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Biomedical subjects

H R Konrad

Publications and source records attributed to H R Konrad.

At least 37 records · Page 2Linked to original sources
PubMed1989

Vestibular evoked potentials in response to direct unilateral mechanical stimulation.

Evoked potentials produced by direct unilateral mechanical stimulation of the cannulated horizontal semicircular canal were investigated parametrically in anesthetized adult cats (40 mg/kg pentobarbital). Stimuli were fluid pressure pulses in a closed hydraulic system (no net flow), which was coupled to the lateral semicircular canal near the ampulla. Hydraulic waveform output and fluid pressure was monitored in situ via a parallel hydraulic circuit during experiments. Maximum fluid displacement at the level of the horizontal canal was 0.025 microliters. The intensity, duration, and presentation rate of the stimulus were varied during experiments. Field potentials were recorded differentially using subdermal electrodes, with the active lead in the region of the mastoid referenced to a distant nasal site. A total of 256 trials was accumulated for each run using an averaging computer. Evoked responses were physiologically vulnerable and reproducible, with little variance among animals. Response amplitude increased monotonically until saturation was noted and responses followed the temporal structure of the pressure wave. Polarity reversal with differing electrode placement suggests that the generator site lies within the mastoid. Further, intense broad-band acoustic stimuli and eighth nerve sectioning did not affect the vestibular evoked potentials, but could be shown to abolish the auditory evoked potentials. Results of these experiments support the notion that vestibular evoked potentials are related to the first derivative of the pressure pulse waveforms. Future experiments will be directed toward the assessment of vestibular physiology and pharmacology with this evoked response method.

Acoustic Stimulation↗
PubMed1989

Simultaneous auditory stimuli shorten saccade latencies.

Eye movement responses induced by vestibular, smooth pursuit, and optokinetic stimulation are largely dependent on the velocity of the stimulus. Saccade latencies, on the other hand, are a function of the anatomic and physiologic components of the reflex. By producing an audible click simultaneously with the movement of a visual target used to stimulate a saccadic eye movement, the saccade latency is significantly shortened. This does not appear to be due to alerting. It is probably due to an auditory input to the superior colliculus which decreased threshold for initiating a saccadic eye movement. Twenty normal participants were tested with or without the click stimulus. Latencies were significantly shorter when the click stimulus was presented simultaneously with the eye movement. The anatomic pathways in this reflex are reviewed in the presentation. This study provides further information on sensory interaction in saccade reflexes and emphasizes the need to control stimulus conditions during saccade testing.

Acoustic Stimulation↗
PubMed1986

Intractable vertigo--when not to operate.

Patients with episodic vertigo--or one severe episode of vertigo--may respond to vestibulosuppressive medications or operations on the labyrinth. In patients with constant incapacitating vertigo or disequilibrium, the clinician should suspect nonlabyrinthine disease. A careful history and physical and neurologic examinations will provide clues to underlying disease and direct the selection of further objective tests.

Adult↗
PubMed1984

Laryngotracheoesophageal cleft in a newborn.

A case of laryngotracheoesophageal cleft in a newborn is presented. A newborn presenting with respiratory distress underwent contrast radiographic studies, direct laryngoscopy, bronchoscopy, and esophagoscopy, demonstrating a complete laryngotracheoesophageal cleft, esophageal diverticulum and microgastria. Attempts to maintain an adequate airway by ligation of the salivary ducts and ligation of the distal esophagus were unsuccessful. Continued biliary drainage per endotracheal tube postoperatively afforded a presumptive diagnosis of bronchobiliary fistula. The child expired on its fourth day of life. A review of the literature and modalities of therapy for these rare and unusual combinations of foregut anomalies is discussed. This is the first reported case of a newborn with the combination of laryngotracheoesophageal cleft, bronchobiliary fistula, microgastria and esophageal diverticulum.

Abnormalities, Multiple↗
PubMed1984

Content knowledge and problem-solving skill in reviewing medical charts.

