Agree with washU and Mayo. Columbia/Cornell at NY Pres (two separate programs), Hopkins, Harvard, UCSF, Duke, Cleveland Clinic OH, Case Western.
There are many good ones but those are some of the best in my opinion. I base this from personal experience (I'll be a neuromuscular fellow next year and did a lot of homework) and on the scope of their training (they had to offer EMG with peripheral nerve ultrasound, Botox and biopsy/path with autonomic and EP exposure to make the list).
These are 1 yr spots with an option to add/apply for a second year if desired. Mayo has three distinct years but you could probably just do the EMG year (the other two years are "Muscle" and "Nerve".