No test rules MS in or out it is just a piece of the puzzle. The two tests that are most important are a brain MRI done with MS Protocal and contrast and a Lumbar Puncture done for MS. Blood work to rule out other conditions is done. The neurological exam is very important that is reflexes, following the finger, balancing, walking, etc. That tells a neurologist where there is damage in the Central Nervous system. Your history is very important and then your symptoms. The neurologist goes by the McDonald Criteria you can look it up if you are curious. It mainly says you have to have two separate attacks in two different parts of the nervous system at two different times.
For most of us MS is not a quick diagnose. I doctor might want to watch you over time every three to six months.Sometimes they do not take the word of other doctors even other neurologists.
EMGs are done to look for peripheral nervous system causes of your symptoms. Multiple sclerosis is a central nervous system condition. If your EMGs are abnormal, the test would point away from MS being the cause of your issues.