Hello iskimud.

Your correct, CTS and ulnar nerve involvement would not explain leg numbness. It's also possible the numbness in those areas are related but it's also possible you could be dealing with more than on issue and/or cause.

Have you had any other testing besides the brain MRI? If your leg is involved a MRI of the spine would be something to ask your doctor about. An EMG might also be helpful. These are just suggestions.