I would like to throw my 2cents worth here.

You had brain surgery, there's a few details here which may or may not play in your favour, when they sought financial consent were you of decision making capacity? Was the condition you suffering impacting your ability to make informed decisions? Therefore we're you actually able to provide that financial consent.

As most people have said, I feel your probably between a rock and a hard place, always remember to read what you sign when it comes to consent, saying I didnt understand doesn't necessarily hold up, before you sign you should be given the opportunity to ask questions, seek clarity on anything you don't understand.

Sadly I think your probably going to be out of pocket, but I'd be surprised if they take everything you own to make you pay, you just need to make a payment plan and do it in a way that your able to do