Verbal memory deficits associated with fornix atrophy in carbon monoxide poisoning

Magnetic resonance (MR) images and neuropsychological testing data of 69 ca rbon monoxide (CO) poisoned patients were prospectively obtained within I d ay of CO poisoning, two weeks and six months. CO patients' Day cross-sectio nal fornix surface area measurements, corrected for head size by using a fo rnix-to-brain ratio (FBR), were compared to normal age and gender-matched c ontrols. Additionally, a within-subjects analysis was performed comparing t he mean areas between CO patients' Day 1, 2 weeks and 6-month FBR. The FBR was correlated with patients' neuropsychological data. There were no signif icant differences between CO patients' Day 1 fornix measurements compared t o normal control subjects. However, significant atrophic changes in the for nix of CO poisoned patients occurred at two weeks with no progressive atrop hy at 6 months. By 6 months, CO patients showed significant decline on test s of verbal memory (when practice effects were taken into account), whereas visual memory, processing speed and attention/concentration did not declin e. This study indicates that CO results in brain damage and cognitive impai rments in the absence of lesions and other neuroanatomic markers.