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Normal diffusion-weighted MRI during stroke-like deficits
H Ay1, F S Buonanno, G Rordorf
1Stroke Service of the Neurology Department, Massachusetts General Hospital and Harvard Medical School, Boston 02114, USA.
Background:
Diffusion-weighted MRI (DWI) represents a major advance in the early diagnosis of acute ischemic stroke. When abnormal in patients with stroke-like deficit, DWI usually establishes the presence and location of ischemic brain injury. However, this is not always the case.
Objective:
To investigate patients with stroke-like deficits occurring without DWI abnormalities in brain regions clinically suspected to be responsible.
Methods:
We identified 27 of 782 consecutive patients scanned when stroke-like neurologic deficits were still present and who had normal DWI in the brain region(s) clinically implicated. Based on all the clinical and radiologic data, we attempted to arrive at a pathophysiologic diagnosis in each.
Results:
Best final diagnosis was a stroke mimic in 37% and a cerebral ischemic event in 63%. Stroke mimics (10 patients) included migraine, seizures, functional disorder, transient global amnesia, and brain tumor. The remaining patients were considered to have had cerebral ischemic events: lacunar syndrome (7 patients; 3 with infarcts demonstrated subsequently) and hemispheric cortical syndrome (10 patients; 5 with TIA, 2 with prolonged reversible deficits, 3 with infarction on follow-up imaging). In each of the latter three patients, the regions destined to infarct showed decreased perfusion on the initial hemodynamically weighted MRI (HWI).
Conclusions:
Normal DWI in patients with stroke-like deficits should stimulate a search for nonischemic cause of symptoms. However, more than one-half of such patients have an ischemic cause as the best clinical diagnosis. Small brainstem lacunar infarctions may escape detection. Concomitant HWI can identify some patients with brain ischemia that is symptomatic but not yet to the stage of causing DWI abnormality.
Insights
Normal diffusion-weighted MRI (DWI) in stroke patients may indicate a stroke mimic or an ischemic event. Hemodynamic-weighted MRI (HWI) can help identify early ischemic changes not visible on DWI.
Area of Science:
- Neurology
- Radiology
- Neuroimaging
Background:
- Diffusion-weighted MRI (DWI) is crucial for diagnosing acute ischemic stroke.
- DWI abnormalities typically confirm ischemic brain injury.
- However, normal DWI findings can occur in patients with stroke-like deficits.
Purpose of the Study:
- To investigate patients presenting with stroke-like deficits but normal DWI in suspected brain regions.
- To determine the underlying causes of these deficits.
Main Methods:
- Reviewed 782 consecutive patients with stroke-like deficits and normal DWI in implicated brain areas.
- Analyzed clinical and radiological data for pathophysiological diagnosis.
- Utilized hemodynamic-weighted MRI (HWI) for perfusion assessment.
Main Results:
- 63% of patients had cerebral ischemic events; 37% had stroke mimics (e.g., migraine, seizures, tumor).
- Ischemic events included lacunar and hemispheric syndromes, with some diagnosed via follow-up imaging or TIA.
- HWI revealed decreased perfusion in regions that later showed infarction.
Conclusions:
- Normal DWI necessitates exploring non-ischemic causes for stroke-like symptoms.
- Over half of these patients ultimately have an ischemic cause.
- HWI aids in detecting early symptomatic brain ischemia not yet evident on DWI, especially for small infarcts.