Electrophysiological evaluation of the neuromuscular junction: a brief review / Avaliação eletrofisiológica da junção neuromuscular: breve revisão

Abstract The nerve terminal and muscle membrane compose the neuromuscular junction. After opening the voltage-gated calcium channels, action potentials from the motor axons provoke a cascade for the acetylcholine release from synaptic vesicles to the synaptic cleft, where it binds to its receptor at the muscle membrane for depolarization. Low amplitude compound muscle action potential typically presents in presynaptic disorders, increasing by more than 100% after a 10-second effort in the Lambert-Eaton myasthenic syndrome and less in botulism. Needle electromyography may show myopathic motor unit action potentials and morphological instability ("jiggle") due to impulse blocking. Low-frequency repetitive nerve stimulation (RNS) is helpful in postsynaptic disorders, such as myasthenia gravis and most congenital myasthenic syndromes, where the number of functioning acetylcholine receptors is reduced. Low-frequency RNS with a decrement >10% is abnormal when comparing the 4th to the first compound muscle action potential amplitude. High-frequency RNS is helpful in presynaptic disorders like Lambert-Eaton myasthenic syndrome, botulism, and some rare congenital myasthenic syndromes. The high-frequency RNS releases more calcium, increasing the acetylcholine with a compound muscle action potential increment. Concentric needle records apparent single-fiber action potentials (spikes). A voluntary activation measures the jitter between spikes from two endplates. An electrical activation measures the jitter of one spike (one endplate). The jitter is the most sensitive test for detecting a neuromuscular junction dysfunction. Most neuromuscular junction disorders are responsive to treatment.

Resumo O nervo terminal e a membrana muscular compõem a junção neuromuscular. Após a abertura dos canais de cálcio dependentes de voltagem, os potenciais de ação do axônio motor provocam uma cascata de eventos que libera acetilcolina das vesículas para a fenda sináptica, ligando-se ao receptor na membrana muscular para despolarização. O potencial de ação muscular composto de baixa amplitude ocorre nas desordens pré-sinápticas, aumentando em mais de 100% após esforço de 10 segundos na síndrome miastênica de Lambert-Eaton e menos no botulismo. A eletromiografia pode mostrar potenciais de ação da unidade motora miopáticos e instabilidade morfológica ("jiggle") devido ao bloqueio do impulso. Estimulação nervosa repetitiva (ENR) de baixa frequência é útil nos distúrbios pós-sinápticos, como miastenia gravis e a maioria das síndromes miastênicas congênitas, quando há número reduzido de receptores de acetilcolina funcionantes. ENR de baixa frequência com decremento >10% é anormal comparando-se à amplitude do quarto com o primeiro potencial de ação muscular composto. ENR de alta frequência é útil nas doenças pré-sinápticas, como síndrome miastênica de Lambert-Eaton, botulismo e algumas síndromes miastênicas congênitas raras. ENR de alta frequência libera mais cálcio, aumenta acetilcolina, resultando em incremento do potencial de ação muscular composto. O eletrodo de agulha concêntrico registra potenciais de ação aparente de fibra única (PAAFU). Ativação voluntária mede jitter entre dois PAAFUs (duas junções neuromusculares). Ativação elétrica mede jitter de um PAAFU (uma junção neuromuscular). Jitter é o teste mais sensível para detectar disfunção de junção neuromuscular. A maioria dos distúrbios juncionais é responsiva ao tratamento.

The acoustic parameters of perceptually normal voice production in Filipinos: An exploratory study among selected adults in Metro Manila

BACKGROUND AND OBJECTIVES: Acoustic analysis is an objective instrumental method that makes more accurate and reliable assessments of vocal characteristics possible. The aim of the current study was to describe the vocal characteristics of Filipinos with perceptually normal voices in terms of (1) fundamental frequency, (2) intensity, (3) frequency and intensity perturbations, (4) speaking fundamental frequency range, and (5) nasalance.METHODOLOGY: A total of 142 healthy adults aged 18 - 53 years participated in this study. The group was composed of 73 men (26.9 ± 6.4 years old) and 69 women (26.1 ± 6.5 years old). Voice samples were collected using Computerized Speech Laboratory™ (CSL; Model 4300B) during sustained phonation of vowel /a/ and spontaneous speech. Nasometer™ (Model 6200-3) was used to assess nasality while participants read plosive- and sibilant-loaded sentences.RESULTS AND CONCLUSION: The average acoustic values for males were F0 = 125.8 ± 23.4 Hz, SF0 = 122.6 ± 15.6 Hz, SF0 range = 85.8-269 Hz, SPL (speech) = 58.6 ± 5.3 dB, SPL (vowel) = 66.6 ± 6.2 dB, jitter = 0.92 ± 0.48%, shimmer = 2.21 ± 0.73%, nasalance = 12.5-17.1%; for females, F0 = 196.3 ± 23.0 Hz, SF0 = 194.8 ± 19.0 Hz, SF0 range = 97.1- 309.6Hz, SPL (speech) = 57.6 ± 4.3 dB, SPL (vowel) = 65.3 ± 4.5 dB, jitter = 1.12 ± 0.34%, shimmer = 2.7 ± 0.64%, nasalance = 13.1-19.1%. Significant differences were found between male and female subjects for F0, SF0, perturbation measures, and SPL during sustained phonation (p

