Mutational screening of Greek patients with axonal Charcot-Marie-Tooth disease using targeted next-generation sequencing: Clinical and molecular spectrum delineation.

BACKGROUND AND AIMS: Axonal forms of Charcot-Marie-Tooth disease (CMT) are classified as CMT2, distal hereditary motor neuropathy (dHMN) or hereditary sensory neuropathy (HSN) and can be caused by mutations in over 100 genes. We presently aimed to investigate for the first time the genetic landscape of axonal CMT in the Greek population. METHODS: Sixty index patients with CMT2, dHMN or HSN were screened by a combination of Sanger sequencing (GJB1) and next-generation sequencing custom-made gene panel covering 24 commonly mutated genes in axonal CMT. RESULTS: Overall, 20 variants classified as pathogenic or likely pathogenic were identified in heterozygous state in 20 index cases, representing 33.3% of the cohort. Of these, 14 were known pathogenic/likely pathogenic and six were designated as such according to ACMG classification, after in silico evaluation, testing for familial segregation and further literature review. The most frequently involved genes were GJB1 (11.7%), MPZ (5%) and MFN2 (5%), followed by DNM2 (3.3%) and LRSAM1 (3.3%). Single cases were identified with mutations in BSCL2, HSPB1 and GDAP1. INTERPRETATION: A wide phenotypic variability in terms of severity and age of onset was noted. Given the limited number of genes tested, the diagnostic yield of the present panel compares favourably with studies in other European populations. Our study delineates the genetic and phenotypic variability of inherited axonal neuropathies in the Greek population and contributes to the pathogenicity characterization of further variants linked to axonal neuropathies.

The Rise Slope of the Compound Sensory Nerve Action Potential in Normal and Pathological Human Nerves.

In spite of the diagnostic importance of the early phase of the sensory nerve action potential (SNAP), reliable electrodiagnostic metrics for this part of the recorded waveform are lacking. The average rise slope of the SNAP appreciates the steepness of the initial negative deflection of the waveform, which might be a useful metric for the first part of the potential. Sural nerve sensory neurography was performed in patients with various axonal neuropathies, and median nerve sensory studies were carried out in patients with carpal tunnel syndrome. Age-matched healthy individuals served as controls. The rise slope was compared to conventional SNAP parameters such as conduction velocity, latency, duration, and rise time. Overall, 537 sensory studies were prospectively analyzed. The rise slope of the sural SNAP demonstrated superior classification performance in terms of sensitivity (92.5%), specificity (97%), and area under the receiver operating characteristic curve (0.986), as compared to conventional SNAP parameters. Its diagnostic power was similarly excellent in median nerve studies, whereas here a slightly better classification performance was obtained by SNAP latency and conduction velocity. The average rise slope appears to do justice to the tight interplay between amplitude and rise time of the initial negative spike deflection, outperforming many conventional measures. This composite metric proved high diagnostic potency in particular with regard to axonal sensory nerve dysfunction.

Bilateral palsy of the hypoglossal nerve following general anesthesia for emergency surgery. A case report.

INTRODUCTION AND IMPORTANCE: Hypoglossal nerve palsy is a rare condition usually associated with tumors, trauma, stroke or multiple sclerosis. It can be associated with other cranial nerve palsies while injury to this nerve typically affects a patient's articulation by causing lingual motility disturbance and swallowing difficulty. Bilateral isolated hypoglossal nerve palsy is an even more infrequent condition, which can occasionally be due to airway manipulation. CASE PRESENTATION: We describe a case of bilateral hypoglossal nerve damage following general anesthesia for emergency surgery, presenting with dysarthria, immobility of the tongue and dysphagia after extubation. The patient had a gradual recovery of all lost functions during the next four months. CLINICAL DISCUSSION: Bilateral hypoglossal nerve palsy is a very rare entity and tracheal tube malposition or prolonged but unnoticed tracheal cuff pressure especially in the face of low blood pressure, should be considered as possible causative mechanisms for this condition. This underlines the importance of careful positioning of the patient's head and neck during surgery as well as the meticulous and correct performance of routine maneuvers of airway management. CONCLUSION: Bilateral hypoglossal nerve palsy is a very rare entity. Diagnosis and management of twelfth nerve palsy require a multidisciplinary approach to achieve the best patient outcome.

