N-Acetylaspartate concentrations in the thalami of neuropathic pain patients and healthy comparison subjects measured with 1H-MRS

We investigated the absolute concentration of N-acetylaspartate (NAA) in the thalami of neuropathic pain patients and healthy comparison subjects by single-voxel proton magnetic resonance spectroscopy (1H-MRS).1H-MRS was performed with a 1.5-T MR system on a voxel in the thalamus bilaterally in 9 neuropathic pain patients and 14 healthy control subjects.We measured the absolute concentration of NAA using a linear combination model. The NAA concentration in the thalamus decreased significantly on the contralateral side in seven patients and on the ipsilateral side in two patients, as compared with the mean NAA concentration of the healthy control subjects. The NAA concentrations in two patients who did not respond to standard pain treatments were extremely decreased. Our results using 1H-MRS suggest that neuropathic pain seems to be associated with an abnormal balance of the neural activity in the thalamus. The NAA concentration of the thalamus may be related to the efficacy of therapy. 1H-MRS may serve as a useful noninvasive tool for evaluating thalamic neural activity in neuropathic pain patients.