Cerebral Aneurysm (Intracranial Aneurysm) – Top USMLE Diseases

Brain aneurysms, also known as intracranial or cerebral aneurysms, are dilations of the arteries along points of weakness in the brain. The majority of the aneurysms are berry (saccular) in nature and located within the anterior circulation of the circle of Willis. Unruptured aneurysms are typically asymptomatic, unless the aneurysm compresses surrounding structures. The majority of these aneurysms are detected on rupture and presentation of a subarachnoid hemorrhage (SAH). Rarely, they may be detected incidentally on brain imaging done for other reasons. Diagnosing an aneurysm is done via imaging with CTA or MRA. Management depends on the size, risk of rupture, risk of intervention complications, and individual preference. This may include risk factor modifications, surveillance with serial imaging, and interventional measures (such as surgical clipping or endovascular coiling). Ruptured aneurysms carry a high morbidity and mortality rate.

Imaging of the brain is most commonly used for evaluating trauma, stroke, and benign or malignant tumors. Before the advent of CT and MRI, X-ray scanning was widely used to study the skull and spinal bones. Today, CT and MRI, especially the latter, are the preferred imaging methods for the study of the cranial vault and its contents. In conditions where emergent management is decided on the basis of presentation and imaging, CT has the advantage of rapid scan time and wider availability. CT also has good sensitivity and specificity and relatively lower cost. MRI though, provides better parenchymal characterization especially in cases where initial findings are negative on CT (such as in acute ischemia).

Blood supply to the brain can be divided into an anterior and a posterior circulation, which interconnect to form the circle of Willis. The anterior circulation is derived from the internal carotid arteries and consists mainly of the anterior and middle cerebral arteries. The posterior circulation is derived from the vertebral arteries and consists primarily of the cerebellar and posterior cerebral arteries. The primary venous drainage of the brain occurs via the internal jugular vein.

Anticoagulants are drugs that retard or interrupt the coagulation cascade. The primary classes of available anticoagulants include heparins, vitamin K-dependent antagonists (e.g., warfarin), direct thrombin inhibitors, and factor Xa inhibitors. Anticoagulants are used in the treatment and prevention of thrombotic and embolic diseases including cardioembolic ischemic stroke, acute coronary syndrome, and venous thromboembolism, among other conditions. Patients with atrial fibrillation or thrombophilias may require indefinite or lifelong anticoagulation. Accordingly, the route of administration, drug interactions, pharmacokinetics, and availability of reversal factors should be considered while selecting the anticoagulant therapy.