Biomedical subjects
Publications and source records attributed to D A Wiegand.
In 1989, the Acoustic Neuroma Association established a multisurgeon, multi-institutional registry to collect data related to the treatment of patients with acoustic neuroma. This report analyzes information from the 1579 surgically treated patients who were entered in the registry between January 1, 1989, and February 28, 1994.
Intraoperative cranial motor nerve monitoring has improved the preservation of cranial nerve function during cerebellopontine angle and skull base surgery. Further improvements are needed to provide greater selectivity and sensitivity during intraoperative motor nerve stimulation. Use of bipolar stimulator probes has been recommended by previous investigators. The authors hypothesized that a coaxial bipolar stimulator design might provide important advantages over existing designs. This study compared the results of bipolar and monopolar stimulation using a coaxial stimulator probe in a rat model and during neurotologic procedures. The coaxial bipolar probe was superior in selectivity, thereby permitting useful multichannel monitoring. The coaxial design may also offer advantages over previous bipolar stimulator designs.
The use of conventional ultrasound systems to image the upper airway has been limited because ultrasound energy is attenuated by the air column. In an attempt to study upper airway geometry, we developed a computer controlled bi-directional ultrasound system which combines two conventional ultrasound devices with computer image processing to yield images of upper airway structures. Human studies and cadaver studies were performed to evaluate the system. Images acquired by the bi-directional ultrasound system were comparable to images from 3D volume rendered CT scans. This system may provide valuable data in the study of upper airway physiology and pathology.
Computer software for rendering and display of three-dimensional data is becoming readily available for all types of computers. Such programs typically accept data from any source, compute a three-dimensional volume of data, and display it with a variety of rendering options. Although not specifically designed for medical image processing, these programs can provide very detailed and finely rendered images that are useful for surgical planning. We use one such program to display data from standard computed tomography scans, which gives us a photorealistic three-dimensional view of patient anatomy. This view can be modified to render tissues transparent, translucent, or opaque, and thus allows the surgeon to selectively enhance bony architecture, tumors, or other details. Images can be rotated, sliced, and displayed in the surgical position. Image animation can be added to facilitate the display of complex anatomic relationships. Our experience with this technology suggests that such programs can provide the basis for personal surgical workstations for medical image analysis and surgical planning. Further development of such generic imaging systems should allow this useful technology to become widely available for surgical planning and education. We discuss our experience with a typical generic imaging workstation.
Previous investigators (van Lunteren et al. J. Appl. Physiol. 62: 582-590, 1987) have suggested that the geniohyoid and sternohyoid muscles may act as upper airway dilators in the cat. To investigate the effect of geniohyoid and sternohyoid contraction on inspiratory upper airway resistance (UAR), we studied five adult male cats anesthetized with ketamine and xylazine during spontaneous room-air breathing. Inspiratory nasal airflow was measured by sealing the lips and constructing a nose mask. Supraglottic pressure was measured using a transpharyngeal catheter placed above the larynx. Mask pressure was measured using a separate catheter. Geniohyoid and sternohyoid lengths were determined by sonomicrometry. Geniohyoid and sternohyoid contraction was stimulated by direct muscle electrical stimulation with implanted wire electrodes. Mean inspiratory UAR was determined for spontaneous breaths under three conditions: 1) baseline (no muscle stimulation), 2) geniohyoid contraction alone, and 3) sternohyoid contraction alone. Geniohyoid contraction alone produced no significant reduction in inspiratory UAR [unstimulated, 17.75 +/- 0.86 (SE) cmH2O.l-1.s; geniohyoid contraction, 19.24 +/- 1.10]. Sternohyoid contraction alone also produced no significant reduction in inspiratory UAR (unstimulated, 15.74 +/- 0.92 cmH2O.l-1.s; sternohyoid contraction, 14.78 +/- 0.78). Simultaneous contraction of the geniohyoid and sternohyoid muscles over a wide range of muscle lengths produced no consistent change in inspiratory UAR. The geniohyoid and sternohyoid muscles do not appear to function consistently as upper airway dilator muscles when UAR is used as an index of upper airway patency in the cat.
