Aneurysmal subarachnoid hemorrhage: pathobiology, current treatment and future directions

Abstract

Aneurysmal subarachnoid hemorrhage is the most devastating form of stroke. Many pathological mechanisms ensue after cerebral aneurysm rupture, including hydrocephalus, apoptosis of endothelial cells and neurons, cerebral edema, loss of blood–brain barrier, abnormal cerebral autoregulation, microthrombosis, cortical spreading depolarization and macrovascular vasospasm. Although studied extensively through experimental and clinical trials, current treatment guidelines to prevent delayed cerebral ischemia is limited to oral nimodipine, maintenance of euvolemia, induction of hypertension if ischemic signs occur and endovascular therapy for patients with continued ischemia after induced hypertension. Future investigations will involve agents targeting vasodilation, anticoagulation, inhibition of apoptosis pathways, free radical neutralization, suppression of cortical spreading depolarization and attenuation of inflammation.

Keywords:

• cerebral aneurysm
• cortical spreading depolarization
• delayed cerebral ischemia
• early brain injury
• endothelial cells
• inflammation
• smooth muscle cell
• subarachnoid hemorrhage
• vasospasm

Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending or royalties.

Key issues

• After the initial aneurysm hemorrhage, multiple pathological mechanisms account for neuronal injury including: hydrocephalus, apoptosis, cerebral edema, loss of blood–brain barrier, abnormal cerebral autoregulation, microthrombosis, cortical spreading depression and vasospasm.

• Current treatment of delayed cerebral ischemia (DCI) involves nimodipine, maintenance of euvolemia, induced hypertension for symptomatic DCI and possible endovascular treatment for patients with DCI symptoms refractory to induced hypertension.

• Cortical spreading depolarization is the latest mechanisms targeted for in DCI after aneurysmal subarachnoid hemorrhage and future trials will use ketamine to suppress cortical spreading depolarizations.

• Other future therapy for DCI will include agents to block apoptotic pathways, agents to prevent smooth muscle cell contraction and proliferation and low-dose anticoagulation to prevent microthrombosis.