Exclusion Criteria: Contraindications to hyperbaric oxygen therapy e.g. pulmonary emphysema or bullae, claustrophobiia, seizure diorder Inability of the patient to tolerate pressurization e.g. Eustachian tube dysfunction Stroke within the previous 6 months Extreme cognitive impairment Major depression Other uncontrolled co-morbidities, e.g. diabetes, hypertension, thyroid disorders, carotid artery stenosis (>70%), renal or hepatic dysfunction History of brain tumor, head trauma, electric shock therapy, brain irradiation History of migraine headaches