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Injury to the facial nerve is a significant risk during resection of cerebellopontine angle tumors. To minimize the risk of facial nerve injury, intraoperative electromyographic monitoring of facial musculature is frequently used. However, the reliability of such monitoring systems for detection of thermal nerve injury resulting from the use of carbon dioxide lasers has not been systematically evaluated. We determined the sensitivity of a computerized electromyographic monitor for detection of laser facial nerve injury in an anesthetized rat model. The mandibular and buccal branches of the facial nerve were isolated in 12 rats. A carbon dioxide laser was used to create controlled sites of thermal injury to both nerves over a 3-hour period. When a laser injury was created distal to previous injury sites, electromyographic discharge was noted in 72% to 82% of injuries. Laser injury proximal to previous injury sites was detected with 33% efficiency. These detection rates did not change significantly over a 3-hour period. This preliminary data suggests that electromyographic monitoring of facial musculature allows detection of facial nerve injury caused by carbon dioxide lasers.
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Patients with neuromuscular disease may develop respiratory failure requiring mechanical ventilation. We describe a sternohyoid muscle biopsy technique as a diagnostic aid in such patients undergoing tracheostomy for prolonged ventilatory support. The biopsy procedure is quick and without added discomfort or morbidity for the patient. Our preliminary observations in three patients suggest that the sternohyoid muscle biopsy may be a useful diagnostic tool in this selected group of patients.
Sleep-related reduction in geniohyoid muscular support may lead to increased airway resistance in normal subjects. To test this hypothesis, we studied seven normal men throughout a single night of sleep. We recorded inspiratory supraglottic airway resistance, geniohyoid muscle electromyographic (EMGgh) activity, sleep staging, and ventilatory parameters in these subjects during supine nasal breathing. Mean inspiratory upper airway resistance was significantly (P less than 0.01) increased in these subjects during all stages of sleep compared with wakefulness, reaching highest levels during non-rapid-eye-movement (NREM) sleep [awake 2.5 +/- 0.6 (SE) cmH2O.l-1.s, stage 2 NREM sleep 24.1 +/- 11.1, stage 3/4 NREM sleep 30.2 +/- 12.3, rapid-eye-movement (REM) sleep 13.0 +/- 6.7]. Breath-by-breath linear correlation analyses of upper airway resistance and time-averaged EMGgh amplitude demonstrated a significant (P less than 0.05) negative correlation (r = -0.44 to -0.55) between these parameters in five of seven subjects when data from all states (wakefulness and sleep) were combined. However, we found no clear relationship between normalized upper airway resistance and EMGgh activity during individual states (wakefulness, stage 2 NREM sleep, stage 3/4 NREM sleep, and REM sleep) when data from all subjects were combined. The timing of EMGgh onset relative to the onset of inspiratory airflow did not change significantly during wakefulness, NREM sleep, and REM sleep. Inspiratory augmentation of geniohyoid activity generally preceded the start of inspiratory airflow. The time from onset of inspiratory airflow to peak inspiratory EMGgh activity was significantly increased during sleep compared with wakefulness (awake 0.81 +/- 0.04 s, NREM sleep 1.01 +/- 0.04, REM sleep 1.04 +/- 0.05; P less than 0.05). These data indicate that sleep-related changes in geniohyoid muscle activity may influence upper airway resistance in some subjects. However, the relationship between geniohyoid muscle activity and upper airway resistance was complex and varied among subjects, suggesting that other factors must also be considered to explain sleep influences on upper airway patency.
