( Introduction6huit des onze patients. Même Eve serévé<strong>la</strong>, lors de cette étude, présenter une<strong>neuropathie</strong> périphérique asymptomatiqueconfirmée histologiquement après unebiopsie du nerf sural en 2000 alors qu’elleavait 19 ans. Nous étions fascinés par lestrois sujets exempts de <strong>neuropathie</strong> périphérique,puisqu’ils nous indiquaient queles cellules ciliées internes et leur synapseavec le nerf cochléaire étaient égalementdes candidats au siège de l’anomalie à l’originede l’affection. Brain décida de publiercet article en accord avec sa tradition d’êtrel’un des seuls journaux médicaux à reconnaître<strong>la</strong> valeur de descriptions individuellesou portant sur de petits groupes de patientspour identifier des problèmes spécifiquestouchant les fonctions cérébrales ou sensorielles.Nous n’eûmes plus de répit. YvonneSininger et moi-même organisâmes en2000 une conférence sur <strong>la</strong> NeuropathieAuditive qui réunit 75 personnes et fournitles bases d’un ouvrage intitulé « AuditoryNeuropathy » publié en 2001 et dans lequelnous avons résumé l’ensemble de nosconnaissances. « Eve » et « Adam » contribuèrentà l’introduction du livre en décrivantavec force leur expérience subjectivede patient atteint de Neuropathie Auditive.L’éditeur utilisa l’une de mes aquarellesimpressionnistes illustrant les cellules duganglion de Corti pour <strong>la</strong> couverture.J’ai préparé ces réflexions pour <strong>la</strong> nouvellemonographie en <strong>la</strong>ngue française qui rassembleles données accumulées sur l’affectiondepuis 1991. Beaucoup d’informationsse sont accumulées amenant à <strong>la</strong> fois c<strong>la</strong>rificationet confusion. Mon collègue FanGang Zeng, à Irvine, a décrit les déficitspsycho-acoustiques spécifiques de <strong>la</strong>Neuropathie Auditive chez les adultes etles enfants. Il s’agit en effet d’un déficit detraitement des indices temporels. La<strong>neuropathie</strong> <strong>auditive</strong> est diagnostiquéedans environ 10% des enfants déficientsauditifs si l’on réalise le dépistage néonatalde <strong>la</strong> surdité avec les oto-émissions acoustiques,et j’espère « combinées avec lesPEAP » et non pas « ou les PEAP ».L’imp<strong>la</strong>ntation cochléaire s’est révéléebénéfique chez de très nombreux patients.Son échec constaté chez quelques uns estsimi<strong>la</strong>ire aux échecs de l’imp<strong>la</strong>nt chez lespatients atteints de surdité neurosensoriellec<strong>la</strong>ssique.Quels sont les mécanismes de ceséchecs ? Récemment une f<strong>la</strong>mbée dedécouvertes sur les mécanismes génétiqueset molécu<strong>la</strong>ires sous-tendant <strong>la</strong> <strong>neuropathie</strong><strong>auditive</strong> a eu lieu. L’affection n’est pasrare, et au fur et à mesure que <strong>la</strong> compréhensionque nous en avons s’accroît, nousdeviendrons capable d’agir efficacement surcette condition chez l’homme. Le rôle ducortex auditif dans le traitement de l’informationdistordue fournie par le nerfcochléaire constitue un élément essentielpour <strong>la</strong> compréhension des mécanismescompensatoires de <strong>la</strong> perception. HenryMichalewski à Irvine et Hillel Pratt à Haifaont joué un rôle fondamental dans ces nouvellesétudes.J’espère que quand vous évoquerez <strong>la</strong>Neuropathie Auditive, vous penserez perturbationde l’activité du nerf cochléaireaffectant de manière symptomatique lespercepts auditifs dépendant des indicestemporels. La Neuropathie Auditive peutêtre causée par de très nombreuses étiologiesprovoquant des signes et symptômescommuns avec toutefois différentes anomaliesspécifiques des cellules ciliées internes,du nerf cochléaire et des synapses les articu<strong>la</strong>nt.Je considère les cellules ciliées internesen tant qu’élément nerveux spécialiséproduisant des neurotransmetteurs maispas de potentiel d’action. Ce conceptpossède <strong>la</strong> vertu d’encourager à envisager<strong>la</strong> synapse entre <strong>la</strong> cellule ciliée interne etle nerf cochléaire comme présentant desdéficits au niveau tant pré- que postsynaptiquedans <strong>la</strong> Neuropathie Auditive.L’identification des sites, des protéines etde leurs déficits sous-jacents permettrad’é<strong>la</strong>borer des traitements spécifiques.L’utilisation de modèles animaux expérimentauxest d’une importance crucialepour ces développements.Je m’attends à ce que <strong>la</strong> plupart d’entrenous connaissent quelques uns des symptômesde <strong>la</strong> Neuropathie Auditive pour ceuxqui auront <strong>la</strong> chance de vivre assez longtemps.Avec l’âge en effet nous développonsdes déficits à <strong>la</strong> fois synaptiques etneuraux. Le nerf auditif n’y échappera pas.Eve m’a appris l’une des thérapeutiques lesplus efficaces