Negative Stroke Workup but Persistent Symptoms: What It Means

A negative CT/MRI does not definitively rule out stroke, especially in the acute window.

Why Imaging Can Miss Stroke

• CT sensitivity: ~40–60% for acute ischemic stroke at 3–6 hrs; misses small/posterior fossa infarcts.
• MRI DWI sensitivity: ~90–95% at 24 hrs, but false negatives occur with very small (<5 mm) brainstem/cortical infarcts, or if scanned too early (<3–6 hrs for DWI positivity in some cases).
• TIA (Transient Ischemic Attack): By definition, no infarct on imaging (symptoms resolve <24 hrs, usually <1 hr).
• Posterior circulation strokes: Often missed on CT; MRI DWI better but not perfect.

Clinical Diagnosis Trumps Imaging

Stroke is a clinical diagnosis based on sudden focal neurological deficit. Imaging supports, but cannot exclude.

If Symptoms Suggest Stroke

• Call 911 immediately.
• Even if initial scan negative: admit for observation, repeat MRI in 12–24 hrs, vascular imaging (CTA/MRA), cardiac monitoring.
• Start secondary prevention (antiplatelet, statin, risk factor control) if clinical picture fits.

FAST: Face drooping, Arm weakness, Speech difficulty → Time to call emergency services. Do not wait for a scan.