Orthostatic intolerance (OI) refers to a group of clinical conditions, including postural orthostatic tachycardia syndrome (POTS) and neurally mediated hypotension (NMH), in which symptoms worsen with upright posture and are ameliorated by recumbence. The main symptoms of chronic orthostatic intolerance syndromes include light-headedness, syncope or near syncope, blurring of vision, headaches, problems with short-term memory and concentration, fatigue, intolerance of low impact exercise, palpitations, chest pain, diaphoresis, tremulousness, dyspnea or air hunger, nausea, and vomiting. This review discusses what is known about the pathophysiology of this disorder, potential treatments, and understanding its role in the patient with chronic headache pain.
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