Short segment sensory nerve stimulation in suspected ulnar neuropathy at the elbow: A pilot study.

INTRODUCTION: Routine ulnar nerve conduction studies may be normal in very mild ulnar neuropathies at the elbow (UNE). Short segment ulnar sensory stimulation across the elbow may detect mild abnormalities in these cases. METHODS: Short segment ulnar sensory nerve stimulation was performed in 20 controls and 15 patients with clinically suspected mild UNE. Greatest peak latency shift and amplitude drop between 2 adjacent stimulation sites were calculated. RESULTS: The upper limit of normal for peak latency shift and amplitude reduction between sites was 0.7 ms and 15%, respectively. Abnormal latency shift was detected in 12 of 15 patients and focal sensory conduction block in 6 of 15 patients. In 5 of 7 patients in whom all other studies were normal, sensory inching was abnormal. DISCUSSION: Ulnar sensory short segment stimulation may provide diagnostic confirmation and localization of the site of nerve compression in mild UNE, and may improve UNE detection when all other studies are normal. Muscle Nerve 59:125-129, 2019.

Needle electromyography and histopathologic correlation in myopathies.

INTRODUCTION: Needle electromyography (EMG) findings help confirm myopathy and may indicate specific pathologic changes on muscle biopsy. METHODS: We conducted a retrospective chart review of 218 consecutive patients referred for muscle biopsy. Presence of specific needle EMG findings was correlated with pathologic findings of inflammation, necrosis, splitting, and vacuolar changes. Sensitivity, specificity, and positive and negative predictive values of specific EMG findings for pathologic changes were calculated. RESULTS: Short-duration motor unit potentials (MUP) were sensitive (83%-94%) but not specific (34%-49%) for pathologic changes. Fibrillation potentials were 65%-74% sensitive and 58%-81% specific for inflammation, necrosis, splitting, or vacuolar changes. The absence of fibrillation potentials had high negative predictive value (82%-93%) for inflammation, splitting, or vacuolar changes. DISCUSSION: Fibrillation potentials and short-duration MUPs predict pathologic changes of muscle fiber necrosis, splitting, and/or vacuolar changes (as seen with inflammatory myopathies and muscular dystrophies). Absence of fibrillation potentials suggests other myopathologic changes (e.g., congenital myopathy). Muscle Nerve 59:315-320, 2019.

A systematic review of Gamma-aminobutyric Acid Receptor Type B autoimmunity.

OBJECTIVE: To review the available research to describe the clinical characteristics and neoplastic associations of patients with gamma-aminobutyric acid receptor type B (GABAB-R) autoantibodies. METHODS: Literature was reviewed on PubMed, Mendeley literature search, and the American Academy of Neurology database for articles published from June 2008 to October of 2018 using a variety of key words. These key words include: "gamma-aminobutyric acid seizures," "gamma-aminobutyric acid limbic encephalitis", "GABA(B) receptor antibodies," "autoimmune encephalitis," "autoimmune epilepsy," "GABA(B) encephalitis, " and "GABA paraneoplastic." With the results, the papers were reviewed in a systematic manner. RESULTS: A total of 10 studies were reviewed. A summary of the demographic, clinical, and serological findings of the cases detailed in the literature are provided. An additional illustrative case is described. In total, 94 patients were reviewed. CONCLUSIONS: GABAB-R autoimmune disease is characterized by refractory seizures or status epilepticus and frequent association with small cell lung cancer. Additionally, a substantial minority of patients have non-inflammatory CSF.

Eosinophilic fasciitis with subjacent myositis.

INTRODUCTION: Eosinophilic fasciitis (EF) is a rare disorder that can present with muscle symptoms that mimic other neuromuscular diseases. METHODS: We report the case of a 43-year-old woman with chronic muscle aches, tightness, and stiffness with hypertrophied, well-defined muscles despite physical inactivity, and thickened skin with reduced elasticity and discoloration. RESULTS: Except for mild peripheral eosinophilia, laboratory studies, including blood count, electrolytes, paraneoplastic panel, muscle enzymes, thyroid function, and serum protein electrophoresis, were normal. Nerve conduction studies and needle electromyography were normal. Magnetic resonance imaging of the thighs demonstrated superficial and deep fascial thickening with T2 hyperintensity and post-gadolinium enhancement. Fascial and muscle biopsy demonstrated an inflammatory exudate in the perimysium and endomysium with fragmented perimysial connective tissue and thickened, inflamed fascia. EF was diagnosed. The patient was treated with methotrexate and prednisone followed by improvement of muscle stiffness and tightness. CONCLUSION: EF should be considered when patients present with muscle pain or enlarged muscles. Muscle Nerve 56: 525-529, 2017.

