Natural history of the spontaneous reperfusion of human cerebral infarcts as assessed by 99mTc HMPAO SPECT

Objective-Little is known about the effect of spontaneous reperfusion of human cerebral infarcts. Single photon emission computerised tomography (SPECT) data were analysed from a study using Tc-99(m) HMPAO (Tc-99(m) hexamethylpropyleneamine oxime) in human cerebral infarction for the frequency of reperfusion and to see if it affected infarct size, oedema, haemorrhagic transformation, or functional outcome. Methods-Fifty sequential cases of ischaemic stroke were studied with 124 Tc-99(m) HMPAO SPECT at around one day, one week, and three months after stroke along with detailed clinical and functional assessments. Results-Visually apparent reperfusion occurred in 14 of 50 patients (28%) with a mean delay of 5.8 days and reperfusion was seen in seven others in whom it was identified on the basis of changes in perfusion deficit volume. It occurred in 13 of 23 embolic events but only in three of 23 other events. In only two cases did spontaneous reperfusion occur early enough to preserve tissue or function. Reperfusion did not otherwise reduce infarct size, or improve clinical or functional outcome, and was not associated with oedema but an association with haemorrhagic transformation was suggested. Reperfusion significantly decreased the apparent perfusion defect as measured by SPECT one week from the ictus, but was mostly non-nutritional and transient. The mean volume of tissue preserved by nutritional reperfusion was 10 cm(3), but this was unequally distributed between cases. Late washout of Tc-99(m) HMPAO from areas of hyperaemic reperfusion may be a good prognostic marker but is a rare phenomenon and too insensitive to be of general applicability. Conclusions-Spontaneous reperfusion after cerebral infarction occurs in 42% of cases within the first week but is associated with clinical improvement in only 2%. It has few adverse consequences although it may be associated with haemorrhagic transformation.