[A case of idiopathic orthostatic hypotension with selective involvement of postganglionic noradrenergic neurons].

A 44-year-old man had a 30-year history of orthostatic hypotension and diarrhea. One month before admission, he suddenly lost consciousness by defecation, and was hospitalized. He became alert within two days, but he could not sit up due to severe orthostatic hypotension. At that point, he was transferred to our hospital. On admission, talipes and microdactylia were noted. Neurological examination revealed brisk patellar tendon reflexes. Anhidrosis or impotence was not present. Analyses of blood and urine yielded normal results. Cardiological examination revealed no abnormality that could be responsible for the hypotension. MR images of the brain were also normal. However, single photon emission tomography revealed diffuse hypoperfusion of the brain. A head-up tilt (50 degrees) test induced a remarkable fall in systolic blood pressure from 149 (heart rate; 65/min) to 64 mmHg (83). Immersion of hand in ice-cold water failed to increase blood pressure. Heart rate variation and cystometry results, which represent the function of parasympathetic nerves, were normal. Warming of his body caused normal sweating. Intravenous injection of low doses of norepinephrine and methoxamine increased blood pressure while isoproterenol remarkably increased heart rate, suggesting that both alpha- and beta-receptors developed supersensitivity. Instillation of 5% cocaine and 5% tyramine into the conjunctival sac failed to cause pupillary dilation. Clinical findings and pharmacological challenge test results suggested that the main lesion of his autonomic nervous system was selectively confined to the postganglionic sympathetic nerves and noradrenergic (not cholinergic) neurons. The autonomic failure of our patient can be classified as idiopathic orthostatic hypotension. However, most patients with idiopathic orthostatic hypotension or pure autonomic failure complain of anhidrosis and impotence, which were not noted in our patient. These symptomatic differences may be the result of the highly selective involvement of noradrenergic neurons in the postganglionic sympathetic system in our patient.