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Subarachnoid hemorrhage
Bleeding into the brain's subarachnoid space / From Wikipedia, the free encyclopedia
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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]
Subarachnoid hemorrhage | |
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Other names | Subarachnoid haemorrhage |
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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 | |
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] |
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]