Dimberg, Elliot L.

ABSTRACTIntroduction: The utility of F‐waves in assessing radiculopathies is debated. The aim of this study is to determine the frequency of abnormal minimum tibial F‐wave latencies compared to an F‐estimate and an absolute reference value in patients with electromyography (EMG) confirmed S1 radiculopathies. Methods: A retrospective review of F‐waves in patients with an EMG‐confirmed isolated S1 radiculopathy was performed. The minimum and mean latencies of 8 tibial F‐waves were compared with the calculated F‐estimate and to an absolute reference value, and the frequencies of abnormal responses were determined. Results: Of the 50 patients with an S1 radiculopathy, 4% had prolongation of the minimum reproducible F‐wave latency, and 8% had prolongation of the mean latency relative to the calculated F‐estimate. Conclusions: The minimum and mean F‐wave latencies are infrequently abnormal when compared with an estimated F‐wave latency in S1 radiculopathies and are insensitive in the assessment of S1 nerve root injury. Muscle Nerve 49: 809–813, 2014

Background and purposeAnoctamin 5 (ANO5) is a putative intracellular calcium‐activated chloride channel. Recessive mutations in ANO5 cause primary skeletal muscle disorders (limb‐girdle muscular dystrophy 2L and distal muscular dystrophy), which are phenotypically similar to dysferlinopathy, a muscular dystrophy due to dysferlin‐encoding gene (DYSF) mutations.MethodsThis study reports the phenotype and genotype of seven unrelated patients with ANO5‐muscular dystrophy.ResultsThree patients had amyloid deposition in muscle and two had cardiac involvement. An additional patient without skeletal muscle amyloidosis had cardiac involvement with septal hypokinesis and supraventricular tachycardia requiring ablation. Amyloid subtyping using laser capture microdissection and mass spectrometry‐based proteomic analysis did not identify ANO5 or any fragment of ANO5 in the amyloid deposits, but detected other known amyloidogenic proteins. Three patients had myotonic discharges without clinical myotonia. Four ANO5 mutations are novel, including a heterozygous 0.4 Mb deletion involving the entire ANO5 gene.ConclusionsThe results of the present study suggest that ANO5 mutations can be associated with amyloid deposition in muscle, but the nature of the amyloid deposits remains indeterminate, as does their relationship with cardiac involvement. ANO5 analysis should be considered in cases of muscle amyloid deposition of indeterminate etiology. Electrical myotonia can accompany ANO5‐muscular dystrophy.

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