CONTRIBUTION OF DIASCHISIS TO THE CLINICAL DEFICIT IN HUMAN CEREBRAL INFARCTION

Background and Purpose Regions of decreased cerebral blood flow are of ten seen on single-photon emission computed tomography (SPECT) after s troke and have been widely reported to add to the clinical deficit. Ho wever, such reports have not distinguished between correlation and cau sation. We analyzed 124 serial SPECT scans performed in 50 patients to assess the role of diaschisis in the clinical deficit after stroke. M ethods SPECT with the use of Tc-99m-hexamethylpropyleneamine oxime (Tc -99m-HMPAO) was performed in a prospective, unselected series of 50 pa tients with cerebral infarcts studied at a median of 1.1, 6.8, and 95 days after ictus. Patients were also assessed with the use of the Cana dian Neurological Scale, the Barthel Index, a neuropsychological evalu ation, and infarct volume measurement. Results One hundred twenty-four serial SPECT scans were done in 50 patients. Diaschisis was identifie d at 168 sites. There was insufficient correlation between diaschisis and the clinical measurements to support the suggestion that diaschisi s independently causes clinical deficits beyond those due to the infar ct itself. Unlike the clinical status, diaschisis showed little tenden cy to resolve during the 3-month follow-up period of the study. Severa l of the instances of correlation were shown to be of a noncausal kind , with both the diaschisis and the clinical deficit being due to the l esion directly; there was no known mechanism for the diaschisis to cau se the clinical deficit. Conclusions Diaschisis does not independently add to the clinical deficit after stroke. It is more likely that it s imply represents Dart of the damage done by the stroke.