J Neurol Surg A Cent Eur Neurosurg 2014; 75 - p73
DOI: 10.1055/s-0034-1383800

Is Intracranial Aneurysm Rupture Related to Solar Activity?

M. N. Stienen 1, N. R. Smoll 2, M. Battaglia 4, B. Schatlo 5, C. Woernle 6, C. Fung 7, M. Röthlisberger 8, R. T. Daniel 9, A. R. Fathi 5, G. Hildebrandt 1, K. Schaller 10, P. Bijlenga 10
  • 1Department of Neurosurgery, Kantonsspital St. Gallen, St. Gallen, Switzerland
  • 2Gippsland Medical School, Monash University, Melbourne, Australia
  • 3Frankston Hospital, Department of Surgery, Melbourne, Australia
  • 4Fachhochschule Nordwestschweiz FHNW, Hochschule für Technik, Institut für 4D-Technologien, Windisch, Switzerland
  • 5Department of Neurosurgery, Kantonsspital Aarau, Aarau, Switzerland
  • 6Department of Neurosurgery, University Clinic Zürich, Zürich, Switzerland
  • 7Department of Neurosurgery, Inselspital Bern, Bern, Switzerland
  • 8Department of Neurosurgery, University Clinic Basel, Basel, Switzerland
  • 9Department of Neurosurgery, CHUV, Lausanne, Switzerland
  • 10Department of Neurosurgery, University Clinic Geneva, Geneva, Switzerland

Aims: Several intrinsic and extrinsic risk factors for the rupture of intracranial aneurysms have been identified. Still, the cause precipitating aneurysm rupture remains unknown in many cases. In addition, it has been observed that aneurysm ruptures are clustered in time but the trigger mechanism remains obscure. As solar activity has been associated with cardiovascular mortality and morbidity we decided to study its association to aneurysm rupture in the Swiss population.

Methods: Patient data was extracted from the Swiss SOS database, at time of analysis covering 918 patients with angiography-proven aSAH treated at seven Swiss neurovascular centers between 2009 and 2011. The number of aneurysm rupture per day (Rupture Frequency = RF) was correlated to the absolute amount and the change in various parameters of interest representing continuous measurements of solar activity (radioflux (F10.7 index), solar proton flux, solar flare occurrence, planetary K-index/planetary A-index) using Poisson regression analysis.

Results: Precise determination of the date of aSAH was possible in 816 (88.9%). During the period of interest there were 517 days without recorded aSAH. There were 398, 139, 27 and 12 days with 1, 2, 3, and 4 ruptures per day. Five or 6 ruptures were only noted on a single day each. Poisson regression analysis demonstrated a significant correlation of F10.7 index and RF (incidence rate ratio (IRR) = 1.006303; standard error (SE) 0.0013201; 95% confidence interval (CI) 1.003719 - 1.008894; p < 0.001), according to which every 1-unit increase of the F10.7 index increased the count for an aneurysm to rupture by 0.63%. As the F10.7 index is known to correlate well with the Space Environment Services Center (SESC) sunspot number, we performed additional analyses on SESC sunspot number and sunspot area. Here, a likewise statistically significant relationship of both the SESC sunspot number (IRR 1.003413; SE 0.0007913; 95%CI 1.001864 - 1.004965; p < 0.001) and the sunspot area (IRR 1.000419; SE 0.0000866; 95%CI 1.000249 - 1.000589; p < 0.001) emerged. All other variables analyzed showed no correlation with RF.

Conclusion: Using valid methods, we found higher radioflux, sunspot number and sunspot area to be associated with an increased count of aneurysm rupture.