CVA & Visual Pathways

🧠 CVA & Visual Pathways

Ischaemic vs haemorrhagic stroke, the visual pathway from retina to occipital cortex, and how to localise a lesion from the pattern of visual field loss alone.

Stroke — The Essentials

A stroke (CVA — cerebrovascular accident) is a sudden focal neurological deficit caused by interruption of the blood supply to part of the brain. The key distinction — ischaemic or haemorrhagic — is invisible clinically and requires a CT scan to determine. Never give thrombolysis without a CT: giving it to a haemorrhagic stroke is fatal.

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Ischaemic Stroke

85% of all strokes — The Blockage

MechanismThrombosis, embolism (AF, carotid atheroma), or small vessel (lacunar) disease

OnsetDeficit typically maximal at onset — immediate full picture

HeadacheUsually absent or mild

ConsciousnessUsually preserved initially unless large territory

CT earlyOften normal in first hours — loss of grey-white differentiation appears later

TreatmentThrombolysis (tPA) if within 4.5 h, thrombectomy if large vessel occlusion; aspirin + statin

PrognosisDepends on territory; cortical collaterals may limit infarct. Penumbra is salvageable.

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Haemorrhagic Stroke

~15% of strokes — The Bleed

MechanismCharcot-Bouchard microaneurysm rupture (hypertension) — classic site: basal ganglia

OnsetDeficit progressively worsens over minutes to hours as haematoma expands

HeadacheProminent — often severe at onset

ConsciousnessFrequently depressed — raised ICP from expanding haematoma

CT earlyHyperdense (bright white) collection immediately visible — no delay

TreatmentReverse anticoagulation, BP control, neurosurgical referral. NO thrombolysis.

PrognosisGenerally worse than ischaemic — high mortality, mass effect, herniation risk

CT Before Thrombolysis — The Single Most Important Rule in Stroke

Ischaemic and haemorrhagic strokes can appear clinically identical — both cause sudden focal neurological deficits. Giving IV tPA (thrombolysis) to a haemorrhagic stroke dramatically worsens the bleed and is likely fatal. A CT head takes minutes and distinguishes them immediately. There are no clinical features that reliably exclude haemorrhage.

Protocol: any suspected stroke → CT head immediately → if no haemorrhage and ischaemic stroke confirmed → consider thrombolysis if within 4.5 hours and no contraindications.

Quick Comparison

Feature	Ischaemic (85%)	Haemorrhagic (15%)
Headache	Absent or mild	Prominent, often severe
Vomiting	Uncommon	Common (raised ICP)
Consciousness	Usually preserved	Often depressed
Onset of deficit	Maximal at onset	Progressive deterioration over minutes–hours
CT early	Often normal in first hours	Immediately hyperdense
Thrombolysis	✅ May be indicated (if within 4.5 h)	🚫 Absolutely contraindicated
BP management	Permissive hypertension acutely (maintain perfusion pressure)	Lower BP cautiously (reduce ongoing bleed)

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