Myasthenia gravis, atypical polyneuropathy and multiple autoimmune phenomena in the same patient, with HLA-immunogenetic profile expectable for Greek chronic inflammatory demyelinating polyneuropathy: a case report.

PURPOSE: The comorbidity of myasthenia gravis (MG), with other autoimmune disorders like systemic lupus erythematosus (SLE), is relatively frequent but the co-occurrence with chronic inflammatory demyelinating polyneuropathy (CIDP) along with various autoimmune manifestations in the absence of thymoma is of extreme rarity. Our aim is to report a case of a woman who presented the concomitant appearance of MG, axonal sensory-motor polyneuropathy and hepatitis that may indicate an underlying pathogenetic link among the different autoimmune disorders. MATERIALS AND METHODS/RESULTS: We present a case of a 54-year-old woman, with a generalized MG and a chronic sensory-motor polyneuropathy, hypothyroidism, anaemia, hepatitis, livedo reticularis and facial flush, of assumed autoimmune background, like SLE, although with persistent negative ANA antibodies, from the beginning and through the whole following years. The Human Leukocyte Antigen (HLA)-DRB1 genotyping showed a profile of alleles (DRB1*11:01/11:04) compatible with CIDP of mainly female gender in Greece and frequencies close to those of Sjogren's syndrome and scleroderma's in the Greek population. The diagnostic problems, the atypical clinical, electrophysiological and immunological features are discussed, along with the rarity of the case, with this exceptional combination of autoimmune manifestations, which could be truly associated under the clinical umbrella of a systemic disease, like SLE. However, our patient did not ever fulfil the SLE criteria. CONCLUSIONS: To raise awareness among clinicians about the exceptional combination of autoimmune manifestations driven by a specific HLA background.

HINT1-related neuropathy in Greek patients with Charcot-Marie-Tooth disease.

Autosomal recessive axonal neuropathy with neuromyotonia (ARAN-NM) is a rare hereditary neuropathy within the Charcot-Marie-Tooth disease (CMT) spectrum, linked to mutations in the histidine triad nucleotide-binding protein 1 (HINT1) gene. HINT1-related neuropathy is particularly common in selected populations from Central and Eastern Europe but rare in Western European cohorts. It has not been investigated to date in the Greek population. We presently investigated the frequency of HINT1-neuropathy in a selected cohort of 42 Greek index patients with autosomal recessive or sporadic axonal hereditary neuropathy according to standard molecular genetics procedures. We identified 4 patients with biallelic mutations in HINT1, comprising 9.5% of all cases and 44.4% of cases also displaying neuromyotonia. The c.110G> C (p.Arg37Pro) HINT1 mutation was present in all cases (2 homozygous) and the c.250T> C (p.Cys84Arg) in 2 cases (compound heterozygous). HINT1-related neuropathy patients were characterized by early onset and neuromyotonia. Two patients had noteworthy clinical features, one case developing myoclonic epilepsy and the other displaying "adducted thumbs." We conclude that HINT1-related neuropathy is common in selected Greek patients with hereditary neuropathy within the CMT spectrum, in accordance with some, but not all, European populations.

Multimodal Neurophysiological and Neuroimaging Evidence of Genetic Influence on Motor Control: A Case Report of Monozygotic Twins.

