Electrodiagnostic Testing for Carpal Tunnel Syndrome When Routine Median Sensory and Thenar Motor Responses Are Absent.

PURPOSE: The cardinal symptoms of carpal tunnel syndrome (CTS) include pain in the affected hand(s). The median/second lumbrical nerve (Med2ndL) seems relatively preserved in severe CTS, with previous small studies suggesting its value in electromyogram to localize a median neuropathy to the wrist when both initial routine sensory and thenar motor responses are absent. METHODS: This is a retrospective analysis of 208 hands in 183 patients with electrophysiologically markedly severe CTS (absent routine sensory and thenar motor median responses) who underwent stimulation of both the Med2ndL and ulnar/second dorsal interosseous (Uln2ndDIn) motor nerves. A Med2ndL distal latency of ≥ 0.5 milliseconds when compared with the Uln2ndDIn supported the diagnosis of CTS. The presence or absence of hand pain was recorded if these data were available. RESULTS: Some 83.7% of hands (172/208) in 183 patients with markedly severe CTS had preservation of the Med2ndL meeting criteria for CTS. In those with pain data available, 77.1% (81/105) of hands had no pain. Of those 105 hands, 87 had preservation of the Med2ndL with 79.3% (69/87) demonstrating no pain. CONCLUSIONS: This is a large study that demonstrates the relative preservation of the Med2ndL response in markedly severe CTS. Assessment of the Med2ndL should be considered to electrophysiologically support CTS when routine sensory and thenar motor responses are absent. In addition, most patients with electrophysiologically markedly severe CTS had no pain.

AANEM - IFCN glossary of terms in neuromuscular electrodiagnostic medicine and ultrasound.

Modern neuromuscular electrodiagnosis (EDX) and neuromuscular ultrasound (NMUS) require a universal language for effective communication in clinical practice and research and, in particular, for teaching young colleagues. Therefore, the AANEM and the IFCN have decided to publish a joint glossary as they feel the need for an updated terminology to support educational activities in neuromuscular EDX and NMUS in all parts of the world. In addition NMUS has been rapidly progressing over the last years and is now widely used in the diagnosis of disorders of nerve and muscle in conjunction with EDX. This glossary has been developed by experts in the field of neuromuscular EDX and NMUS on behalf of the AANEM and the IFCN and has been agreed upon by electronic communication between January and November 2019. It is based on the glossaries of the AANEM from 2015 and of the IFCN from 1999. The EDX and NMUS terms and the explanatory illustrations have been updated and supplemented where necessary. The result is a comprehensive glossary of terms covering all fields of neuromuscular EDX and NMUS. It serves as a standard reference for clinical practice, education and research worldwide.

AANEM - IFCN Glossary of Terms in Neuromuscular Electrodiagnostic Medicine and Ultrasound.

Modern neuromuscular electrodiagnosis (EDX) and neuromuscular ultrasound (NMUS) require a universal language for effective communication in clinical practice and research and, in particular, for teaching young colleagues. Therefore, the AANEM and the IFCN have decided to publish a joint glossary as they feel the need for an updated terminology to support educational activities in neuromuscular EDX and NMUS in all parts of the world. In addition NMUS has been rapidly progressing over the last years and is now widely used in the diagnosis of disorders of nerve and muscle in conjunction with EDX. This glossary has been developed by experts in the field of neuromuscular EDX and NMUS on behalf of the AANEM and the IFCN and has been agreed upon by electronic communication between January and November 2019. It is based on the glossaries of the AANEM from 2015 and of the IFCN from 1999. The EDX and NMUS terms and the explanatory illustrations have been updated and supplemented where necessary. The result is a comprehensive glossary of terms covering all fields of neuromuscular EDX and NMUS. It serves as a standard reference for clinical practice, education and research worldwide. HIGHLIGHTS: Optimal terminology in neuromuscular electrodiagnosis and ultrasound has been revisited. A team of international experts have revised and expanded a standardized glossary. This list of terms serves as standard reference for clinical practice, education and research.

Novel biallelic variants in MSTO1 associated with mitochondrial myopathy.

