segment
- M2 - insular segment
- M3 - opercular segment
- M4 - cortical segment
15
Q
Where does the M1 (horizontal) segment of the MCA run to and from?
A
- it runs from the origin at the internal carotid artery to the bifurcation of the MCA at the limen insulae
- the limen insulae is located just as the MCA passes out through the lateral sulcus by the insula
16
Q
Where does the M2 (insular) segment of the MCA run to and from?
A
- it runs from the bifurcation at the limen insulae to the cortical branches
- there are 2 branches formed at the limen insulae - one runs superiorly and one runs inferiorly
- both of these branches run along the insula
17
Q
Where do the M3 (opercular) and M4 (cortical) segments of the MCA run?
A
- M3 describes the opercular branches that run within the lateral fissure
- M4 describes the cortical branches that emerge from the lateral fissure onto the surface of the cortex
18
Q
Which branches arise from the M1 (horizontal) segment of the MCA?
A
- lenticulostriate arteries
- anterior and polar temporal arteries
- uncal artery
19
Q
Which branches arise from the superior and inferior terminal branches of the M2-M4 segments of the MCA?
A
Superior terminal branch:
- orbitofrontal artery
- pre-Rolandic artery
- Rolandic artery
Inferior terminal branch:
- anterior & posterior parietal arteries
- angular artery
- anterior, middle & posterior temporal arteries
20
Q
In general, what territories are supplied by the MCA?
A
- majority of the lateral surface of the hemispheres
- internal capsule
- basal ganglia
21
Q
Where does the anterior cerebral artery arise from it?
How does it travel in the brain?
A
- it is the smaller of the 2 terminal branches of the internal carotid artery
- it passes anteromedially towards the midline in the longitudinal fissure
- it then passes anterior to the genu of the corpus callosum and then curves posteriorly
22
Q
Which structures are supplied by the anterior cerebral artery?
A
- it supplies blood to the medial aspect of the hemisphere, including parts of the frontal and parietal lobes
- it supplies the precentral and postcentral gyri
- it supplies the olfactory bulb and tract, anterior hypothalamus, parts of the caudate nucleus, internal capsule and putamen
23
Q
What are the 2 major branches of the ACA?
A
- callosomarginal artery
- pericallosal artery
24
Q
What is supplied by the callosomarginal artery?
A
- the paracentral lobule and portions of the cingulate gyrus
25
What is supplied by the pericallosal artery?
* this continues along the dorsal margin of the corpus callosum to supply the **_precuneus_**
* this is part of the parietal lobe that is caudal to the paracentral lobule
26
What are the 3 segments of the anterior cerebral artery?
**_A1:_**
* from origin of ACA at **internal carotid artery** to the **_anterior communicating artery_**
**_A2:_**
* from the anterior communicating artery to the **_origin of the callosomarginal artery_**
**_A3:_**
* this runs distal to the callosomarginal artery and is also the **_pericallosal artery_**
27
What are the 2 main branching patterns of the anterior cerebral artery?
* A2 gives off the callosomarginal artery and continues as the pericallosal artery
**Cortical branches arise from the callosomarginal artery**
* The callosomarginal artery is absent
**Cortical branches arise directly from the pericallosal artery**
*(Cortical branches go over by about 1cm onto the lateral aspect of the brain)*
28
Why can occlusion of the anterior cerebral artery lead to paralysis and loss of sensation of the contralateral leg?
* the ACA supplies the **_precentral gyrus_**, which processes **sensory information** from the contralateral leg
* it also supplies the **_postcentral gyrus_**, which **initiates motor control** of the contralateral leg
* occlusion of the ACA leads to loss of motor control (paralysis) and loss of sensation of the contralateral leg
29
What are the main branches of the anterior cerebral artery?
1. anterior communicating artery
2. medial striate artery (recurrent artery of Heubner)
3. orbital branches
4. frontopolar branches
30
What is the function of the anterior communicating artery?
What arises from this vessel?
* it connects the **_right and left anterior cerebral arteries_** at the level of the **optic chiasm**
* a group of small arteries arise from the anterior communicating and anterior cerebral arteries and penetrate the brain tissue perpendicularly
these supply blood to the **_anterior hypothalamus_** - including **preoptic and suprachiasmatic areas**
31
Where do intracranial aneurysms commonly occur in the anterior circulation?
What can this present with?
* at the junction between the anterior communicating artery and anterior cerebral artery
* these aneurysms can cause visual defects due to their proximity to the optic chiasm
32
What is supplied by the medial striate artery (recurrent artery of Heubner)?
* anteromedial part of the head of the caudate nucleus
* parts of internal capsule
* putamen
* septal nuclei
*it arises from the ACA at the level of the optic chaism and penetrates the perforated substance*
33
What is supplied by the orbital and frontopolar branches of the ACA?
**_Orbital branches:_**
* supply the orbital and medial surfaces of the frontal lobe
**_Frontopolar branches:_**
* supply the medial aspects of the frontal lobe
* (Both orbital and frontopolar branches arise from the A2 segment of the ACA)*
34
What is the origin of the posterior cerebral artery?
How does it travel from its origin?
* it is formed from the **_terminal bifurcation of the basilar artery_**
* it courses around the midbrain towards the dorsal (posterior) aspect of the brain
35
What is supplied by the posterior cerebral artery?
* most of the midbrain
* thalamus
* subthalamic nucleus
36
How can the posterior cerebral artery be divided in to 4 segments?