Reduction in the activity of upper airway "dilator" muscles during sleep may allow the pharyngeal airway to collapse in some individuals. However, quantitative studies concerning the effect of sleep on specific upper airway muscles that may influence pharyngeal patency are sparse and inconclusive. We studied seven normal men (mean age 27, range 22-37 yr) during a single nocturnal sleep study and recorded sleep staging parameters, ventilation, and geniohyoid muscle electromyogram (EMGgh) during nasal breathing throughout the night. Anatomic landmarks for placement of intramuscular geniohyoid recording electrodes were determined from a cadaver study. These landmarks were used in percutaneous placement of wire electrodes, and raw and moving-time-averaged EMGgh activities were recorded. Sleep stage was determined using standard criteria. Stable periods of wakefulness and non-rapid-eye-movement (NREM) and rapid-eye-movement (REM) sleep were selected for analysis. The EMGgh exhibited phasic inspiratory activity during wakefulness and sleep in all subjects. In six of seven subjects, mean and peak inspiratory EMGgh activities were significant (P less than 0.05) reduced during stages 2 and 3/4 NREM sleep and REM sleep compared with wakefulness. This reduction of EMGgh activity was shown to result from a sleep-related decline in the level of tonic muscle activity. Phasic inspiratory EMGgh activity during all stages of sleep was not significantly different from that during wakefulness. Of interest, tonic, phasic, and peak EMGgh activities were not significantly reduced during REM sleep compared with any other sleep stage in any subject. In addition, the slope of onset of phasic EMGgh activity was not different during stage 2 NREM and REM sleep compared with wakefulness in these subjects.(ABSTRACT TRUNCATED AT 250 WORDS)
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Salmonella abscess in the head and neck is an uncommon occurrence. Such abscesses most often present in patients with underlying systemic processes or in those receiving iatrogenic immunosuppression. We report a 53-year-old woman with a retropharyngeal abscess treated with clindamycin and ampicillin. Treatment required surgical debridement and long-term antibiotics. There is a predilection for salmonella to affect tissue having underlying pathology, so that local tissue biopsy and long-term follow-up to document tissue reversions to normal are required.
Surgical treatment of acoustic neuroma has been reviewed in the medical literature, but assessment of outcome from the patient's perspective has received little attention. The Acoustic Neuroma Association (A.N.A.) is a large organization of acoustic neuroma patients which provides information and support services. This article reports the subjective assessment of symptoms, diagnosis, treatment, and outcome as evaluated by 541 A.N.A. members. This retrospective study presents an extensive overview of the experience of acoustic neuroma patients treated at a variety of institutions, and provides a unique perspective not previously represented in the medical literature.
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BACKGROUND: After resection of cranial and skull base tumors, fibrin-thrombin solutions can provide a temporary biologic seal of dural closures until final healing occurs. We investigated several variables affecting the strength of these "tissues glues" for repair of dural defects using in vitro methods to model clinical repairs. METHODS: The competence of human cryoprecipitate-thrombin (CPT) "tissue glues" in providing a watertight seal for patched rat fascia and human cadaveric dural defects was assessed. A saline column was fabricated to allow for controlled pressure (up to 700 mm) to be applied over an open aperature containing the repaired defect. Variables of repair included time after repair, defect size, and mixing temperature. RESULTS: Wide variations in the strength of different cryoprecipitate glues were found. Time allowed after repair did not significantly affect the repair strength. Cooling the components of the glue solution prior to mixing significantly increased repair strength. Similar results were found for different defect sizes. CONCLUSIONS: Under controlled in vitro conditions, integrity of fibrin glue repairs varied widely. This was not attributable to differences in solution fibrinogen concentration. Cooling the "tissue glue" components prior to mixing significantly increased repair strength of patched tissue defects.
A convenient, inexpensive test to identify multiple sclerosis during periods of symptomatic remission would be clinically advantageous. Recent studies have suggested that examination of acoustic reflex onset latency and rise time may be useful in detecting some forms of retrocochlear auditory pathology. This prospective, single-blinded study compares these features of the human acoustic reflex in a control sample, a sample with sensorineural hearing loss, and a sample with multiple sclerosis, to determine the usefulness of acoustic reflex measurements as a screening test for otherwise asymptomatic multiple sclerosis. Acoustic reflex threshold, onset latency, and rise time measurements were similar for all groups. This finding suggests that tests for abnormalities of acoustic reflex rise time and onset latency, under the conditions used in this study, may not be sufficiently sensitive to screen for the presence of otherwise asymptomatic multiple sclerosis.
The need for an easily generated, simulated QRS complex to facilitate preimplantation sensitivity testing of ventricular programmed pacemakers has led to the adoption of the sine squared waveform as the standard test pulse, by the Pacemaker Standards Subcommitte of the Association for the Advancement of Medical Instrumentation (AAMI). A simple circuit is presented that provides an accurate sine squared pulse with easily adjustable pulse width (base frequency). A suggested circuit for incorporating this sine squared pulse generator into a complete pacemaker test waveform generator/cardiac simulator is also presented.