What is the next step in management for a patient with suspected cerebellar acute stroke and a false negative Magnetic Resonance Imaging (MRI) result, with a high clinical suspicion remaining?

Management of Suspected Cerebellar Acute Stroke with False Negative MRI

If clinical suspicion for cerebellar stroke remains high despite negative initial MRI, continue standard acute stroke care and obtain repeat MRI within 24 hours to 7 days after symptom onset, as DWI-MRI can be falsely negative in approximately 50% of small posterior fossa strokes within the first 48 hours. 1

Understanding the Problem

• False negative rates are substantial in cerebellar strokes: DWI-MRI misses approximately 50% of small ischemic strokes in the posterior fossa within the first 48 hours of symptom onset 1
• MRI remains superior to CT overall: Despite false negatives, MRI detects acute ischemic stroke in 46% of patients versus only 10% with CT, and has 83% sensitivity for any acute stroke versus 26% for CT 2
• The "fogging" phenomenon: Subacute cerebellar infarcts may be missed on imaging due to this specific imaging artifact 3

Clinical Predictors That Should Raise Your Suspicion

When initial MRI is negative but you're considering cerebellar stroke, look for these high-risk features:

• Combined neurological symptoms are the strongest predictor (odds ratio 16.72) of lesions missed on initial MRI 1
• Central oculomotor signs increase likelihood of missed lesions (odds ratio 2.8) 1
• Focal abnormalities on examination increase likelihood (odds ratio 3.3) 1
• Persistent severe vertigo, nausea, and vomiting even after nystagmus resolves suggests cerebellar pathology 4
• Changing direction or type of nystagmus over 6-24 hours is atypical for benign peripheral vestibular disorders and suggests central pathology 4

Conversely, transient symptoms reduce the likelihood (odds ratio 0.3) of missed lesions 1

Immediate Management Steps

Continue Standard Stroke Care

• Do not delay treatment decisions when clinical presentation strongly suggests stroke despite negative imaging 1
• Maintain close neurological monitoring with standardized stroke scales (NIHSS) 5
• Monitor vital signs including blood pressure, heart rate, temperature, and oxygen saturation 5

Obtain Comprehensive Vascular Imaging (If Not Already Done)

• CT angiography (CTA) from aortic arch to vertex for rapid assessment of large vessel occlusion, even when parenchymal changes aren't visible 1, 5
• MR angiography (MRA) is preferred for patients with renal insufficiency or contrast allergy 1
• Vascular imaging may identify occlusions (such as superior cerebellar artery or posterior inferior cerebellar artery) even when DWI is negative 6, 3

Blood Pressure Management

• For patients NOT receiving thrombolysis: Only lower blood pressure when systolic exceeds 220 mmHg or diastolic exceeds 120 mmHg, as aggressive reduction may worsen ischemia 5
• For thrombolysis candidates: Blood pressure must be reduced below 185/110 mmHg before treatment 5

Follow-Up Imaging Strategy

Schedule repeat MRI 24 hours to 7 days after symptom onset, as delayed imaging significantly improves detection of initially missed strokes 1, 4

• Repeat MRI should be performed at least 24 hours after symptom onset in patients with atypical nystagmus patterns or persistent symptoms 4
• The optimal window is 3-7 days after symptom onset for maximum sensitivity 1
• This approach is particularly critical for patients with isolated severe vertigo or dizziness who initially presented within 2-6 hours of onset 4

Ongoing Monitoring and Assessment

Neurological Observation

• Periodically observe nystagmus 6-24 hours after symptom onset, as changes in direction or type suggest central pathology 4
• Continue frequent neurological assessments (every 1-4 hours depending on clinical stability) 5
• Monitor for signs of cerebellar swelling or posterior fossa mass effect, which carries substantial morbidity and mortality 6

Laboratory Monitoring

• Continue monitoring blood glucose, electrolytes, and coagulation parameters 5
• These tests should not have delayed initial imaging but remain important for ongoing management 5

Swallowing Assessment

• Complete swallowing screening within 24 hours using a validated tool to prevent aspiration 5
• Keep patient NPO until screening is completed 5

Common Pitfalls to Avoid

• Discharging patients with negative imaging when clinical suspicion remains high: The false negative rate is too substantial to rely solely on initial imaging 1, 4
• Failing to obtain vascular imaging: CTA or MRA may reveal vessel occlusions even when parenchymal changes aren't yet visible 1
• Not repeating MRI in the appropriate timeframe: Waiting at least 24 hours is critical, as earlier repeat imaging may still be negative 4
• Attributing symptoms to benign peripheral vestibular disorders without considering atypical features like changing nystagmus patterns or persistent symptoms after nystagmus resolution 4
• Aggressive blood pressure lowering in non-thrombolysis candidates: This may decrease cerebral perfusion and worsen ischemia 5

Special Considerations for Cerebellar Territory

• Superior cerebellar artery (SCA) infarctions may benefit from MRI mismatch-based thrombolysis even in extended time windows when perfusion-diffusion mismatch is demonstrated 6
• Posterior inferior cerebellar artery (PICA) territories can be visualized with territorial arterial spin labeling MRI and supply at least the medial posterior cerebellar surface 3
• Small cerebellar infarcts typically affect the cortex and may present as incidental cavities on follow-up imaging 3