Acoustic Outcomes After Laryngomicrosurgery for Reinke's Edema

BACKGROUND AND OBJECTIVES: The management of Reinke's edema includes usually medical treatment and voice therapy. Laryngomicrosurgery (LMS) is also necessary, especially to improve airway obstruction. However, voice outcome after LMS has not been determined well. The aim of this study was to evaluate effectiveness of LMS for Reinke's edema and analyze the voice outcomes after LMS. MATERIALS AND METHODS: Twenty-five patients with Reinke's edema who underwent LMS from September 2007 to December 2016 were enrolled in this study. We analyzed reflux finding score (RFS), reflux symptom index (RSI), and acoustic parameters before and after surgery. RESULTS: Male was 15 (60%) and female was 10 (40%), and mean age was 49.6 years. Preoperative mean value of RFS decreased significantly up to 3 months after LMS (18.3±2.2 and 10.0±2.2 at preoperative and 3 months postoperatively, respectively). The mean value of Jitter decreased significantly before and after surgery (2.71±2.81% and 1.06±1.21% before and after LMS, p=0.041). The mean value of Shimmer also decreased significantly before and after surgery (7.97±3.63% and 4.83±1.85%, respectively, p=0.006). CONCLUSION: LMS is effective in the treatment of Reinke's edema. It results in favorable acoustic outcomes and laryngoscopic findings in properly selected patients.

Can chemo-radiotherapy for non-laryngeal cancer affect acoustics of voice – a preliminary study.

Background: Treatment for cancer using chemo-radiotherapy and radiotherapy are age old treatment procedures which are found to be efficient in eradicating cancerous cells thereby improving overall quality of life of the individual. Though they seem to improve the disease condition, they adversely affect different bodily systems and functions. One such effect is noted in literatures on regard of voice acoustics. Knowledge in voice acoustics in these participants would adequately provide management options before and after treatment. In our study we aim to estimate extend of voice changes in participants undergoing radiation therapy for non-laryngeal head and neck cancer. Methods: Multidimensional voice profile (MDVP) was used to assess voice parameters on three time basis such as pre-treatment, immediate post treatment and one month after post treatment. Results: Significant difference was seen between all the three time points namely; pre-treatment, post treatment and one month after post treatment were observed. Conclusion: The study revealed that, radiation therapy significantly affects the voice parameters in the same way as it affects other parts of the body. Though these effects seem to be of higher significance, during and immediate treatment; the recovery on late post treatment is satisfactory.

Evolución en la calidad de la voz en pacientes disfónicos del Hospital de La Serena tratados con terapia vocal / Changes in the quality of voice in dysphonic patients in the La Serena Hospital Treated with vocal therapy

Introducción: La terapia fonoaudiológica de la disfonía contempla un conjunto de recursos subjetivos cuya eficacia debe ser cuantificada. Objetivo: En el presente trabajo se pretende cuantificar objetivamente la evolución en la calidad de la voz de pacientes disfónicos usando como referencia los índices de perturbación de la frecuencia fundamental (Jitter) e intensidad (Shimmer), y determinar si la evolución es coherente con la evaluación subjetiva del fonoaudiólogo. Material y método: Se seleccionaron 27pacientes disfónicos que completaron la terapia vocal entre 2009y 2011 y que corresponden al 38% de las consultas fonoaudiológicas por disfonía, en el Hospital de La Serena. Cada paciente, además de la evaluación subjetiva, contó con una aplicación de análisis acústico inicial y final con el programa PRAAT. Se contrastaron los resultados aplicando análisis estadístico con el software SPSS. Resultados: Los resultados muestran que se reducen las perturbaciones de la frecuencia e intensidad registradas con el análisis acústico en la misma proporción que el grado subjetivo de la disfonía y que dichas variaciones son independientes a otras variables como la edad, sexo y tipo de disfonía. Conclusión: Se destaca la importancia de la intervención fonoaudiológica en el tratamiento de la disfonía y la relevancia de la aplicación del análisis acústico como medio de evaluación y seguimiento objetivo.

