Interactive Evolution for Cochlear Implant Fitting

1. Pierrick Legrand (1,2), Claire Bourgeois-République (4), Vincent Péan (5), Esther Harboun-Cohen (6), Jacques Levy-Vehel (2), Bruno Frachet (6), Evelyne Lutton (2), Pierre Collet (3) Entry for the 2007 « Humies » award Interactive Evolution for Cochlear Implant Fitting (1) IMB, Institut de Mathématiques de Bordeaux, UMR CNRS 5251, Université de Bordeaux 2, 146 rue Léo Saignat, 33076 Bordeaux cedex, France (2) COMPLEX Team - INRIA Rocquencourt, B.P. 105, 78153 Le Chesnay cedex, France (3) Laboratoire d'Informatique du Littoral, ULCO BP719, 62100 Calais cedex, France (4) LE2I, UMR 5158 CNRS, 9 avenue A. Savary, B.P. 47870, 21078 Dijon cedex, France (5) CRT Innotech, 1 Promenade Jean Rostand, 93005 Bobigny cedex, France (6) Hôpital Avicenne, Service ORL, 125 rte de Stalingrad, 93000 Bobigny, France 2007 Humies competition

2. Presentation of the problem • A Cochlear implant is an array of electrodes surgically inserted in the cochlea of a deaf patient in order to directly stimulate his auditory nerve. • A DSP converts sounds picked up by a microphone into impulses on the electrodes (and stimulations of the auditory nerve). • Question: how does one stimulate an auditory nerve in such a way that a deaf patient can not only hear, but understand speech again ? 2007 Humies competition

3. Cochlear Implants in 2007 • First implants nearly 50 years ago, starting with one electrode, then 2 electrodes, … • Nowadays, up to 22 electrodes, and more than 100k implanted patients in the world (> 5000 patients in France since Jan. 2007). • Although many patients hear well (40% can use the phone), some of them still have problems: • For some (rare) patients, everything is fine after the first « fitting » session (i.e. parameters tuning). • For most patients, less than 10 fitting sessions are needed. • For some patients, things are more problematic… 5 to 10 fitting sessions / year with no satisfactory result. 2007 Humies competition

4. History of the proposed entry • In 2001, PhD starting on the feasibility of using an Interactive EA to help the expert find a better fitting. • In Nov. 2004, an IEA is tested on a real patient implanted for 10 years, with speech understanding problems (the patient typically understands less than 50% of the words). • A simplified evaluation protocol is devised, taking only 4 mn (rather than more than 30mn). • Expert fitting after 10 years gave an evaluation of 48.5/100. • After 90 evaluations (1.5 days), IEA finds a fitting giving an evaluation of 91.5/100, mainly by shutting down all electrodes of the CI but 2 ! 2007 Humies competition

5. 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 E 1 E 2 E 3 E 4 E 5 E 6 E 7 E 8 E 9 E 13 E 15 E 14 Obtained results with patient A Best fitting found by the human expert practitioner in 10 years The IEA found that for patient A, minimising the [T,C] interval of all electrodes but 7 and 9 gave the best result ! 2007 Humies competition

6. Results with other patients Tests with other patients below speech understanding (evaluation on consonant recognition tests (VCV) and discrimination tests (ASE)). Human (expert practitioner) Interactive EA (= random) 2007 Humies competition

7. Accepted ideas before this work • Orthophonists thought that only an extensive evaluation of a patient’s audition was meaningful. • Testing more than 2 or 3 fittings during a session was considered as unrealistic. • It was believed that due to neural plasticity, a patient needed several days to get used to a fitting = no proper evaluation could be done immediately after the fitting. • It was believed that for a cochlear implant, the more electrodes, the better. • In order to maximise the quality of the information passed to the auditory neural area, all experts and CI manufacturers currently advocate to maximise the [T-C] interval for each electrode. 2007 Humies competition

8. Outcomes of the IEA • Thanks to the IEA, some quick evaluation protocols (4mn) were tested, and shown to be reliable (reproductible results after 1 month). • The results of the IEA showed that although probably not very precise, the 4mn protocol was good enough to drive an optimisation algorithm. • Great results were obtained on patient A, by testing 90 fittings in 1.5 days (considered as impossible before). • On patient A, the best results were obtained by minimising all but 2 electrodes ! • When activating electrode 4, results dropped from 82 down to 58.5 => some functional electrodes can have a negative effect on speech understanding ! The problem is combinatorial (2^22 combinations !) • The current belief that for all patients, one should maximise the [T,C] range of all electrodes is simply wrong. (If some functional electrodes can be detrimental, maximising all electrodes is sure to give a bad result !) • An IEA may be a way to find the good combination among millions. New result New result 2007 Humies competition

9. Claims regarding the Humies’07 contest • Obtained results were always better or equal than the best current accepted method (maximising [T,C] interval for each electrode). • Results have been published in medical symposia as a new scientific result, independently from the fact that it was mechanically created. • Results have shown that maximising the [T,C] interval of all electrodes (most recent solution after more than 40 years of human research) is not good for all patients, and that some functional electrodes could be detrimental to speech understanding. • Result helps to solve a problem of indisputable difficulty (directly stimulating the auditory nerve to recreate sound sensations allowing a deaf patient to understand speech !) by offering a way to find a good combination of electrodes among several million, with a very small number of evaluations). • Result won a competition with another human : on patient A, result was far better than best result obtained by a human expert after 10 years of fitting attempts. 2007 Humies competition

10. Why is this entry the best ? The presented work has allowed to: • Find a great fitting for at least one patient (not generalisable yet, but making a big difference at least for him !) • Open new directions on CI fitting, as the results of the IEA have shown that: • A simplified hearing evaluation could be enough to drive an optimisation algorithm. • A patient could determine whether a fitting was better than another within minutes only (and not days), therefore opening the path to automatic CI fitting. • For some patients, maximising the [T,C] interval for all electrodes may not be a good idea. • Some functional electrodes may be detrimental to speech understanding. • Using an IEA could be a way to find a good combination of electrodes (impossible right now). These revolutionary outcomes may change the life of many Implanted Patients for whom the system is not working well enough 2007 Humies competition