Preliminary experience with this model suggested a CBF threshold for infarction.20 The present study is an expanded assessment of the brain's tolerance to focal ischemia. Ischemic insults of varied severity and duration were produced. Neurological function, local CBF, and pathology were correlated. We found that local CBF defines ischemia thresholds for function and structure: when local flow falls below a paralysis threshold, function is reversibly lost; when flow drops further below an infarction threshold, anatomic damage becomes irreversible.
Hewlett-Packard Model 9815A programmable calculator manufactured by Hewlett-Packard Corp., San Diego, California.
This work was supported in part by the National Institute of Neurological Diseases and Stroke Grants NS13165 and NS10828, and in part by Teacher-Investigator Award NS11001 to Dr. Crowell.