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 from each other with respect to cerebral hemodynamic parameters.

METHODS

Seventeen TMB patients and 23 hTIA patients with a moderate to severe stenosis or an occlusion of the internal carotid artery (ICA) underwent magnetic resonance (MR) angiography, (1)H MR spectroscopy and transcranial Doppler sonography. Thirty-one control subjects were investigated to obtain reference values for the MR investigations. Quantitative flow was measured in the ICAs, the basilar artery and the middle cerebral arteries (MCA). Metabolic changes in the MCA territory were studied by assessing N-acetyl-aspartate (NAA)/choline ratios and prevalences of lactate. The prevalence of collateral flow was assessed in the circle of Willis and the ophthalmic arteries. The vasomotor reactivity was studied by measuring the CO(2) reactivity of the MCA territories.

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 CO(2) 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 symptomatology (p < 0.01), i.e. whether patients had TMB or hTIA, and not with ipsilateral MCA flow (p = 0.2) or ipsilateral CO(2) reactivity (p = 0.7).

CONCLUSION

The results of this study indicate that there are no cerebral hemodynamic differences between TMB patients and hTIA patients. It is therefore unlikely that hemodynamic factors account for differences in clinical characteristics between the two patient groups.