The most interesting Magnetic Resonance Imaging (MRI) studies on affective disorders are high incidence of focal sign hyperintensities in subcortical white matter. Although this is a nonspecific finding like ventriculomegaly, there is the probability of damage to pathways connecting limbic and frontal regions with bazal ganglia. This can be seen also in atherosclerosis, aging, ischemia and demyelinating disorders. Cause of appearance in young bipolar patients deserves attention. There are also a number of anecdotal reports about the coexistence of bipolar disorders and Multiple Sclerosis (MS). In a few case reports depression or psychosis are presented to be the first manifestation of MS without neurological symptoms. Here 9 years of affective disorder history with only manic episodes that was manifested with neurological symptoms in the latest episode, is presented. Increased deep tendon reflexes, bilateral dorsal planter responses, bilateral positive Hoffmann reflex, dysdiadokokinesia, suspected right hemihypoaesthesia were found. Tandem walk was also disturbed. MRI findings of this patient revealed hyperintense white matter lesions in periventricular region. As cerebrospinal fluid findings did not support MS, this case was considered as "clinically probable MS" according to Poser scale. As a result, this case suggests us a well-known major neurological disorder, MS, can manifest itself as a major psychatric disorder, mania. Therefore, MS should always be considered in all affective disorder patients.