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Clinical, laboratory and electrodiagnostic studies are the mainstay in the diagnosis of polyneuropathy. An accurate etiological diagnosis is of paramount importance to provide the appropriate treatment, prognosis and genetic counselling. High resolution sonography of the peripheral nervous system allows nerves to be readily visualized and to assess their morphology. Ultrasonography has brought pathophysiological insights and substantially added to diagnostic accuracy and treatment decisions amongst mononeuropathies. In this study the literature on its clinical application in polyneuropathy is reviewed. Several polyneuropathies have been studied by means of ultrasound: Charcot-Marie-Tooth, hereditary neuropathy with liability to pressure palsies, chronic inflammatory demyelinating polyneuropathy, Guillain-Barré syndrome, multifocal motor neuropathy, paraneoplastic polyneuropathy, leprosy and diabetic neuropathy. The most prominent reported pathological changes were nerve enlargement, increased hypo-echogenicity and increased intraneural vascularization. Sonography revealed intriguingly different patterns of nerve enlargement between inflammatory neuropathies and axonal and inherited polyneuropathies. However, many studies concerned case reports or case series and showed methodological shortcomings. Further prospective studies with standardized protocols for nerve sonography and clinical and electrodiagnostic testing are needed to determine the role of nerve sonography in inherited and acquired polyneuropathies.

Objective:We assessed longitudinal patterns of muscle strength, motor function and maximal compound muscle action potential amplitudes (CMAPMAX) in older patients with spinal muscular atrophy (SMA), hypothesizing a continued decline of motor function parameters throughout life.Methods:We measured muscle strength (Medical Research Council, MRC), motor function (Hammersmith Functional Motor Scale Expanded (HFMSE) and Motor Function Measure (MFM)), and CMAPMAX in treatment-naïve patients. We used both longitudinal and cross-sectional data in mixed-models to analyze natural history patterns.Results:We included 250 patients with SMA types 1c–4. Median patient age at assessment was 26.8 years, the number of assessments per patient ranged from 1 to 6. Baseline muscle strength and motor function scores differed significantly between SMA types, but annual rates of decline were largely similar and mostly linear. HFMSE floor effects were present for all patients with SMA type 1c, and adolescents and adults with types 2 and 3a. CMAPMAX differed significantly between SMA types, but did not decline significantly with increasing age. Muscle strength correlated very strongly with motor function (τ > 0.8), but only moderately with CMAPMAX (τ ≈ 0.5–0.6).Conclusion:Muscle strength and motor function decline in older patients with SMA are constant without periods of slower progression or a plateau phase. The floor effects of the HFMSE preclude its use for long-term follow-up of adult patients with SMA types 1c–3a. Muscle strength sum scores represent an alternative, feasible outcome measure for adolescent and adult patients with SMA.

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