SUBARACHNOID HEMORRHAGE

Subarachnoid hemorrhage (SAH) is bleeding into the subarachnoid space surrounding the brain, i.e., the area between the arachnoid membrane and the pia mater. It may arise due to trauma or spontaneously, and is a medical emergency which can lead to death or severe disability even if recognized and treated in an early stage. Treatment is with close observation, medication and early neurosurgical investigations and treatments. Subarachnoid hemorrhage causes 5% of all strokes. 10-15% die before arriving in hospital, and average survival is 50%.

The classic symptom of subarachnoid hemorrhage is thunderclap headache ("most severe ever" headache developing over seconds to minutes). 10% of all people with this symptom turn out to have a subarachnoid hemorrhage, and is the only symptom in about a third of all SAH patients. Other presenting features may be vomiting (non-specific), seizures (1 in 14) and meningismus. Confusion, decreased level of consciousness or coma may be present. Intraocular hemorrhage (bleeding into the eyeball) may occur. Subhyaloid haemorrhages may be visible on fundoscopy (the hyaloid membrane envelopes the vitreous body).

In a patient with thunderclap headache, none of the signs mentioned are helpful in confirming or ruling out hemorrhage, although a seizure makes bleeding from an aneurysm more likely. Oculomotor nerve abnormalities (affected eye looking downward and outward, pupil widened and less responsive to light) may indicate a bleed at the posterior communicating artery.

As a result of the bleeding, blood pressure often rises rapidly, together with a release of adrenaline and similar hormones. As a result, substantial strain is put on the heart, and neurogenic pulmonary edema, cardiac arrhythmias, electrocardiographic changes (some resembling a heart attack) and cardiac arrest (3%) may occur rapidly after the onset of hemorrhage.

Bleeding into the subarachnoid space may occur as a result of injury or trauma. SAH in a trauma patient is often detected when a patient who has been involved in an accident becomes less responsive or develops hemiparesis (one-sided weakness) or changed pupillary reflexes, and Glasgow Coma Score calculations deteriorate. Headache is not necessarily present.

Risk factors for subarachnoid hemorrhage are smoking, hypertension (high blood pressure) and excessive alcohol intake; all are associated with a doubled risk for SAH. Some protection of uncertain significance is conferred by Caucasian ethnicity, hormone replacement therapy, a higher than normal cholesterol and the presence of diabetes mellitus.