Hyperperfusion Syndrome after STA-MCA Bypass in Acute Stage of Brain Infarctions

Object : While there are only a handful of reports in the literature detailing hyperperfusion syndrome (HPS) occurring in the chronic stage of a brain infarction after STA-MCA bypass, there are even fewer detailing its occurrence in the acute stage. If we opt to perform an STA-MCA bypass in the acute stage to minimalize any possible extension of the lesion, it seems reasonable to assume that there is a greater risk of hyperperfusion syndrome, as the cerebral perfusion pressure is lower than that in the chronic stage. To test this assumption, we compared the incidence of hyperperfusion syndrome after STA-MCA bypasses performed in both the acute and chronic stages. Patients and Methods : Over a 4-year period, from April 1st 2002 to May 10th 2006, we performed 53 STA-MCA bypasses, 23 in the acute stage and 32 in the chronic stage. Each case was examined by IMP or Xe SPECT within 2 weeks of the bypass surgery. Where hyperperfusion was evident, cases were divided into one of two groups, according to the location of the hyperperfusion : Group A demonstrating it locally, and Group B demonstrating it hemispherically. Symptomatic cases were also divided into two groups according to the degree of severity, with the mild group exhibiting such things as headaches or transient psychological disturbance, and the severe group reporting convulsions or conscious disturbance etc. Results : Of the 23 acute stage bypasses, 7 cases (30.4%) were classified as Group A and 2 cases (8.7%) as Group B, affecting 9/23 cases, or 39.1% of the acute total. Of these, there were 3 mild symptomatic cases (13.0%), and 1 severe case (4.3%). Of the chronic stage bypasses, 4 cases (12.5%) were classified as Group A and 1 case (3.1%) as Group B, affecting 5/32 cases, or 15.6% of the chronic total. Of these, there was 1 mild symptomatic case (3.1%), and 2 severe cases (6.3%). There were no hemorrhagic transformations. According to these results, acute stage bypasses were not significantly different to chronic ones with regard to the occurrence of symptomatic cases. (p=0.435; Fisher exact method) Conclusion : There were more cases of hyperperfusion in acute stage bypasses than in chronic stage bypasses, but there was no significant difference in symptomatic rates. This implies that it may be feasible to safely perform STA-MCA bypasses in the acute stage without undue concern for the occurrence of hyperperfusion syndrome