Topographical distribution of pontocerebellar microbleeds.

BACKGROUND AND PURPOSE Microbleeds (MBs) visualized by use of T2*-weighted gradient-echo MR imaging are pathologic blood-breakdown products after tiny cerebral hemorrhages. The topographic distribution of the lesions has not been compared with that of symptomatic intracerebral hemorrhage (ICH). The purpose of this study was to evaluate the distribution of MBs in the pontocerebellar region and to compare it with the distribution of ICHs reported in the literature. METHODS We examined 164 consecutive hypertensive patients with ischemic infarction or spontaneous ICH over a 1-year period. Two experienced neuroradiologists assessed cerebral localization of MBs without prior knowledge of the clinical information and in consensus. After obtaining 16 standard axial brain images, we analyzed the anatomic locations and the vascular territories of the MBs in the pontocerebellar area. RESULTS We detected 374 pontocerebellar MBs in 40 patients (8.1 +/- 12.7). Pontine MBs showed a significant predilection for the central portion (middle part along the axial plane, 3.4 +/- 4.9 [P < .01]; medial part along the coronal plane, 3.4 +/- 4.1 [P < .01]) and mostly belonged to the territory of the anteromedial group arising from the basilar artery. Cerebellar MBs had a frequent distribution around the dentate nucleus, occurring significantly more in the lower half, in the medial part (3.4 +/- 4.6; P < .01), and in the middle part along the axial plane (4.8 +/- 7.0; P < .01). CONCLUSION These findings were similar to the topography of ICH described in the literature. Our results suggest that MBs may be a lesional marker for ICH.