Regional cerebral blood flow and its reactivity to acetazolamide in transient ischemic attacks. Study of 20 cases by gamma emission tomography

We have studied regional cerebral blood flow (= test) and reactivity of acetazolamide injection (= retest) in 20 patients who had presented transient ischemic attacks (TIA). The cerebral blood flow was measured by the atraumatic Xenon 133 inhalation method and single photon emission tomography using a specially dedicated tomograph (TOMOMATIC 64), allowing 3 tomographic levels (OM + 1, + 5, + 9 cm). Measurements were realized in a quiet, dark room. Acetazolamide (500 mg or 1000 mg) was injected intravenously immediately after the test, and the retest was performed 15 minutes after, in the same conditions. Results obtained from paired ROIS were analysed in terms of asymmetric index for the test, of relative reactivity for retest in regard of normal values established in a group of healthy volunteers. All patients had neurological examination, vascular explorations and CT scan. Six of the patients showed a bad reactivity (abolished or strongly decreased) which was evoked a significant hemodynamically stenosis, reflecting the loss of collateral capacity. In the other group results were diversified, and we classified these in 4 groups: "normal" (7), "luxury perfusion" (3), "limited infarction" (1), and "incomplete infarction" (3). When these groups were plotted versus duration of onset and delay between the last attack and the moment of the measurement, "incomplete infarction" clearly appears as a step between brief TIA (less of 1 hour) and "limited infarction". So rCBF and reactivity to acetazolamide are of major interest for the physiopathological classification of TIAs, but also for treatment and prognosis.