Enquiry 5, Cerebral and Spinal Cord Circulation

Question 1

What are the main arteries that supply the brain and spinal cord?

Answer 1

• Internal Carotid Artery
• Middle Cerebral Artery MCA
• Anterior Cerebral Artery ACA
• Posterior Cerebral Artery PCA
• Anterior Communicating Artery
• Posterior Communicating Artery
• Ophthalmic Artery
• Anterior Choroidal Artery
• Superior Cerebellar Artery
• Basilar Artery
• Anterior Inferior Cerebellar Artery
• Posterior Inferior Cerebellar Artery
• Vertebral Artery
• Anterior Spinal Artery
• Pontine Arteries

Question 2

What arteries supply blood to the brain at the Circle of Willis?

Answer 2

The internal carotid arteries

Question 3

How much blood does the internal carotid arteries supply? And where does it supply blood to?

Answer 3

Supply 80% of oxygenated blood to the cerebrum.

Question 4

If someone lost blood supply to the circle of willis, can it cause a stroke? How and why?

Answer 4

Stroke may not be an issue if circle is complete as blood can go the other way around the circle (collateral circulation).

Question 5

If someone lost blood supply to the circle of willis, can it cause an aneurysm? How and why?

Answer 5

Circle of willis is a common place for inter cranial aneurysms. Ruptured aneurysm can cause severe headache alongside other symptoms, like visions problems, light sensitivity and stiff neck.

Question 6

How blood gets to the anterior cerebral artery, ACA, and what parts of the central nervous system that artery supplies?

Answer 6

Blood flow to brain via internal carotid artery (neck), branches into anterior cerebral artery. Supplies: - Inner parts of the medial frontal lobes(small amount laterally). - This includes: corpus callosum, frontal, parietal, and cingulate cortex

Question 7

What would the clinical presentation be if someone lost blood supply though ACA?

Answer 7

-Contralateral weakness and sensory loss in lower leg + foot opposite to the lesion -Behavioural changes -Motor speech disorder + aphasia -Minimal sensory changes -Dysarthria - motor speech disorder -Contralateral apraxia- inability to perform learnt tasks. -Urinary incontinence

Question 8

Are ACA infarcts common?

Answer 8

less common because of blood flow from the contralateral side and communicating artery

Question 9

How blood gets to the anterior and posterior communicating arteries? and what parts of the central nervous system that artery supplies?

Answer 9

Anterior: - Connects left and right anterior cerebral arteries - Receives blood from anterior cerebral arteries via internal carotid arteries - Helps to maintain blood flow through the cerebral arterial circle (circle of Willis) Posterior: - Connects and receives blood from the internal carotid arteries and the posterior cerebral arteries - Helps to maintain blood flow through the cerebral arterial circle (circle of Willis)

Question 10

What is the main function of the anterior and posterior communicating arteries?

Answer 10

Provide alternative route to brain blood supply in case of blockage in internal carotid artery or vertebral arteries.

Question 11

What the clinical presentation might be if someone lost blood supply through the anterior and posterior communicating arteries?

Answer 11

• If anterior and posterior communicating arteries are blocked its unlikely to see clinical presentation UNLESS another major artery is also blocked e.g. internal carotid.

Question 12

How blood gets to the middle cerebral artery? and what parts of the central nervous system that artery supplies?

Answer 12

Blood flow rises from the internal carotid artery (ICA). Continues into the lateral sulcus where it then branches to the lateral aspect of the cerebrum. Supplies the cerebrum (mostly lateral side): A lot of the temporal lobe A lot of lateral parietal lobe Most of lateral frontal lobe A little of occipital lobe

Question 13

What the clinical presentation might be if someone lost blood supply through the middle cerebral artery? And what can this cause?

