â– LECTURE OVERVIEW: Acute stroke represents a neurological emergency. Timely differentiation between ischemic and hemorrhagic profiles is critical to determine the therapeutic pathway.
â– CLINICAL DYNAMICS:
1. Ischemic Stroke (85% of cases):
- Origin: Caused by thrombotic or embolic occlusion of a cerebral artery, most commonly the Middle Cerebral Artery (MCA).
- Cascade: Focal tissue ischemia triggers an ischemic cascade, depleting ATP, causing cellular depolarization, toxic glutamate release, and ultimate necrotic cell death.
2. Hemorrhagic Stroke (15% of cases):
- Origin: Caused by the rupture of a blood vessel in the brain parenchyma (intracerebral hemorrhage, often from long-standing hypertension eroding Charcot-Bouchard aneurysms) or into the subarachnoid space (subarachnoid hemorrhage, often from a ruptured saccular berry aneurysm).
â– PHYSIOLOGICAL METABOLIC RECOVERY LOOPS:
Intense pathologic strain initiates systemic arterial, neural, or renal neurohormonal feedback mechanisms to maintain oxygenation, cellular pH balance, and blood pressure in critical territories.
â– GERIATRIC PHYSIOLOGIC ADJUSTMENTS:
Older patients display reduced physiological reserves, altered muscle-to-fat distributions, and distinct renal filtration profiles.
[HY-BOARD-1140]
🌟 Dynamic Clinical Key:
A non-contrast head CT scan is the absolute first-line screening diagnostic of choice. Because acute ischemia is initially invisible on CT, the main purpose is to rule out hemorrhagic stroke before administering fibrinolytic agents like recombinant tPA, which would be fatal if given during active intracranial hemorrhage. Recognize that blocking some compensatory mechanisms (like reducing hyperventilation in respiratory compensation) can hasten acidotic collapse. Always adjust therapeutic doses based on age-related glomerular filtration clearance.