Aim: We aimed to investigate the associations between the seasonal variations and clinical and radiologic characteristic and outcome of patients with Cerebral Venous Thrombosis (CVT).
Methods In a cross-sectional study from August 2012 to September 2016, the frequency and characteristics of CVT between warm months (June to September) and other months were compared.
 Results: Of 174 CVT patients, 128(73.6%) were female. The highest frequency of CVT was seen in June to September. Absence of headache was more common in warm months (P value 0.021). Subarachnoid hemorrhage in CVT patients occurred less frequently in the warm months (p value 0.045). Among risk factors, fasting (P value 0.001) and OCP consumption (P value 0.046) were more frequent in the warm months. No difference was detected between the discharge outcome of the patients in the warm months and other months (p value 0.442).
Conclusion The incidence of CVT increases in warm months. Dehydration and use of OCPs may be relevant. Warm months included the Ramadan, month of fasting, in Islamic calendar (July and august in 2012 & 2013, June and July in 2014 & 2015 &2016). Pattern of hemorrhage was different in warm months. Absence of headache is more frequent in warm months indicating the necessity of considering CVT as a differential diagnosis in patients who refer with other symptoms than headache in warm months. In conclusion, seasonal pattern seems to influence the characteristics of patients with CVT, but not the outcome.

Seasonal pattern of patients with cerebral venous sinus thrombosis and its effects on clinical and radiological characteristics and outcome of patients