Answer 13

Hemianaesthesia (inability to feel touch) affecting face and upper limb - Somatosensory impacted Upper limb more impaired than lower limb - Motor impacted Right MCA - difficulty understanding spatial relationships; neglect; Impairment of nonverbal communication; Dressing apraxia; Constructional apraxia (building or drawing, inability to perform task even though you understand it) - Cognition, language and memory impacted * This can cause a stroke as Middle cerebral artery is the most frequently affected in stroke

Question 14

How blood gets to the posterior cerebral artery, PCA? and what parts of the central nervous system that artery supplies?

Answer 14

• Originates from the Basilar Artery - Branches into the central branches: Thalamoperforating arteries, thalamogeniculate arteries And the Cortical branches: temporal, occipital, parieto-occipital, calcarine arteries - Supplies the Occipital lobe, inferolateral surface of the temporal lobe, midbrain thalamus, choroid plexus (third and lateral ventricle)

Question 15

What the clinical presentation might be if someone lost blood supply through the PCA? And what can this cause?

Answer 15

Symptoms of posterior cerebral artery stroke include: - Contralateral homonymous hemianopia (due to occipital infarction) - Hemisensory loss (due to thalamic infarction) - Loss of sensation on one side of the body - Hemi-body pain (usually burning in nature due to thalamic infarction - Dejerine Roussy Syndrome) - Reduced visual-motor coordination (if bilateral) *Because the PCA supplies the thalamus, PCA infarction can lead to contralateral thalamic syndrome

Question 16

How blood gets to the Basilar Artery? and what parts of the central nervous system that artery supplies?

Answer 16

The Basilar artery is located near the junction of the pons and the medulla. - Blood gets to the basilar artery via the two vertebral arteries, which join together for the basilar artery formation. - The artery, and its branches, are responsible for supplying the pons and most of the cerebellum. The basilar artery then divides to become the posterior cerebral arteries at the junction of the pons and the midbrain.

Question 17

What the clinical presentation might be if someone lost blood supply through the Basilar Artery?

Answer 17

• Vision is affected so it can either become impaired or can be double. - Nauseous or feel dizzy. - Change in behaviour like a dream like state. - Serious problem if lack of blood supply as there’s 90% chance at mortality.

Question 18

How blood gets to the Vertebral Artery? and what parts of the CNS it supplies?

Answer 18

• Vertebral artery is a major artery of the neck. - Branches from right subclavian artery, where it arises from the posterosuperior portion of the subclavian artery. - Enters skull via foramen magnum to reach inferior brain surface. - Unites with left vertebral artery to form basilar artery. -Blood supply to upper part of spinal cord, brainstem, cerebellum, and posterior part of brain

Question 19

What would the clinical presentation of a lesion of the vertebral artery look like?

Answer 19

The reduction of blood flow may result in: - Transient ischemic attack (TIA), a critical sign of impending stroke - Neck and head pain - Intermittent/permanent stroke symptoms like difficulty speaking, impaired coordination and visual loss - End stage clinical presentation may be death. - Loss consciousness - Dizziness/Headaches

Question 20

How blood gets to the Cerebellar Arteries and what parts of the central nervous system your artery supplies

Answer 20

Main cerebellar arteries: - Superior cerebellar artery - Anterior inferior cerebellar artery - Posterior inferior cerebellar artery - Arise from the vertebral arteries to form the basilar artery - Anterior inferior cerebellar supplies the: middle cerebellar peduncle, lower lateral pons, anteroinferior surface of cerebellum, flocculus and choroid plexus of the lateral ventricle - Posterior inferior cerebellar supplies blood to: cerebellum

Question 21

What the clinical presentation might be if someone lost blood supply through the Cerebellar Arteries?

Answer 21

Unsteadiness - Difficulty maintaining sitting and standing balance Ataxia - slurred speech, stumbling, falling and poor coordination Tremor - shaking of the limb during voluntary movement Movement decomposition - moving each joint separately during an activity Dysarthria - slurred or slow speech difficult to understand - Posterior inferior cerebellar artery syndrome - “Wallenberg syndrome”: Vertigo, nausea, vomiting Severe imbalance, facial numbness