Hi my story is slightly different but in a way kind of relates.

I have an arachnoid cyst, had it since my mum was pregnant with me.
The cyst had supposedly disappeared by the time i was born, so my head was left alone, until i showed symptoms at a year old. By the time the cyst was noticed again, it was too big to be removed, so i had my shunt put it.

Over the past year now, ive had lots and lots of problems with my shunt and shunting, that a few months back in June after a shunt failure, my NS at great ormond street in the UK, decided, it would be best to remove the shunt from my head and to drain my cyst by fenestration. The night this was done, I did become ill, my head killed, i couldnt sleep, i felt sick and suffered seizures and a fit. I had never suffered them before this.
But i was told it was all risks that were taken but it should clear up in time once my brain had got used to the new pathways without help from the shunt. 3 weeks later, the fenestration failed. So had my shunt put in.

Couldnt your NS try a fenestration? and if it were to fail then put in a shunt once again, nothing is lost even if it were to fail.

Good luck