Mitochondrial disorders are caused by nuclear and mitochondrial pathogenic variants leading to defects in mitochondrial function and cellular respiration. Recently, the nuclear-encoded mitochondrial fusion gene MSTO1 (Misato 1) has been implicated in mitochondrial myopathy and ataxia. Here we report on a 30-yr-old man presenting with a maternally inherited NM_018116.3:c.651C>G, p.F217L missense variant as well as a paternally inherited arr[GRCh37] 1q22(155581773_155706887) × 1 deletion encompassing exons 7-14 of MSTO1 His phenotype included muscle weakness, hypotonia, early motor developmental delay, pectus excavatum, and scoliosis. Testing revealed elevated plasma creatine kinase, and electromyogram results were consistent with longstanding generalized myopathy. These phenotypic features overlap well with previously reported patients harboring biallelic MSTO1 variants. Additionally, our patient presents with dysphagia and restrictive lung disease, not previously reported for MSTO1-associated disorders. The majority of patients with disease-associated variants in MSTO1 present with biallelic variants suggesting autosomal recessive inheritance; however, one family has been reported with a single variant and presumed autosomal dominant inheritance. The pattern of inheritance we observed is consistent with the majority of previous reports suggesting an autosomal recessive disorder. We add to our knowledge of the syndrome caused by variants in MSTO1 and provide additional evidence supporting autosomal recessive inheritance. We also describe phenotypic features not reported in previous cases, although further research is needed to confirm they are associated with defects in MSTO1.

A case of YY1-associated syndromic learning disability or Gabriele-de Vries syndrome with myasthenia gravis.

Exome sequencing is being used increasingly to evaluate patients with intellectual disability. YY1 is a ubiquitously distributed transcription factor belonging to the GLIKruppel class of zinc finger proteins recently recognized as the causative gene in 23 patients for the Gabriele-de Vries syndrome. We report a new case with similar features and a novel variant in YY1, in a region of the gene, which has not previously been reported. A 25 year old female was referred to clinical genetics with a diagnosis of autoimmune myasthenia gravis, facial dysmorphism and learning disability. Chromosomal microarray and gene panel test for congenital myasthenic syndrome was negative. Whole exome sequencing (WES) revealed a presumed pathogenic de novo novel, heterozygous, truncating variant in the YY1 gene, c.860_864delTTAAAA, p.Ile287Argfs*3. The Ile287 residue is conserved across species and is situated in the transcription repressor domain of the protein. This variant is novel and lies in a domain of the protein where no previously reported variants occur. The phenotypic features of our case closely match those of the reported patients. Autoimmune myasthenia gravis has not been reported in these patients and may constitute an expansion of this phenotypic spectrum or perhaps more likely a second unrelated diagnosis.

Electrophysiology of Cranial Nerve Testing: Spinal Accessory and Hypoglossal Nerves.

Multiple techniques have been developed for the electrodiagnostic evaluation of cranial nerves XI and XII. Each of these carries both benefits and limitations, with more techniques and data being available in the literature for spinal accessory than hypoglossal nerve evaluation. Spinal accessory and hypoglossal neuropathy are relatively uncommon cranial mononeuropathies that may be evaluated in the outpatient electrodiagnostic laboratory setting. A review of available literature using PubMed was conducted regarding electrodiagnostic technique in the evaluation of spinal accessory and hypoglossal nerves searching for both routine nerve conduction studies and repetitive nerve conduction studies. The review provided herein provides a resource by which clinical neurophysiologists may develop and implement clinical and research protocols for the evaluation of both of these lower cranial nerves in the outpatient setting.

Complete dislocation of the ulnar nerve at the elbow: a protective effect against neuropathy?

INTRODUCTION: Recurrent complete ulnar nerve dislocation has been perceived as a risk factor for development of ulnar neuropathy at the elbow (UNE). However, the role of dislocation in the pathogenesis of UNE remains uncertain. METHODS: We studied 133 patients with complete ulnar nerve dislocation to determine whether this condition is a risk factor for UNE. In all, the nerve was palpated as it rolled over the medial epicondyle during elbow flexion. RESULTS: Of 56 elbows with unilateral dislocation, UNE localized contralaterally in 17 elbows (30.4%) and ipsilaterally in 10 elbows (17.9%). Of 154 elbows with bilateral dislocation, 26 had UNE (16.9%). Complete dislocation decreased the odds of having UNE by 44% (odds ratio = 0.475; P = 0.028), and was associated with less severe UNE (P = 0.045). CONCLUSIONS: UNE occurs less frequently and is less severe on the side of complete dislocation. Complete dislocation may have a protective effect on the ulnar nerve. Muscle Nerve 56: 242-246, 2017.

Hypoglossal nerve palsy: 245 cases.

