Magnetization transfer (MT) asymmetry around the water resonance in human cervical spinal cord.

PURPOSE: To demonstrate the presence of magnetization transfer (MT) asymmetry in human cervical spinal cord due to the interaction between bulk water and semisolid macromolecules (conventional MT), and the chemical exchange dependent saturation transfer (CEST) effect. MATERIALS AND METHODS: MT asymmetry in the cervical spinal cord (C3/C4-C5) was investigated in 14 healthy male subjects with a 3T magnetic resonance (MR) system. Both spin-echo (SE) and gradient-echo (GE) echo-planar imaging (EPI) sequences, with low-power off-resonance radiofrequency irradiation at different frequency offsets, were used. RESULTS: Our results show that the z-spectrum in gray/white matter (GM/WM) is asymmetrical about the water resonance frequency in both SE-EPI and GE-EPI, with a more significant saturation effect at the lower frequencies (negative frequency offset) far away from water and at the higher frequencies (positive offset) close to water. These are attributed mainly to the conventional MT and CEST effects respectively. Furthermore, the amplitude of MT asymmetry is larger in the SE-EPI sequence than in the GE-EPI sequence in the frequency range of amide protons. CONCLUSION: Our results demonstrate the presence of MT asymmetry in human cervical spinal cord, which is consistent with the ones reported in the brain.

Abnormal diffusion tensor in nonsymptomatic familial amyotrophic lateral sclerosis with a causative superoxide dismutase 1 mutation.

PURPOSE: To determine whether diffusion abnormalities can be observed in nonsymptomatic family members with a known causative Cu/Zn superoxide dismutase mutation (asymptomatic familial amyotrophic lateral sclerosis; AFALS(+SOD1)) in a family with autosomal dominant familial amyotrophic lateral sclerosis (ALS) using diffusion tensor imaging (DTI). MATERIALS AND METHODS: A total of eight AFALS(+SOD1) subjects (aged 17-43 years) were age-matched with 13 healthy controls (aged 19-45 years) without SOD1 mutations. DTI was carried out on a 1.5T scanner. The diffusion index maps derived were then normalized spatially for voxel-based analysis. region of interest (ROI)-based analysis was also carried out. RESULTS: Our voxel-based and ROI-based analysis showed that AFALS(+SOD1) subjects have decreased fractional anisotropy (FA) (0.5401 vs. 0.5168, P < 0.05) and increased tensor trace (TT) (2.5854 x 10(-3) mm(2)/second vs. 2.6226 x 10(-3) mm(2)/second, P < 0.04) at the posterior limb of the internal capsule compared to the control subjects. Increased radial diffusivity (E((2,3)/2)) was detected on both sides (right = 0.5710 x 10(-3) mm(2)/second vs. 0.5943 x 10(-3) mm(2)/second, P < 0.05; left = 0.5666 x 10(-3) mm(2)/second vs. 0.5872 x 10(-3) mm(2)/second, P < 0.05). No significant change in axial diffusivity (E(1)) was detected. CONCLUSION: Abnormal diffusivity was found at the posterior limb of the internal capsule in AFALS(+SOD1) subjects, hitherto unreported. Our results suggest that DTI may detect diffusion abnormalities in AFALS(+SOD1) subjects before symptoms develop.

Cervical spinal cord BOLD fMRI study: modulation of functional activation by dexterity of dominant and non-dominant hands.

The objective of this study was to investigate the effect of dexterity on the magnitude of signal changes in functional magnetic resonance imaging (fMRI) in the cervical spinal cord with unilateral finger-tapping. Right-handed healthy volunteers were investigated with blood oxygenation level-dependent (BOLD) fMRI. Spinal cord BOLD functional MR images were acquired from 10 healthy right-handed volunteers who performed four sessions of unilateral finger-tapping tasks: left sequential (LS), right sequential (RS), left interleaved (LI), and right interleaved (RI) tasks. Our results from the difficulty measurement test showed that finger-tapping in interleaved order was more difficult than in sequential order. For the functional activation, seven out of 10 subjects had activation in all four fMRI sessions (two of the subjects who showed no detectable activation had problems in volume registration). The mean contrast value of the activation area inside the entire cervical spinal cord was significantly higher in performing LS than RS tasks. The increase in the mean contrast value was because the less skilled and competent right hemisphere required additional processing power for doing the left hand task than the left hemisphere required in doing the right hand task. The analysis of the interleaved finger-tapping tasks did not show any significant difference in the results. This was probably because the interleaved task was similarly challenging for both hands, and required high dexterity. Therefore, differences in activity between the left and right hands were less apparent. Our results showed the modulation of activation intensity in the spinal cord by the dexterity.

Proton-density-weighted spinal fMRI with sensorimotor stimulation at 0.2 T.

Proton-density-weighted fMRI at low field (0.2 T) was carried out in the cervical spinal cord of healthy volunteers in this study to examine the feasibility of detecting proton density alteration accompanying activation in the spinal cord. Subjects were asked to grip both hands simultaneously, providing sensorimotor simulation for spinal fMRI. Over 70% subjects recruited had activation localized at C6-C7 spinal levels with discrete activation detected in both the anterior and posterior horns of the cervical spinal cord, and the average fractional signal change was 4.06%. The 0.2 T low magnetic field and the 24 ms short TE used in this study diminished the BOLD effect to a negligible level, thus the observed signal change was believed to be mainly attributable to proton density increase during neuronal stimulation. Our results suggested the existence of task-driven proton density change in the cervical spinal cord.

Spinal effects of acupuncture stimulation assessed by proton density-weighted functional magnetic resonance imaging at 0.2 T.

Signal changes can be detected by proton density-weighted functional imaging in both the brain and the spinal cord. These are attributed to changes in extravascular water proton (signal enhancement by extravascular protons) density during neuronal activation. In this study, we used this technique to detect correlations between acupoint stimulation and neural activity in the spinal cord. Stimulation of acupoints associated with treatment of sensorimotor deficits (LI4 and LI11) was performed on 11 volunteers. During stimulation, 8 of the 11 subjects had consistent functional activations in C6/C7. A bilateral activation pattern was common. Our findings show that acupoint stimulation modulates activity in the spinal cord.