Introduction: Phonoaudiological dysphonia therapy provides a set of subjective resources whose effectiveness must be quantified. Aim: In the present work is to objectively quantify changes in voice quality of dysphonic patients using as reference indices disturbance of the fundamental frequency (Jitter) and intensity (Shimmer), and determine whether the development is consistent with the subjective evaluation phonoaudiologist. Material and method: 27 patients who completed dysphonic voice therapy between 2009 and 2011, corresponding to 38% of consultations phonoaudiological dysphonia, at the Hospital of La Serena were selected. Each patient in addition to the subjective evaluation, had initial and final application of the PRAAT acoustic analysis program. Results using the SPSS statistical analysis software were compared. Results: The results show that disturbances in the frequency and intensity recorded with acoustic analysis in the same proportion will reduce the perceived degree of hoarseness and that these variations are independent of other variables such as age, sex and type of dysphonia. Conclusion: The importance of speech therapy intervention in the treatment of dysphonia and the relevance of the application of acoustic analysis as a means of objective evaluation and monitoring is emphasized.

Stimulated jitter with concentric needle in 42 myasthenia gravis patients / Jitter estimulado obtido com agulha concêntrica em 42 pacientes com miastenia gravis

Objective: To estimate jitter parameters in myasthenia gravis in stimulated frontalis and extensor digitorum muscles using the concentric needle electrode. Methods: Forty-two confirmed myasthenia gravis patients, being 22 males (aged 45.6±17.2 years-old) were studied. Jitter was expressed as the mean consecutive difference (MCD). Results: MCD in extensor digitorum was 61.6 µs (abnormal in 85.7%) and in frontalis 57.3 µs (abnormal in 88.1%). Outliers represented 90.5% for extensor digitorum and 88.1% for frontalis. At least one jitter parameter was abnormal in 90.5% of the combined studies. Acetylcholine receptor antibody was abnormal in 85.7% of the cases. Conclusions: Stimulated jitter recordings measured from muscles using concentric needle electrode can be used for myasthenia gravis diagnosis with high sensitivity. Extensive normative studies are still lacking and, therefore, borderline findings should be judged with great caution. .

Objetivo: Mensurar os valores do jitter em pacientes com miastenia gravis nos músculos frontalis e extensor digitorum pela técnica estimulada, utilizando-se eletrodo de agulha concêntrica. Métodos: Foram estudados 42 pacientes, sendo 22 homens (idade 45,6±17,2 anos), com miastenia gravis confirmada. O jitter foi expresso como a média das diferenças consecutivas (MDC). Resultados: A MDC para o extensor digitorum foi 61,6 µs (anormal em 85,7%) e para o frontalis 57,3 µs (anormal em 88,1%). Outliers representaram 90,5% para o extensor digitorum e 88,1% para o frontalis. Pelo menos um parâmetro do jitter foi anormal em 90,5% dos estudos combinados. Anticorpo receptor de acetilcolina estava anormal em 85,7% dos casos. Conclusões: Jitter estimulado mensurado por meio de eletrodo de agulha concêntrica pode ser utilizado para diagnóstico de miastenia gravis com elevada sensibilidade. Estudos normativos mais amplos ainda são necessários e, portanto, valores limítrofes devem ser avaliados com cautela. .

Preoperative Voice Parameters Affect the Postoperative Speech Intelligibility in Patients with Cochlear Implantation

OBJECTIVES: Verbal communication depends on a good function of voice and speech organs. Some of the voice characteristics of deaf people differ considerably from those of speakers with normal hearing. After cochlear implantation (CI), auditory control of voice production is possible and the quality of the voice is improved. CI improves quality of voice, speech and hearing with deafness. The aim of our study was to investigate the relationship between acoustic analysis before CI and the speech intelligibility before and after CI. METHODS: Twelve prelingually deafened children implanted unilaterally at the age of 3.4-9 years were included in the study. For all of the children an acoustic analysis of the Slovene vowel 'a' was performed before CI. The fundamental frequency (F0), jitter, shimmer and noise-to-harmonic ratio (NHR) were studied before the implantation. For all of the children the speech intelligibility was performed before and 12 months after CI. Preoperative hearing was divided on existing residual hearing. The results of the acoustic analyses and speech intelligibility before and after CI were compared for preoperative hearing. The results of the speech intelligibility were compared for the age of operation and preoperative acoustic analysis (F0, jitter, shimmer, NHR). RESULTS: Preoperative hearing had no influence on preoperative voice analysis. The children with residual hearing had a high grade of speech intelligibility before and after CI. The preoperative shimmer had positive correlation with postoperative 12 month speech intelligibility (r=0.618, P=0.032). The preoperative jitter had positive correlation with postoperative 12 month speech intelligibility, but was not statistically significant (r=0.479, P=0.116). CONCLUSION: Shimmer on preoperative voice analyses had influence on speech intelligibility after CI.

