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At least 199 records · Page 11Linked to original sources
PubMed2003

Irritated seborrheic keratosis of the external ear canal.

Although a seborrheic keratosis is not rare on the skin of the trunk, extremities, head and neck of an elderly person, it is uncommon to originate in the external ear canal. Even rarer, an irritated subtype may arise in this location. We report the case of a 63-year-old man with an irritated seborrheic keratosis arising in the right external ear canal, who first presented with a bloody discharge from his right ear canal 3 years and 10 months before the subsequent operation. Macroscopically, a dome-like, black elevation was found at the anterior wall of the right external ear canal. A biopsy showed an exophytic papillomatous, hyperkeratotic growth of basaloid cells which revealed some nuclear atypism and mitosis. Squamous eddies and moderate inflammatory infiltrate were noted. Some cellular atypism made us suspect an irritated seborrheic keratosis. Because the patient hated the extirpation, he remained untreated for 3 years and 3 months following his first presentation. The biopsy and a surgical resection of his second presentation confirmed the diagnosis of irritated seborrheic keratosis. Immunohistochemical analysis of Ki-67, p53 and papillomavirus was performed to elucidate its character. We emphasize that irritated seborrheic keratosis does occur in the external ear canal and may cause some diagnostic difficulty. Pathologists should be aware of this fact and avoid overdiagnosis.

Ear Canal↗
PubMed1996

Monaural and binaural spectral cues created by the external ears of the pallid bat.

The acoustic properties of external ears transform the spectra of incident sound in a location-dependent manner, and provide monaural and binaural spectral information used in 2-dimensional localization. Human studies suggest that binaural spectral differences, and spectral peaks and notches in monaural transfer functions, may all provide spatial information. This study examined the acoustic properties of the pallid bat ear to determine directionality, interaural intensity differences spectral peaks and notches in transfer functions, as well as acoustic gain. The pallid bat is a gleaning bat that uses passive sound localization to find prey, and echolocation for general orientation. It is capable of very accurate passive sound localization, and the primary focus of this study was to determine the spectral cues that might support this localization acuity. Results show that the external ears of this bat create spectral maxima and minima that vary systematically with azimuth and elevation. The monaural spectral cues resemble those reported in humans and cats and suggest that similar spectral cues are used across taxa. The ears also create robust interaural spectral differences that vary systematically with both sound azimuth and elevation. These monaural and binaural spectral cues may provide the basis for the 1 degrees angular resolution apparent in it this bat's passive sound localization performance.

Acoustic Stimulation↗
PubMed2000

Individual differences in external-ear transfer functions of cats.

Knowledge of the direction-dependent filter characteristics of the external ears is useful for the study of spatial hearing in experimental animals. The present study examined individual differences in the directional components of external-ear transfer functions (directional transfer functions, DTFs) among 24 anesthetized cats. Ears were fixed in a frontal position. Inter-cat differences in DTFs were quantified across a mid-frequency range from 8 to 16 kHz and across 30 locations in the horizontal plane and vertical midline. Across cats, DTFs showed similar direction dependence, but tended to differ in regard to the center frequencies of spectral features, such as spectral peaks and notches. Certain mid-frequency notches, for instance, varied in frequency across cats by nearly a factor of 2. Scaling of DTFs in frequency could reduce the overall differences between pairs of cats. Scale factors that minimized inter-cat differences ranged as high as 1.57 and correlated moderately with cats' body weights. Nevertheless, appreciable individual differences remained after frequency scaling. Inter-cat differences in DTFs were substantially larger than differences that resulted from variability in positioning the ears. The results suggest some guidelines regarding the conditions under which it is acceptable to apply DTF measurements from one cat to another.

Acoustics↗
PubMed1995

Spatially dependent acoustic cues generated by the external ear of the big brown bat, Eptesicus fuscus.

To measure the directionality of the external ear of the echolocating bat, Eptesicus fuscus, the left or right eardrum of a dead bat was replaced by a microphone which recorded signals received from a sound source that was moved around the stationary head. The test signal was a 0.5-ms FM sweep from 100 kHz to 10 kHz (covering all frequencies in the bat's biosonar sounds). Notches and peaks in transfer functions for 7 tested ears varied systematically with changes in elevation. For the most prominent notch, center frequency decreased from about 50 kHz for elevations at or near the horizontal to 30-40 kHz for elevations 30 degrees-40 degrees below the horizontal. A second notch shifted from about 85 kHz to 70 kHz over these same elevations. Above the horizontal, a peak that flanks these notches changed in amplitude by 15 dB with changes in elevation. Removal of the tragus from the external ear disrupted the systematic movement of notch frequencies with elevation but did not disrupt changes in the peak's amplitude. Smaller changes in notch frequency also occurred with changes in azimuth, so monaural notch information alone cannot determine the position of sound sources away from the median plane. However, because bats routinely keep the head pointed at the target's azimuth, median-plane localization occurs with monaural cues delivered to the two ears. Corresponding changes with elevation occurred in the impulse-response, which consists of a series of 3-6 peaks spaced 10-20 microseconds apart. The time separation of two prominent impulse peaks systematically increased from 22-26 microseconds above the horizontal to about 36-40 microseconds below the horizontal, and removal of the tragus disrupted this time shift below the horizontal.

Animals↗