**_P1:_**
* from origin at bifurcation of basilar artery to origin of **posterior communicating artery**
**_P2:_**
* from posterior communicating artery to the **_quadrigeminal cistern_** at the posterior border of the lateral midbrain
* *can be divided into P2A and P2P segments*
**_P3:_**
* from **quadrigeminal cistern** to the origin of the **calcarine and parieto-occipital arteries**
**_P4:_**
* this describes the **terminal branches** of the PCA - **_calcarine and parieto-occipital_**
37
What are the 4 major branches of the posterior cerebral artery?
What do they supply?
* anterior temporal branches
* posterior temporal branches
* parieto-occipital branches
These supply the **temporal lobes** and **medial /inferior occipital lobe**
* calcarine branches
These supply the **primary visual cortex**
38
39
What small arteries can arise from the P2 segment of the PCA to supply the midbrain?
**_Quadrigeminal arteries_**
* these supply the **inferior and superior colliculi** on the dorsal aspect of the midbrain
40
What is meant by the vertebro-basilar circulation and what does it supply?
* this system includes the **2 vertebral arteries**, the **basilar artery** and their branches
* it supplies the **medulla, pons, midbrain** and **cerebellum**
41
At the level of the medulla, which 3 branches are given off by the vertebral artery?
* anterior spinal artery
* posterior spinal artery
* posterior inferior cerebellar artery (PICA)
42
What regions / structures are supplied by the PICA?
**_Regions of the lateral medulla:_**
* spinothalamic tract
* dorsal & ventral spinocerebellar tracts
* descending sympathetic tract
* descending tract of trigeminal nerve (V)
* nucleus ambiguus
**_Cerebellum:_**
* region of the vermis
* inferolateral surface of cerebellum
43
What syndrome results drom occlusion of the PICA?
**_Lateral medullary (Wallenberg's) syndrome_**
* there is damage to the lateral medulla in the region supplied by the PICA
* damage to the nucleus ambiguus leads to dysphonia, dysarthria and dysphagia
* *this is due to the nucleus ambiguus innervating the laryngeal muscles*
* there is also loss of coordination / balance (ataxia) and vertigo
* there is loss of contralateral P&T sensation if lateral STT is involved
* sensory disturbances from contralateral side of the body and ipsilateral side of the face
44
What are the branches of the basilar artery?
* anterior inferior cerebellar artery (AICA)
* labyrinthine artery
* pontine arteries
* superior cerebellar artery (SCA)
* posterior cerebral artery
45
What is supplied by the AICA?
* ventral and inferior surface of the cerebellum
* some of the lateral surface of the pons
46
What is supplied by the superior cerebellar artery?
* it supplies the rostral pons, caudal midbrain and superior surface of the cerebellum, including:
1. portions of the superior and middle cerebellar peduncles
2. medial & lateral lemniscus
3. part of spinal trigeminal nucleus & tract
4. spinothalalmic tract
47
What is surrounded by the circle of Willis?
What forms this structure?
* it surrounds the **_optic chiasm_** and **_infundibulum of the pituitary gland_**
* it is formed by the anastomosis of the branches of the **internal carotid artery** and the terminal branches of the **basilar artery**
48
What is the clinical importance of the circle of Willis?
if the blood supply in either the internal carotid arteries or vertebro-basilar system is compromised, the circle of Willis provides a **_collateral blood supply_**
49
What are striate arteries and where do they arise from?
* they are small arteries that supply the **deep tissue** of the brain
* they arise from the **_posterior cerebral artery_** and both the **_anterior & posterior communicating arteries_**
50
What is a berry aneurysm?
Where are they most likely to rupture?
* a condition in which weakness in the wall of a cerebral artery or vein causes a **_localised dilation or ballooning_** of the blood vessel
* an aneurysm occurring in the **_posterior circulation_** is more likely to rupture
* *this includes the basilar artery, vertebral artery & posterior communicating artery*
51
What are some causes of berry aneurysms?
* connective tissue disorders
* polycystic kidney disease
* arteriovenous malformations
* untreated hypertension
* tobacco smoking
* cocaine & amphetamines
* head trauma
* heavy caffeine intake
* intravenous drug use
* infection of the arterial wall from bacteraemia
52
What are the symptoms of berry aneurysm?
* typically, they are **_asymptomatic until they rupture_** and then may cause:
1. sudden and unusually severe headache
2. nausea & vomiting
3. vision impairment
4. loss of consciousness
5. no symptoms at all
53
What type of haemorrhage can a ruptured berry aneurysm lead to and what are the symptoms of this?
**_subarachnoid haemorrhage_**
* typically presents with a sudden onset "thunderclap" headache, as well as:
1. nausea & vomiting
2. drowsiness, confusion & loss of consciousness
3. visual abnormalities
4. meningism
5. dizziness
54
Where, specifically, is CSF produced and how is this related to blood supply?
* CSF is produced by the **_choroid plexus_** within the **ventricular system**
* CSF production is an **active process** that requires a blood supply
* the **_lateral ventricle_** produces the most CSF as it is the largest and contains the greatest amount of choroid plexus
55
What is the blood supply to the lateral ventricle and IIIrd ventricle?
* **_anterior choroidal artery_**
this is a branch of the **middle cerebral artery (MCA)** at the junction between the MCA and ICA
* **_lateral posterior choroidal artery_**
* **_medial posterior choroidal artery_**
these are branches of the **posterior cerebral artery (P2)**
56
What is the blood supply to the IVth ventricle?
* anterior inferior cerebellar artery (AICA)
* posterior inferior cerebellar artery (PICA)
