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Biomedical subjects

D Kearns

Publications and source records attributed to D Kearns.

7 recordsLinked to original sources
PubMed1999

Chondroid hamartoma presenting as a neonatal nasal mass.

We present a case of a 3-month-old female with a right nasal mass. Upon evaluation with computed tomography, magnetic resonance imaging and angiography, a large right intranasal mass extending through the cribiform plate, displacing the dura, was noted. The patient underwent a combined midfacial degloving and bifrontal craniotomy for complete resection of the tumor mass. Pathologic evaluation demonstrated a mesenchymal tumor with spindle and stellate cells from which islands of immature cartilage emerged. The spectrum of histologic features closely resembled a mesenchymal chondroid hamartoma typically located in the chest wall. It is the first reported case of a chondroid hamartoma of the head and neck in the literature to date. We examine the characteristics and treatment of this unusual tumor.

Diagnostic Imaging↗
PubMed1998

Passive sound-localization ability of the big brown bat (Eptesicus fuscus).

The passive sound-localization ability (i.e. minimum audible angle) of the big brown bat, Eptesicus fuscus, was determined using a conditioned avoidance procedure in which the animals were trained to discriminate left sounds from right sounds. The mean threshold of three bats for a 100-ms broadband noise burst was 14 degrees, a value that is about average for mammals. A similar threshold of 15 degrees was obtained for one animal when it was retested with one of its own recorded echolocation calls as the stimulus. The two bats tested on pure-tone localization were able to localize high-frequency, but not low-frequency tones, even when a low-frequency tone was amplitude modulated, a result indicating that these bats are not able to use binaural time-difference cues for localization. Finally, given the width of the bat's field of best vision, as determined by a count of its ganglion-cell density, its sound-localization acuity is consistent with the hypothesis that the role of passive sound localization is to direct the eyes to the source of a sound.

Acoustic Stimulation↗
PubMed1994

Sound localization in chinchillas. I: Left/right discriminations.

The ability of chinchillas to localize sound was examined behaviorally using a conditioned avoidance procedure in which the animals were trained to discriminate left from right sound sources. Their minimum audible angle was 15.6 degrees for 100-ms broadband noise making them one of the more accurate rodents, although they are not as accurate as primates and carnivores. Thresholds obtained for filtered noise stimuli demonstrated that chinchillas are equally accurate in localizing either low- or high-frequency noise. Further, they are able to use both interaural phase-difference and interaural intensity-difference cues as demonstrated by their ability to localize both low- and high-frequency pure tones. Finally, analysis of the chinchilla retina supports the hypothesis that the role of auditory localization in directing the eyes to sound sources played a role in the evolution of auditory spatial perception.

Acoustic Stimulation↗
PubMed1994

Hearing in prairie dogs: transition between surface and subterranean rodents.

Behavioral audiograms were determined for four black-tailed and one white-tailed prairie dogs (Cynomys ludovicianus and C. leucurus) using a conditioned avoidance procedure. The hearing of black-tailed prairie dogs ranges from 29 Hz to 26 kHz and that of the white-tailed prairie dog from 44 Hz to 26 kHz (at sound pressure levels of 60 dB). Both species have good low-frequency hearing, especially black-tailed prairie dogs which can hear as low as 4 Hz and are more sensitive than any other rodent yet tested at frequencies below 63 Hz. In contrast, prairie dogs are relatively insensitive in their midrange and have poor high-frequency hearing. It is suggested that the reduced midrange sensitivity and high-frequency hearing are related to their adaptation to an underground lifestyle with its reduced selective pressure for sound localization. In this respect they appear to be intermediate between the more exclusively subterranean rodents (such as gophers and mole rats) and surface dwellers (such as chinchillas and kangaroo rats).

Acoustic Stimulation↗
PubMed1991

The two-headed stethoscope: its use for ruling out airway foreign bodies.

Foreign body aspiration is a common concern for physicians and surgeons who care for children. Evaluating infants and toddlers to rule out this possible diagnosis is often fraught with difficulties. Specifically, the standard stethoscope is of limited use unless unilateral asymmetry of breath sounds can be appreciated. Inspiratory and expiratory chest X-rays in children often appear to show a very similar diaphragmatic excursion and, unless the object is radiodense, the determination of foreign body aspiration is frequently not possible. Other procedures, such as flexible or rigid endoscopy, are more invasive and are reserved for children with positive findings or a less acute but more perplexing scenario. We present the use of the two-headed stethoscope as an option for evaluation of children to rule out foreign body aspiration. Our experience with this instrument over the past 10 years has consistently allowed us to non-invasively differentiate the presence or absence of objects in the airway.

Airway Obstruction↗
PubMedDate not supplied

Fibrous dysplasia.

The controversy is this case centers around the management of this lesion, not the differential diagnosis. All the consultants agreed that the history, physical, and CT findings were consistent with various fibroosseous lesions, the most likely being fibrous dysplasia. The need for additional tests varied with a bone scan (Dr. Kearns), a bone scan and CT scan (Dr. McGill), and MRI, MRI angiogram, bone survey, BUN, creatinine, calcium, and phosphorus (Dr. Potsic). Cosmetic and functional changes were considered priorities for the consultants, with orbital compression, malocclusion, tooth eruption, nasal obstruction, and sinusitis (Dr. Kearns), nasolacrimal duct obstruction and orbital compression (Drs. McGill and Potsic) being the concerns. Because this lesion is benign and slow-growing, the consensus is that surgery should be reserved for functional or cosmetic compromise. But how aggressive should one be and what approach should be used? The approaches varied with midface degloving or lateral rhinotomy (Dr. Kearns), midface degloving (Dr. McGill), or a Caldwell-luc and lateral rhinotomy (Dr. Potsic). Assessment of this tumor postoperatively should be with patient examinations and serial CT scans. None of the consultants worried about sarcomatous changes in this tumor.

Facial Bones↗