Shengguang S. Yin

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.

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 Bells 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 Bells palsy. The percentage of electroneurographic response varied with different days after onset. ENoG showed minimal responses at weeks 1 3 after onset of Bells palsy in most patients. The study of the time-course in the children with Bells 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 Bells 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.

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.

Evaluation of Bilateral Vocal Fold Dysfunction: Paralysis Versus Fixation, Superior Versus Recurrent, and Distal Versus Proximal to the Laryngeal Nerves

The initial finding of reduced movement or immobility of the bilateral vocal folds may be caused by different etiologies. Bilateral vocal fold dysfunction (BVFD) could originate from neurological, myogenic, or articular causes, each treated by routine examination and completely different surgical procedures. In clinical practice, laryngoscopy rarely indicates the underlying causes of BVFD. Cases with straightforward etiologies may undergo changes in pathophysiologic status and present more complex clinical pictures. A battery of methods have been used to evaluate BVFD including fiberoptic laryngoscopy, videostroboscopy, spirometry, laryngeal electromyography (LEMG), and magnetic resonance imaging (MRI). LEMG plays an important role in determining the diagnosis in terms of laryngeal paralysis, laryngeal joint fixation or dislocation, or posterior commisure synechiae. Bilateral vocal fold paralysis (BVFP), though uncommon, has a multitude of etiologies and is a potentially life-threatening condition. BVFP is often caused by iatrogenic lesions in adults and by congenital anomalies in infants and children. Neurological lesions are the second most common cause of BVFP in adu1ts.l

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.

Audiological findings in glomus tumours

Glomus tumours involving the middle ear and the cerebellopontine angle are reported with emphasis on audiological findings. Magnetic resonance imaging (MRI), angiographic and pathological results are presented. Audiological tests, including impedance audiometry, evoked otoacoustic emissions and auditory brainstem responses, are valuable in evaluation of the effect of glomus tumours on the auditory system as well as their pathological extent.

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.

68: Physiological Testing of Facial Paralysis: A Combination of the Acoustic Reflex and Electroneurography

after the opera t ion . There was only one report (The Laryngoscope, November 1993, from Switzerland) that revealed a normal laryngeal growth after this operation. Methods: Three patients aged 9, 6, and 6 years underwent this operation in March, May, and June 1989 due to an inability to find a lumen of the subglottic stenosis. Results: There was no immediate complication, and the patients were decannulated shortly after the operation. We were able to follow up the third patient in August 1995. It revealed a normal growth of the larynx. Conclusion: This finding supports the previous report regarding laryngeal growth. We had a 100% success rate in three children, and we consider the operation useful for children.