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Peripheral Nerve Diffusion Tensor Imaging: Assessment of Axon and Myelin Sheath Integrity.

Heckel A, Weiler M, Xia A, Ruetters M, Pham M, Bendszus M, Heiland S, Baeumer P - PLoS ONE (2015)

Bottom Line: FA correlated with dml (r=-0.63, p=0.002, Bonf. corr.) and sNCV (r=0.68, p=0.001, Bonf. corr.) but not with markers of axon integrity.DTI is particularly sensitive, since these findings are observed in healthy participants.Our results encourage future studies to evaluate the potential of DTI in differentiating axon from myelin sheath injury in patients with manifest peripheral neuropathies.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroradiology, Heidelberg University Hospital, Heidelberg, Germany; Department of Diagnostic Radiology, Freiburg University Hospital, Freiburg, Germany.

ABSTRACT

Purpose: To investigate the potential of diffusion tensor imaging (DTI) parameters as in-vivo biomarkers of axon and myelin sheath integrity of the median nerve in the carpal tunnel as validated by correlation with electrophysiology.

Methods: MRI examinations at 3T including DTI were conducted on wrists in 30 healthy subjects. After manual segmentation of the median nerve quantitative analysis of fractional anisotropy (FA) as well as axial, radial and mean diffusivity (AD, RD, and MD) was carried out. Pairwise Pearson correlations with electrophysiological parameters comprising sensory nerve action potential (SNAP) and compound muscle action potential (CMAP) as markers of axon integrity, and distal motor latency (dml) and sensory nerve conduction velocity (sNCV) as markers of myelin sheath integrity were computed. The significance criterion was set at P=0.05, Bonferroni corrected for multiple comparisons.

Results: DTI parameters showed a distinct proximal-to-distal profile with FA, MD, and RD extrema coinciding in the center of the carpal tunnel. AD correlated with CMAP (r=0.50, p=0.04, Bonf. corr.) but not with markers of myelin sheath integrity. RD correlated with sNCV (r=-0.53, p=0.02, Bonf. corr.) but not with markers of axon integrity. FA correlated with dml (r=-0.63, p=0.002, Bonf. corr.) and sNCV (r=0.68, p=0.001, Bonf. corr.) but not with markers of axon integrity.

Conclusion: AD reflects axon integrity, while RD (and FA) reflect myelin sheath integrity as validated by correlation with electrophysiology. DTI parameters consistently indicate a slight decrease of structural integrity in the carpal tunnel as a physiological site of median nerve entrapment. DTI is particularly sensitive, since these findings are observed in healthy participants. Our results encourage future studies to evaluate the potential of DTI in differentiating axon from myelin sheath injury in patients with manifest peripheral neuropathies.

No MeSH data available.


Related in: MedlinePlus

Scatter plots relating electroneurographic parameters with DTI parameters.Significant correlations surviving Bonferroni correction for multiple comparisons (see Table 2) are displayed. FA: fractional anisotropy; AD: axial diffusivity; RD: radial diffusivity; CMAP compound muscle action potential; dml: distal motor latency; sNCV: sensory nerve conduction velocity.
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pone.0130833.g003: Scatter plots relating electroneurographic parameters with DTI parameters.Significant correlations surviving Bonferroni correction for multiple comparisons (see Table 2) are displayed. FA: fractional anisotropy; AD: axial diffusivity; RD: radial diffusivity; CMAP compound muscle action potential; dml: distal motor latency; sNCV: sensory nerve conduction velocity.

Mentions: Correlation analysis between electroneurographic parameters and DTI parameters (Table 2) revealed a significant correlation between FA and electrophysiological measures of myelin sheath integrity. Specifically, FA correlated strongly with both distal motor latency (r = -0.63, p = 0.002, Bonferroni corr.) and sensory nerve conduction velocity (r = 0.68, p<0.001, Bonferroni corr.). There was also a moderate correlation with SNAP (r = 0.48), which was, however, not significant (p = 0.11, Bonferroni corr.). AD correlated significantly with CMAP as marker of axon integrity (r = 0.50, p = 0.04, Bonferroni corr.). AD did not show a meaningful correlation with SNAP (r = 0.14) and did not correlate with electrophysiological markers of myelin sheath integrity. MD did not show any significant correlation with electrophysiological parameters when applying strict statistical criteria. RD correlated with sensory nerve conduction velocity as marker for myelin sheath integrity (r = -0.53, p = 0.024, Bonferroni corr.). Correlation with the second marker of myelin sheath integrity, distal motor latency, was moderate (r = 0.46) but not significant applying strict statistical criteria (p = 0.10, Bonferroni corr.). RD did not correlate with electrophysiological markers of axon integrity. Scatter plots of the four significant findings are displayed in Fig 3.


