Πέμπτη, 31 Ιανουαρίου 2019
The Effect of Stimulus Polarity on the Relation Between Pitch Ranking and ECAP Spread of Excitation in Cochlear Implant Users
Abstract
Although modern cochlear implants (CIs) use cathodic-leading symmetrical biphasic pulses to stimulate the auditory nerve, a growing body of evidence suggests that anodic-leading pulses may be more effective. The positive polarity has been shown to produce larger electrically evoked compound action potential (ECAP) amplitudes, steeper slope of the amplitude growth function, and broader spread of excitation (SOE) patterns. Polarity has also been shown to influence pitch perception. It remains unclear how polarity affects the relation between physiological SOE and psychophysical pitch perception. Using a within-subject design, we examined the correlation between performance on a pitch-ranking task and spatial separation between SOE patterns for anodic and cathodic-leading symmetric biphasic pulses for 14 CI ears. Overall, there was no effect of polarity on either ECAP SOE patterns, pitch ranking performance, or the relation between the two. This result is likely due the use of symmetric biphasic pulses, which may have reduced the size of the effect previously observed for pseudomonophasic pulses. Further research is needed to determine if a pseudomonophasic stimulus might further improve the relation between physiology and pitch perception.
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A Retrospective Analysis of Dental Implant Survival in HIV Patients
Abstract
Aim
This 5 years retrospective cohort survival study compared failure rates of dental implants placed in HIV (+) and HIV (‐) patients relative to several risk factors.
Materials and Methods
Between 2006 and 2015, 484 implants placed in HIV (+) patients and 805 implants placed in HIV (‐) patients, were assessed for survival. The effects of HIV were estimated using propensity weighting. The effects of age, smoking status, diabetes, restoration status, gender, implant type, placement site, hepatitis C status, baseline CD4 count and CD4%, post placement average CD4%, nadir CD4%, nadir CD4 count and antiviral therapy were analyzed.
Results
Implants placed in HIV (+) patients and HIV (‐) patients had similar failure rates (HR=1.4, P=0.34). Increased failure rates were observed in HIV (+) patients with baseline CD4%≤20 (HR=2.72, P=0.04), post placement CD4% average ≤20% (HR=2.71, P=0.04), protease inhibitor administration (HR=2.74, P=0.04), smoking (HR=2.61, P=0.05) and anterior maxillary placement (HR=5.82, P<0.01). Hepatitis C co‐infection, viral titer, baseline CD4 count, gender, implant type and restoration type were non‐contributory.
Conclusion
Implants placed in HIV (+) patients had similar survival rates as HIV (‐) patients. Failure rates increase significantly when confounding risk factors are present in HIV (+) patients.
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from ! ORL Sfakianakis via paythelady.61 on Inoreader http://bit.ly/2S1bpmX
via IFTTT
The Effect of Stimulus Polarity on the Relation Between Pitch Ranking and ECAP Spread of Excitation in Cochlear Implant Users
Abstract
Although modern cochlear implants (CIs) use cathodic-leading symmetrical biphasic pulses to stimulate the auditory nerve, a growing body of evidence suggests that anodic-leading pulses may be more effective. The positive polarity has been shown to produce larger electrically evoked compound action potential (ECAP) amplitudes, steeper slope of the amplitude growth function, and broader spread of excitation (SOE) patterns. Polarity has also been shown to influence pitch perception. It remains unclear how polarity affects the relation between physiological SOE and psychophysical pitch perception. Using a within-subject design, we examined the correlation between performance on a pitch-ranking task and spatial separation between SOE patterns for anodic and cathodic-leading symmetric biphasic pulses for 14 CI ears. Overall, there was no effect of polarity on either ECAP SOE patterns, pitch ranking performance, or the relation between the two. This result is likely due the use of symmetric biphasic pulses, which may have reduced the size of the effect previously observed for pseudomonophasic pulses. Further research is needed to determine if a pseudomonophasic stimulus might further improve the relation between physiology and pitch perception.
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