Traumatic Brain Injury (TBI)

This factor accounts for less than 1% of all intracranial aneurysm (IA) cases. These aneurysms occur when an artery wall is torn due to injury, resulting in a clot formation. Although the incidence of aneurysm formation associated with TBI is small, it must be considered a risk for trauma patients for several months post-injury, especially with a head or mid-lower face injury.

Sepsis

This occurs when a piece of fat, bone or a nitrogen bubble (emboli) travels through the blood stream, depositing organisms that stick to the vessel wall, causing inflammation and cell death. These aneurysms account for 2-6% of IA’s and are associated usually with infections of the heart valves or pulmonary veins. They can be treated both medically and surgically, but carry a high risk of death.

Smoking and High Blood Pressure (Hypertension)

While the relative incidence of traumatic brain injury and sepsis-caused aneurysms and subarachnoid aneurismal hemorrhage (SAH) are low, smoking and hypertension represent a much greater threat. Smoking is a substantial risk to both IA and SAH. It is correlated with younger age of SAH onset by 5-10 yrs, increased vasospasm (clinically confirmed constriction of the arterial vessel walls), and the development of hypertension. This leads to the reported spontaneous aneurismal SAH risk for smokers as being twice that of nonsmokers. There appears to be a relationship between IA & SAH and hypertension. The American Heart Association reports one study showing the frequency of hypertension to be 8.3 times higher among SAH patients as compared to a control group.

Miscellaneous Factors

Studies identify several other factors contributing to IA and SAH to various degrees-age, gender, alcohol use, seasonal variations, and atherosclerosis among others. Nakagawa et al. found increasing IA with increasing age and female gender. Drinking 150 grams of alcohol or more per week has been associated with SAH. Several studies have associated atherosclerosis with IA’s and SAH. Some studies have even pointed to weather changes and atmospheric pressure as potential risk factors. More investigation is required to confirm the association of these factors.