A comparison of cerebral hemodynamic parameters between transient monocular blindness patients, transient ischemic attack patients and control subjects

Purpose: To assess whether patients with transient monocular blindness (TMB ) and patients with hemispheric transient ischemic attacks (hTIA) differ fr om each other with respect to cerebral hemodynamic parameters. Methods: Sev enteen TMB patients and 23 hTIA patients with a moderate to severe stenosis or an occlusion of the internal carotid artery (ICA) underwent magnetic re sonance (MR) angiography, H-1 MR spectroscopy and transcranial Doppler sono graphy. Thirty-one control subjects were investigated to obtain reference v alues for the MR investigations. Quantitative flow was measured in the ICAs , the basilar artery and the middle cerebral arteries (MCA). Metabolic chan ges in the MCA territory were studied by assessing N-acetyl-aspartate (NAA) /choline ratios and prevalences of lactate. The prevalence of collateral fl ow was assessed in the circle of Willis and the ophthalmic arteries. The va somotor reactivity was studied by measuring the CO2 reactivity of the MCA t erritories. Results: Quantitative flow in the cerebropetal arteries and the MCAs did not differ between TMB patients and hTIA patients. Also patterns of collateral flow, prevalence of lactate and CO2 reactivity were similar. The mean ipsilateral NAA/choline ratio was lower in hTIA patients compared with TMB patients (p < 0.01), and was predominantly correlated with symptom atology (p < 0.01), i.e. whether patients had TMB or hTIA, and not with ips ilateral MCA flow (p = 0.2) or ipsilateral CO2 reactivity (p = 0.7). Conclu sion: The results of this study indicate that there are no cerebral hemodyn amic differences between TMB patients and hTIA patients. It is therefore un likely that hemodynamic factors account for differences in clinical charact eristics between the two patient groups, Copyright (C) 2000 S. Karger AG, Basel.