Background: Cerebrovascular event peaks occur in the morning (≈ 9:00 am) with another one peak in the evening (≈ 8:00 pm) and a trough at night. Knowledge about circadian influences on mechanisms involved in cerebrovascular events is important for optimising the timing of therapy, preventing behavioural triggers at potentially risky circadian phases and selecting the timing of diagnostic procedures. This work aims to evaluate circadian and circannual patterns of stroke onset, and variation in pattern of stroke onset in the month of Ramadan. Patients and methods: The study was conducted on 98 stroke patients and 98 age-and sex-matched normal subjects. All patients had a documented time of stroke symptom onset. End-tidal carbon dioxide and core body temperature were served as measures of endogenous circadian phase. Cerebral blood flow velocity was measured using transcranial colour-coded duplex. Circadian rhythm of blood pressure and heart rate variability were also assessed. Results: Both ischaemic and haemorrhagic stroke showed a circadian variation regarding their onset, with the peak in the morning and the nadir during night-time. We found a pathologically reduced or abolished circadian blood pressure variation after stroke. Conclusion: Stroke was more frequent in the morning; also, it was less likely to occur during the summer and autumn than the winter or spring. Stroke prevention with therapies that target the morning rise in risk factors could be advantageous in reducing the overall risk of stroke.

Background Acute ischemic stroke is defined as decrease in the brain blood supply caused by a blood vessel burst or being blocked by a thrombus, resulting in decreased oxygen and nutrients supply, causing brain tissue damage. Diffusion weighted sequences (DWI) gave us data on the pathophysiology of ischemia and may contribute to therapeutic decisions. Susceptibility weighted (SWI) sequences also have the potential to assess tissue viability. An ischemic area showed increased oxygen extraction fraction and slow flow contributed to greater level of deoxyhemoglobin and vein dilatation, which increases the prominence of vessels on SWI. This prominent vessel sign (PVS) on SWI has been reported due to increased oxygen extraction and matches well with venous and capillary deoxyhemoglobin levels. We aimed in this study to highlight the role of the addition of susceptibility weighted MR images to diffusion weighted images of the brain in the diagnosis of patients with acute stroke. Results: Prominent vessel sign (PVS) on SWI was found in 46 (76.7%) patients. Twelve (20%) patients had haemorrhage (low signals) on SWI and 2 (3.3%) patients had no SWI findings. DWI showed a sensitivity of (100%) and SWI showed a sensitivity of (96.7%) for the detection of infarct All of the 60 (100%) patients showed hyperintense signals on T2WIs, FLAIR sequences, and on DWI and hypointense signals on the ADC map. Conclusions: SWI is a potential adjunct in individuals with acute infarction, SWI may be helpful in identifying asymmetrical conspicuous hypointense arteries, positive DWI-SWI mismatch is an indicator of the ischemic penumbra and a prognostic indicator for infarct expansion.