REDUCED N-ACETYLASPARTATE IN THE BRAIN OBSERVED ON IN-VIVO PROTON MAGNETIC-RESONANCE SPECTROSCOPY IN PATIENTS WITH MENTAL-RETARDATION

Volume-selective proton magnetic resonance spectroscopy (H-1-MRS) of the brain was performed with a 1.5T magnet in 28 patients with unclassified mental retardation (MR) and in 25 age-matched healthy children, Peaks of N-acetylaspartate (NAA), choline (Cho), and creatine (Cr), but not of lactate, were observed in both groups on H-1-MRS. In all our subjects of this age range, H-1-MRS revealed an increase with advancing age in the ratio of NAA/Cho (P =.0031), but no developmental change in the NAA/Cr and Cho/Cr ratios. The NAA/Cho ratio was lower in patients with MR than in controls (P =.0016). The NAA/Cr ratio tended to be lower in the MR group, and the Cho/Cr ratio did not differ between patients with MR and controls, These results suggest that in patients with MR, NAA decreases and a disorder and/or dysfunction of neurons in the brain exists.