Ischemic vs Hemorrhagic Stroke: How to Tell Them Apart
Both ischemic and hemorrhagic stroke present as a sudden focal neurological deficit and are treated as emergencies where time is brain. The core axis that separates them is whether blood flow is blocked (ischemia) or blood has escaped into the brain (hemorrhage) — a distinction made by non-contrast CT before any reperfusion therapy can be given.
How to tell them apart
| Feature | Ischemic stroke | Hemorrhagic stroke |
|---|---|---|
| Underlying mechanism | Blocked blood flow — cardioembolic (e.g., atrial fibrillation), atherosclerotic/artery-to-artery embolism, or small-vessel (lacunar) disease | Blood escaping into tissue — intracerebral hemorrhage (bleeding within parenchyma) or subarachnoid hemorrhage (bleeding into subarachnoid space) |
| Non-contrast CT findings | Often normal in the hyperacute phase; a normal CT excludes hemorrhage but does not by itself confirm ischemic stroke — stroke mimics must still be considered. An established infarct appears later as hypodensity | Blood is visible acutely — e.g., a basal ganglia hemorrhage with mass effect and midline shift, or blood filling the subarachnoid cisterns |
| Most common cause | Embolism and thrombosis; cardioembolic sources include atrial fibrillation with left atrial appendage thrombus | Depends on the subtype — for intracerebral hemorrhage (ICH), chronic hypertension causing lipohyalinosis and rupture of small penetrating arteries is most common (with cerebral amyloid angiopathy favoring lobar bleeds in the elderly, plus AVM, tumor, and anticoagulation); for subarachnoid hemorrhage (SAH), rupture of a saccular (berry) aneurysm is the most common cause, followed by AVM |
| Headache and depressed consciousness | Typically a focal deficit without prominent headache; deficit often maximal at onset | May present with sudden severe headache and progressive drowsiness; subarachnoid hemorrhage classically causes thunderclap headache |
| Reperfusion therapy | Candidate for IV thrombolysis and/or mechanical thrombectomy when within the time window and no contraindications | CT evidence of hemorrhage is an absolute contraindication to IV thrombolysis; anticoagulation must be reversed |
| Blood pressure management | Permissive hypertension in the acute phase: BP is tolerated up to 220/120 mmHg in patients not receiving thrombolysis, but must be lowered to <185/110 mmHg before IV tPA and kept <180/105 mmHg after. Antihypertensives are typically initiated/resumed after about 24 hours in stable patients for secondary prevention | Early BP lowering (e.g., systolic target around 140 mmHg) is often recommended per INTERACT2 data, though ATACH-2 tempered this by showing no clear benefit and potential harm with very aggressive/rapid reduction |
| Role of neurosurgery | Not a primary intervention; care centers on reperfusion and secondary prevention | Neurosurgical consultation and ICU monitoring are part of immediate management, especially with mass effect or herniation; ruptured aneurysms in SAH require securing by clipping or coiling |
| Concerning early signs | Large vessel occlusion syndrome (e.g., aphasia plus dense hemiparesis, high NIHSS) | Signs of raised intracranial pressure and impending herniation — a progressively decreasing level of consciousness with posturing, and a fixed, dilated ('blown') pupil with the eye deviated 'down and out' from ipsilateral CN III compression in uncal herniation (the fixed, dilated pupil reflects loss of parasympathetic fibers, while the 'down-and-out' eye position reflects unopposed lateral rectus and superior oblique action), together with Cushing's triad (hypertension, bradycardia, irregular respirations) |
The reasoning
Anchor on the clinical scenario: a sudden focal deficit is a stroke until proven otherwise, and the immediate task is to determine treatable versus contraindicated therapy. Non-contrast CT is the arbiter — it does not confirm ischemia but reliably reveals blood. A normal CT in a patient with acute deficits excludes hemorrhage; it points toward ischemic stroke only after mimics such as hypoglycemia, seizure with Todd paralysis, migraine, and conversion disorder are considered, and if within the window with no contraindications it opens the door to thrombolysis and thrombectomy. Visible blood, especially with severe headache or depressed consciousness, signals hemorrhage and shifts management toward BP control, anticoagulation reversal, and neurosurgery. History helps predict which is more likely: atrial fibrillation off anticoagulation favors cardioembolic ischemia, whereas poorly controlled hypertension with sudden headache and a basal ganglia location favors hypertensive ICH, and a thunderclap headache with blood in the cisterns favors aneurysmal SAH.
Key tests
- Non-contrast CT head: normal or subtle in hyperacute ischemic stroke, but directly shows blood in hemorrhagic stroke — this is the first study and rules out hemorrhage before thrombolysis
- CT angiography (CTA): in ischemic stroke, evaluates for large vessel occlusion (e.g., ICA or M1) to guide thrombectomy; in SAH, identifies a ruptured saccular aneurysm
- Lumbar puncture: performed when subarachnoid hemorrhage is suspected clinically (thunderclap headache) but CT is normal — xanthochromia supports SAH
- Point-of-care glucose: mandatory to exclude hypoglycemia, a common stroke mimic, in any patient with acute focal deficits
What they share
- Sudden onset of a focal neurological deficit
- Vascular risk factors, especially hypertension
- Present as neurological emergencies where rapid evaluation is essential
- Can produce contralateral hemiparesis, hemisensory loss, and other territory-based deficits
- Hypertension drives both large-vessel atherosclerosis/cardioembolism and small-vessel rupture
- Conjugate horizontal gaze deviation toward the side of a large destructive hemispheric lesion (unopposed contralateral frontal eye field) can occur with either a large infarct or a large hemorrhage
Pitfalls
- Interpreting a normal hyperacute CT as 'no stroke' — a normal CT is expected in early ischemic stroke; it excludes hemorrhage but does not confirm ischemia, and stroke mimics must still be excluded
- Giving IV thrombolysis without excluding hemorrhage — CT evidence of hemorrhage is an absolute contraindication
- Missing subarachnoid hemorrhage when CT is normal; if suspicion is high, proceed to lumbar puncture
- Conflating the etiologies of the two hemorrhage subtypes — chronic hypertensive small-vessel rupture (and amyloid angiopathy) is the leading cause of intracerebral hemorrhage, whereas ruptured saccular (berry) aneurysm is the leading cause of subarachnoid hemorrhage; these are tested separately on boards
- Forgetting that hemorrhagic conversion of an ischemic stroke can occur, blurring the initial distinction
- Confusing conjugate gaze deviation toward a large hemispheric lesion — a localizing sign seen in both large ischemic and hemorrhagic strokes — with herniation, which instead produces a fixed, dilated ('blown') pupil and an eye that is deviated 'down and out' (complete CN III palsy), depressed consciousness, and Cushing's triad
- Conflating the two components of the CN III palsy of uncal herniation: 'down-and-out' describes the eye/globe position (unopposed lateral rectus and superior oblique), whereas the pupil itself is fixed and dilated from loss of parasympathetic fibers — remember that compressive CN III palsy is pupil-involving, unlike pupil-sparing ischemic/microvascular CN III palsy
- Failing to lower BP to <185/110 mmHg before tPA, or over-aggressively lowering BP (below the 220/120 permissive threshold) in a non-thrombolysis ischemic stroke patient
- Overlooking posterior circulation strokes, which present with non-specific symptoms like dizziness and ataxia and can be either ischemic or hemorrhagic (e.g., cerebellar bleed)
Practice this the way the exam tests it — on branching cases where your decisions shape the patient.