INTRODUCTION: Apart from a case series of 100 subjects in 1996 and several small cohorts, there have been no large retrospective series of cranial nerve XII (CN XII) palsy. METHODS: From 1984 to 2014, 245 cases of CN XII palsy were identified via retrospective chart review using historical and exam findings that confirmed the diagnosis. In addition to clinical characteristics, univariate and multivariate models were investigated to predict neoplastic CN XII palsy. RESULTS: Major etiologic categories included: postoperative (29.3%), idiopathic (15.1%), primary neoplastic (14.2%), metastatic malignancy (13.0%), inflammatory (7.3%), radiation (6.1%), and traumatic (4.1%). A multivariate model revealed male gender and a personal history of cancer as predictive of neoplastic CN XII palsy. CONCLUSIONS: The most frequent etiologies and disease categories of CN XII palsy were identified, and male gender and personal history of cancer were found to be predictive of a neoplastic cause of CN XII palsy. Muscle Nerve 54: 1050-1054, 2016.

Focal and entrapment neuropathies.

Of the many patterns of peripheral nerve disorders in diabetes mellitus (DM), isolated clinical involvement of single nerves, though less common than distal symmetric polyneuropathy and perhaps polyradiculoneuropathy, constitute an important collection of characteristic syndromes. These fall into four anatomical regions of the body: cranial, upper limb, truncal, and lower limb territories. Each of these groups of mononeuropathies has its own ensemble of epidemiologic patterns, clinical presentations, laboratory and radiologic findings, differential diagnosis, management principles and prognosis.

Acute hypoxic hypoxia and isocapnic hypoxia effects on oculometric features.

INTRODUCTION: Visual performance impairment after hypoxia is well recognized in military and civilian aviation. The aims of this study were: 1) to assess oculometric features such as blink metrics, pupillary dynamics, fixations, and saccades as cognitive indicators of early signs of hypoxia; and 2) to analyze the impact of different hypoxic conditions ["hypoxic hypoxia" (HH) and "isocapnic hypoxia" (IH)] on specified oculometrics during mental workloads. METHODS: Oculometric data were collected on 25 subjects under 3 conditions: normoxia, HH (8% O2 + balance N2), and IH (7% O2 + 5% CO2 + balance N2). The mental workload task consisted of reading aloud linear arrays of numbers after exposure to gas mixtures. RESULTS: Blink rates were significantly increased under hypoxic conditions (by +100.7% in HH and by +92.8% in IH compared to normoxia). A faster recovery of blink rate was observed in transitioning from IH (23.6% vs. 76.3%) to normoxia. The percentage change in pupil size fluctuation was increased under HH more than under IH (29% vs. 4.4%). Under HH average fixation time and target area size were significantly higher than under IH. Total saccadic times under hypoxic conditions were significantly increased compared with normoxia. CONCLUSIONS: These results suggest that oculometric changes are indicators of hypoxia, which can be monitored using compact, portable, noninvasive eye-tracking devices in a cockpit analogous environment to detect hypoxia-induced physiological changes in aircrew. Comparative results between HH and IH support the potential role of carbon dioxide in augmenting cerebral perfusion and hence improved tissue oxygen delivery.

Quality improvement in neurology: Distal symmetric polyneuropathy quality measures.

Peripheral neuropathy is a common neurologic disorder, affecting 2% to 8% of the population in population-based studies with confirmation by neurologist examination. These prevalence numbers are remarkably stable across developed countries. In 1999, 8.6% of Medicare beneficiaries had neuropathy as a primary or secondary diagnosis, and the cost of treatment was estimated at $3.5 billion (Consumer Price Index adjusted to 2013 $4.9 billion), which did not include outpatient medications. Peripheral neuropathy has many causes and varies in regard to its clinical manifestations and severity. Distal symmetric polyneuropathy (DSP) is the most common pattern of peripheral neuropathy generally and the most common phenotype of neuropathy due to diabetes. Reported prevalence rates of DSP among diabetic patients range from 15% to 37% across large population-based studies, and the prevalence among those with impaired glucose tolerance has been reported to be 11%. DSP can result in weakness, sensory loss, pain, autonomic dysfunction, gait impairment, falls, disability, and impaired quality of life.

Early detection of hypoxia-lnduced cognitive impairment using the King-Devick test.