Utility of minimum F-wave latencies compared with F-estimates and absolute reference values in S1 radiculopathies: are they still needed?

INTRODUCTION: 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.

Improving referring physicians' understanding of electromyography reports when qualifying radiculopathies: a need for standardized terminology.

Electromyographic (EMG) reporting of radiculopathies is not standardized, and the terminology used in reports can be misinterpreted by referring physicians. Physicians who refer patients for EMG studies at the Mayo Clinic were surveyed about their understanding of 6 different EMG interpretations of an S1 radiculopathy. Of 45 responders, the terms "acute, active," "chronic, inactive," and "old" were interpreted consistently by 95%, 98%, and 84% of responders, respectively. Physicians had the most difficulty understanding the meaning of "chronic" in isolation, "chronic, active," or "old with uncompensated denervation." These findings suggest a need to educate referring physicians on the meaning of the terms used in EMG reports and to develop standard guidelines for qualifying radiculopathies. Based on our observations, guidelines for the reporting of radiculopathies have been adopted in the Mayo Clinic Florida EMG laboratory.

The effect of paired stimuli on blink reflex latencies in normal subjects.

INTRODUCTION: In this study we assessed the effect of paired stimuli on the latencies and amplitudes of the blink reflex. METHODS: Blink reflexes were performed with single and paired (5-ms interstimulus interval) stimuli in 47 patients. The changes in latencies between paired and single stimuli were calculated. RESULTS: Paired stimulation produced two types of R1 waveform morphologies: single- and double-peaked waveforms. Increases in R1 and contralateral R2 latencies with paired stimulation were significantly higher in those with single-peaked R1 responses compared to those with double-peaked R1 responses. CONCLUSIONS: Interpreting the blink reflex latencies using paired stimulation requires visualization of the R1 waveform morphology. A double-peaked R1 response requires no change in normal latency values, but the latency of a single-peaked R1 should be interpreted from the second shock artifact. The effect on the R2 latency is variable.

The office evaluation of weakness.

The office evaluation of weakness can be a daunting task. Many different disorders affecting many different parts of the nervous system can manifest with "weakness," and several nonneurologic conditions may present with complaints of weakness. It is the job of the neurologist to determine whether a patient has neurologic weakness or suffers simply from fatigue. The physician then must properly localize the pathophysiologic site of weakness. The author focuses on neuromuscular causes of weakness affecting muscle, the neuromuscular junction, peripheral nerve, or the anterior horn cell. General historical and examination clues to localization will be discussed. A localization-based evaluation will be outlined, with more specific recommendations regarding the evaluation of a few specific disorders offered. Localization-specific laboratory, electrodiagnostic, imaging, and pathologic investigations will be presented.

Two Years of Improved Neurological Function With Nusinersen in a 48-Year-Old Patient With Spinal Muscular Atrophy Type 3.

INTRODUCTION: Nusinersen antisense oligonucleotide infusions have been shown to be effective in the treatment spinal muscular atrophy. The majority of the evidence has been collected in young type 1 and type 2 patients, and evidence of efficacy in adult patients is limited. CASE REPORT: A 48-year-old woman with spinal muscular atrophy type 3 who has received the loading dose and 8 maintenance infusions over an 8-month period. Grip and pinch strength, measured by hand-held dynamometry measured at baseline and in 6 to 12 months interval improved over a 24-month period. She also reported multiple other subjective improvements in function. CONCLUSIONS: This is the first published case of nusinersen in a middle-aged adult with spinal muscular atrophy. Sustained clinically meaningful improvement may be possible with nusinersen initiation in mid adulthood.

Diagnostic modelling and therapeutic monitoring of immune-mediated necrotizing myopathy: role of electrical myotonia.

