The feasibility and technical aspects of trigemino-cervical reflex elicitation in humans under general anesthesia.

OBJECTIVE: To analyze the feasibility, neurophysiological aspects, stimulation patterns, and topographic distribution of trigemino-cervical reflex (TCR) components in humans under general anesthesia. METHODS: This prospective observational study enrolled 20 participants who underwent posterior fossa surgery, surgical proceduresin thecraniovertebral junction,or spinal cord surgery. TCR responses were simultaneously recorded in the sternocleidomastoid (SCM) and trapezius muscles after electrical stimulation of the supraorbital and infraorbital nerves. TCR responses were recorded preoperatively and intraoperatively using single-pulse and multipulse (trains of 2-7 electrical stimuli) stimulation, respectively. Two stimulus duration patterns were evaluated: 0.2-0.5 ms and 0.5-1.0 ms. RESULTS: Intraoperatively, short- and long-latency TCR components were obtained in the SCM ipsilateral to the stimulation with variable recordability. Short-latency responses were the most commonly recorded components. A longer stimulus duration (0.5-1.0 ms) seems to favor the elicitation of TCR responses under general anesthesia. CONCLUSIONS: Short-latency components recorded in the SCM ipsilateral to the stimulation could be regularly elicited under general anesthesia when a larger stimulus duration (0.5-1.0 ms) was applied. SIGNIFICANCE: This is the first study to demonstrate the elicitation of TCR components in humans under general anesthesia. This neurophysiological technique can potentially optimize intraoperative neurophysiological monitoring during brainstem surgery.

Technical Aspects of Eliciting Trigeminocervical and Trigeminospinal Reflexes in Humans: A Scoping Review.

SUMMARY: This scoping review aims to summarize the technical strategies for obtaining trigeminocervical reflex (TCR) and trigeminospinal reflex (TSR) responses. Studies published on TCR or TSR elicitation in humans through electrical stimulation of trigeminal nerve branches were eligible for this scoping review. The data of interest included stimulation parameters, site of stimulation, recording parameters, and the feasibility of TCR and TSR elicitation, in healthy participants. Short-latency TCR responses were regularly obtained in both anterior and posterior neck muscles after electrical stimulation of the supraorbital and infraorbital nerves under voluntary muscle activation. However, without voluntary muscle activation, we found evidence of elicitation of short-latency TCR components only in the posterior neck muscles after supraorbital or infraorbital nerve stimulation. Long-latency TCR responses were regularly obtained in the anterior and posterior neck muscles in studies that evaluated this technique, regardless of the trigeminal branch stimulation or muscle activation status. Short-latency TSR components were not obtained in the included studies, whereas long-latency TSR responses were regularly recorded in proximal upper limb muscles. This scoping review revealed key heterogeneity in the techniques used for TCR and TSR elicitation. By summarizing all the methodological procedures used for TCR and TSR elicitation, this scoping review can guide researchers in defining optimized technical approaches for different research and clinical scenarios.

Difficulty producing high-pitched sounds in singing: correlations with laryngostroboscopy and electromyographic findings / Dificuldade na produção de sons agudos no canto: correlações com a laringoestroboscopia e achados eletromiográficos

Abstract Introduction: Difficulties or limitations in producing high-pitched sounds while singing may be due to the vocal technique used or organic factor. The observation of such difficulty or limitation by singing teachers is one of the main reasons affected individuals are referred to otolaryngologists. Objective: To evaluate the laryngostroboscopic and electromyographic changes in the cricothyroid muscles of singers with difficulties or limitations producing high-pitched sounds. Methods: This is a cross-sectional study. Ten singers with difficulty producing high-pitched sounds underwent voice, laryngostroboscopic, and electromyographic evaluations. Results: None of the evaluated singers presented signs of impairment of the superior laryngeal nerve on laryngostroboscopy. The electromyographic findings for the cricothyroid muscle were normal for all singers. Six singers presented vocal fold lesions, seven had signs suggestive of laryngopharyngeal reflux, and two presented vascular changes. Conclusion: No signs suggestive of superior laryngeal nerve paresis or paralysis were observed on laryngostroboscopy and electromyography of the cricothyroid muscle in singers with difficulties or limitations producing high-pitched sounds. The presence of vocal fold lesions should be investigated in this population.

