Sorenson, Eric J.

We retrospectively reviewed 2030 childhood electromyograms performed over an 11-year period (2004-2014). Twenty children (1%) with myotonic discharges were identified and placed into 2 groups. Group A (electrical and clinical myotonia) comprised 9 children (8 with myotonia congenita and 1 with paramyotonia congenita); all of them had diffuse myotonic discharges without clinical weakness or elevated creatine kinase. Group B (electrical myotonia without clinical myotonia) comprised 11 children (4 with inflammatory myopathy; 3, congenital myopathy, 3, muscular dystrophy; and 1, congenital muscular dystrophy). Clinical weakness was demonstrated in all of them and elevated creatine kinase in 6; all had a myopathic electromyogram and scattered myotonic discharges. We conclude that myotonic discharges are a rare but characteristic spontaneous discharge identified during electrodiagnostic studies in children. The presence of electrical and clinical myotonia provides helpful clues to differentiate between various muscle disorders in children.

Background and purposeTo describe speech, neurological and imaging characteristics of a series of patients presenting with progressive spastic dysarthria as the first and predominant sign of a presumed neurodegenerative disease.MethodsParticipants were 25 patients with spastic dysarthria as the only or predominant speech disorder. Clinical features, pattern of MRI volume loss on voxel‐based morphometry and pattern of hypometabolism on F18‐fluorodeoxyglucose positron emission tomography (FDG‐PET) scan are described.ResultsAll patients demonstrated speech characteristics consistent with spastic dysarthria, including strained voice quality, slow speaking rate, monopitch and monoloudness, and slow and regular speech alternating motion rates. Eight patients did not have additional neurological findings on examination. Pseudobulbar affect, upper motor neuron pattern limb weakness, spasticity, Hoffman sign and positive Babinski reflexes were noted in some of the remaining patients. Twenty‐three patients had electromyographic assessment and none had diffuse motor neuron disease or met El Escorial criteria for amyotrophic lateral sclerosis. Voxel‐based morphometry revealed striking bilateral white matter volume loss affecting the motor cortex (BA 4), including the frontoparietal operculum (BA 43) with extension into the middle cerebral peduncle. FDG‐PET showed subtle hypometabolism affecting the premotor and motor cortices in some patients, particularly in those who had a disease duration longer than 2 years.ConclusionsA neurodegenerative disorder that begins focally with spastic dysarthria due to involvement of the motor and premotor cortex and descending corticospinal and corticobulbar pathways is characterized. The descriptive label ‘progressive spastic dysarthria’ to best capture the dominant presenting feature of the syndrome is proposed.

ABSTRACTIntroduction: Repetitive discharges may be recorded during nerve conduction studies (NCS) or during needle electromyography in a muscle at rest. Repetitive discharges that occur during voluntary activation and are time‐locked to voluntary motor unit potentials (MUP) have not been described. Methods: Retrospective review of motor unit potential induced repetitive discharges (MIRDs) identified in the EMG laboratory. Characteristics of each MIRD, patient demographics, other EMG findings in the same muscle, and electrophysiological diagnosis were analyzed. Results: MIRDs were observed in 15 patients. The morphology and number of spikes and duration of MIRDs varied. The discharges fired at rates of 50–200 Hz. All but 2 patients had EMG findings of a chronic neurogenic disorder. Conclusions: MIRDs are rare iterative discharges time‐locked to a voluntary MUP. The pathophysiology of MIRDs is unclear, but their presence may indicate a chronic neurogenic process. Muscle Nerve 48: 977–979, 2013

ABSTRACTIntroduction: Needle electromyography (EMG) of the diaphragm carries the potential risk of pneumothorax. Knowing the approximate depth of the diaphragm should increase the test's safety and accuracy. Methods: Distances from the skin to the diaphragm and from the outer surface of the rib to the diaphragm were measured using B mode ultrasound in 150 normal subjects. Results: When measured at the lower intercostal spaces, diaphragm depth varied between 0.78 and 4.91 cm beneath the skin surface and between 0.25 and 1.48 cm below the outer surface of the rib. Using linear regression modeling, body mass index (BMI) could be used to predict diaphragm depth from the skin to within an average of 1.15 mm. Conclusions: Diaphragm depth from the skin can vary by more than 4 cm. When image guidance is not available to enhance accuracy and safety of diaphragm EMG, it is possible to reliably predict the depth of the diaphragm based on BMI. Muscle Nerve 49: 666–668, 2014

Introduction : Real time ultrasound imaging of the diaphragm is an under‐used tool in the evaluation of patients with unexplained dyspnea or respiratory failure. Methods : We measured diaphragm thickness and the change in thickness that occurs with maximal inspiration in 150 normal subjects, with results stratified for age, gender, body mass index, and smoking history. Results : The lower limit of normal diaphragm thickness at end expiration or functional residual capacity is 0.15 cm, and an increase of at least 20% in diaphragm thickness from functional residual capacity to total lung capacity is normal. A side to side difference in thickness at end expiration of > 0.33 cm is abnormal. Diaphragm thickness and contractility are minimally affected by age, gender, body habitus, or smoking history. Conclusions : This study confirms previous findings in much smaller groups of normal controls for quantitative ultrasound of the diaphragm and provides data that can be applied widely to the general population. Muscle Nerve 47: 884–889, 2013

Introduction: Median nerve ultrasound shows increased cross‐sectional area (CSA) in carpal tunnel syndrome (CTS) and diabetic peripheral neuropathy (PN). The role of ultrasound in diagnosing CTS superimposed on diabetic PN is unknown. The objective of this study is to evaluate ultrasound for diagnosis of CTS in diabetic PN. Methods: Prospective recruitment of diabetics with electrodiagnostically proven PN, subdivided into cases (with CTS) or controls (without CTS). The gold standard for CTS was clinical diagnosis. NCS were correlated with blinded median nerve CSA ultrasound measurements. Results: Eight cases (CTS) and eight controls (no CTS) were recruited. Nerve conduction studies (NCS): Median nerve distal latencies (antidromic sensory; palmar; lumbrical motor; and lumbrical motor to ulnar interosseous difference) were significantly prolonged in CTS cases. No ultrasound measurement (distal median CSA, wrist‐forearm ratio, wrist‐forearm difference) reached significance to detect CTS. Area under the curve was greatest for lumbrical distal latency by receiver operator characteristic analysis (0.85). Conclusions: In this pilot study, NCS may be superior to ultrasound for identification of superimposed CTS in diabetic PN patients, but larger numbers are needed for confirmation. Muscle Nerve 47: 437–439, 2013