The term subarachnoid hemorrhage (SAH) is referring to bleeding into to subarachnoid space, between the membranes. The bleeding could be spontaneous, intracranial or in the brain tissue. Most likely cause of this condition is head injury. The common use of the term SAH is describing a non-traumatic, spontaneous hemorrhage, caused by the ruptured aneurism in the brain or arteriovenous malformation(AVM).
The subarachnoid bleeding is serious condition affecting local and global function of the brain.
This condition has high morbidity and high mortality, and about 15% of the patients die on the way to the hospital. Despite the improving treatment, ¼ of all the people die of SAH in first 24 hours and 50% of the patients die in 6 months.Black female are more likely to be affected by SAH, and older patients with preexisting illnesses have a higher risk of both morbidity and mortality.
Possible causes of SAH include aneurism, AVM, and fibromuscular dysplasia, blood dyscrasias, amyloid angiopathy, traumas, neoplasms, infection, vasculitis, etc. Some of the SAH cases have no apparent reason, and they are called idiopathic SAH.
Aneurism can be caused by a combination of congenital and acquired factors. Abnormalities in the muscle and elastic tissue of the arterial media may lead to aneurisms, as well as atherosclerosis, hypertension and hemodynamic stress.
Abuse of alcohol and smoking are risk factors for subarachnoid hemorrhage, and some claim that the same can be said about the hypertension.
It is known that pregnancy increase the risk of AVM rupture.
Repeated bleeding is most likely to occur in first 48 hours after the SAH and it is more common in the patients which have SAH caused by an aneurism. The mortality rate of this complication is about 40%.
Hydrocephalus is developed in about 30% of the patients. It happens mostly in people with aneurism SAH, because of fibrosis in subarachnoid space. As a consequence this complication may cause unconsciousness of the patient, a few days or weeks after SAH.
Other possible complications in patients suffering from this condition include vasospasm, cerebral edema and electrolyte misbalance.
Patients having SAH might experience seizures, sympathetic hyperactivity, changes of their ECG (electrocardiogram, measuring and recording heart rhythm), arrhythmias, decrease of blood volume and mass of red blood cells.
More than 20% of patients had seizures or seizure episodes, but the specialists don’t recommend the prophylactic use of anti-epileptics. Therapy is needed in cases of suspected MCA aneurism, intraparenchimal bleeding, infarct or existing hypertension or seizures.