Brain surgery

More about brain arteriovenous malformation hemorrhage and rehemorrhage.
The peak age for hemorrhage from an AVM is somewhere in the late teens (age 15-20 yrs). There is a 10% instant mortality associated with the first hemorrhage, and up to 30% mortality associated with each rebleed (rehemorrhage). The first hemorrhage has a 30-50% chance of causing some neurological impairment (deficit). The hemorrhage itself is usually within the substance of the brain (intraparenychmal hemorrhage), but also may be subarachnoid (outer or under surfaces of the brain), or within the fluid filled spaces of the brain (intraventricular), or just under the leather covering of the brain (subdural).
Some tendencies regarding hemorrhage are the following (subject to debate): the hemorrhage rate may be higher in the following: (i) kids; (ii) AVMs located in the back portion of the brain (hindbrain, posterior fossa); (iii) smaller AVMs (?higher pressure in these); (iv) pregnancy.
Hemorrhage rates: The average (annual) rate of hemorrhage for a newly diagnosed AVM that has not bled before is somewhere between 2-4% per year. The mean time between diagnosis of an AVM and first hemorrhage is somewhere around 7-8 years, but this obviously varies from person to person. The chance of death with a newly diagnosed AVM is approximately 1% per year, much higher after hemorrhage as mentioned above.
The risk of hemorrhage from the AVM itself after treatment with radiation (e.g., stereotactic radiosurgery such as GammaKnife or LINAC) is not reduced, in fact may be slightly higher than normal AVM hemorrhage rates, till the AVM is completely obliterated by such treatment (which can take 2-3 years).
Rehemorrhage rates: Depending on what you read, the (annual) rehemorrhage rate from an AVM (i.e., the chance of second bleed) is somewhere between 6-18% in the first year following diagnosis. Over the next few years, this rate decreases to somewhere around 3-4% per year. As mentioned above, rehemorrhage carries a very high rate of death and permanent disability.

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