Journal of neurology
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Aneurysmal subarachnoid hemorrhage (aSAH) occurs more often during working hours and in the evening, and thus at times of relatively high blood pressure, with an even distribution over the days of the week in most studies. Perimesencephalic hemorrhage (PMH) is a non-aneurysmal subset of subarachnoid hemorrhage (SAH) without known circadian fluctuation. We studied the time and day of onset in a large series of patients with PMH. ⋯ PMH occurs less often during night hours. The pattern of PMH during the day shows similarities to that seen in aSAH, although the differences over the day are not statistically significant, as they are in aSAH. The occurrence of PMH is evenly distributed over the days of the week, as it is in aSAH.