As to whether just spinal scans are appropriate depends on your symptoms and where the neuro thinks the damage or lesions are. So eg if you had nystagmus, unsteady gait, balance issues it might indicate a cerebellar lesion so then its better to image the brain. If you had bladder, bowel issues and a numb leg maybe spine maybe more appropriate (I think I’m just throwing that out but don’t quote me).
Technically if they are considering MS as differential it should be brain and spine as you could still have brain lesions.(though number and position of lesions doesn’t always tie in with symptoms hence why people can still have MS with a normal MRI the chances are much much more slimmer though and usually they expect lesions to develop on repeating over time).
Maybe query it with the neuro to make sure you are having the correct scans