Subarachnoid haemorrhage

What it is

Subarachnoid haemorrhage is one of the two hemorrhagic strokes, set against intracerebral hemorrhage. It is bleeding due to trauma, or rupture of an aneurysm such as a saccular aneurysm, or of an arteriovenous malformation, and it takes a rapid time course. The blood lies in the circle of Willis, the cisterns and the fissures.

Causes and risk

Among the stroke subtypes the row is headed spontaneous subarachnoid hemorrhage, and the two causes given there are rupture of an arterial saccular, that is berry, aneurysm, or an arteriovenous malformation. Polycystic kidney disease is a risk factor: intracranial berry aneurysms, and the subarachnoid hemorrhage that follows their rupture, are among the manifestations outside the kidney in the adult dominant form. In that same disease a third cranial nerve palsy points to a posterior communicating artery aneurysm, and a family history of young stroke, from a ruptured berry aneurysm resulting in subarachnoid hemorrhage, belongs to the same picture. A drawn page carries the 2nd and the 3rd of three causes of subarachnoid hemorrhage, and the 1st is not on it. The 2nd is aneurysms, and the most common among the aneurysms are the saccular cerebral, also known as berry, aneurysms, most on the anterior half. Genetic disorders like Marfan syndrome can predispose people, and an aneurysm can rupture with increased intracranial pressure. The 3rd is arteriovenous malformation, where the veins can rupture. The polycystic kidney numbers are given as well. Intracranial berry aneurysms occur in 40% of patients with the adult dominant disease, with a 9% mortality rate from subarachnoid hemorrhage. On the same list of extra-renal manifestations are intra-abdominal cysts of liver, pancreas and spleen, mitral valve prolapse, diverticular disease and abdominal aortic aneurysm, and polycythemia from increased erythropoietin, while the renal complications are urolithiasis in 20-30% of patients and end-stage renal failure by age 60 in 50%. The artery most often implicated in subarachnoid hemorrhage is the PCoA, from a ruptured aneurysm.