Considering genetic influence on brain structure and function, including motor control, we report a case of right-handed monozygotic twins with atypical organization of fine motor movement control that might imply genetic influence. Structural and functional organization of the twins' motor function was assessed using transcranial magnetic stimulation (TMS), fMRI with a motor-task paradigm, and diffusion tensor imaging (DTI) tractography. TMS revealed that both twins presented the same unexpected activation and inhibition of both motor cortices during volitional unilateral fine hand movement. The right ipsilateral corticospinal tract was weaker than the left contralateral one. The motor-task fMRI identified activation in the left primary motor cortex and bilateral secondary motor areas during right-hand (dominant) movement and activation in the bilateral primary motor cortex and secondary motor areas during left-hand movement. Based on DTI tractography, both twins showed a significantly lower streamline count (number of fibers) in the right corticospinal tract compared with a control group, which was not the case for the left corticospinal tract. Neither twin reported any difficulty in conducting fine motor movements during their activities of daily living. The combination of TMS and advanced neuroimaging techniques identified an atypical motor control organization that might be influenced by genetic factors. This combination emphasizes that activation of the unilateral uncrossed pyramidal tract represents an alternative scheme to a "failure" of building a standard pattern but may not necessarily lead to disability.

Jitter Remains Stable Throughout a Single Fiber EMG Session in Healthy and Myasthenic Muscles.

Fatigability is the hallmark of myasthenia gravis (MG). It is not clear, however, whether there is an analogous increase in jitter during the course of a single fiber electromyography (SFEMG) session. The individual jitter values of all potentials of 76 normal and 44 myasthenic orbicularis oculi muscles were assigned a rank number according to their temporal order in which they were collected and linear regression was performed to determine if the slope of the regression line was significantly different from zero. Control and MG subjects displayed rather flat linear regression lines with non-significant positive or negative slopes. Accordingly, ROC analysis yielded areas under the curve near 0.5. We conclude that there is no systematic jitter increase during the collection of 20 potential pairs in a typical SFEMG session.

Unusual presentation of thoracic disc herniation.

We report a 57 year- old man with lateral abdominal wall bulging. MRI showed thoracic disk herniation at the T11-T12 level. Needle electomyogram disclosed acute denervation in paraspinal and abdominal muscles innervated from T11 root. Eight months later the swelling was reduced significantly. Thoracic disc herniations are rare and three similar cases have been described previously.

Identifying jitter outliers in single fiber electromyography: Comparison of four methods.

BACKGROUND: Little is known about how different outlier estimation methods affect cutoff limits for outliers in single fiber electromyography. METHODS: We compared in a prospective fashion the established 18th jitter value (18thjv) method to three, whole-distribution based, outlier detection methods: the interquartile range (IQR), the log-normal, and the Z-score method. The reference limits were probed in a normal cohort and in myasthenia gravis (MG) patients. RESULTS: Differences in outlier cutoff values between the different methods were in the range of 2 µs. The number of abnormal muscles according to the computed criteria was similar for all four methods in the control group. Classification metrics (sensitivity, specificity, Youden's statistic, and predictive values) were also similar among the different methods. In the MG group, however, the Z-score method failed to identify the abnormal jitter values. Accordingly, Kappa agreement was substantial to perfect (0.658 to 1) between the three methods (18thjv, IQR, and log-normal), but was equivalent to chance between the three methods and the Z-score in the MG group. CONCLUSIONS: The established 18thjv method proved largely robust when compared to whole-distribution based methods, and its use in clinical practice is justified. Simple estimation of outlier limits by adding two SDs to the mean of the data, leads to unacceptable deviations from the true cutoff values. Moreover, in a clinical scenario in which the final electrodiagnosis depends only on the number of outliers, it is meaningful to accept a tolerance zone of about 2 µs, which is the approximate variation range among the different methods.

Vibratory testing with the 64 Hz Rydel-Seiffer tuning fork and its relation to the sural nerve action potential.

