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Semester 5 - CNS > Session 9 - Stroke > Flashcards

Session 9 - Stroke Flashcards

1
Q

What are the two main arteries that supply blood to the brain?

A

ICA and Vertebral arteries

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2
Q

What are the branches of the ICA in the skull?

A

o Ophthalmic Arteries
o Posterior Communicating Arteries
o Middle Cerebral Arteries
 Lateral surfaces of the cerebral cortex
o Anterior Cerebral Arteries
 Supplies medial surfaces of the frontal and parietal lobes

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3
Q

What does ICA travel through to reach the brain matter?

A

The carotid canal

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4
Q

How do the vertebral arteries enter the hollow of the skull?

A

Through the foramen magnum and joins to form the basilar artery, which supplies the cerebellum and brainstem

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5
Q

What does the basilar artery pair into/

A

Posterior cerebral arteries

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6
Q

What does the anterior cerebral artery supply?

A

Medial surfaces of the frontal and parietal lobes

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7
Q

What does the middle cerebral artery supply?

A

Lateral surfaces of cerebral cortex

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8
Q

What does the posterior cerebral artery do?

A

Inferior surface of the Brain

Occipital lobes

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9
Q

What is the circle of willis?

A

The Anterior and Posterior Cerebral Arteries are joined together through communicating branches to form the Circle of Willis at the base of the brain.

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10
Q

What is autoregulation in the brain?

A

A change in CPP causes an appropriate compensatory change in cerebral blood vessels. This means that CPP can fluctuate (within certain limits) without causing a significant change in cerebral blood flow.
o Decreased CPP causes cerebral vasodilation
o Increased CPP causes cerebral vasoconstriction

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11
Q

What is chemoregulation of the cerebral blood supply?

A 
The build-up of metabolic by-products results in cerebral vasodilation
o	Decreased extracellular pH
o	Decreased pO2
o	Increased pCO2
The opposite will cause cerebral vasoconstriction
o	Increased extracellular pH
o	Increased pO2
o	Decreased pCO2
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12
Q

What is cerebral perfusion pressure?

A

Net pressure gradient causing cerebral blood flow to the brain

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13
Q

What is the equation for CPP

A

CPP=Mean Arterial Pressure-Intracranial Pressure

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14
Q

Define stroke

A

A stroke is a clinical syndrome of abrupt loss of focal brain function lasting over 24 hours (or causing death) that is due to either spontaneous haemorrhage into brain substance or inadequate blood supply to a part of the brain.

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15
Q

Name the two main types of stroke

A

Ischaemic stroke

Haemorrhagic stroke

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16
Q

How common is ischaemic stroke?

A

80-85% of strokes

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17
Q

What are the two main causes of ischaemic stroke

A

o Large vessel atheroma/embolism (e.g. ICA) – 75-80%

o Cardiac Embolism (Atrial Fibrillation) – 20%

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18
Q

What is the most common symptom of ischaemic stroke?

A

Hemiparesis

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19
Q

What is a haemorrhagic infarct?

A

o Thrombus occludes vessel, necroses distal tissue and then either a)dissolves and blood floods into area through necrotic capillaries (perhaps due to thrombolysis) or b) collateral circulation, which is insufficient to support metabolic needs of tissue floods area with blood
o Results in haemorrhagic (red) infarct
o Most common in embolus

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20
Q

How common are haemorrhagic strokes?

A

15%

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21
Q

What is a primary haemorrhagic stroke?

A

No structural lesion

22
Q

What is a secondary cause of haemorrhagic stroke?

A

Structural lesion

23
Q

Why would a young man present with haemorrhagic stroke?

A

Cocaine, amphetamine

24
Q

What occurs in the frontal lobe?

A

Motor area
Brocas area
Micturition inhibition
Disinhibition

25
Q

What occurs in the parietal lobe?

A

Sensory area
Optic radiations
- Inferior homonymus Quandrantopia

26
Q

What occurs in the temporal lobe?

A 
Auditory/vestibular function
Taste and smell
Wernicke's area
Memory circuits
Optic radiation
- Superior homonymous quadrantanopie
27
Q

What occurs in the occipital lobe?

A

Primary visual cortex

28
Q

What happens in the cerebellum/brainstem?

A

Motor and sensory tracts
Cranial Nerve nuclei
Cerebellum

29
Q

Give some vascular risk factors for stroke?

A 
o	Non-Modifiable
	Age, gender
	Family history
	Previous stroke/TIA
o	Lifestyle
	Smoking
	Sedentary lifestyle
	Heavy alcohol intake
	Poor diet
o	Medical
	Hypertension
	Hypercholesterolaemia
	Diabetes mellitus
	Arrhythmia
30
Q

What are the inititial investigations in stroke?

A

o BM (check for hypoglycaemia)
o Haematological – FBC, INR
o ECG (check for AF)
o Brain imaging

31
Q

What is a CT scan used for?

A

 Will demonstrate haemorrhage immediately
 Does not rule out ischaemic stroke (but may visualise an infarct)
 CT superior for haemorrhage and bony anatomy, and can be done quickly
 More sensitive to calcification in a lesion, which is useful in tumour diagnosis
 Emergency patients undergo CT

32
Q

What is an MRI used for?

