Stroke

Question 1

Define the terms ‘stroke’ and ‘TIA’

Answer 1

Stroke - abrupt loss of focal brain function lasting >24h, due to spontaneous haemorrhage or inadequate blood supply
TIA - sudden onset, focal, occasionally global, presumed to be vascular, resolves completely within 24h

Question 2

Describe the composition of the circle of Willis

Answer 2

Anterior circulation - internal carotid, middle cerebral, anterior cerebral, posterior communicating
Posterior circulation - basilar, vertebral, posterior cerebral

Question 3

Describe the area supplied and relevant branches of carotid arteries, middle cerebral artery, vertebral artery, basilar artery, posterior communicating artery

Answer 3

Carotid artery:
Internal –> brain (opthalmic, PCA, anterior choroidal)
External –> face, scalp, mouth, jaw
Middle cerebral - where most strokes occur
Vertebral - PICA is largest branch
Basilar - overlies pons, supplies most of brainstem
PCA - goes around midbrain, supplies midbrain, thalamus, temporal and occipital lobes

Question 4

Describe the notion of autoregulation as it applies to cerebrovasculature

Answer 4

Physiological mechanisms that maintain cerebral blood flow during changes in blood pressure
Metabolic - negative feedback system, driven by balance of demand and supply
Myogenic - vascular smooth muscle in arterioles
Neurogenic - smooth muscle controlled via sympathetic innervation, NO at parasympathetic fibres

Question 5

Describe what is meant by cerebral perfusion pressure (CPP)

Answer 5

CPP = mean arterial pressure (MAP) - intracranial pressure (ICP)
Normally between 70-90 mmHg

Question 6

Describe the main blood supply of the spinal cord and which artery is most commonly occluded

Answer 6

Anterior spinal artery (single) - most common occlusion
Posterior spinal arteries (paired)
Segmental arteries (21)
Artery of Adamkiewicz - damage can result in anterior spinal artery syndrome –> loss of urinary and fecal continence, impaired motor function of legs

Question 7

Describe the symptoms of damage to the different lobes

Answer 7

Frontal - motor area, Broca’s area, prefrontal cortex, personality and behaviour changes
Parietal - primary sensory cortex, visuospatial issues, optic radiation –> inferior quadrantanopia/hemianopia
Temporal - central representation, auditory/vestibular, taste and smell, Wernicke’s area, memory circuits, optic radiation –> superior quadrantanopia
Occipital - visual cortex
Cerebellum/brainstem - motor and sensory tracts, cranial nerve nuclei, balance, coordination

Question 8

Describe the various factors that can lead to disturbed perfusion of the brain

Answer 8

Lack of substrate:
Blood - blockage in vessels, systemic hypotension, raised ICP
Glucose - systemic hypoglycaemia, impaired cerebral circulation
Oxygen - airways/breathing problem, CO poisoning
Abnormal activity:
Fitting increases metabolic requirement
Local damage:
Loss of speech/motor use

Question 9

Describe the sequence of events occurring in the brain with increasing intracranial pressure

Answer 9

Compensation - blood/CSF/brain is squeezed out –> tentorial/uncal herniation

Question 10

Describe the consequences of raised ICP on the patient’s clinical condition

Answer 10

Signs - change in behaviour, loss of consciousness, neurological signs, change in pupil reaction, low BP, pulse, breathing rate

Question 11

Describe common clinical scenarios which lead to raised ICP

Answer 11

Haematoma

Tumour

Question 12

Describe the mechanisms leading to brain damage and intracranial haemorrhage in head injury

Answer 12

Diffuse axon all injury

Bleeding –> extradural/subdural/subarachnoid

Question 13

Describe the principles that underpin, advantages and disadvantages of CT and MRI scans of the brain

Answer 13

CT:
X-ray beam rotates around the patient, detectors measure amount of X-Rays that make it through patient, more dense = white, cross sectional image is produced
Advantages - faster, cheaper, less sensitive to patient motion, easier to perform in claustrophobic/large patients, accurate detection of calcification and metal foreign bodies, performed at no risk to patients sign implantable medical devices
Disadvantages - radiation cancer risk, reaction to CT contrast, not suitable for pregnant women, artefacts from bone/metal
MRI:
Strong magnetic field and radio waves,
Advantages - does not use ionising radiation, preferred in children and patients requiring multiple scans, greater range of soft tissue contrast, depicts anatomy in greater detail, more sensitive and specify for brain abnormalities, performed in any imaging plane without physically moving patient
Disadvantages - no metal, take a long time, claustrophobic, expensive

Question 14

Consider blood supply to the brain and consequences of its disturbances or disruptions

Answer 14

Circle of Willis

Consequences - stroke, TIA

Question 15

Describe the Oxfordshire Classification of Stroke Project (OCSP)

Answer 15

TACS (20%) - proximal occlusion of ICA/MCA, large volume infarct, superficial and deep territories –> contralateral hemiparesis, hemianopia, higher cerebral dysfunction = high mortality
PACS (35%) - occlusion of MCA branch, restricted infarct = 2 of above 3 or restricted moron deficit (face or arm or leg) or isolated cortical signs = high early recurrence rate
LACS (20%) - single perforating artery, basal ganglia/pons = pure motor, pure sensory, sensorimotor, ataxic hemiparesis = silent, underdiagnosed
POCS (25%) = brainstem, cerebellar or occipital involvement = complex presentation, thrombosis

Question 16

Describe the treatment and prevention of stroke

Answer 16

Treatment:
Intravenous thrombolysis (alteplase) within 3hr
Endovascular intervention
Aspirin
Management in acute stroke unit
Rehabilitation
Carer involvement
Education/training
Prevention:
Antithrombotic
Treat hypertension/hypercholesterolaemia/diabetes
Carotid surgery
Lifestyle changes
Medication compliance