Subarachnoid Hemorrhage

Subarachnoid hemorrhage is bleeding between the middle membrane covering of the brain and the brain itself. Specifically it occurs within the cerebrospinal fluid-filled spaces surrounding the brain (also known as the subarachnoid space).

Subarachnoid hemorrhage (SAH) is bleeding in the subarachnoid space that can be caused by rupture of a cerebral aneurysm or by arteriovenous malformation. Although aneurysmal SAH typically begins abruptly, produces a headache that is most severe at onset, and is described by patients as the worst headache of their life, a minority has less severe (though generally very distinctive) symptoms. Prompt evaluation with CT scan and LP excludes this condition. SAH may present with a large bleed and an abnormal neurologic examination or with minimal headache at the time of ED presentation and a normal neurologic exam (in the case of a "sentinel bleed"). It is critical to make the diagnosis of cerebral aneurysm at the time of a sentinel bleed, since debilitating hemorrhage may follow if neurosurgical intervention is delayed.

Causes

Subarachnoid hemorrhage is most often caused by abnormalities of the arteries at the base of the brain, called cerebral aneurysms. These are small areas of rounded or irregular swellings in the arteries. Where the swelling is most severe, the blood vessel wall become weak and prone to rupture. The cause of cerebral aneurysms is not known. They may develop from birth or in childhood and grow very slowly. Some people have not one, but several aneuryms. Subarachnoid hemorrhage can occur at any age, including teenagers and young adults. Subarachnoid hemorrhage is slightly more common in women than men.

Symptoms

• Headache +++++: often abrupt onset of severe headache("worst headache of life"). Headache is usually global; can be associated with nausea, vomiting, and transient loss of consciousness, classically during exercise but can be at rest.
• Warning headache +++: a distinctive "thunderclap" headache, also referred to as a sentinel bleed, preceding the major SAH by days to weeks; thought to be caused by a minor leak of blood, bleeding into the wall of the aneurysm, or thrombosis at the site of the aneurysm
• Neck pain: from blood irritating the meninges (can be the only presenting complaint)
• Back and radicular pain: occurs later in some patients from irritation as the blood settles into the lumbar thecal sac
• Altered mental status with severe bleeds

Signs

• May have normal examination
• Meningismus (frequent)
• Retinal subhyaloid hemorrhage ++ : significant bleeding often with a fluid level seen on funduscopic examination
• Focal or generalized neurologic abnormalities (variable)

Treatment

The aim of treatment is to stop the bleeding and damage to the brain and reduce the risk of recurrence. Treatment and monitoring during the 3 weeks immediately following the hemorrhage are important since that is the period when complications and rerupture are most likely to occur. Medication may be prescribed to prevent seizures, and sedatives may be used to aid relaxation. Absolute bedrest is necessary to prevent a rerupture.

Treatment is usually required, which may be either via a craniotomy (opening a hole in the skull) and clipping of the aneurysm (placing a metal clip across the base of the aneurysm so as to separate it from the circulation), or endovascular coiling (placing platinum coils within the aneurysm from the inside of the blood vessel itself). Sometimes a surgeon can repair a broken blood vessel depending on the location and size of the aneurysm. If unbroken aneurysms are discovered, the doctor may suggest surgery to repair these before they break. Multiple aneurysms are present in as many as 20% of cases.

Prevention

Identification and successful treatment of an incidentally found aneurysm would prevent subarachnoid hemorrhage.