Skills in reviewing medical charts have been demonstrated components of clinical competence related to knowledge base, level of clinical experience, and basic observational skills. A study of the generalizability of performance on chart review exercises, which controlled for knowledge in the content area, was undertaken to determine their potential in evaluating students' problem-solving ability. Results of the study indicate that the case specificity which has characterized simulated problem-solving tasks is largely case, rather than content, specificity: correlations between scores on single charts demonstrated no consistent relationships for measures of proficiency, efficiency, and diagnostic accuracy. However, averaging the scores on two charts and then computing correlations resulted in significant positive measures for both proficiency and efficiency. The effects of length and difficulty level on the generalizability of tests of problem-solving ability are areas suggested for future research.

Clinical Clerkship↗
PubMed1984

Opening and closing mechanisms of the larynx.

Opening and closing of the larynx are determined by the intrinsic and extrinsic muscles acting on the elastic forces in the tongue, pharynx, larynx, and trachea. The pharynx is opened or closed by two mechanisms: (1) Contractions of the cricothyroid and of the intrinsic muscles of the larynx open and close the vocal cords. (2) The false cords, ventricle, and true cords accordion open or close in a bellows mechanism. We conclude that the posterior cricoarytenoid opens the laryngeal airway. The cricothyroid together with the posterior cricoarytenoid accentuates this opening. The larynx is also opened by the geniohyoid, mylohyoid, sternothyroid, and middle constrictor. The thyrohyoid, cricothyroid, sternohyoid, and inferior constrictor close the laryngeal airway. Abnormalities in the soft tissues of the neck or of the innervation of the larynx, pharynx, and neck muscles may severely interfere with patency of the laryngeal airway. This occurs in such conditions as vocal cord paralysis, sleep apnea, multiple sclerosis, amyotrophic lateral sclerosis, spastic dysphonia, mandibular fractures or hypodevelopment, and cerebrovascular disease.

Animals↗
PubMed1983

Eye tracking abnormalities in patients with cerebrovascular disease.

Ten patients with disequilibrium, ataxia, and cerebrovascular abnormalities were studied using computer aided eye tracking and vestibular function tests. The patients had severe abnormalities in smooth pursuit (decreased gain) and saccade tests (increased delay, decreased accuracy). Optokinetic responses were less affected. The gain of the vestibulo-oculomotor reflex was sometimes affected. Patients with eye tracking abnormalities frequently had symptoms of difficulty reading and watching television. When the lesion was asymmetrical, abnormal eye tracking tests usually pointed to the side of the lesion. Computer aided eye tracking tests are a useful adjunct to the evaluation of the patient with suspected vascular disease. They help to locate areas of central nervous system dysfunction, and produce an objective measurement of the severity of impairment. Conversely, when impairment of the smooth pursuit or saccade system is detected in patients being evaluated for disequilibrium, an assessment of the patients' cerebrovascular system should be considered.

Adult↗
PubMed1980

Granular cell myoblastoma involving the recurrent laryngeal nerve.

An unusual granular cell myoblastoma occurred surrounding the recurrent laryngeal nerve. Available information regarding the origin, biological behavior, and treatment of such tumors arising from the cervical trachea was reviewed. Frequently, the histologic features cause this lesion to be mistaken for a malignant tumor, and errors in diagnosis and treatment may be made. To our knowledge, encasement of a major motor nerve in the neck by a granular cell neoplasm has never before been reported. Since the overwhelming majority of these tumors behave in a benign fashion, we recommend that the surgeon attempt to spare functionally important nerves in rare instances when they are grossly surrounded by tumor.

Adult↗
PubMed1979

Tracheal carcinoma after tracheostomy.

The trachea is rarely the site of origin of a primary malignant tumor. Causal factors have not been determined, but cigarette smoking is one suspected cause. We report an unusual case of tracheal carcinoma that occurred many years after permanent tracheostomy for benign disease, and we review other cases of posttraumatic tracheal cancer. This study suggests that trauma can be a factor in the development of certain malignant tumors of the trachea.

