Posterior circulation abnormalities in moyamoya disease : a radiological study.

Moyamoya disease (MMD) is an uncommon entity outside Japan. Though the clinical and radiological features are well described, involvement of the posterior circulation has not been highlighted. Out of 10 patients of MMD studied, the posterior circulation was involved in 9 (3 bilateral, 6 unilateral). The P1 segment was most commonly affected. Interestingly, no infarcts were seen in the territory of the posterior circulation in any patient. Five patients showed recent haemorrhages on scan. It was thalamic haemorrhage in four and subarachnoid in one patient. The posterior circulation is frequently involved in MMD as evident on angiography. However, ischaemic events of the posterior circulation are not frequent, as the posterior circulation acts as collateral pathway for the diseased anterior circulation till later stages of the disease.