Major patterns of laryngeal electromyography and their clinical application.

Laryngeal electromyography (LEMG) is clinically valuable in the evaluation of laryngeal dysfunction and vocal fold immobility. To facilitate clinical application of this electrophysiologic test, a detailed description of modified LEMG techniques is presented. The techniques were applied for simultaneous bilateral recordings of the thyroarytenoid, cricothyroid, and posterior cricoarytenoid muscles. The basic patterns of LEMG are classified into three different types: normal, neuropathy, and myopathy. In an attempt to characterize these patterns, we have reported eight LEMG-documented cases: unilateral laryngeal paralysis, bilateral laryngeal paralysis, cricoarytenoid joint dislocation, cricoarytenoid joint ankylosis, laryngeal myopathy, pharyngeal paralysis (soft palate paralysis), spasmodic dysphonia, and unilateral laryngeal paralysis with anastomosis. The significance of the major LEMG patterns is discussed.

Laryngeal evoked brainstem responses in humans: a preliminary study.

Laryngeal evoked brainstem responses (LBRs) were recorded in normal human subjects in an attempt to develop a central laryngeal function test and enhance our understanding of neurolaryngologic disorders. The results showed that the human LBR consists of five positive peaks and five negative peaks reproducible within 10 ms after a vibratory stimulation to the superior laryngeal nerve (SLN). The waveform reproducibility was verified by blocking the SLN and topically anesthetizing the hypopharyngeal cavity. The morphology and latency of peak 5 were similar to results obtained in animal LBR experiments. It was concluded that a vibratory stimulation to the SLN was a noninvasive method to elicit far-field potentials from the central laryngeal pathway. These findings encourage further effort to establish normative data and explore clinical correlations.

Time course of Bell palsy.

This study was designed to quantitatively characterize the time course of facial palsy and the relationship between electroneurography and the facial nerve grading percentage as a function of onset time. Bilateral electroneurographic recordings during different stages in the course of the disease were repeated and compared with categorized videotaped facial movements using the House-Brackmann facial nerve grading system in 32 patients with Bell palsy. Preliminary results of this study demonstrate a time gap between the percentage of electroneurographic response and the category of the facial nerve grading system during the same period of disease progress. A theoretical model of the time course and specific patterns regarding the recovery of facial function is established. The theoretical time course of facial palsy is divided into 3 stages; preclinical, clinical, and postclinical. Based on the time course of electroneurographic and facial grading functions, the period between 10 and 14 days after onset was found to be most valuable for prediction of recovery. According to this theoretical model, a given time course pattern based on the results of serial electroneurographic recordings provides reliable prognostic information on recovery from Bell palsy.

Audiologic manifestations of Noonan syndrome.

A comprehensive audiologic study of a family with Noonan syndrome is reported together with a review of 20 cases of this syndrome with regard to hearing sensitivity and middle ear status. An incidence of progressive sensorineural hearing loss at the high frequencies is found for 50% of the ears. It is emphasized that early audiologic management may improve the quality of life for patients with Noonan syndrome.

Effects of brain stem lesions on cochlear function: mechanism of hearing improvement after removal of a brain stem tumor.

EOAEs are well correlated with changes of hearing sensitivity during the clinical course of brain stem lesions, as shown in this case study. They may serve as sensitive indicators to evaluate the possible effects of a brain stem lesion on cochlear function and monitor the attempted preservation of hearing during CPA or brain stem surgeries. It is thereby suggested that EOAEs should be included in an audiologic test battery in a differential diagnosis of retrocochlear lesions.

Laryngeal reflexomyographic responses in rabbits: a neurolaryngological study of glottal movement.

The role of the laryngeal reflex in glottal movement has been reported, but its mechanism remains unclear. To further investigate the neurophysiological characteristics of glottal movement, we recorded the laryngeal reflexomyographic responses (LRMRs) to electrical stimulation of the superior laryngeal nerve (SLN) in rabbits. The procedure involved simultaneous recording of the LRMRs from the thyroarytenoid muscles by means of bipolar hooked wire electrodes after electrical stimulation to the SLN. The results demonstrated characteristic patterns of the responses, consisting of R1 and R2, similar to those found in humans. The R1 response was obtained with a latency of 10.7 +/- 0.78 ms. The ipsilateral R2 response was obtained with a latency of 43.76 +/- 4.67 ms in all rabbits, and the contralateral R2 response with a latency from 42.6 to 50.2 ms in 4 rabbits. It was concluded that LRMRs may serve as a potential central laryngeal function test in the investigation of glottal movement control.

