Experience with two types of electromyography monitoring electrodes during thyroid surgery.

PURPOSE: To prevent damage to the recurrent laryngeal nerve during thyroid or parathyroid surgery, spontaneous and evoked electromyography (EMG) can be used to locate the recurrent laryngeal nerve or determine when the nerve is being disturbed. Two commercial electrodes have been introduced to receive laryngeal EMG. This study compares the clinical performance of the two electrodes. PATIENTS AND METHODS: The Xomed-Treace endotracheal tube electrode (Xomed-Treace, Jacksonville, FL) and the RLN postcricoid laryngeal electrode (RLN Systems, Jefferson City, MO) were placed concomitantly in 11 patients during 14 surgical procedures. RESULTS: The RLN electrode provided feedback as to placement by providing a heart-beat artifact. The RLN electrode was found to be both more sensitive and more electrically noisy. On stimulation, the Xomed tube electrode produced generally higher EMG amplitudes, perhaps because of the different muscles they monitor. In one case, the Xomed tube failed to provide-EMG responses. Only at low electrical stimulation intensities could left and right vocalis muscles be identified with the Xomed tube. A laryngologist was needed to place the RLN electrode, whereas the attending anesthesiologist was able to place the Xomed tube. CONCLUSION: Both electrodes provided useful EMG information and helped confirm the location of the recurrent laryngeal nerve. Who will place the electrode, tumors extrinsic or intrinsic to the larynx, cost, and size requirements should be considered when choosing an electrode.

Intraoperative neural monitoring. An introduction for perioperative nurses.

Intraoperative neural monitoring is a new science with many potential applications. Anesthesia providers, audiologists, neurophysiologists, and neurologists use intraoperative monitoring to make patient care decisions in the OR. Perioperative nurses' knowledge of anesthesia, anatomy, physiology, surgical procedures, monitoring technology, and electrode application contributes to successful intraoperative monitoring, as does collaboration by the entire surgical team.

Fabrication of a new headset for air- and bone-conduction audiometry.

The construction of a new audiometric headset which supports both ac and bc transducers is described. The bc transducer can be adjusted from 0-1500 g force. Future development should be directed toward (1) determining if such a headset is adjustable and stable on different size heads, (2) determining the test-retest reliability of the force measuring system, (3) reshaping the headset to make it smaller and more comfortable, and (4) consolidating the power/amplifier supply into a single unit.

Reliability of a sound-generating otoscope.

A sound-generating otoscope was compared with standard audiometric testing. Subjects of different ages and with different auditory pathologies were examined. The sound-generating otoscope was found to agree 92.4% of the time. Errors occurred more often with subjects having normal hearing. No single frequency delivered by the otoscope produced a significantly higher error rate than had been reported by other investigators. The otoscope can also be used to detect collapse of the external auditory meatus that might occur during regular audiometric testing.

Noise exposure levels from model airplane engines.

Previous research indicates that noise levels from unmuffled model airplane engines produce sufficient noise to cause TTS. The present study explored SPLs of smaller engines under 3.25 cc (.19 cu. in.) and the effectiveness of engine mufflers. Results showed that model airplanes can exceed a widely used damage risk criterion (DRC) but that engine mufflers can reduce levels below DRC. Handling model gasoline engines should be added to the list of recreational activities such as snow-mobile and motorcycle riding, shooting, etc. in which the participant's hearing may be in jeopardy. Suggestions are presented to the model engine enthusiast for avoiding damage to hearing.

Presbycusis: the need for a clinical definition.

The term presbycusis is vague and needs specific signs and symptoms for its definition. Several types of presbycusis, depending on the type of lesion, have been proposed. This article suggests a working definition of "classic presbycusis," which may be defined as a syndrome involving (1) a bilaterally symmetric sensorineural hearing loss, (2) absent or partial recruitment, (3) negative noise history, and (4) poorer speech discrimination than indicated by pure tones (phonemic regression).

The incidence of hearing disorders in the schoolchildren of Trinidad.

Two thousand forty-seven (2047) ears of elementary school children of the Republic of Trinidad were screened with pure-tone and immitance tests. Approximately 20 percent of the ears showed type B and C tympanograms, compared with only 2 percent failing a 30 dB, 4 K Hz pure tone. In 13 percent an ipsilateral middle ear muscle reflex could not be elicited. Results are reported in terms of the subjects' racial background. This study tends to support the theory of a genetic origin of otitis media.

The incidence of hearing disorders in schoolchildren of Trinidad

Two thousand forty-seven (2047) ears of elementary school childern of the Republic of Trinidad were screened with pure-tone and immitance tests. Approximately 20 percent of the ears showed type B and C tympanograms, compared with only 2 percent failing a 30dB, 4 KHz tone. In 13 percent an ipsilateral middle ear muscle reflex could not be elicted. Results are reported in terms of the subjects' racial background. This study tends to support the theory of a genetic origin of otitis media. (AU)

Stapedial reflex and anxiety in fluent and disfluent speakers.

Stapedial reflex thresholds were obtained from fluent and disfluent subjects with and without anxiety. Anxiety conditions were measured by monitoring palmar skin resistance with a psychogalvanometer. Eight of nine disfluent speakers had decreased mean stapedial-reflex thresholds ( -2.5 to -10 dB) at 500 or 1000 Hz or both when anxiety was present. This phenomenon did not occur in the fluent group. Only two of the nine fluent subjects showed reflex change with anxiety and the mean reflex change was shown in an increase of +2.5 dB. The disfluent group's mean stapedial reflex was significantly different with and without anxiety status (a = 0.01). Mean reflex for the fluent group did not change with anxiety.

The fistula and Hennebert tests.

The fistula and Hennebert tests are used to detect the structural integrity of the bony labyrinth or to detect when the membranous labyrinth is in contact with the footplate of the stapes. Both tests may be administered with the manometer of an electroacoustic impedance instrument. When vertigo is a symptom, these tests should be a part of the routine impedance test battery.

Preventing collapse of external auditory meatus during audiometry.

Occlusion of the external auditory meatus resulting from earphone pressure can produce a pseudoconductive hearing loss. I describe a method for detecting ear canal collapse by otoscopy and I suggest a method of correcting the problem with a polyethylene tube prosthesis.

The use of visual stimuli during auditory assessment.

Two groups of male subjects beyond 50 years of age were given audiometric tasks with and without visual stimulation to determine if visual stimuli changed auditory perception. The first group consisted of 10 subjects with normal auditory acuity; the second, 10 with sensorineural hearing losses greater than 30 decibels. The rate of presentation of the visual stimuli, consisting of photographic slides of various subjects, was determined in experiment I of the study. The subjects, while viewing the slides at their own rate, took an audiotry speech discrimination test. Advisedly they changed the slides at a speed which they felt facilitated attention while performing the auditory task. The mean rate of slide-changing behavior was used as the "optimum" visual stimulation rate in experiment II, which was designed to explore the interaction of the bisensory presentation of stimuli. Bekesy tracings and Rush Hughes recordings were administered without and with visual stimuli, the latter presented at the mean rate of slide changes found in experiment I. Analysis of data indicated that (1) no statistically significant difference exists between visual and nonvisual conditions during speech discrimination and Bekesy testing; and (2) subjects did not believe that visual stimuli as presented in this study helped them to listen more effectively. The experimenter concluded that the various auditory stimuli encountered in the auditory test situation may actually be a deterrent to boredom because of the variety of tasks required in a testing situation.