Chiwen ~
The always-astute Debbi is entirely correct regarding medical insurance usually refusing to cover a medical problem that existed prior to the issuance of the policy.
Medical insurance companies view your ongoing condition (in your case, an acoustic neuroma) as something you brought with you, as it were, not something that happened while you were insured. Its like buying an automobile collision policy and expecting the insurer to pay for your car's dented fender resulting from an accident that happened last year, while you were uninsured. This is not entirely unreasonable on their part. We don't take out fire insurance on our home after we've had a fire and then expect the insurance company to pay for the prior damage. The same logic applies to medical insurance. However, there are exceptions and they are worth checking out.