A

 due to infarction
 MRI superior for white matter disease (?)
 MRI better for long term detection of haemorrhage – sign disappear on CT after a few weeks, whereas indefinite on MRI
 Non-emergency patients undergo MRI

33
Q

What are the three constituents of the cranial cavity?

A

Brain, blood and CSF

34
Q

What is normal intracranial pressure?

A

0-10mmHg

35
Q

When does ICP reach 20mmHg normally?

A

Coughing and straining

36
Q

What common pathologies cause raised ICP?

A

Haemorrhage, tumours, meningitis and cerebral infarction

37
Q

What are three areas which can herniate in raised ICP?

A

o The Cingulate Gyrus
o The Uncus
o The Cerebellar Tonsils

38
Q

What compartments make up the brain?

A

o Falx Cerebri – In the midline between the two cerebral hemispheres
o Tentorium Cerebelli – Lies on the superior face of the cerebellum

39
Q

Name four types of herniation

A

o Subfalcine Herniation

o Central Herniation

o Uncal Herniation

o Tonsillar Herniation

40
Q

What is the path of raised ICP?

A
  1. Localising Signs
  2. Decreasing levels of consciousness
  3. Coma
  4. Death (if untreated)
41
Q

Give some causes of raised ICP

A

o Brain
 Head injury
 Infection (Meningitis/encephalitis)
o Blood
 Coughing (Stop a patient coughing by intubating/ventilating them under anaesthesia as part of a protective plan)
 Impaired venous drainage
o Cerebrospinal Fluid
 Subarachnoid haemorrhage (Cerebral blood vessels are very sensitive to CO2 and will dilate, causing a rise in ICP)
 Blockage in ventricular system (Ventricular shunt to treat)
o Haematoma
 Trauma – Extradural, subdural, intracerebral
 Haemorrhagic stroke
o Tumour
 Primary brain
 Secondary

42
Q

How does direct head trauma cause raised ICP?

A

Head injuries are common and result in the brain being shaken inside the skull.

This causes direct injury to the brain resulting in oedema or haemorrhage due to the rupture of arteries or veins, producing extradural or subdural haematoma and consequent rise in intracranial pressure.

43
Q

Outline the monro-kellie hypothesis for the sequence of events which stem from raised ICP and lead to brain herniation

A

o Any increase in Brain, Blood or CSF can cause an increase in ICP, and will usually have an impact on the other two unaffected constituents
o Small increases in ICP (<25mmHg) will cause displacement of the CSF in the spinal cord
o Once ICP reaches pressure of mean systemic BP, it will reduce Cranial perfusion pressure (CPP = BP – ICP)
o This will cause cushing’s reflex to kick, with the body increasing systemic blood pressure and cause dilation of cerebral blood vessels
o This raised ICP further, causing reduction in cerebral flow and perfusion
o This can result in a midline shift, in which one of the brain hemispheres is compressed by the other, potentially causing blockage of a ventricle and hydrocephalus (Further raised ICP!)
o Brainstem compression can then occur (see above for types)

44
Q

Give some of the long term sequlae of head injury

A

o Neurological deficit
o Infection
o Epilepsy
o Chronically raised pressure if the circulation of CSF has been impaired by scarring

45
Q

How do you know if a head injury is serious?

A 
o	Mechanism of injury
	How much force went through the brain
o	Signs of brain injury
	Change in consciousness
	Knocked out/Amnesia – Quite a lot of force needed!
	Focal neurology
o	Patter of change
	Got better or worse since?
o	Primary injury
	Can’t change
o	Secondary Injury
	E.g. Hypoxia, hypotension, blood clot
	Recognise and treat quickly
46
Q

Outline the blood supply to the spinal cord

A

o Anterior Spinal Artery
 Supplies anterior two thirds
o 2x Posterior Spinal Arteries (Paired)
 Supplies posterior third

47
Q

What is the anterior spinal artery forme dby?

A

The union of branches of the vertebral arteries

48
Q

What special artery supplies the lower thoracic or upper lumbar segments of the spinal cord?

A

The artery of adamkiewicz

49
Q

What is anterior spinal artery syndrome, and what are its causes?

A 
Occlusion of the Anterior Spinal Artery is most common (95%). Causes include:
o	Disease of the Aorta
	Aneurysm, trauma, dissection, atherosclerosis
o	Aortic Surgery
o	Vasculitis
o	Sickle cell disease
o	Hypotension
o	Cardiac emboli
o	Disc herniation, compressing vessels
50
Q

What will you find on examination of a patient with anterior spinal syndrome?

A

o Spinal Shock initially
 Flaccid weakness
 Areflexia
 Anaesthesia
o Complete motor paralysis below the level of the lesion due to interruption of the Corticospinal Tract
o Loss of pain and temperature (Interruption of Anterior and Lateral Spinothalamic Tracts)
 Fine touch and vibration preserved as Dorsal Column is supplied by the Posterior Spinal Artery
o Progress to Upper Motor Neurone signs with muscle atrophy
o Sensory level pattern of loss

51
Q

What is the differential for anterior spinal syndrome

A 
o	Mass lesion
	Tumour, abscess, granuloma, haematoma, herniated disk
o	Intraspinal haemorrhage
o	Acute inflammation
o	Demyelination
o	Sarcoid, TB, Syphilis

Semester 5 - CNS (25 decks)

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