<B>subarachnoid hemorrhage </B>

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subarachnoid hemorrhage

Etiology:

• Most common cause of subarachnoid hemorrhage outside of trauma is a ruptured berry aneurysm.
• The berry aneurysm is a small, saclike structure at the branchpoints of arteries with a wall which does not contain a media or internal elastic lamina and therefore can easily rupture during periods of hypertension or stress.
• Most commanly ruptures when the patient is in his 40's or 50's.
• May also rupture intracerebrally.

Pathogenesis:

• Aneurysms are thought to be due to congenital absence of the media and internal elastic lamina with balloning as the blood pulsates through the vessels over the years.
• Ruptures when an area becomes thinned and there is a period of hypertension or straining.

Epidemiology:

• Berry aneurysms are found incidently at autopsy 1-2% of the time. Vascular malformations are much less common.
• Aneurysms occur on the anterior Circle of Willis 80% of the time. Anterior communicating artery and middle cerebral artery at the trifurcation are the most comman places to arise.

General Gross Description:

• Subarachnoid hemorrhage is blood in the leptomeninges usually at the base of the brain and most often due to rupture of a berry aneurysm, vascular malformation, or trauma.

General Microscopic Description:

• Microscopically in subarachnoid hemorrhage there are red and white blood cells in the leptomeninges.
• After three days macrophages can be seen as well to clean up degenerating blood cells.

Clinical Correlations:

• Subarachnoid hemorrhage due to a ruptured berry aneurysm or vascular malformation usually produces the sudden onset of a severe headache, the worst, headache of the patient's life followed by progressive depression of consciousness to the point of coma if the hemorrhage is large enough.
• If the patient is in good enough condition an aneurysm may be clipped with a metal clip at its neck or a vascular malformation may be occluded by intrarterial plastic material.

References:
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