Despite its widespread use, little is known regarding the ability of the semi-quantitative Rydel-Seiffer tuning fork to designate peripheral nerve function. We sought to determine in a large sample of normal and abnormal nerves the relationship between vibration sense and compound sensory nerve action potential (SNAP) parameters recorded in a corresponding innervation area. Vibratory thresholds were determined on a scale of 0 to 8 with a 64 Hz Rydel-Seiffer tuning fork placed on the lateral malleolus of 303 subjects. Sural nerve sensory neurography was employed to derive SNAP parameters, which were related to vibration sense by means of multiple linear regression. ROC curve analysis was performed to determine the classification efficacy of the tuning fork in distinguishing normal from abnormal sural nerve responses. SNAP amplitude was the most significant predictor in the whole subjects group and in the subgroup of subjects with normal SNAPs, whereas conduction velocity played a major role in subjects with abnormal SNAPs. Age was significantly associated with vibration perception, particularly in subjects with normal SNAPs. With an area under the curve of 0.730, vibration sense was a fair classifier for decreased SNAP amplitudes. The optimal vibratory cutoff was 4.2. Age is a major determinant of vibratory test results, highlighting the importance of aging of central and peripheral pathways in mediating vibration sense. Hence, neurophysiological testing cannot be omitted in the context of polyneuropathy work-up, since even at the optimal cutoff threshold, vibratory examination still displays 40% false negative test results.

The usefulness of electrodiagnostic consultation in an outpatient clinic.

The aim of this study was to record all patients referred to a private outpatient clinic for electrodiagnostic consultation during one calendar year. The demographic data of the patients, the specialty of the referring physicians, the referral diagnosis, the electromyographic (EMG) diagnosis and the concordance of referral and EMG diagnosis among all the referring physician's specialties were recorded. There were one thousand patients (385 men and 615 women). 65.7% of the patients were referred from orthopedists and 22.4% from neurologists. EMG was normal in 498 patients (49.8%). Abnormal in 47.3% of the patients referred by orthopedists and 58.9% of those referred by neurologists. Carpal tunnel syndrome (CTS) was the most frequent electrophysiological diagnosis (26.8%), followed by polyneuropathy (8.9%), radiculopathy (7.1%) and mononeuropathy (4.6%). In this study electrodiagnostic consultation was abnormal in only half of the referred patients. The high proportion of normal EDX tests in this study denotes the need for more accurate clinical diagnosis in order to reduce the time spent and resources. The orthopedist is the initial physician to whom patients with neuromuscular symptoms are seen in the majority of cases. Neurologists seem to be more familiar with neuromuscular symptoms and diseases.

Diagnostic Accuracy of Muscle Biopsy and Electromyography in 123 Patients with Neuromuscular Disorders.

BACKGROUND/AIM: Diagnostic accuracy of muscle biopsy and electromyography (EMG) in patients with myopathy varies widely among studies. The goal of this study was to examine the diagnostic accuracy of each method in the diagnosis of patients with suspected myopathy, and determine the level of agreement between the two methods. PATIENTS AND METHODS: The files of all patients with a presumed myopathy were retrospectively reviewed. All patients with detailed muscle biopsy and EMG data were included. RESULTS: A total of 123 patients were included. Accuracy of biopsy was 80.4% compared to 70.7% for EMG. Biopsy was sensitive and specific in all neuromuscular disorders. EMG was accurate in neurogenic disorders. Biopsy and EMG agreement was 70.7%. CONCLUSION: Muscle biopsy is more accurate than EMG in patients with myopathy. Muscle biopsy-EMG discordance can be attributed to different muscle sampling and to disorders with both neurogenic and myopathic features, such as acquired and mitochondrial myopathies.

Electromyographic Study of Thoracic Paraspinal and Rectus Abdominis Muscles in Amyotrophic Lateral Sclerosis.

PURPOSE: The aim of our study was the comparison of active denervation (fibrillation and/or positive sharp wave potentials) in thoracic paraspinal muscles with rectus abdominis in patients with definite amyotrophic lateral sclerosis. METHODS: Ninety-five consecutive patients with clinically definite amyotrophic lateral sclerosis according to the revised El Escorial criteria were studied prospectively over a 5-year period. Concentric needle electromyogram was performed in thoracic paraspinal muscles, in the rectus abdominis at the T9 level, and in limb muscles. RESULTS: Active denervation was present in thoracic paraspinal muscles in 75 patients (79%) and in rectus abdominis in 62 patients (65.3%) (P = 0.02). No significant difference was found between the two muscles regarding the type of onset (bulbar, upper, and lower limbs), amyotrophic lateral sclerosis functional rating scale values, and creatine phosphokinase levels. CONCLUSIONS: Thoracic paraspinal muscles are the first to be tested in patients with amyotrophic lateral sclerosis. Absence of active denervation in T-PSM is rarely associated with active denervation in rectus abdominis.

