Distribution of cerebral microembolism in the anterior and middle cerebralarteries

Background and purpose-Cerebral infarcts occur more frequently along the mi ddle (MCA) than the anterior cerebral artery (ACA) territory. The reason(s) for this difference remains speculative. The objective of this study was t o investigate the distribution of cerebral microemboli as detected by trans cranial Doppler ultrasound (TCD) along the MCA and ACA territories. Methods -Records of consecutive patients examined for the presence of cerebral micr oembolism during a 32-month period at the Neurovascular Laboratory were rev iewed. Of the original 375 TCD studies in 268 patients, 28 studies in 24 pa tients demonstrated microembolic signals (MES) and monitored the MCA and AC A on the same side. TCD studies were performed on TC-2000 or TC-2020 instru ments. MES positive studies were saved and off-line reviewed. MES satisfied previously established criteria. Results-MES were more frequent in the MCA than the ACA in 85.7% (24/28) of studies (P<0.01). Of the total number of MES (n=979), 29.6% (n = 290) were detected in the ACA and 70.4% (n = 689) i n the MCA (P<0.01). The mean ( +/- SD) intensity of MCA MES of 12.2 (+/- 2. 4) dB was significantly lower than that of ACA MES of 14.8 (+/- 3.2) dB (P = 0.05). The mean (+/- SD) duration of MCA MES of 38.1 (+/- 45.3) ms was lo nger than that of ACA MES of 30.7 (+/- 34.0) ms (P = 0.05). Conclusions-Cer ebral microembolism occurs more frequently in the MCA than the ACA, which m ay explain the uneven distribution of cerebral infarcts along these arteria l territories. Furthermore, there are significant differences in the charac teristics of ACA and MCA MES.