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MUSC Otolaryngology - Head & Neck Surgery E-Update                 April 2016 
  Spring forward!

April's article is again brought to you by one of our six new faculty members, Ted R. McRackan, M.D., Director, Lateral Skull Base Program.
These newsletters are designed to provide brief, practical, clinical updates in areas where we all struggle in managing our patients. Your feedback or questions about the E-Update articles, your patients, or any other ENT issue are always welcome. Write to us at entupdate@musc.edu - And please forward this E-Update to your colleagues who may also benefit from sharing the latest ENT topics. As always, your support is deeply appreciated.

Yours sincerely,
Paul R. Lambert, M.D.
Professor and Department Chair

Novel Metrics to Evaluate Image-Guided Cochlear Implant Programming Outcomes
Ted R. McRackan, M.D.

Cochlear implantation (CI) is the standard of care for patients with bilateral severe-to-profound sensorineural hearing loss. To date, more than 300,000 patients have been implanted worldwide with 50,000 implanted last year. Modern CIs contain between12-22 electrodes, which are spaced with the intention of each electrode stimulating a unique area of the spiral ganglia.  Threading of the electrodes into the cochlea is largely done blindly with limited post-operative knowledge of the geometric relationship between electrode array and the neural interface within the cochlea.  This information is critical because suboptimal electrode positions within the cochlea have been shown to decrease speech understanding due to channel interaction.
Figure 1:  Left panel displays the CI electrode array in the cochlea in a post-operative CT.  Middle panel shows the modiolus (green) with respect to the CI electrode channels (grey spheres).  Right panel shows the distance (red line) from the electrode channels (red circles) to the cochlear/neuronal interface (color mapped based on frequency).  Used with permission from Jack Noble, Vanderbilt University.
Image-guided CI programing (IGCIP) has recently been developed by our collaborators at Vanderbilt University to more precisely locate CI electrode position with respect to the neural interface.  This provides a means to systematically deactivate suboptimally placed electrodes that result in channel interaction and may impair hearing outcomes ( Figure 1). Preliminary data have shown that IGCIP results in clinically and statistically significant improvements in speech understanding as compared to conventional programming procedures.  Image guided CI programming represents one of the most substantial changes in CI programming in the past 30 years and we are excited to evaluate it in our patient population.  While IGCIP represents a major programming development, the metrics we use to measure CI outcomes have not advanced in a similar fashion.  In addition, some CI users whose measured speech recognition did not improve significantly following IGCIP nevertheless reported substantially increased benefit from their newly programmed device.

Word and sentence recognition scores are the primary measures that have been used to guide CI programming and assess CI outcomes for the past 20-30 years.  However, these scores do not capture the wide range of subjective listening and communication experiences of CI users. The overall goal of our research is to expand outcomes related to cochlear implantation beyond the traditional measures narrowly defined by speech understanding.
First, increased listening effort and related fatigue reported by individuals with mild-to-moderate hearing loss may be especially relevant for CI users who have severe-to-profound hearing loss and are listening to unfamiliar speech representations.  Importantly, listening effort can vary among individuals with similar magnitude of hearing loss and speech recognition abilities and, therefore, could explain large and unexplained individual differences in outcomes for CI users and differences between measured and self-reported outcomes. Pupillometry has been used in the cognitive sciences to characterize mental effort where effort is defined as an increase in pupillary dilation with increasing task difficulty ( Figure 2). Characterizing listening effort through the use of pupillometry has been a focus of the MUSC Hearing Research Program.  However, pupillometry has not been widely applied to CI users and IGCIP represents an ideal opportunity to do so.
Figure 2:  Graph depicting the change in pupil diameter as a patient attempts to correctly identify a word or sentence during a task.  The degree of pupillary dilation corresponds to the effort a patient applies to complete the listening task.  Used with permission from Stefanie Kuchinsky.
Second, health related quality of life (HRQOL) instruments have become increasingly important in understanding the impact of a medical intervention on a patient's life.  Numerous studies have shown the positive effect of CIs on HRQOL, but there is no universally accepted and validated QOL measure for CI patients.  In fact, this has been identified as a research gap in the American Academy of Otolaryngology-Head and Neck Surgery's upcoming "Minimal Reporting Standard for Adult Cochlear Implantation."  We are currently developing the first CI QOL metric using patient centered focus groups and the strict methods of the NIH's Patient Reported Outcomes Measurement Information System.  In doing so, we will create an instrument that correlates with patients' subjective experience, is more responsive to intervention and changes in patient performance, and meets modern outcome reporting standards.

Our immediate goals are to develop and apply innovative clinical and research tools for CI outcomes and broaden our understanding of the benefit of IGCIP through analysis of relationships among listening effort, QOL, speech recognition, and other hearing-related outcomes.  In the longer term, we aim to evaluate listening effort and QOL in bilateral CI recipients and patients undergoing implantation with residual hearing.  Additionally, we will work to apply pupillometry in the pediatric CI population as an early objective measure of hearing performance.  Through the multidisciplinary expertise of Dr. Judy R. Dubno and Dr. Mark Eckert in the Department of Otolaryngology-Head and Neck Surgery's Hearing Research Program, Dr. Craig Velozo of the MUSC College of Health Professions, and Dr. Robert Labadie and our other collaborators at Vanderbilt University, we have the capability of expanding a new area of research that may have significant clinical benefit for CI patients.
Ted R. McRackan, M.D.

Assistant Professor

M.D.: Medical University of South Carolina
Residency: Vanderbilt University Medical Center
Fellowship: House Ear Clinic
Special Interests: Adult and pediatric ear disorders, cochlear implants, chronic ear infections and cholesteatoma, acoustic neuromas and skull base disorders, and vestibular disorders
Email: mcrackan@musc.edu

E-Update Articles 
Look for these articles in upcoming issues!
May: Dynamic re-animation options for facial paralysis

June: Is Meniere's Disease a Migraine of the Inner Ear?

July: Contemporary Management of Recurrent Respiratory Papilloma

To view any of our past E-Updates visit our
Continuing Education
Southern States Rhinology Course
April 20 - 23, 2016

The ABC's of Maxillofacial Prosthodontics Medical and Dental Billing 
June 17, 2016

The Charleston Course: 6th Annual Otolaryngology Literature Update
August 5 - 7, 2016

31st Annual F. Johnson Putney Lectureship in Head & Neck Cancer 

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