Motor and extra-motor gray matter integrity may underlie neurophysiologic parameters of motor function in amyotrophic lateral sclerosis: a combined voxel-based morphometry and transcranial stimulation study.

The association between gray matter (GM) density and neurophysiologic changes is still unclear in amyotrophic lateral sclerosis (ALS). We evaluated the relationship between GM density and motor system integrity combining voxel-based morphometry (VBM) and transcranial magnetic stimulation (TMS) in ALS. We included 17 ALS patients and 22 healthy controls (HC) who underwent 3D-T1-weighted imaging. Among the ALS group, we applied left motor cortex single-pulse TMS. We used whole-brain VBM comparing ALS and HC in GM density. We also conducted regression analysis to examine correlations between GM density and the following TMS parameters: motor evoked potential (MEP)/M ratio and central motor conduction time (CMCT). We found significantly decreased GM density in ALS patients in several frontal, temporal, parietal/occipital and cerebellar regions (p < 0.001 uncorrected; cluster-extent threshold k = 100 voxels per cluster). With regards to TMS parameters, ALS patients showed mostly increased MEP/M ratio and modest prolongation of CMCT. MEP/M ratio was associated with GM density in (a) rolandic operculum/inferior frontal gyrus/precentral gyrus; anterior cingulate gyrus; inferior temporal gyrus; superior parietal lobule; cuneus; superior occipital gyrus and cerebellum (positive association) and (b) paracentral lobule/supplementary motor area (negative association). CMCT was associated with GM density in (a) inferior frontal gyrus and middle cingulated gyrus (positive association) and (b) superior parietal lobule; cuneus and cerebellum (negative association). Our findings support a significant interaction between motor and extra-motor structural and functional changes and highlight that motor and extra-motor GM integrity may underlie TMS parameters of motor function in ALS patients.

Gray matter and white matter changes in non-demented amyotrophic lateral sclerosis patients with or without cognitive impairment: A combined voxel-based morphometry and tract-based spatial statistics whole-brain analysis.

The phenotypic heterogeneity in amyotrophic lateral sclerosis (ALS) implies that patients show structural changes within but also beyond the motor cortex and corticospinal tract and furthermore outside the frontal lobes, even if frank dementia is not detected. The aim of the present study was to investigate both gray matter (GM) and white matter (WM) changes in non-demented amyotrophic lateral sclerosis (ALS) patients with or without cognitive impairment (ALS-motor and ALS-plus, respectively). Nineteen ALS-motor, 31 ALS-plus and 25 healthy controls (HC) underwent 3D-T1-weighted and 30-directional diffusion-weighted imaging on a 3 T MRI scanner. Voxel-based morphometry and tract-based spatial-statistics analysis were performed to examine GM volume (GMV) changes and WM differences in fractional anisotropy (FA), axial and radial diffusivity (AD, RD, respectively). Compared to HC, ALS-motor patients showed decreased GMV in frontal and cerebellar areas and increased GMV in right supplementary motor area, while ALS-plus patients showed diffuse GMV reduction in primary motor cortex bilaterally, frontotemporal areas, cerebellum and basal ganglia. ALS-motor patients had increased GMV in left precuneus compared to ALS-plus patients. We also found decreased FA and increased RD in the corticospinal tract bilaterally, the corpus callosum and extra-motor tracts in ALS-motor patients, and decreased FA and increased AD and RD in motor and several WM tracts in ALS-plus patients, compared to HC. Multimodal neuroimaging confirms motor and extra-motor GM and WM abnormalities in non-demented cognitively-impaired ALS patients (ALS-plus) and identifies early extra-motor brain pathology in ALS patients without cognitive impairment (ALS-motor).