The Jitter Spatial Frequency Sweep VEP: a new paradigm to study spatiotemporal development of pattern - and motion - processing mechanisms in human infants

We introduce a new VEP paradigm - the Jitter Spatial Frequency (JSF) Sweep VEP - that permits efficient mapping of the spatiotemporal tuning of the developmental motion asymmetry (DMA). Vertical sinewave gratings undergoing 90º horizontal oscillatory displacements (6 or 10 Hz) were presented while their SF was swept over 2 to 5 octaves during each VEP trial. JSF sweep VEPs were recorded from 28 infants (8-43 weeks), and symmetric (second-harmonic, F2) and asymmetric (F1) components of the VEP were measured. JSF sweeps can provide four useful estimates: (1,2) the high-SF cutoff of F1 and F2 responses estimates the spatial resolution of direction-selective (DS) and non-DS mechanisms, respectively; (3) the low-SF cutoff for F1 estimate the SF-boundary between mature (F1 absent) and immature (F1 present) DS mechanisms; and (4) the F1 high-SF cutoff estimates the lower velocity limit of cortical DS cells. For 6 Hz, the low-SF F1 cutoffs increased two times faster than traditional (contrast-reversal) VEP grating acuity (0.5 vs ~0.25 octaves/month), and twice that of the high-SF F1 and F2 cutoffs. This implies that no single mechanism can account for the DMA at both low and high SFs. At 10 Hz, the DMA exhibited no significant development, consistent with slower maturation of DS mechanisms at higher ST frequencies. The F2 high-SF cutoffs were higher than F1 at both 6 and 10 Hz, suggesting higher spatial resolution for non-DS (pattern) vs DS (motion) mechanisms. Finally, the lower velocity limit of the DS mechanisms decreased from ~2 deg/sec at 8 weeks, to 0.75 deg/sec at 33 weeks, similar to analogous limits for direction-of-motion identification in adults (~0.5 - 1 deg/sec), and close to prior VEP estimates in infants (0.6 deg/sec).

Diagnostic value of single fiber electromyography in diabetic peripheral neuropathy / 临床神经病学杂志

Objective To study the diagnostic value of single fiber electromyography (SFEMG) in diabetic peripheral neuropathy (DPN).Methods The values of jitter and fiber density (FD) in 36 patients with diabetes mellitus of 2 type were determined by Viking Ⅳ, while conventional nerve conduction studies (NCS) were performed,and the fasting blood glucose and glycosylated hemoglobin A 1C (HbA 1C ) were measured.Results The values of jitter were associated with FD, and both jitter and FD were positively related to HbA 1C .18 cases with abnormal NCS showed increased jitter(11 cases with block),and increased FD in 14 cases; the remaining 18 cases with normal NCS,7 cases with increased jitter(3 cases with block),the increased FD in 5 cases.Conclusion Denervation reinnervation reflected by jitter and FD was associated with the metabolic status. SFEMG could be served as sensitive means to early diagnosis of DPN, and might detect subclinical peripheral neuropathy of diabetes.

A Study for Changes of Acoustic Parameters between Pre and Postoperative Voice in Laryngeal Nodule and Polyp / 대한이비인후과학회지

BACKGROUND: Laryngeal nodule and laryngeal polyp are the most common diseases that cause hoarseness and their incidences are increased currently. Since the invention of computerized voice analysis, it became possible to display voice quantitatively and visibly. MATERIALS AND METHODS: To evaluate the voice of 30 patients with laryngeal nodule and polyp before and after laryngomicrosurgery, the sound spectrogram of the Korean vowel /e/ were analyzed. RESULTS: 1) The valuable parameters for measuring the voice improvement were the range of fundamental frequency fluctuation, jitter and shimmer before and after surgery of laryngeal nodule and polyp. 2) On the first postoperative day, the change of the acoustic parameters of laryngeal nodule and polyp on postoperative showed statistically significant improvements. 3) The acoustic parameters of laryngeal nodule and polyp came within the normal range by the 7th postoperative day. 4) The extent of change in the acoustic parameters of laryngeal polyp was greater than in laryngeal nodule. CONCLUSION: We concluded that the valuable parameters for measuring the voice improvement were the range of fundamental frequency fluctuation, jitter and shimmer. The normalization of this parameter occurred at the first operative week.