INTRODUCTION: Hypoxic incapacitation continues to be a significant threat to safety and operations at high altitude. Noninvasive neurocognitive performance testing is desirable to identify presymptomatic cognitive impairment, affording operators at altitude a tool to quantify their performance and safety. METHODS: There were 25 subjects enrolled in this study. Cognitive performance was assessed by using the King-Devick (K-D) test. The performance of the subjects on the K-D test was measured in normoxia followed by hypoxia (8% 02 equivalent to 7101 m) and then again in normoxia. RESULTS: K-D test completion time in hypoxia for 3 min was significantly longer than the Baseline Test (54.5 +/- 12.4 s hypoxic vs. 46.3 +/- 10.4 s baseline). Upon returning to normoxia the completion time was significantly shorter than in hypoxia (47.6 +/- 10.6 s post test vs. 54.5 +/- 12.4 s hypoxic). There was no statistically significant difference between baseline test and post test times, indicating that all subjects returned to their normoxic baseline levels. SpO2 decreased from 98 +/- 0.9% to 80 +/- 7.8% after 3 min on hypoxic gas. During the hypoxic K-D test, SpO2 decreased further to 75.8 +/- 8.3%. CONCLUSIONS: In this study the K-D test has been shown to be an effective neurocognitive test to detect hypoxic impairment at early presymptomatic stages. The K-D test may also be used to afford a reassessment of traditional measures used to determine hypoxic reserve time.

Surgeon fatigue and postural stability: is robotic better than laparoscopic surgery?

OBJECTIVE: To compare muscular fatigue and postural stability of surgeons before and after laparoscopic and robotic surgery. SUBJECTS AND METHODS: The design of this study is Class II. A consecutive cohort of patients presenting at an academic tertiary-care center for scheduled gynecologic surgery was used. Routine surgical care was examined with testing of surgeon fatigue and postural measures before and after the procedure. Motor fatigue was measured using a quantitative grip dynamometer, and postural stability was measured using a nondominant, single-leg stance. A subjective fatigue score was recorded following surgery. RESULTS: Primary surgeons completed testing before and after 56 surgeries. A trend toward decline in postural stability was observed more in the laparoscopy group than in the robotic group (P=.29). The fatigue index and subjective fatigue scores were not significantly different. CONCLUSIONS: Similar changes in postural stability and muscular strength were observed following laparoscopic and robotic surgery. The optimal measurement tool to capture surgical fatigue remains elusive. Fatigue differences may have been more pronounced if surgical procedure degree of difficulty had been more consistent between groups.

Oculo-vestibular recoupling using galvanic vestibular stimulation to mitigate simulator sickness.

INTRODUCTION: Despite improvement in the computational capabilities of visual displays in flight simulators, intersensory visual-vestibular conflict remains the leading cause of simulator sickness (SS). By using galvanic vestibular stimulation (GVS), the vestibular system can be synchronized with a moving visual field in order to lessen the mismatch of sensory inputs thought to result in SS. METHODS: A multisite electrode array was used to deliver combinations of GVS in 21 normal subjects. Optimal electrode combinations were identified and used to establish GVS dose-response predictions for the perception of roll, pitch, and yaw. Based on these data, an algorithm was then implemented in flight simulator hardware in order to synchronize visual and GVS-induced vestibular sensations (oculo-vestibular-recoupled or OVR simulation). Subjects were then randomly exposed to flight simulation either with or without OVR simulation. A self-report SS checklist was administered to all subjects after each session. An overall SS score was calculated for each category of symptoms for both groups. RESULTS: The analysis of GVS stimulation data yielded six unique combinations of electrode positions inducing motion perceptions in the three rotational axes. This provided the algorithm used for OVR simulation. The overall SS scores for gastrointestinal, central, and peripheral categories were 17%, 22.4%, and 20% for the Control group and 6.3%, 20%, and 8% for the OVR group, respectively. CONCLUSIONS: When virtual head signals produced by GVS are synchronized to the speed and direction of a moving visual field, manifestations of induced SS in a cockpit flight simulator are significantly reduced.

The effect of galvanic vestibular stimulation on distortion product otoacoustic emissions.

