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A diffusion-weighted MRI study of acute ischemic distal arm paresis
1Department of Neurology, Universitaetsklinikum Mannheim, University of Heidelberg, Germany. gass@neuro.ma.uni-heidelberg.de
Objective:
To study the site of the ischemic lesion, the underlying cause, and the prognosis of acute stroke with distal arm paresis.
Method:
The authors investigated 14 consecutive patients with acute distal arm paresis with a diagnostic stroke protocol and early MRI, including T2-weighted images, diffusion-weighted images (DWI), and perfusion-weighted images (PWI). Acute DWI lesions were shown on coregistered T2-weighted images for analysis of the exact anatomic lesion location.
Results:
Patients showed a uniform (7/14), radial (3/14), or ulnar (4/14) distribution of hand paresis. In all cases, DWI identified small lesions located in the motor cortex. Topographic lesion analysis, which was correlated with the clinical deficit, showed lesions centered in the hand knob area (2/14), involving the lateral (6/14), medial (4/14), or both (2/14) borders of the hand knob. PWI (calculated time-to-peak maps) did not show a mismatch between the DWI lesion and the PWI lesion. In six patients, DWI and PWI lesions were identical in size and location; no definite perfusion deficit was seen in eight patients. In agreement with PWI, no patient showed clinical worsening, and six patients recovered completely within a week. Further investigations showed a potential source of embolus in 11 cases.
Conclusions:
Acute ischemic distal arm paresis is usually caused by a small cortical lesion in the motor hand cortex attributable to distal Rolandic artery obstruction without additional tissue at risk. These findings confirm the observed benign clinical course and its apparent main cause (artery-to-artery or cardiac embolism).
Insights
Acute stroke causing distal arm weakness typically results from small cortical lesions in the motor hand area. These ischemic strokes often stem from embolism and generally have a favorable prognosis with rapid recovery.
Area of Science:
- Neurology
- Neuroimaging
- Stroke Medicine
Background:
- Distal arm paresis is an uncommon presentation of acute stroke.
- Identifying the precise location and cause of such strokes is crucial for prognosis.
Purpose of the Study:
- To investigate the anatomical site and cause of ischemic lesions in patients with acute distal arm paresis.
- To determine the prognosis and clinical course of these specific stroke cases.
Main Methods:
- 14 patients with acute distal arm paresis underwent a stroke protocol including T2-weighted, diffusion-weighted (DWI), and perfusion-weighted (PWI) MRI.
- Lesion location was precisely analyzed using coregistered DWI and T2-weighted images, correlated with clinical deficits.
Main Results:
- Small cortical lesions in the motor cortex, specifically the hand knob area, were identified in all patients via DWI.
- No significant mismatch between DWI and PWI lesions was observed, suggesting limited tissue at risk.
- Most patients showed clinical improvement within a week, with potential embolic sources identified in 11 cases.
Conclusions:
- Acute ischemic distal arm paresis is typically caused by small cortical lesions in the motor hand cortex, often due to distal Rolandic artery obstruction.
- The observed benign clinical course and recovery are attributed to distal embolism (artery-to-artery or cardiac) affecting a small area.
- These findings highlight the importance of early MRI in localizing small cortical lesions and understanding the favorable prognosis in distal arm paresis stroke.