In a patient with left‑sided ischemic stroke symptoms, a normal initial non‑contrast CT, no clinical evidence of posterior‑circulation involvement, and compensated Child‑Pugh A cirrhosis, should a brain MRI be performed about 24 hours after symptom onset?

MRI at 24 Hours for Left-Sided Ischemic Stroke with Normal Initial CT

Yes, perform brain MRI at approximately 24 hours after symptom onset in this patient with left-sided ischemic stroke symptoms and normal initial CT, even without posterior circulation features. This recommendation is supported by major stroke guidelines and directly impacts diagnosis confirmation, secondary prevention strategies, and patient outcomes.

Diagnostic Yield Justifies 24-Hour MRI

• Approximately 25% of acute stroke patients with initially normal CT will show acute or subacute infarction on MRI performed within 1-2 days, confirming the diagnosis and enabling appropriate secondary prevention. 1

• In emergency department patients presenting with stroke symptoms and negative CT, MRI obtained within 24 hours identifies acute ischemic stroke in 11.5% of cases, which would otherwise remain undiagnosed. 1

• MRI detects acute ischemic stroke in 46% of patients within the first 3 hours versus only 10% for CT, with this diagnostic superiority persisting throughout the acute period. 2

Guideline-Based Timing Recommendations

• The American College of Cardiology explicitly recommends repeat brain imaging (CT or MRI) at 24 hours after initial stroke event or thrombolytic therapy, regardless of clinical stability. 3

• This 24-hour follow-up scan is required before initiating anticoagulants or antiplatelet agents for secondary stroke prevention, making it a critical decision point. 3

• The American Heart Association supports that follow-up brain imaging with MRI within 1-2 days has widespread diagnostic yield and clinical utility. 1

Impact on Secondary Prevention and Management

• Confirming stroke diagnosis with MRI directly influences management by identifying intracranial atherosclerotic disease, which supports aggressive antiatherosclerotic targets and often indicates dual antiplatelet therapy. 1, 4

• MRI findings inform critical secondary prevention decisions including antiplatelet agent selection, anticoagulation decisions (if cardioembolic source identified), statin intensity, and blood pressure goals. 3

• Diagnosis confirmation improves patient education and prognostication, which enhances adherence to prescribed prevention regimens—directly impacting long-term morbidity and mortality. 1, 4

Why This Applies to Anterior Circulation Strokes

While posterior circulation strokes have particularly high false-negative rates on initial imaging, the 25% diagnostic yield of 24-hour MRI applies to all stroke locations, including anterior circulation. 1

• The recommendation for 24-hour follow-up imaging is not limited to posterior circulation strokes—it applies to all acute stroke presentations with initially negative or equivocal imaging. 3

• Even in left-sided (anterior circulation) presentations, small cortical or subcortical infarcts may be missed on initial CT but become apparent on diffusion-weighted MRI. 2

Practical Implementation Algorithm

For your patient with left ischemic stroke symptoms, normal initial CT, and Child-Pugh A cirrhosis:

1. Perform MRI brain without contrast at 24 hours post-symptom onset (DWI, FLAIR, gradient echo sequences). 3, 2

2. The cirrhosis (Child-Pugh A, compensated) does not contraindicate MRI and gadolinium is not required for stroke diagnosis. 2

3. Complete the MRI before initiating antiplatelet or anticoagulation therapy to exclude hemorrhagic transformation and confirm infarct pattern. 3

4. Use MRI findings to guide secondary prevention intensity (antiplatelet choice, statin dose, blood pressure targets). 3, 4

Common Pitfalls to Avoid

• Do not assume a normal initial CT excludes stroke—up to 25% will have confirmed infarction on 24-hour MRI. 1

• Do not start anticoagulation before 24-hour imaging if there is any consideration for this therapy, as hemorrhagic transformation must be excluded. 3

• Do not limit follow-up MRI only to posterior circulation strokes—anterior circulation strokes also benefit from confirmation imaging. 1, 3

• Recognize that diffusion-weighted imaging can still be falsely negative in approximately 50% of small posterior fossa strokes within 48 hours, but this is less common in anterior circulation. 1