A further consequence of this process is neurogenic pulmonary edema where a process of increased pressure within the pulmonary circulation causes leaking of fluid from the pulmonary capillaries into the air spaces, the alveoli, of the lung.Subarachnoid hemorrhage may also occur in people who have had a head injury. Symptoms may include headache, decreased level of consciousness and hemiparesis (weakness of one side of the body). SAH is a frequent occurrence in traumatic brain injury, and carries a poor prognosis if it is associated with deterioration in the level of consciousness.While thunderclap headache is the characteristic symptom of subarachnoid hemorrhage, less than 10% of those with concerning symptoms have SAH on investigations. A number of other causes may need to be considered. Causes
Most cases of SAH are due to trauma such as a blow to the head. Traumatic SAH usually occurs near the site of a skull fracture or intracerebral contusion. It often happens in the setting of other forms of traumatic brain injury. In these cases prognosis is poorer; however, it is unclear if this is a direct result of the SAH or whether the presence of subarachnoid blood is simply an indicator of a more severe head injury.In 85 percent of spontaneous cases the cause is a cerebral aneurysm—a weakness in the wall of one of the arteries in the brain that becomes enlarged. They tend to be located in the circle of Willis and its branches.
They also have a higher risk of severe disability and persistent vegetative state, and traumatic SAH has been correlated with other markers of poor outcome such as post traumatic epilepsy, hydrocephalus, and longer stays in the intensive care unit. More than 90 percent of people with traumatic subarachnoid bleeding and a Glasgow Coma Score over 12 have a good outcome.There is also modest evidence that genetic factors influence the prognosis in SAH. For example, having two copies of ApoE4 (a variant of the gene encoding apolipoprotein E that also plays a role in Alzheimers disease) seems to increase risk for delayed ischemia and a worse outcome. The occurrence of hyperglycemia (high blood sugars) after an episode of SAH confers a higher risk of poor outcome. Long-term outcomes
Neurocognitive symptoms, such as fatigue, mood disturbances, and other related symptoms, are common sequelae. Even in those who have made good neurological recovery, anxiety, depression, posttraumatic stress disorder, and cognitive impairment are common; 46 percent of people who have had a subarachnoid hemorrhage have cognitive impairment that affects their quality of life. Over 60 percent report frequent headaches. Aneurysmal subarachnoid hemorrhage may lead to damage of the hypothalamus and the pituitary gland, two areas of the brain that play a central role in hormonal regulation and production. More than a quarter of people with a previous SAH may develop hypopituitarism (deficiencies in one or more of the hypothalamic–pituitary hormones such as growth hormone, luteinizing hormone, or follicle-stimulating hormone).