N-acetylaspartate concentration in psychotic disorders: T2-relaxation effects

We used proton magnetic resonance spectroscopy (H-1 MRS) to quantify N-acetylaspartate (NAA) concentrations and apparent spin-spin (T2) relaxation times, which also include diffusion attenuations, in first episode and chronic psychosis patients compared to matched healthy controls. 104 patients diagnosed with psychotic disorders and 50 matched controls were scanned at 4 Tesla. H-1 MRS data were collected at four echo times (TE = 30, 90, 150 and 200 ms) using PRESS. NM concentrations referenced to water and apparent T2 relaxation times of NM and water were calculated. At TE = 30 ms, NM concentration without T2 correction was significantly lower in chronic psychosis patients compared to age-matched healthy controls (p = 0.013, N = 61 and 26, respectively) but normal in first episode patients compared to matched controls (N = 43 and 24, respectively). After T2 correction, no significant differences remained between the groups. While diffusion attenuation was not independently accounted for, these findings indicate that T2 relaxation makes a major impact on NM concentration measures in psychotic disorders. Thus, it may be neuronal microenvironment indexed by NAA and water T2 relaxation times and not neuronal integrity indexed by NAA concentration that underlies the widely reported NM concentration reductions in psychotic disorders. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study used H-1 MRS to quantify NAA concentrations and T2 relaxation times in first episode and chronic psychosis patients. The results suggest that T2 relaxation has a significant impact on NM concentration measures.