Carcinoma, Squamous Cell↗
PubMed1979

Pediatric otoscopy and photography of the tympanic membrane.

A further miniaturization of the lens telescopes (Hopkins Rod) has resulted in a telescope (length, 6 cm; diameter, 2.7 mm) that is suitable for pediatric otoscopy. The adaptation of otoscopic specula, a lightweight motor-driven remote flash camera, and movie and video photography to this telescope has resulted in a system that represents a significant advance in the examination of the ear. In this study, we document ear diseases in children with the use of color photographs.

Child↗
PubMed1979

Immediate postembolization excision of glomus jugulare tumors: advantages of new combined techniques.

Preoperative percutaneous transfemoral catheter embolization of feeding vessels in glomus jugulare tumors, followed by immediate application of standard surgical techniques, presents the treatment of choice, allowing meticulous microsurgery with virtually complete hemostasis. Therefore, the surgeon can operate in a bloodless environment throughout the compressed and intricate anatomic field, amidst such important yet vulnerable structures as cranial nerves, inner ear, carotid artery, jugular bulb, venous sinuses, and dura, while reducing surgical error and functional deficit for the patient. Review of the last 11 cases of glomus jugulare tumors at UCLA shows that even extensive Alford grade 2 tumors of the middle ear, jugular bulb, and mastoid had only minor blood losses with this combined technique of embolization-immediate surgery, as compared with earlier surgical methods. Pertinent literature on glomus jugulare and its treatment is reviewed. Combined embolization and immediate surgery offer the best approach for treatment of resectable glomus jugulare tumors.

Adult↗
PubMed1978

Epidermoid carcinoma of the palate.

A retrospective study was made of 80 cases of epidermoid carcinoma of the palate that were treated at the UCLA Center for the Health Sciences between 1955 and 1977. Tumor size larger than 3 cm, extension to neighboring structures, and contralateral, bilateral, and "fixed" lymph node metastases substantially decreased survival. The presence of ipsilateral nodes and the modality of treatment used (surgery or irradiation) did not appear to affect the outcome. Three-year cure rates for all cases was 40%. Ninety percent of recurrences took place during the first two years after treatment, and additional cancers developed in the upper aerodigestive tract of 20% of the patients.

Adult↗
PubMed1978

Lethal thyroid carcinoma.

Forty-three patients who died of thyroid carcinoma (29 well-differentiated and 14 poorly differentiated tumors) were evaluated to define the parameters that affect the lethal nature of this tumor. Differentiated, limited extent of tumor and a young age at diagnosis correlated favorably with length of survival. Sex showed a trend in favor of female patients, while specific histologic characteristics and extent of resection showed no positive correlation. Based on these findings and a review of the literature, we recommend a radical approach in the management of localized, poorly differentiated tumors. For well-differentiated cancer, resection of the thyroid gland and the paratracheal, jugular, and upper mediastinal lymph nodes is advised.

Adenocarcinoma↗
PubMed1977

Transpalatal approach to deeper cranial structures.

The approach to deep midline cranial structures is technically difficult. The transpalatal approach has a relatively wide exposure as compared to the transnasal, transantral and transethmoidal approches. The added advantage of a medial approach which follows medial landmarks and the flexibility of being able to extend exposure to the maxillary sinuses and pterygomaxillary space makes this an attractive approach for large lesions in the nasal passages, nasopharynx and sphenoid sinuses. Large mucoperiosteal flaps, care to avoid the palatine vessels, and application of palatal splint postoperatively, minimize complications and patient discomfort. The authors have used this approach to repair nasopharyngeal atresia, remove nasopharyngeal angiofibromas, approach the pituitary, craniopharyngioma and isolated sphenoid sinus opacification as well as sphenoid sinusitis with cavernous sinus thrombosis.

Biopsy↗