Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you with your wee one today.
I am very sorry to hear that Spike has a severe hydrocephalus. As you have noted, shunt surgery is really the only corrective treatment option (even in children). Now in regards ***** ***** surgical success is very much dependent on the individual and their particular level of severity. Therefore, this can skew the prognosis time frames that we have for these types of procedures. In fact, while the median survival time is a few years as you noted, there are a significant number of cases that do much better (ie up to 6 years in a recent study). That said some others will do worse.
Therefore, if his signs are too severe to continue as he is (and that level of pain you noted certainly raises that as being a concern for this situation), it is worth sitting down with his specialist for a discussion on his risks/benefits of the surgery. If the severity of brain
changes match the signs, then he may not be a good candidate to put through this procedure and we'd have to consider using the steroids and pain medications as needed for as long as he is comfortable. But if based on their MRI scan, his brain changes are not severe and a shunt would be straight forward for him, then it is something to seriously consider undertaking to give him a chance to potentially have a good few years as a normal dog if possible.
Please take care,