Resumo Introdução: Dificuldades ou limitações na produção de sons agudos durante o canto podem ser decorrentes da técnica vocal utilizada ou de fatores orgânicos. A observação dessa dificuldade ou limitação pelos professores de canto é uma das principais razões pelas quais os indivíduos afetados são encaminhados aos otorrinolaringologistas. Objetivo: Avaliar as alterações laringoestroboscópicas e eletromiográficas no músculo cricotireóideo de cantores com dificuldades ou limitações na produção de sons agudos. Método: Estudo de coorte transversal. Dez cantores com dificuldade de produzir sons agudos foram submetidos a avaliações de voz, laringoestroboscópicas e eletromiográficas. Resultados: Nenhum dos cantores avaliados apresentou sinais de comprometimento do nervo laríngeo superior na laringoestroboscopia. Os achados eletromiográficos para o músculo cricotireóideo foram normais para todos os cantores. Seis cantores apresentaram lesões nas pregas vocais, sete apresentaram sinais sugestivos de refluxo laringofaríngeo e dois apresentaram alterações vasculares. Conclusão: Não foram observados sinais sugestivos de paresia ou paralisia do nervo laríngeo superior na laringoestroboscopia e eletromiografia do músculo cricotireóideo em cantores com dificuldades ou limitações na produção de sons agudos. A presença de lesões nas pregas vocais deve ser investigada nessa população.

Difficulty producing high-pitched sounds in singing: correlations with laryngostroboscopy and electromyographic findings.

INTRODUCTION: Difficulties or limitations in producing high-pitched sounds while singing may be due to the vocal technique used or organic factor. The observation of such difficulty or limitation by singing teachers is one of the main reasons affected individuals are referred to otolaryngologists. OBJECTIVE: To evaluate the laryngostroboscopic and electromyographic changes in the cricothyroid muscles of singers with difficulties or limitations producing high-pitched sounds. METHODS: This is a cross-sectional study. Ten singers with difficulty producing high-pitched sounds underwent voice, laryngostroboscopic, and electromyographic evaluations. RESULTS: None of the evaluated singers presented signs of impairment of the superior laryngeal nerve on laryngostroboscopy. The electromyographic findings for the cricothyroid muscle were normal for all singers. Six singers presented vocal fold lesions, seven had signs suggestive of laryngopharyngeal reflux, and two presented vascular changes. CONCLUSION: No signs suggestive of superior laryngeal nerve paresis or paralysis were observed on laryngostroboscopy and electromyography of the cricothyroid muscle in singers with difficulties or limitations producing high-pitched sounds. The presence of vocal fold lesions should be investigated in this population.

Effects of the stimulus phase on the air-conducted ocular vestibular evoked myogenic potential in healthy subjects.

OBJECTIVE: The study aimed to examine the effect of the stimulus phase of air-conducted sound on ocular vestibular evoked myogenic potentials (oVEMPs). METHODS: oVEMPs were recorded after air-conducted sounds (500Hz, 4ms duration), presented with initial condensation (positive), rarefaction (negative), and alternant polarities from 12 healthy subjects. RESULTS: Most responses showed a bifid n10 peak separated by ∼1.9ms. The most prominent sub-peak after condensation was shorter than the most prominent sub-peak after rarefaction; however, the first sub-peak was shorter after the rarefaction stimuli. When a third sub-peak appeared, it occurred before the most prominent sub-peak after condensation and after the most prominent sub-peak after rarefaction. The latency difference between this third sub-peak and the closest sub-peak was shorter than the difference among the others sub-peaks, in both cases; the oVEMPs after alternating stimuli was an amalgam of the responses to the different stimuli. CONCLUSIONS: The findings suggest that the negative to positive change of the stimulus was the main event responsible for the stimulation, and that when a third sub-peak appeared it was related to the initiation or the end of the stimulus. SIGNIFICANCE: These findings suggested that the oVEMP response, obtained by air conducted sound, was secondary to stimulation of the same type of afferent vestibular unit, independent of the stimulus polarity.

MUNIX: Reproducibility and clinical correlations in Amyotrophic Lateral Sclerosis.

OBJECTIVE: To study the reproducibility, diagnostic yield to detect denervation, and clinical correlations of the Motor Unit Number Index (MUNIX) in subjects with Amyotrophic Lateral Sclerosis (ALS). METHODS: MUNIX evaluation was performed in three muscles twice on the same day to assess reproducibility. Cut-off values for the MUNIX were based on data from 51 healthy subjects (controls) to evaluate the sensitivity of the technique to detect denervation in 30 subjects with ALS. RESULTS: The method had good reproducibility. The variability was greater in the ALS group. In 23 ALS subjects (77%), low MUNIX values were detected. Most of the muscles with low MUNIX had also low compound muscle action potential (CMAP) and strength, but these parameters were normal in 9% of muscles. According to ROC curve analysis, MUNIX was generally accurate (AUC=0.9504) for discriminating between healthy individuals and subjects with at least one denervated muscle. CONCLUSIONS: MUNIX variability was higher in the ALS group. The method showed good diagnostic performance for the detection of denervation in a sample of patients with ALS. SIGNIFICANCE: This study demonstrated that in addition to being a quantitative tool MUNIX can detect denervation in subjects with ALS.

