WATERSHED ISCHEMIA DEMONSTRATED WITH ACETAZOLAMIDE ENHANCED TC-99M HMPAO SPECT

A 75-year-old man who had a small right parietal infarction 8 months e arlier underwent baseline and acetazolamide enhanced Tc-99m hexamethyl propylene amineoxime brain SPECT imaging. The acetazolamide study demo nstrated a bilaterally symmetric perfusion deficit posteriorly near th e midline. The baseline study was essentially normal. This finding was felt to represent watershed ischemia at the junction of the anterior circulations (anterior cerebral and middle cerebral arteries) and the posterior circulation (posterior cerebral artery). Carotid arteriograp hy subsequently demonstrated left subclavian steal syndrome with retro grade flow through the left vertebral artery.