Galvanic stimulation has long been used as a nonmechanical means of activating the vestibular apparatus through direct action on the vestibular nerve endings. This stimulation has been reported to be safe, but no studies have examined the potential changes in the corresponding cochlear receptors. The aim of the present study was to evaluate the effect of galvanic vestibular stimulation (GVS) on distortion product otoacoustic emissions (DPOAEs). Fourteen subjects underwent DPOAEs during several conditions of GVS. The DPOAEs ranged from ∼ 1 kHz to ∼ 8 kHz at 65/55 dB for f1/f2 and with an f2/f1 ratio of 1.2. The subjects were evaluated at 10 stimulation conditions that ranged from -2.0 mA to +2.0 mA for each frequency. Statistical analysis showed no significant differences in DPOAE amplitudes for all conditions with and without GVS. Results also showed no significant differences between DPOAE amplitudes before and after GVS. Multivariate analysis found subject variability in DPOAE amplitude, which was not thought to be GVS related. Results indicated that GVS produced neither temporary nor permanent changes in DPOAEs.

Muscle restricted vasculitis causing dropped head syndrome: a case report and review of the literature.

A 52-year-old man presented with a severe head drop and proximal extremity weakness. Magnetic resonance imaging of the cervical spine showed T2 hyperintensity in cervical paraspinal muscles. Electrodiagnostic studies revealed an axial myopathy isolated to paraspinal muscles. A splenius capitis muscle biopsy confirmed an acute myopathy associated with nonsystemic vasculitis. The patient improved on steroids, intravenous immunoglobulin, and monthly pulse doses of cyclophosphamide. Our case emphasizes that a subgroup of patients with dropped head syndrome have treatable conditions.

Muscle categorization using PDF estimation and Naive Bayes classification.

The structure of motor unit potentials (MUPs) and their times of occurrence provide information about the motor units (MUs) that created them. As such, electromyographic (EMG) data can be used to categorize muscles as normal or suffering from a neuromuscular disease. Using pattern discovery (PD) allows clinicians to understand the rationale underlying a certain muscle characterization; i.e. it is transparent. Discretization is required in PD, which leads to some loss in accuracy. In this work, characterization techniques that are based on estimating probability density functions (PDFs) for each muscle category are implemented. Characterization probabilities of each motor unit potential train (MUPT) are obtained from these PDFs and then Bayes rule is used to aggregate the MUPT characterization probabilities to calculate muscle level probabilities. Even though this technique is not as transparent as PD, its accuracy is higher than the discrete PD. Ultimately, the goal is to use a technique that is based on both PDFs and PD and make it as transparent and as efficient as possible, but first it was necessary to thoroughly assess how accurate a fully continuous approach can be. Using gaussian PDF estimation achieved improvements in muscle categorization accuracy over PD and further improvements resulted from using feature value histograms to choose more representative PDFs; for instance, using log-normal distribution to represent skewed histograms.

Skin biopsy for diagnosis of small fiber neuropathy: a critically appraised topic.

BACKGROUND: Patients with lower extremity sensory symptoms and pain but without clinical or standard neurophysiological examination abnormalities may have a small fiber neuropathy. Skin biopsy with intraepidermal nerve fiber density (IENFD) assessment has been promoted as a diagnostic tool for such patients. OBJECTIVES: To evaluate the diagnostic utility of skin biopsy with IENFD in patients with suspected small fiber neuropathy. METHODS: The objective was addressed through the development of a structured critically appraised topic. This included a clinical scenario, structured question, search strategy, critical appraisal, results, evidence summary, commentary, and bottom line conclusions. Participants included consultant and resident neurologists, a medical librarian, clinical epidemiologists, and content experts in the field of neuromuscular neurology. RESULTS: One primary article was selected for review. A retrospective study using skin biopsy with IENFD detected abnormalities in 88.1% of 67 patients who had symptoms suggestive of sensory neuropathy but normal nerve conduction studies compared with 10% of healthy controls. Skin biopsy was more often abnormal in this setting than either the clinical examination (signs of small fiber impairment) or quantitative sensory testing but formal evaluation of sensitivity and specificity are compromised by inclusion of the diagnostic tests within the definition of the reference standard. Skin biopsy with IENFD was abnormal in 81% of patients clinically diagnosed with mixed large and small fiber neuropathy, 0/22 patients with large fiber neuropathy and 0/16 patients with nonperipheral neuropathic disorders. CONCLUSION: Detection of reduced IENFD using skin biopsy may be sensitive and specific for clinically-defined syndromes consistent with small fiber neuropathy. Skin biopsy appears to have greater diagnostic utility than the neurologic examination and quantitative sensory testing, both of which rely heavily on subjective patient perception. Prospective studies that evaluate quantitative methodology (rather than modalities that rely on patient report) and do not include the diagnostic tests in the reference standard are needed. Consensus is needed regarding a reference standard definition for small fiber neuropathy.