Analysis for Circumstantial Factors in Onset of Subarachnoid Hemorrhage

ABSTRACT

Seasonal and climatic variations have been linked to the occurrence of some types of cerebrovascular disease. However, the conditions that lead to intracranial aneurysm rupture are not known. The purpose of the present study was to determine whether predisposing factors are more related to intracranial aneurysm rupture and to determine relation of the stressful condition to intracranial aneurysm rupture. In order to determine the predisposing factors, the authors have examined the relationship between seasonal variation and predisposing factors of cerebral aneurysm. The author investigated activities of the patients and events as well as diurnal and seasonal variations in the onset of subarachnoid hemorrhage(SAH) in 336 consecutive patients. The results showed that the onset of SAH was associated with working in 11.0%, defecation and/or urination in 8.3%, sleeping in 6.9% and 4.2% walking. Hypertensive patients in aneurysmal rupture was 36.0%. Subarachnoid hemorrhage occurred during stressful events in 36.3% of the patients, during nonstreneous events in 34.8% and during rest or sleep in 9.8%. The activities or events preceding subarachnoid hemorrhage were not known in the remaining 18.8%. Men were more likely to have suffered their hemorrhages during stressful events than women(47% vs 30%). Peak times of intracranial aneurysm rupture usually occurred from 6 to 11 A.M.(36.0%) and from 4 to 6 P.M.(20.5%). The seasonal variation of the onset of SAH showed the incidence to be slightly higher in winter than in any other seasons. We concluded that the occurrence of subarachnoid hemorrhage display seasonal and diurnal variation. And the precipitation of aneurysmal rupture have two important factors; increased arterial blood pressure and decreased cerebrospinal fluid pressure around the aneurysm. Also, the onset of the subarachnoid hemorrhage is related to the physiological circadian periodicity of blood pressure, climatic change and stressful events.