Fisher et al classified subarachnoid hemorrhage as seen on CT scans. The authors are from the Massachusetts General Hospital.
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Subarachnoid Blood on CT Scan
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Grade (Group)
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none detected
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I
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diffuse deposition as a thin layer with all vertical layers < 1.0 mm in thickness
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II
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diffuse deposition as a thin layer >= 1.0 mm in thickness OR localized clots
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III
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(intracerebral OR intraventricular blood clots) AND (no subarachnoid blood OR diffuse blood)
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IV
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Severe vasospasm was commonly seen when the following were present:
(1) blood clots larger than 5 x 3 mm
(2) layers of blood >= 1 mm
Severe vasospasm was commonly seen in patients with Group III findings.
