It was the neuropsychologist who made the MCI diagnosis. My husband had been seeing a neurologist for many years to treat a tremor. As time went by, I noticed cognitive changes and accompanied him to one of the neurologist appointments to address the problem. That doctor ordered an MRI and several other tests, but I'm afraid I don't recall what they were. He didn't find any pathologies, so time passes. Years go by and my husband's symptoms become more pronounced. I again accompanied my husband to the neurologist and pressed my case. He suggested a neuropsychologist. We had to wait an inordinately long time (maybe 6 or 8 months) for that appointment. The neuropsychologist spent several hours talking to my husband and administering written and verbal tests. After that, the neuropsychologist contacted the neurologist and gave him the results...MCI.
Another thing to keep in mind is that not many neuropsychologists accept insurance. We were lucky to find one that did take our insurance, and that probably contributed to our long wait.
The medication that the neurologist prescribed is donepezil. It's not working at all. My husband's memory is still declining.
I hope this information can help you in some way. I hope your future is not the one you fear.