Delayed diagnosis of immune-mediated necrotizing myopathy leads to increased morbidity. Patients with the chronic course without 3-hydroxy-3-methylglutaryl-coenzyme-A reductase-IgG or signal recognition particle-IgG are often challenging to diagnose. Immunotherapy response can also be difficult to assess. We created a statistical model to assist immune-mediated necrotizing myopathy diagnosis. Electrical myotonia versus fibrillations were reviewed as biomarkers for immunotherapy treatment response. Identified were 119 immune-mediated necrotizing myopathy cases and 938 other myopathy patients. Inclusion criteria included all having electrophysiological evaluations, muscle biopsies showing inflammatory/necrotizing myopathies, comprehensively recorded neurological examinations, and creatine kinase values. Electrical myotonia was recorded in 56% (67/119) of retrospective and 67% (20/30) of our validation immune-mediated necrotizing myopathy cohorts, and significantly (P < 0.001) favoured immune-mediated necrotizing myopathy over other myopathies: sporadic inclusion body myositis (odds ratio = 4.78); dermatomyositis (odds ratio = 10.61); non-specific inflammatory myopathies (odds ratio = 8.46); limb-girdle muscular dystrophies (odds ratio = 5.34) or mitochondrial myopathies (odds ratio = 14.17). Electrical myotonia occurred in immune-mediated necrotizing myopathy seropositive (3-hydroxy-3-methylglutaryl-coenzyme-A reductase-IgG 70%, 37/53; signal recognition particle-IgG 29%, 5/17) and seronegative (51%, 25/49). Multivariate regression analysis of 20 variables identified 8 (including electrical myotonia) in combination accurately predicted immune-mediated necrotizing myopathy (97.1% area-under-curve). The model was validated in a separate cohort of 30 immune-mediated necrotizing myopathy cases. Delayed diagnosis of cases with electrical myotonia occurred in 24% (16/67, mean 8 months; range 0-194). Half (8/19) had a chronic course and were seronegative, with high model prediction (>86%) at the first visit. Inherited myopathies were commonly first suspected in them. Follow-up evaluation in patients with electrical myotonia on immunotherapy was available in 19 (median 21 months, range 2-124) which reduced from 36% (58/162) of muscles to 7% (8/121; P < 0.001). Reduced myotonia correlated with immunotherapy response in 64% (9/14) as well as with median creatine kinase reduction of 1779 U/l (range 401-9238, P < 0.001). Modelling clinical features with electrical myotonia is especially helpful in immune-mediated necrotizing myopathy diagnostic suspicion among chronic indolent and seronegative cases. Electrical myotonia favours immune-mediated necrotizing myopathy diagnosis and can serve as an adjuvant immunotherapy biomarker.

Needle EMG of Thenar Muscles in Less Severe Carpal Tunnel Syndrome.

INTRODUCTION: The value of needle electromyography (EMG) in thenar muscles in patients with less severe carpal tunnel syndrome is controversial. METHODS: Patients referred for electrodiagnostic testing for carpal tunnel syndrome, in which nerve conduction study demonstrated median sensory nerve conduction study abnormalities and either normal median motor nerve conduction study or only prolonged median motor distal latencies (DLs) (with normal amplitudes) were prospectively studied. Patients with low-median compound muscle action potential amplitudes or any other EMG abnormality were excluded. Needle EMG of a thenar muscle was performed to assess for the presence and grade of fibrillation potentials and motor unit potential abnormalities. The frequency of abnormalities was recorded. Statistical comparison between patients with and without needle EMG abnormalities was performed. RESULTS: One-hundred two patients were included (50 with normal median motor DLs and 52 with abnormal DLs). Minimal or equivocal thenar needle EMG abnormalities were found in 12% of subjects with normal DLs. In patients with abnormal DLs, 32.6% had abnormalities, 15.4% with a mild degree of fibrillation potentials, and 25.0% with mild motor unit potential abnormalities. Patients with abnormal DLs and needle EMG abnormalities had significantly lower compound muscle action potential amplitudes compared to those without needle EMG changes. CONCLUSIONS: Patients with carpal tunnel syndrome with no involvement of the median motor nerve conduction study are unlikely to demonstrate prominent abnormalities on needle EMG of thenar muscles, and needle EMG of the thenar muscles is not necessary. However, in patients with carpal tunnel syndrome in which the median motor DL is prolonged but compound muscle action potential amplitudes are absolutely normal, needle EMG should be considered, as it may provide value in indicating some axonal loss despite a normal median compound muscle action potential amplitude.

Rheumatology and Neurology.

