Ultrasound is useful for non-invasive visualization of focal nerve pathologies probably resulting from demyelination, remyelination, edema or inflammation. In patients with progressive muscle weakness, differentiation between multifocal motor neuropathy (MMN) and amyotrophic lateral sclerosis (ALS) is essential regarding therapy and prognosis. Therefore, the objective of this study was to investigate whether nerve ultrasound can differentiate between ALS and MMN. Systematic ultrasound measurements of peripheral nerves and the 6th cervical nerve root (C6) were performed in 17 patients with ALS, in 8 patients with MMN and in 28 healthy controls. Nerve conduction studies of corresponding nerves were undertaken in MMN and ALS patients. Electromyography was performed in ALS patients according to revised El-Escorial criteria. ANOVA and unpaired t test with Bonferroni correction revealed significant differences in cross-sectional areas (CSA) of different nerves and C6 diameter between the groups. Nerve enlargement was found significantly more frequently in MMN than in other groups (p < 0.001). Receiver operating characteristics analysis revealed detection of enlarged nerves/roots in at least four measurement points to serve as a good marker to differentiate MMN from ALS with a sensitivity of 87.5% and a specificity of 94.1%. Ultrasonic focal nerve enlargement in MMN was often not colocalized with areas of conduction blocks found in nerve conduction studies. Systematic ultrasound measurements in different nerves and nerve roots are valuable for detecting focal nerve enlargement in MMN, generally not found in ALS and thus could serve as a diagnostic marker to differentiate between both entities in addition to electrodiagnostic studies.

The objective of this study is to evaluate the nerve ultrasound characteristics in genetically distinct inherited neuropathies, the value of the modified ultrasound pattern sum score (mUPSS) to differentiate between the subtypes and the correlation of ultrasound with nerve conduction studies (NCS), disease duration and severity. All patients underwent a standardized neurological examination, ultrasound, and NCS. In addition, genetic testing was performed. Consequently, mUPSS was applied, which is a sum-score of cross-sectional areas (CSA) at predefined anatomical points in different nerves. 31 patients were included (10xCharcot-Marie-Tooth (CMT)1a, 3xCMT1b, 3xCMTX, 9xCMT2, 6xHNPP [Hereditary neuropathy with liability to pressure palsies]). Generalized, homogeneous nerve enlargement and significantly increased UPS scores emphasized the diagnosis of demyelinating neuropathy, particularly CMT1a and CMT1b. The amount of enlargement did not depend on disease duration, symptom severity, height and weight. In CMTX the nerves were enlarged, as well, however, only in the roots and lower limbs, most prominent in men. In CMT2 no significant enlargement was detectable. In HNPP the CSA values were increased at entrapped sites, and not elsewhere. However, a distinction from CMT1, which also showed enlarged CSA values at entrapment sites, was only possible by calculating the entrapment ratios and entrapment score. The mUPSS allowed distinction between CMT1a (increased UPS scores, entrapment ratios <1.0) and HNPP (low UPS scores, entrapment ratios >1.4), while CMT1b and CMTX showed intermediate UPS types and entrapment ratios <1.0. Although based on few cases, ultrasound revealed consistent and homogeneous nerve alteration in certain inherited neuropathies. The modified UPSS is a quantitative tool, which may provide useful information for diagnosis, differentiation and follow-up evaluation in addition to NCS and molecular testing.

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