Proton Magnetic Resonance Spectroscopy of the Primary Motor Cortex in Patients With Motor Neuron Disease

Abstract

Spectroscopic changes in the motor cortices of patients with ALS correspond with a reduction in levels of NAA and an elevation in levels of choline and inositol compounds. Since NAA is exclusively expressed in neurons, the observed decrease of NAA reflects neuronal loss or dysfunction. Inositol and choline are associated with plasma membrane metabolism, so the release of these compounds may be related to membrane disorders.

Early detection and longitudinal changes in amyotrophic lateral sclerosis by 1 H MRSI

“…Cross-sectional analyses revealing increased Cho levels in motor fiber regions but not in the motor cortex have been previously reported. 14,22 Our interpretation of increased Cre and Cho concentrations in the motor cortex is probably due to increased gliosis and membrane phospholipid breakdown. The significant changes reported for the least affected motor cortex demonstrate that disease activity is present throughout the motor cortex.…”

“…Cre represents a combination of creatine and phosphocreatine, a putative marker of gliosis, 3,6 and Cho is thought to be a marker associated with membrane phospholipids. 7In most previous MRS studies of ALS,4,[8][9][10][11][12][13][14][15][16][17][18][19][20] sampling of metabolite signals from the motor cortex was limited, because measurements were restricted to a rectangular region within the brain that was sufficiently distant from the skull to avoid interferences with an intense signal from extracranial lipids. Furthermore, because the selected regions of interest were generally large, including unavoidably some white matter and nonmotor tissue, results from these studies may have been skewed to the extent that white matter and nonmotor regions contributed to the metabolite signal from the motor cortex.…”

Neuroimaging in Amyotrophic Lateral Sclerosis

“…Most of the 1 H-MRS studies in ALS have demonstrated that either NAA concentrations [54,55] or ratios of NAA/Cr, [15,18,19,56] NAA/Cho [15,17,55], and NAA/(Cr+Cho) [57] are reduced in the motor cortex (FIG. 2).…”

“…Increased mI has also been found in the motor cortex in ALS patients [17,18]. Using a higher field magnet (3 Tesla), Kalra et al [63] reported that the NAA/mI ratio provided both better sensitivity and specificity for detecting ALS than individual metabolites and demonstrated the strongest correlation with disease severity.…”

“…In the search for the UMN markers, several neuroimaging modalities, especially diffusion tensor imaging (DTI) [8][9][10][11][12][13][14][15][16], proton magnetic resonance spectroscopy ( 1 H-MRS) [14,15,[17][18][19][20], perfusion imaging [21], magnetization transfer imaging [22] (MTI) and functional magnetic resonance imaging (fMRI) [23][24][25], have been used with varying success. This article presents an overview of these neuroimaging methods and their potential roles in ALS.…”