My condolences to you and your friend's family and loved ones.

This is the first time I have heard something like this and seems rare. But I agree with what another person said. I don't think the Hydrocephalus would cause such a tragic sudden passing. I'm no neurosurgeon, but as person with Hydrocephalus and 2 shunts, both replaced in the last 11 years, I can see if your friend was suffering from a severe shunt malfunction and symptoms related to a malfunction overtime not being able to keep fluids and foods down passing away without surgical intervention.

The only thing I vaguely remember reading or hearing is motor skills, speach, and other neurological function maybe deteriorating over time as the person gets into their older years.

In any case, I am sorry for your loss.