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Basic Anatomy & Pathophysiology of ischemic stroke
1. Ischemic Stroke: Basic
Anatomy and Pathophysiology
Dr. Ajay Kumar Agarwalla
Phase- A Resident (Neurology)
Blue Unit, Neurology dept. ,
BSMMU
2. Road Map
⢠Artery supply of the brain
⢠Findings associated with occlusion
⢠Key features of cerebral blood flow
⢠Auto regulation of cerebral blood flow
⢠Pathophysiology of infarction in brain
⢠Factors influence ischemic stroke
4. Anterior Cerebral Artery Occlusion
Contralateral hemiparesis and hemisensory loss involving mainly the
leg and foot (paracentral lobule of cortex)
Inability to identify objects correctly, apathy, and personality changes
(frontal and parietal lobes)
5. Contralateral hemiparesis and
hemisensory loss involving
mainly the face and arm
(precentral and postcentral
gyri)
Aphasia if the left hemisphere
is affected (rarely if the right
hemisphere is affected)
Contralateral homonymous
hemianopia (damage to the
optic radiation)
Middle Cerebral Artery
Occlusion
6. Contralateral homonymous
hemianopia with some
degree of macular sparing
(damage to the calcarine
cortex)
Visual agnosia (ischemia of
the left occipital lobe)
Impairment of memory
(damage of medial aspect
of the temporal lobe)
Posterior Cerebral Artery
Occlusion
7. Key features of blood flow in
BRAIN
⢠ In an adult, CBF is typically
ďź750 ml/min or
ďź45-50ml/100g/min or
ďź15 % of the cardiac output (CO)
In normal individuals, CBF remains constant when
the mean arterial pressure varies between
â60 and 160 mmHgâ
8. Ideal Cerebral Auto regulationIdeal Cerebral Auto regulation
Lassen NA. Physiol Rev. 1959;39:183-238
Strandgaard S, Paulson OB. Stroke.1984;15:413-416
9. Matter of Concern
Cerebral Blood Flow (CBF) :
⢠Less than 23ml/100g/min, physiological
electrical function of the cell begins to fail-
âischemic penumbraâ.
⢠Below 10 ml/100g/min, ionic membrane
transport failure, Irreversible cell death- which
leads to- âinfarctionâ.
10.
11. Factors Influence Ischemic Stroke
⢠Rate and onset of duration
⢠Collateral circulation
⢠Systemic circulation
⢠Hypercoagulable states
⢠Increased temperature
⢠Hyper/hypo glycemia
12. Reference
Snells Clinical Neuroanatomy, 7th
edition
Davidsonâs Principles and Practice of Medicine, 22nd
edition
Harrisonâs Principles of Internal Medicine, 19th
edition
http://what-when-how.com/neuroscience/blood-supply-of-the-
http://en.wikipedia.org/wiki/Cerebral_blood_flow
Stroke Pathophysiology Sid Shah, MD
Editor's Notes
It is a characteristic of the brain to adjust its own blood supply. The brain accounts for only 2-3% of total body weight and does not do any mechanical work, yet it receives 20% of all cardiac output.
Ideally, when aterial blood pressure increase or decrease between 70-150 mmhg , the cerebral autoregulation can make the blood flow velocity constant , beyond the range, the blood flow velocity will increase or decrease dramaticaly with the blood pressure
A thrombus or an embolus can occlude a cerebral artery and cause ischemia in the
affected vascular territory. It is often not possible to distinguish between a lesion caused
by a thrombus and one caused by an embolus. Thrombosis of a vessel can result in
artery-to-artery embolism. Mechanisms of neuronal injuy at the cellular level are
governed by hypoxia or anoxia from any cause that is reviewed below.
At a gross tissue level, the vascular compromise leading to acute stroke is a dynamic
process that evolves over time. The progression and the extent of ischemic injury is
influenced by many factors.
2-5
Rate of onset and duration: the brain better tolerates an ischemic event of short duration
or one with slow onset.
Collateral circulation: the impact of ischemic injury is greatly influenced by the state of
collateral circulation in the affected area of the brain. A good collateral circulation is
associated with a better outcome.
Health of systemic circulation: Constant cerebral perfusion pressure depends on
adequate systemic blood pressure. Systemic hypotension from any reason can result in
global cerebral ischemia.
Hematological factors: a hypercoagulable state increases the progression and extent of
microscopic thrombi, exacerbating vascular occlusion.
Temperature: elevated body temperature is associated with greater cerebral ischemic
injury.
Glucose metabolism: hyper- hypoglycemia can adversely influence the size of an infarct.