© Cambridge University Press 2011. In children and adolescents, multiple sclerosis (MS) has an impact on the developing central nervous system and can result in transient or fixed deficits of gross motor and/or fine motor skills, sensory perceptual processing, bowel/bladder function, vision, balance, and coordination. The heterogeneous presentation and disease course of MS makes symptom prediction difficult. Large brain lesions may be present in non-eloquent regions and not produce symptoms. Conversely, small lesions in dense axonal tracts may produce multiple symptoms. We have the inability to predict, as of yet, which lesions will heal completely, and which will become permanent and produce residual symptoms. Heat-induced “pseudorelapses” may also occur and these must be clearly differentiated from a true clinical relapse, although to a patient the experience can be one and the same. In addition to sensory and motor symptoms, pediatric MS patients may experience ongoing difficulties with fatigue and mental health issues, independent of relapses and lesion distribution, which significantly impact daily function and quality of life. Paroxysmal symptoms such as the sensation of tightness around the chest or intermittent muscle spasms can be very distressing. Some deficits may be under-recognized due to the young age of the patient (i.e. visual or sensory symptoms in a pre-schooler or increased urinary frequency in the diaper-wearing toddler).