PURPOSE OF REVIEW: This article reviews the various rheumatologic disorders that have neurologic complications and manifestations. RECENT FINDINGS: Recent advances have improved the understanding of the true epidemiology of many rheumatologic diseases and their complications. Many years of observation have clarified findings even in rarer disorders. Classification and diagnostic criteria have been updated and validated. As newer pharmacologic agents have become available, new information regarding efficacy and toxicity has emerged. SUMMARY: Rheumatologic disorders are common, as can be their neurologic complications. In many instances, these complications are treatable, but clinicians' understanding of the underlying disorder, its neurologic risks, and the risk of therapy is required.

Whole Exome Sequencing Identifies Atypical Welander Distal Myopathy in Patient.

Welander distal myopathy is a rare autosomal dominant disorder characterized by muscle weakness in the hands and feet. Exome sequencing of affected families discovered a segregating p.Glu384Lys pathogenic variant in TIA-1 as the main genetic cause of Welander distal myopathy. TIA-1 encodes an RNA-binding protein which serves as a key component of stress granules. This protein also regulates splicing and translation of mRNA. Our patient developed progressive weakness in his hands and feet during his late 40s that was misdiagnosed as a neuropathy that caused muscle atrophy. Follow-up genetic testing revealed a p.Glu384Lys pathogenic variant in TIA-1, and he was then diagnosed with Welander distal myopathy. Our case report underlines the importance of electrodiagnostic and genetic testing of patients.

Whole exome sequencing of a patient with suspected mitochondrial myopathy reveals novel compound heterozygous variants in RYR1.

BACKGROUND: Pathogenic variants in ryanodine receptor 1 (RYR1, MIM# 180901) are the cause of congenital myopathy with fiber-type disproportion, malignant hyperthermia susceptibility type 1, central core disease of muscle, multiminicore disease and other congenital myopathies. METHODS: We present a patient with global developmental delay, hypotonia, myopathy, joint hypermobility, and multiple other systemic complaints that were noted early in life. Later she was found to have multiple bone deformities involving her spine, with severe scoliosis that was corrected surgically. She was also diagnosed with ophthalmoplegia, chronic hypercapnic respiratory failure, and hypertension. At 22 years of age she presented to the genetics clinic with a diagnosis of mitochondrial myopathy and underwent whole exome sequencing (WES). RESULTS: Whole exome sequencing revealed two novel compound heterozygous variants in RYR1 (c.7060_7062del, p.Val2354del and c.4485_4500del, p.Tyr1495X). CONCLUSION: Review of her clinical, pathologic, and genetic findings pointed to a diagnosis of a congenital myopathy with fiber-type disproportion.

Novel myelin protein zero mutation (Arg36Trp) in a patient with acute onset painful neuropathy.

We present a patient with acute onset painful polyneuropathy found to have a novel MPZ mutation (Arg36Trp). The Arg36Trp mutation described in this report occurs at a putative adhesion interface. An alternative explanation for his polyneuropathy was not found and his mother was identified to have polyneuropathy and carry the same mutation. Two hundred normal controls were without this base alteration. The temporal profile of the index case may provide further indirect evidence suggesting an immune mechanism contributing to the pathogenesis of some cases of MPZ mutations. We predict that other rapid symptom onset polyneuropathies will be found to have direct genetic susceptibility.

Whole Exome Sequencing Leading to the Diagnosis of Dysferlinopathy with a Novel Missense Mutation (c.959G>C).

Dysferlinopathy is an uncommon, progressive muscular dystrophy that has a wide phenotypic variability and primarily supportive management (Nguyen et al., 2007; Narayanaswami et al., 2014). Amyloid myopathy is a distinct, rare disorder that can present similarly to inflammatory myopathies and requires a high clinical suspicion for early intervention to prolong survival. Amyloid myopathy is typically associated with other systemic manifestations of amyloidosis, but rare cases of isolated amyloid myopathy have been described (Mandl et al., 2000; Hull et al., 2001). Positive Congo red stains on tissue biopsy remain the gold standard for diagnosis (Spuler et al., 1998; Karacostas et al., 2005). A high clinical suspicion and meticulous diagnostic workup that includes novel techniques are necessary for identifying these rare disorders. We report a middle-aged man with progressive leg muscle weakness who was initially treated as having amyloid myopathy but was later diagnosed as having dysferlinopathy by Whole Exome Sequencing (WES) analysis. We also report a novel missense mutation (c.959G>C) to help correlate in any patient with presumed dysferlinopathy and to add to the already known genotype of this disorder.