Critical evaluation of neurolaryngological disorders.

Otolaryngological examinations, videostroboscopic image analysis, and laryngeal electromyography were used as a test battery for a critical evaluation in 80 patients. Vocal fold movements were categorized into mobility, restricted mobility, immobility with different positions, and overactive movement. Laryngeal electromyographic examinations were conducted in all patients, and the results were classified into normal, neuropathic, and myopathic patterns. The electromyographic data were integrated with videostroboscopic findings, interpreted with knowledge of biomechanical and electrophysiological mechanisms of the larynx, and correlated clinically with underlying diseases. It is suggested that neurolaryngological procedures are most clinically useful when dictated by a decision-making algorithm.

Value of electromyography in differential diagnosis of laryngeal joint injuries after intubation.

Laryngeal joint injury or arytenoid dislocation is not an uncommon complication resulting from intubation trauma, and is best evaluated by laryngeal electromyography (EMG) combined with laryngoscopic examinations. Two cases of cricoarytenoid joint injuries after intubation are reported along with laryngeal EMG findings. Early diagnosis of arytenoid dislocation is important for appropriate surgical management and better prognosis. However, the reported cases, because of delayed referrals, showed prolonged cricoarytenoid joint injuries associated with thyroarytenoid muscle denervation or myopathy, and resultant vocal fold immobility. The results of laryngeal EMG in cricoarytenoid joint injuries can be classified into three different patterns: 1) normal recruitment, 2) myopathy, and 3) denervation or reinnervation of the thyroarytenoid muscles. It is particularly valuable to sample different portions of the thyroarytenoid muscles with EMG in order to evaluate different patterns or pathologic changes of the muscles and nerve paralysis.

Current evaluation of pseudohypacusis: strategies and classification.

Some cases of pseudohypacusis may involve medicolegal aspects and require a confirmed and quantitative diagnosis. These challenging cases must be identified, and then evaluated with basic audiologic and sophisticated electrophysiologic tests. Data on 64 patients with pseudohypacusis collected over a 4-year period are reported. A classification system was developed from an analysis of these cases and is presented for clinical evaluation and diagnosis. In many cases, conventional audiologic evaluation involving pure tone and speech audiometry may be adequate and sufficient for diagnosis. In more complex cases, evoked otoacoustic emissions (EOAEs) and auditory brain stem responses (ABRs) are needed for confirmation of peripheral auditory sensitivity. We found that EOAEs were the most rapid economical, and objective method, and confirmed the diagnosis of hearing loss in 78.1% of cases. Fifteen percent of subjects required ABRs to substantiate the diagnosis. The reliability of basic audiologic tests based on previous clinical investigations and data from the literature are discussed. We conclude that a thorough knowledge and understanding of pseudohypacusis is essential to verify the existence of pseudohypacusis, to determine its type, and to quantify the auditory thresholds.

Neurophysiological evaluation of acute facial paralysis in children.

Objective evaluation of facial nerve paralysis represents a unique challenge to the clinician. Electroneurography (ENoG) and the acoustic reflex (AR) have been widely used as neurophysiological tests in an assessment of facial nerve function. However, ENoG or AR alone does not suffice diagnostic and prognostic purposes of facial function evaluation in children. To further investigate the diagnostic aspects of facial nerve paralysis, the prognostic value of AR and ENoG, and the time course of the disease in pediatric population, a series of 30 children with acute facial paralysis were investigated by correlation of findings from video-taped House-Brackmann facial grading system. AR and ENoG. The results showed that AR was absent or abnormal for thresholds in 68.2% of patients with Bell's palsy and normal middle ear function. Shorter duration and higher percentage of recovery were found in the children with a normal AR than those with an abnormal AR. Three children showed an abnormal tympanogram and hearing loss associated with acute facial paralysis. These findings should alert the clinician to the presence of a specific, treatable disease in the evaluation of Bell's palsy. The percentage of electroneurographic response varied with different days after onset. ENoG showed minimal responses at weeks 1 3 after onset of Bell's palsy in most patients. The study of the time-course in the children with Bell's palsy demonstrated a functional gap in the early (< 1 week) and late clinical stage (after 6 weeks) of the disease, suggesting that ENoG predicted well only during weeks 1-4 after onset. In general, ENoG showed a good recovery in children, however, recurrent Bell's palsy becomes a concern. The need for neurophysiological follow-up for possible incomplete recovery of the facial nerve is emphasized. It is recommended that AR and ENoG should be included in the diagnostic workup when evaluating pediatric facial function.