I have also had the CHIARI surgery and experienced similar symptoms, for me it was leukoencephalapathy, which can look a lot like a stroke on an MRI, and is common after spinal decompression. I don't know where you are located but Dr.Rob Parrish out of Methodist in Houston did my surgery and I liked him as a neurosurgeon, and Dr.Eugene Lai is an excellent neurologist, also from Houston.
You know your body better than anyone so please don't give up and if you don't get answers don't hesitate to ask for a second or third opinion. I went through at least a dozen docs before my primary care doc found the CHIARI, while the others told me I was imagining my symptoms or that I was just depressed, by the time I saw my neurosurgeon he told me I would have been dead in a week due to the intracranial pressure or the heart problems caused by the CHIARI. Don't give up!