“99mTc-dynamics study” and computed tomography (CT) were analyzed on patients with ischemic lesions of the unilateral middle cerebral artery. Regions of interest (ROIs) were placed symmetrically on both hemispheres in frontal static scanning image, and their count ratios to the background were plotted on the time scale. Mode of transit time (MOTT) of the patients were prolonged bilaterally compared to the controls. The prolongation was more marked on the lesion side especially in acute cases, and it gradually became normal with the passage of time from onset. The plotted curves (count ratio dynamics) of the ROIs on the lesion side were clearly divided into the following four types: gradually increasing pattern (Type I); pattern of higher count ratio than contralateral side without gradual increase (Type II) ; decreasing pattern and lower count ratio than contralateral side (Type III) ; and gradually decreasing pattern almost identical to the contralateral side (Type IV). There is no correlation between MOTTs and the four types of count ratio dynamics. Therefore, the factors affecting the MOTT (the primary hemodynamics) seemed to be different from those of count ratio dynamics (pathological changes following ischemia). These types were very characteristically distributed by the duration from onset. The majority of Type I was distributed after the 4th week from onset and a small percentage in earlier phases. Type II was similar to Type I, but it seemed to be seen in relatively earlier phases. Type III was characteristically distributed in two phases; ultra-acute phase and late chronic phase. Type IV was distributed over all phases, except ultra-acute. The findings of CT also had close correlations to difference in type. The results from Type I indicated that the increasing pattern of gamma-ray ratio in acute cases seemed to reveal the accumulation of radio-isotope (RI) at the extravascular spaces probably due to disruption of blood-brain barrier (B.B.B.). In chronic cases, the accumulation of RI would be due to neovascularization without B.B.B. and/or to necrotic brain tissue. Type II suggested focal hyperemia (luxury perfusion). The ultra-acute cases in Type III usually showed normal CT findings but they frequently changed to Type I or Type II along the course of time. Type III seen in the ultra-acute phase was thought to reveal the state of low perfusion not associated with massive disruption of B.B.B. In late chronic phase having massive low density (LD) without mass effect (ME) or contrast enhancement (CE), may suggest the terminal stage of massive infarction. Type IV suggests mild or no change of cerebral circulation.
It is concluded that Type I and Type II cases with ME and CE are contraindicative for surgical revascularization in acute phase, because they have disrupted B.B.B. massively. On the other hand, Type III and Type II cases with normal CT findings have an indication for vascular reconstructive surgery.
