Central nervous system disorders

IV./4.1.: Epidemiology

European and US statistics show that 84% of strokes are ischemic and 16% are of hemorrhagic origin. The occurrence of subarachnoid hemorrhage is somewhat varying in these statistics; its incidence is between 7 to 10/ 100 000 people, in Hungary this number is 8/ 100 000. The gender ratio is 1.6:1 for female to male patients and the average age at the onset of the disease is 55 years. While the incidence of ischemic stroke and intracerebral bleeding significantly declined in the last decades, the frequency of subarachnoid hemorrhage is unchanged in the last 30 years.

Subarachnoid hemorrhage leads to death in approximately 50% of the cases. The mortality rate is highest in the first two weeks of the illness; 10% of the patients die during the transport to the hospital and 24% of them die in the first 24 hours of the bleeding. However, the average mortality rate has significantly diminished in the last 30 years - due to the modern diagnostics and neurosurgical procedures, and the introduction of complex pharmacotherapy focusing on “neuroprotection”. Albeit theses modern approaches, one-third of the survivors of subarachnoid hemorrhage are going to be permanently disabled and will depend on lifelong medical care. 46% of these patients also show signs of cognitive decline.

The subarachnoid bleeding most often originates from the aneurysms located at the junctions of the proximal branches of the circle of Willis. The thin wall of the aneurysm raptures; in mild cases the so-called “crying aneurysms” could lead to continuous microbleeding. 85% of the aneurysms are located of the anterior part of the circle of Willis, while the rest is at the posterior part. Approximately 20% of the patients have multiple aneurysms on the circle of Willis.