 A baseline TCD examination will be performed in each subject MS patients and controls over the temporal bone window on both sides. Middle cerebral artery wave forms will be identified at a depth range of 40-60 mm and a stable forward waveform with good intensity will be selected. TCD probes 2 MHz will be mounted by a head frame to ensure a constant angle of insonation throughout the procedure. Mean, peak-systolic and end-diastolic blood flow velocities can be directly recorded from the machine. Blood pressure BP and heart rate will be measured with a finger plethysmograph. The cuff will be applied to the middle finger of the left hand, first placed at the heart level to calibrate the system, afterwards the hand is placed next to the subject in rest. Near-infrared spectroscopy will be performed to measure cerebral frontal lobe oxygen saturation. NIRS is performed with two large sensors, attached on patients forehead bilaterally. In bright environments, a light-blocker to cover the sensors will be used to reduce interference from ambient light. Continuously NIRS recording with a 2s interval refreshment. Measurements will be done in upright and supine positions. The expected duration of the entire TCD protocol is 30 minutes. 