Pattern of peripheral nerve involvement in Machado-Joseph disease: neuronopathy or distal axonopathy? A clinical and neurophysiological evaluation.

OBJECTIVE: Neuropathy is a well-recognized feature in spinocerebellar ataxia type 3 (SCA3) or Machado-Joseph disease (MJD), but the pattern of neuropathy is still a matter of debate. This study aimed to evaluate peripheral nerve involvement in MJD patients. Neurophysiological and clinical data were analyzed to distinguish neuronopathy from length-dependent distal axonopathy. METHODS: In the present study we evaluated 26 patients with clinical and molecular-proven MJD and investigated their peripheral nerve involvement. Neurophysiological and clinical data were compared and correlated aiming to distinguish neuronopathy from distal axonopathy. RESULTS: The neurophysiological evaluation showed that 42.3% of the patients had polyneuropathy. Among these patients, 81.8% presented neuronopathy. CONCLUSION: We concluded that neuronopathy is the most common form of peripheral nerve involvement in MJD patients.

Is neuropathy involved with restless legs syndrome in Machado-Joseph disease?

OBJECTIVE: To evaluate a group of spinocerebellar ataxia type 3 (SCA3) or Machado-Joseph disease (MJD) (SCA3/MJD) patients and assess whether there is an association between neuropathy and serum ferritin levels and restless legs syndrome (RLS). METHODS: Twenty-six SCA3/MJD patients underwent electromyography studies to check for neuropathy. Their serum ferritin levels were measured as well. These findings were evaluated based on the presence or not of RLS and its severity. RESULTS: The proportion of neuropathy in the RLS group was not significantly higher compared to the non-RLS group (23 vs. 15%, Fisher's exact test, p = 1.000). Furthermore, no association was found between RLS and ferritin levels. CONCLUSION: We found no correlation between neuropathy or ferritin levels and RLS in SCA3/MJD patients.

Reproducibility in nerve conduction studies and F-wave analysis.

OBJECTIVE: Reproducibility testing of nerve conduction studies and F-wave latencies in a group of healthy volunteers. METHODS: A total of 32 healthy volunteers underwent sensory and motor nerve conduction studies of the ulnar and tibial nerves, including F-waves, elicited by 32 stimuli, repeated in two different days by the same examiner. RESULTS: The F-wave latencies showed less variability than the other parameters of conduction studies, and, among them, the F-wave mean latency of the tibial nerve has been the one with the higher reproducibility. CONCLUSIONS: F-wave latencies were the parameters with best reproducibility, followed by conduction velocities and amplitudes. SIGNIFICANCE: Our data showed that the F-wave mean latency is a parameter with a high reliability, considering the reproducibility, for sequential studies.

Various aspects of F-wave values in a healthy population.

OBJECTIVE: To characterize various aspects of F-wave in a healthy population and establish normative data for future clinical use. METHODS: A total of 100 healthy volunteers underwent sensory and motor nerve conduction studies of the ulnar and tibial nerves, including F waves elicited by 32 stimuli. RESULTS: The F-wave measurements (mean +/- SD for ulnar vs tibial nerve) consisted of persistence (83 +/- 19 vs 97 +/- 5%), minimum, mean and maximum latencies (26.5 +/- 2.1, 28.1 +/- 2.2, and 30.4 +/- 2.3 vs 47.0 +/- 4.1, 49.6 +/- 4.4, and 52.5 +/- 4.4 ms), minimum, mean and maximum F-wave conduction velocities (FWCV) (55.0 +/- 2.7, 60.0 +/- 2.3, and 64.0 +/- 3.0 vs 49.0 +/- 2.9, 52.2 +/- 3.1, and 55.5 +/- 3.4 m/s), chronodispersion (3.9 +/- 0.9 vs 5.5 +/- 1.4 ms), mean amplitude (347 +/- 152 vs 384 +/- 148 microV) and mean duration (8.6 +/- 2.9 vs 13.0 +/- 4.5 ms). Additional measures, registered by electronic averaging, included latency (27.4 +/- 2.3 vs 48.6 +/- 4.7 ms), duration (9.6 +/- 2.2 vs 16.4 +/- 4.2 ms), and amplitude (299 +/- 156 vs 208 +/- 116 microV). CONCLUSIONS: The use of a height nomogram serves well as an acceptable means to adjust F latencies for the limb length. In addition to the commonly used minimal latency, maximal FWCV, and persistence, clinically relevant measures with a narrow variability includes mean and maximal latencies, chronodispersion, and mean duration. In particular, mean latency obtained with 10 stimuli gave accurate results either for group or individual analysis. SIGNIFICANCE: The data help establish an adequate manner of recording F-wave latencies in clinical evaluation.