Peripheral Nerve Diffusion Tensor Imaging: Assessment of Axon and Myelin Sheath Integrity.

Heckel A, Weiler M, Xia A, Ruetters M, Pham M, Bendszus M, Heiland S, Baeumer P - PLoS ONE (2015)

Scatter plots relating electroneurographic parameters with DTI parameters.Significant correlations surviving Bonferroni correction for multiple comparisons (see Table 2) are displayed. FA: fractional anisotropy; AD: axial diffusivity; RD: radial diffusivity; CMAP compound muscle action potential; dml: distal motor latency; sNCV: sensory nerve conduction velocity.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4482724&req=5

pone.0130833.g003: Scatter plots relating electroneurographic parameters with DTI parameters.Significant correlations surviving Bonferroni correction for multiple comparisons (see Table 2) are displayed. FA: fractional anisotropy; AD: axial diffusivity; RD: radial diffusivity; CMAP compound muscle action potential; dml: distal motor latency; sNCV: sensory nerve conduction velocity.
Mentions: Correlation analysis between electroneurographic parameters and DTI parameters (Table 2) revealed a significant correlation between FA and electrophysiological measures of myelin sheath integrity. Specifically, FA correlated strongly with both distal motor latency (r = -0.63, p = 0.002, Bonferroni corr.) and sensory nerve conduction velocity (r = 0.68, p<0.001, Bonferroni corr.). There was also a moderate correlation with SNAP (r = 0.48), which was, however, not significant (p = 0.11, Bonferroni corr.). AD correlated significantly with CMAP as marker of axon integrity (r = 0.50, p = 0.04, Bonferroni corr.). AD did not show a meaningful correlation with SNAP (r = 0.14) and did not correlate with electrophysiological markers of myelin sheath integrity. MD did not show any significant correlation with electrophysiological parameters when applying strict statistical criteria. RD correlated with sensory nerve conduction velocity as marker for myelin sheath integrity (r = -0.53, p = 0.024, Bonferroni corr.). Correlation with the second marker of myelin sheath integrity, distal motor latency, was moderate (r = 0.46) but not significant applying strict statistical criteria (p = 0.10, Bonferroni corr.). RD did not correlate with electrophysiological markers of axon integrity. Scatter plots of the four significant findings are displayed in Fig 3.

Bottom Line: FA correlated with dml (r=-0.63, p=0.002, Bonf. corr.) and sNCV (r=0.68, p=0.001, Bonf. corr.) but not with markers of axon integrity.DTI is particularly sensitive, since these findings are observed in healthy participants.Our results encourage future studies to evaluate the potential of DTI in differentiating axon from myelin sheath injury in patients with manifest peripheral neuropathies.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroradiology, Heidelberg University Hospital, Heidelberg, Germany; Department of Diagnostic Radiology, Freiburg University Hospital, Freiburg, Germany.

ABSTRACT

Purpose: To investigate the potential of diffusion tensor imaging (DTI) parameters as in-vivo biomarkers of axon and myelin sheath integrity of the median nerve in the carpal tunnel as validated by correlation with electrophysiology.

Methods: MRI examinations at 3T including DTI were conducted on wrists in 30 healthy subjects. After manual segmentation of the median nerve quantitative analysis of fractional anisotropy (FA) as well as axial, radial and mean diffusivity (AD, RD, and MD) was carried out. Pairwise Pearson correlations with electrophysiological parameters comprising sensory nerve action potential (SNAP) and compound muscle action potential (CMAP) as markers of axon integrity, and distal motor latency (dml) and sensory nerve conduction velocity (sNCV) as markers of myelin sheath integrity were computed. The significance criterion was set at P=0.05, Bonferroni corrected for multiple comparisons.

Results: DTI parameters showed a distinct proximal-to-distal profile with FA, MD, and RD extrema coinciding in the center of the carpal tunnel. AD correlated with CMAP (r=0.50, p=0.04, Bonf. corr.) but not with markers of myelin sheath integrity. RD correlated with sNCV (r=-0.53, p=0.02, Bonf. corr.) but not with markers of axon integrity. FA correlated with dml (r=-0.63, p=0.002, Bonf. corr.) and sNCV (r=0.68, p=0.001, Bonf. corr.) but not with markers of axon integrity.

Conclusion: AD reflects axon integrity, while RD (and FA) reflect myelin sheath integrity as validated by correlation with electrophysiology. DTI parameters consistently indicate a slight decrease of structural integrity in the carpal tunnel as a physiological site of median nerve entrapment. DTI is particularly sensitive, since these findings are observed in healthy participants. Our results encourage future studies to evaluate the potential of DTI in differentiating axon from myelin sheath injury in patients with manifest peripheral neuropathies.

No MeSH data available.


Related in: MedlinePlus