Subarachnoid hemorrhage

Subarachnoid hemorrhage
Other names	Subarachnoid haemorrhage
CT scan of the brain showing subarachnoid hemorrhage as a white area in the center (marked by the arrow) and stretching into the sulci to either side
Pronunciation	/ˌsʌbəˈræknɔɪd ˈhɛmərɪdʒ/
Specialty	Neurosurgery, Neurology
Symptoms	Severe headache of rapid onset, vomiting, decreased level of consciousness[1]
Complications	Delayed cerebral ischemia, cerebral vasospasm, seizures[1]
Types	Traumatic, spontaneous (aneurysmal, nonaneurysmal, perimesencephalic)[1]
Causes	Head injury, cerebral aneurysm[1]
Risk factors	High blood pressure, smoking, alcoholism, cocaine[1]
Diagnostic method	CT scan, lumbar puncture[2]
Differential diagnosis	Meningitis, migraine, cerebral venous sinus thrombosis[3]
Treatment	Neurosurgery or radiologically guided interventions[1]
Medication	Labetalol, nimodipine[1]
Prognosis	45% risk of death at 30 days (aneurysmal)[1]
Frequency	1 per 10,000 per year[1]

Subarachnoid hemorrhage (SAH) is bleeding into the subarachnoid space—the area between the arachnoid membrane and the pia mater surrounding the brain.^[1] Symptoms may include a severe headache of rapid onset, vomiting, decreased level of consciousness, fever, weakness, numbness, and sometimes seizures.^[1] Neck stiffness or neck pain are also relatively common.^[2] In about a quarter of people a small bleed with resolving symptoms occurs within a month of a larger bleed.^[1]

SAH may occur as a result of a head injury or spontaneously, usually from a ruptured cerebral aneurysm.^[1] Risk factors for spontaneous cases include high blood pressure, smoking, family history, alcoholism, and cocaine use.^[1] Generally, the diagnosis can be determined by a CT scan of the head if done within six hours of symptom onset.^[2] Occasionally, a lumbar puncture is also required.^[2] After confirmation further tests are usually performed to determine the underlying cause.^[2]

Treatment is by prompt neurosurgery or endovascular coiling.^[1] Medications such as labetalol may be required to lower the blood pressure until repair can occur.^[1] Efforts to treat fevers are also recommended.^[1] Nimodipine, a calcium channel blocker, is frequently used to prevent vasospasm.^[1] The routine use of medications to prevent further seizures is of unclear benefit.^[1] Nearly half of people with a SAH due to an underlying aneurysm die within 30 days and about a third who survive have ongoing problems.^[1] Between ten and fifteen percent die before reaching a hospital.^[4]

Spontaneous SAH occurs in about one per 10,000 people per year.^[1] Females are more commonly affected than males.^[1] While it becomes more common with age, about 50% of people present under 55 years old.^[4] It is a form of stroke and comprises about 5 percent of all strokes.^[4] Surgery for aneurysms was introduced in the 1930s.^[5] Since the 1990s many aneurysms are treated by a less invasive procedure called endovascular coiling, which is carried out through a large blood vessel.^[6]

A true subarachnoid hemorrhage may be confused with a pseudosubarachnoid hemorrhage, an apparent increased attenuation on CT scans within the basal cisterns that mimics a true subarachnoid hemorrhage.^[7] This occurs in cases of severe cerebral edema, such as by cerebral hypoxia. It may also occur due to intrathecally administered contrast material,^[8] leakage of high-dose intravenous contrast material into the subarachnoid spaces, or in patients with cerebral venous sinus thrombosis, severe meningitis, leptomeningeal carcinomatosis,^[9] intracranial hypotension, cerebellar infarctions, or bilateral subdural hematomas.^[10]