Seasonal variation and Incidence of rupture of intracranial aneurysm : A prospective study and Literature review.

Objectives: Some studies have found an association of incidence of aneurysmal Sub arachnoid hemorrhage (aSAH) seasonal variations and weather patterns but others have refuted this. With conflicting reports in the literature, we tried to find out whether climatic conditions influence the incidence of aSAH.
Patients and Methods: This was a prospective single centre study involving patients with aSAH operated in a tertiary care hospital over one calendar year. Meteorological parameters like temperature, barometric pressure, humidity and sunshine hours were noted for 2 consecutive days prior to the ictus and on the day of ictus.
Results: 392 patients of aSAH who underwent clipping were enrolled. There was no significant difference in the incidence of aSAH across various seasons (p > 0.05). Pre ictus fall in temperature lead to a surge in number of cases. 241 patients (61.5%) reported were from geographical areas which had experienced a fall in temperature over preceding 2 days, with a mean fall in temperature of 1.1(SD 2.1) degree celsius (p less then 0.05). The incidence of aSAH patients in low sunshine hour seasons (1.13 patients/day) was significantly more than that in higher sunshine hour seasons (0.9 patients/day) (p less than 0.05 ).
Conclusions: Seasonal variation had no direct bearing on the incidence of aSAH. Pre ictus fall in temperature lead to a rise in number of cases. Also, higher incidence of aneurysmal subarachnoid haemorrhage was seen in lower sunshine hour seasons.