37 year old female w/ Obstructive Hydrocephalus

I have been dx'ed w/ obstructive hydo.  The cause has been determined as aqueductal stenosis.  I have sought 2 medical
opinions from 2 highly respected neurosurgeons.  It appears
to 1 of the surgeons (who specializes in hydro) that, due to my
extremely large ventricles, my condition was probably congenital,
and I have compensated for the extra CSF all of my life.

Because I have become symptomatic (not that symptoms were not present before, but that they have became worse), surgery has been advised.  The surgery that both surgeons suggest is the endoscopic third ventriculostomy (ETV).  Both surgeons feel that this surgery should be successful and that I am a prime candidate.

After our 2nd opinion, I have come up with several questions.

#1 -- When a hydro patient has a shunt, there is a system of regulating the flow of CS Fluid through the valve.  In the case of a ETV patient, what regulates the flow?

#2 -- If the CSF simply drips through a hole poked in the base of the 3rd ventricle, can it drain too quickly?  If so, then what happens?

#3 -- Once this procedure is preformed, are there any lifetime restrictions? Or lifetime restrictions for hydro patient in general?  i.e. -- Can I still ride roller coasters, go horseback riding, whitewater rafting, or other head jarring actives?

#4 -- When I was young, I often hung upside down for extended periods of time to observe the world upside down.  Could this have caused, or aggravated, my condition?  Was there a danger to this (promoting aneurysms, etc.), and should I discourage my children from doing the same?

[CCF-Neuro-M.D.-JT]

1.Many surgeons put in an access reservoir with the endoscopic ventriculostomy so they can go in at a later date to monitor the pressure, drain off CSF externally, or give antibiotics through it.  However, there is no valve as there is for shunts, nor does there need to be. It is as you put it, simply a hole in the floor of the third ventricle.
2.It's remotely possible, but the reverse is much more common. (reverse, meaning the hole closes up and hydrocephalus recurs). The problem really is not that you're making too much CSF and suddenly "too much" is going to drain through, rather it's just not draining the way it should. The CSF has to get from one place to another anyway, and the procedure will allow it to pass through instead of being blocked at the aqueduct. But in the case that there is overdrainage or a CSF leak, this can result in a subdural hematoma (less than 1% of cases).
3.It depends on a number of factors including the presence of any other neurological deficit, primary cause of the hydrocephalus, and degree of risk of the activity. I don't think there's any set legal restriction as there is with seizures and driving. But I would use common sense in any activity with a risk of head injury. Every case is different, and I have seen children with shunts for hydrocephalus who do almost all the things that other kids do such as amusement park rides. This is a very good question for your surgeon who is familiar with your case and will be able to individualize any possible restrictions.
4.No. If you don't have a tumor, scarring from previous surgery, infection, bleeding, or radiation and it truly is just aqueductal stenosis then you were probably born with it. Good luck.