Diffusion tensor imaging yields valid quantitative biomarkers in CIDP and might aid in diagnosis with high diagnostic accuracy. Fractional anisotropy and RD may serve as parameters of myelin sheath integrity, but AD is unable to reflect axonal damage in CIDP.

• Peripheral nerve diffusion tensor imaging (DTI) parameters depend on demographic variables. • Fractional anisotropy (FA) declines with increasing age and weight. • Gender does not systematically affect peripheral nerve DTI. • The formula presented here allows adjustment of FA for demographic variables.

Patients with Fabry disease have severely enlarged dorsal root ganglia with dysfunctional perfusion. This may be due to glycolipid accumulation in the dorsal root ganglia mediating direct neurotoxic effects and decreased neuronal blood supply. These alterations were less pronounced in peripheral nerve segments. Thus, the dorsal root ganglion might play a key pathophysiologic role in the development of neuropathy and pain in Fabry disease.

The objective of this study was to evaluate large coverage magnetic resonance neurography (MRN) in chronic inflammatory demyelinating polyneuropathy (CIDP). In this prospective study, 18 patients with CIDP and 18 healthy controls were examined by a standardized MRN protocol at 3 T. Lumbosacral plexus was imaged by a T2-weighted 3D sequence and peripheral nerves of the upper and lower extremity by axial T2-weighted turbo spin-echo sequences. Lesions were characterized by nerve cross-sectional area (CSA) and T2-weighted signal (nT2). Additionally, T2 relaxometry of the sciatic nerve was performed using a multi-spin-echo sequence. All patients received a complementary electrophysiological exam. Patients with CIDP exhibited increased nerve CSA and nT2 compared to controls (p < 0.05) in a proximally predominating pattern. Receiver operating characteristic analysis revealed the best diagnostic accuracy for CSA of the lumbosacral plexus (AUC = 0.88) and nT2 of the sciatic nerve (AUC = 0.88). CSA correlated with multiple electrophysiological parameters of demyelinating neuropathy (F wave latency, nerve conduction velocity) of sciatic and median nerve, while nT2 only correlated with F wave latency of sciatic and not median nerve. T2 relaxometry indicated that MR signal increase in CIDP was due to an increase in proton-spin-density (p < 0.05), and not due to the increase in T2 relaxation time. Both nT2 and CSA might aid in the diagnosis of CIDP, but CSA correlates more robustly with established electrophysiological parameters for CIDP. Since the best diagnostic accuracy was shown for proximal nerve locations, MRN may be a useful complementary tool in selected CIDP cases.

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Objectives To assess the interreader and test-retest reliability of magnetization transfer imaging (MTI) and T2 relaxometry in sciatic nerve MR neurography (MRN). Materials and methods In this prospective study, 21 healthy volunteers were examined three times on separate days by a standardized MRN protocol at 3 Tesla, consisting of an MTI sequence, a multi-echo T2 relaxometry sequence, and a high-resolution T2-weighted sequence. Magnetization transfer ratio (MTR), T2 relaxation time, and proton spin density (PSD) of the sciatic nerve were assessed by two independent observers, and both interreader and test-retest reliability for all readout parameters were reported by intraclass correlation coefficients (ICCs) and standard error of measurement (SEM). Results For the sciatic nerve, overall mean ± standard deviation MTR was 26.75 ± 3.5%, T2 was 64.54 ± 8.2 ms, and PSD was 340.93 ± 78.8. ICCs ranged between 0.81 (MTR) and 0.94 (PSD) for interreader reliability and between 0.75 (MTR) and 0.94 (PSD) for test-retest reliability. SEM for interreader reliability was 1.7% for MTR, 2.67 ms for T2, and 21.3 for PSD. SEM for test-retest reliability was 1.7% for MTR, 2.66 ms for T2, and 20.1 for PSD. Conclusions MTI and T2 relaxometry of the sciatic nerve are reliable and reproducible. The values of measurement imprecision reported here may serve as a guide for correct interpretation of quantitative MRN biomarkers in future studies. Key Points • Magnetization transfer imaging (MTI) and T2 relaxometry of the sciatic nerve are reliable and reproducible. • The imprecision that is unavoidably associated with different scans or different readers can be estimated by the here presented SEM values for the biomarkers T2, PSD, and MTR. • These values may serve as a guide for correct interpretation of quantitative MRN biomarkers in future studies and possible clinical applications.

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Although heterozygous, Fabry females show severe enlarged dorsal root ganglia with a concomitant dysfunctional perfusion, even in patients with minor disease progression and in patients who are not considered for enzyme replacement therapy yet. Alterations in dorsal root ganglia volume and perfusion might serve as a very early in vivo marker for involvement of the peripheral nervous system in Fabry disease, even in patients with residual enzyme activity.