CEREBRAL HYPOPERFUSION IN ORTHOSTATIC HYPOTENSION WITH GLOBALLY DENERVATED MYOCARDIUM

A 57-yr-old woman had frequent syncope when rising from a seated posit ion. Her blood pressure fell from 140/80 mmHg to 60-70/40 mmHg while c hanging positions. Iodine-123-metaiodobenzylguanidine ([I-123]MIBG) di d not accumulate in the heart, whereas Tl-201-Cl (Tl-201) did. Raise-u p Tc-99m-hexamethyl-propyleneamine oxime (Tc-99m-HMPAO) brain SPECT re vealed decreased activity in the bilateral frontal areas, and subseque nt supine Tc-99m-HMPAO brain SPECT revealed filling in these areas, in dicating that the cerebral blood Row (CBF) was transiently decreased i n the frontal areas more than others in a standing position. The plasm a norepinephrine (NE) level of this patient was normal during supine r est, but when she stood up, failure to increase the plasma level of NE uncovered a sympathetic nervous dysfunction. The CBF abnormality in p atients with orthostatic hypotension may be due to a ''functional'' he modynamic mechanism that induces orthostatic stress. This patient had transient hypoperfusion in the frontal areas when standing, without or ganic cerebral arterial stenosis, Only CBF in the frontal areas reveal ed relative hypoperfusion. These regions might be highly susceptible t o a change in blood flow. The causes of orthostatic hypotension of thi s patient were autonomic failure with a disturbance of the sympathetic nerve endings, which was revealed by Tc-99m-HMPAO blain SPECT and car diac [I-123]MIBG imaging.