Stephen B. Lewis MD FRACS

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Neuroscience 2007 Stroke
Stephen B. Lewis MD FRACS Department of
Neurosurgery University of Florida
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• General overview
• Ischemic stroke a) Thrombotic vs
  embolic b) Factors affecting extent c)
  Effect of location c) Lacunar c)
  Territorial
• Hemorrhagic stroke a) Aneurysms b)
  Hypertension
• Cerebral herniation

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A sudden and often severe cerebral vascular
catastrophe that may temporarily or permanently
impair brain function
Types 1. Ischemic blockage within blood
vessel a. Thrombotic locally generated
obstruction b. Embolic occlusion secondary
to traveling particle originating
proximally in bloodstream 2. Hemorrhagic
bleeding from blood vessel resulting in
clot formation within brain
substance or over its surface

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Favored locations

• Heart
• Sites of atheromatous disease - aorta -
  common carotid bifurcation - distal
  intracranial vertebral artery - proximal half
  basilar artery - perforating microvessels

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• Emboli lodge at bifurcations - ICA
  bifurcation - basilar artery tip
• Final lodgement a function of - hemodynamic
  forces - size
• Perforator (lacunar) strokes - thrombotic (local
  disease)
• Territorial strokes - embolic or thrombotic

MCA
ACA
Basilar apex
PCA
Basilar A.
Vertebral A.
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Stroke factors affecting extent of stroke

• Anastomotic channels - ACoA -
  PCoA - Between territories

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Clinical example when things fail
Stroke factors affecting extent of stroke

• 46 yo rh WM
• Carpenter
• Very hot day dehydrated, felt unwell
• Sudden onset of leg weakness

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Stroke factors affecting extent of stroke

• Perforating vessels - end arteries - poor
  collateral supply - lenticulostriates affected

Lenticulostriates
Sylvian Fissure
A2
HA
M1 (pre-bifurcation)
M1 (post-bifurcation)
M2 segments
Genu
M3 segments
ICA
M4 segments (cortical branches)
M4
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• Small perforating vessels - may be silent
  (lacunes in putamen, others) - may be devastating
  (lenticulostriates)

• Terminal large vessel occlusion - large number of
  syndromes - MCA upper div facio brachial
  motor, hemisensory loss, Brocas aphasia - MCA
  lower div Wernickes aphasia, visual
  disturbance, behavioural

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• Terminal large vessel occlusion - dependent
  upon territory supplied

• PICA a) Vestibular nuclei
  NV b) Inf cereb peduncle ipsi
  ataxia c) Spinal CN V ipsi PT face d)
  CN IX loss afferent limb gag rf e) CN X
  ipsi pharyngeal, laryngeal
  paralysis f) Spinal lemniscus (ST
  tract) contra. PT from limbs
  trunk g) Desc sympathetics ispi Horners

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• One-third of all ischemic strokes
• Etiology arteriosclerotic occlusion of
  perforators in the basal
  ganglia, brainstem, and
  centrum semiovale
• Associated with HTN and diabetes
• Lesions lt 1.5 mm3 (often not seen on CT)

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Clinical example

• 56 yo rh WF
• Diabetes, hypertension, smoker
• Sudden onset left pure motor hemiparesis

• Classical clinical syndromes
• - Pure motor
• - Pure sensory

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• Two-thirds of all ischemic strokes
• Arterial branch or stem occlusions
• Etiology embolic or local thrombosis
• Prognosis related to severity of presenting
  symptoms, size of lesion, and patients age
  comorbidities

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Onset of clinical symptoms
100
EMBOLIC STROKE THROMBOTIC STROKE
NORMAL NEUROLOGIC FUNCTION
0
minutes
hours
days
years
months
TIME
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• Supratentorial
• - sudden motor/sensory deficit
• - plus cortical symptoms such as aphasia,
  apraxia, neglect, homonymous visual deficits

Infratentorial - sudden motor/sensory deficit -
Plus additional brainstem or cerebellar
disturbances
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Cerebral aneurysms

• Cerebral arteries have subarachnoid course
• Aneurysms outpouching of intima
• Aneurysms occur at bifurcation points

ACoA 35
MCA 20
P Comm 25
Basilar 10
Vertebral 5
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Cerebral aneurysms

• Symptoms due to SAH - sentinal
  headache - worst headache of life

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Cerebral aneurysms

• Symptoms due to location - mass effect on
  optic nerve

• 49 yo rh W M
• Gradual onset - bumping into
  things - inferior nasal field cut right eye

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(No Transcript)
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Hypertensive hemorrhage

• Rupture occurs in middle/distal portions of
  penetrating arteries
• Incidence doubles with each decade after age 35
• Hypertensive history (remote recent)
• Occurs basal ganglia, thalamus, cerebellum,
  pons, deep white matter

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• Rigid structure
• Contains - brain - blood - CSF
• Additional contents may result in raised pressure

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Causes of raised ICP
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Cerebral herniation - effect of raised ICP
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Subfalcine herniation

• Anterior cerebral artery
• - medial surface

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• Uncal herniation compressing PCA onto 3rd cranial
  nerve

L
R
PCA occlusion - occipital lobe infarction
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• General overview
• Ischemic stroke a) Thrombotic vs
  embolic b) Factors affecting extent c)
  Effect of location c) Lacunar c)
  Territorial
• Hemorrhagic stroke a) Aneurysms b)
  Hypertension
• Cerebral herniation