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.

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.