Patient description: The patient is a 20 year old Caucasian female presents to the clinic with one-sided vision lost and facial weakness, dysarthria and numbness lasting for 1 day. She visited her PCP and underwent brain MRI which revealed a single plaque in the brainstem. After few months, she experienced lower extremities weakness led to balance problem. The second MRI revealed another lesion in the left cerebral hemisphere. The diagnosis of Relapsing Remitting Multiple Sclerosis (RRMS) is confirmed after the second MRI. Her past surgical history is significant for a C-section 2 years ago and she has a one child. She is divorced and is not currently in any sexual relationship. She smokes 10 cigarettes per day and drinks alcohol occasionally. She is working as an editor in a publisher company and she is happy that she can keep working from home most of the time. She is under the treatment of RRMS from 7 months ago.

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Cerebrovascular Accident Patients will have a clinically and radiologically documented stroke in the subacute (2 weeks to 6 months to after onset) or the chronic state (more than 6 months after onset), having a lesion in subcortical regions including the basal ganglia, thalamus, internal capsule, or a combination of these structures, or cerebellum unilaterally. These lesions can extend to the surrounding areas, however not including the cerebral areas where H-MRS ROI will be located. Both ischemic infarction and hemorrhage will be included; however, in cases of hemorrhage, we will cases with deformation in the cerebral hemisphere due to mass effect of the hemorrhage, hydrocephalus, or extension to the ventricles. Patients will be 18 years of age or older. Healthy controls entering the study must be free of serious somatic disease as determined by a standard physical and neurological examination. Controls will be aged over 18 years. Female patients and controls of child bearing potential will have a pregnancy test and specific interview prior to the study to ensure that pregnant patients will not participate in the study. Both patients and controls will be asked to abstain from alcohol for one week before each of the PET and H-MRS scans  A. Patients with MRI findings consistent with brain tumors, trauma or AVMs will be excluded. B. Patients with multiple stroke lesions will be excluded, except for prior asymptomatic lacunar infarctions or stroke lesions which are not known to cause diaschisis in the frontal cortex (occipital cortex). C. Patients with severe stenosis (greater than 70%) or occlusion in internal cervical arteries and in the proximal portions of middle or frontal cerebral arteries detected by angiography or MRA will be excluded. Subjects with medical disorders which can affect the concentration of cerebral metabolites, including renal failure, hepatic failure and untreated electrolyte abnormality will be excluded. Subjects with poorly controlled diabetes mellitus (casual plasma glucose concentration greater than or equal to 200 mg per dL (11.1 mmol per L) or fast plasma glucose concentration greater than or equal to 126 mg per dL (7.0 mmol per L) will be excluded. Subjects who are taking sleeping drugs or tranquilizers will be asked to stop taking them for two days prior to each of the PET and H-MRS scans. D. Subjects with a pre-stroke history of schizophrenia or bipolar disorders will be excluded. E. Subjects with implanted devices such as pacemakers, medication pumps or defibrillators, metal in the cranium except mouth, intracardiac lines, history of shrapnel injury or any other condition/device that may be contraindicated or prevent the acquisition of MRI. F. Subjects with cancer will be excluded. G. Patients not capable of giving an informed consent will be excluded H. Ethnic origin and race will not be biased for inclusion. Participation of children: Children will be excluded from the study because we need to study a homogeneous group of subjects by age and developmental changes in metabolites will complicate this study. Additionally, young children will not be sufficiently cooperative for the long periods of testing. Moreover, the radiation dose of the PET studies would subject them to relatively greater risk than the adults