dans cette affection. Chacund’entre nous peut l’appliquer facilement :« Apprenez à lire sur mes lèvres ».October 4, 2007-11-07Laguna Beach, CaliforniaA HISTORYOFAUDITORYNEUROPATHY,A HEARING DISORDER DISRUPTING AUDITORYNERVE ACTIVITY AND AUDITORY TEMPORALPROCESSESMedicine is especially engaging when a storycan be re<strong>la</strong>ted to a diagnosis. For example aspecial sleep disorder is aptly named afterOndine, a beautiful French water nymph orgoddess. She became enamored of a mortalman and married him forsaking her immortalstatus and powers. Her immortal beauty soonbegan to fade and her husband’s fancy wandered.She found him one day asleep in the armsof another. She awakened him and summonedher remaining powers to will that if he everwere to sleep he would lose the ability toLes Cahiers de l’Audition - Vol. 20 - n°6 - Novembre/Décembre 2007
Introduction )breathe and would die. The disease thataffects the ability to initiate breathing onlyduring sleep is known as “Ondine’s curse”,a more compelling term that CentralHypoventi<strong>la</strong>tion Syndrome, a loss of centralmotor drive for breathing when subjects sleep.This foray into sleep disorders provides thereason for telling you the story of AuditoryNeuropathy from the perspective of myencounters in 1988 with Eve, the first personI saw with what has become known asAuditory Neuropathy. She was eleven yearsand described her problem succinctly as “I canhear but not understand”. She was of normalbirth and development. When she was eightteachers noticed that she was not “understandingin c<strong>la</strong>ss”. Her parents and elder sister (byone year) were unaware of a hearing problem.She was then and still is a pleasant and directperson without social ambiguities putting torest considerations of “hysteria” or “conversiondisorder.”Audiologists tested her and defined a mild elevationof threshold for low frequencies. Herability to understand speech perception wasimpaired beyond that expected for the mildthreshold loss. The auditory brainstem potentials,or ABRs, that we now use as part of ascreening battery for “hearing” in newborninfants, showed either no reproducible wavesor low amplitude components during the firstfew ms after the click stimulus. Eve was referredto the House Ear Clinic in Los Angeleswhere she was seen by Yvonne Sininger andManny Don who recognized that the ABRchanges were the key to understanding thisyoung girl and they referred her to me at theUniversity of California in Irvine, just an hoursouth of Los Angeles. Proximity assumes manyforms. I had first met Yvonne Sininger in SanFrancisco when she was doing her doctoralthesis on auditory brainstem potentials andManny Don had been my graduate student atStanford University in 1968 and <strong>la</strong>ter was mycolleague at Irvine in 1973, when we first wereexploring the generators of ABR components.Eve and her family worked closely with the<strong>la</strong>boratories at Irvine and House Ear for thenext two years to help us understand theparadox of “preserved hearing” with absentABRs. Not only were ABRs absent but so weremiddle and long <strong>la</strong>tency responses. We soondistinguished that the early ABR componentswere actually receptor hair cell cochlear microphonicsonly evident when the clicks were presentedas condensation or rarefaction singlepo<strong>la</strong>rity clicks. In routine clinical evaluations itwas customary to use alternating click po<strong>la</strong>rityto cancel the electrical artifacts of the stimulithat appeared in the averaged responses. Thealternating click po<strong>la</strong>rities also cancelled thebiological cochlear microphonic potentials.Thedefinition of cochlear microphonics were evidenceof preserved cochlear receptor hair cellfunction while the absence of ABRs suggesteda problem at the level of the auditory nerveand or the synapse with the inner hair cell. Thetesting for otoacoustic emissions, the faintsounds produced by receptor outer hair cells,were not introduced in the clinic till the followingyear and when examined OAEs were alsopresent in Eve.We made detailed psychophysical studies inEve and showed impairments of those perceptsdependent on temporal cues whereasintensity and frequency cues were preserved.Thus, monaural tasks such as speech perception,thresholds for distinguishing two clicksfrom a single click, and thresholds for detectingsilent periods in noise (gap detection)were impaired. Binaural tasks requiring integrationof temporal information from the twoears such as localization of binaural clicks,identification of binaural beats accompanyingthe presentation of low frequency signals tothe two ears differing by a few Hz, and thereduction of monaural noise masked thresholdsby adding the same masking noise tothe opposite (masking level differences orMLDs) were very impaired. Eve’s sister wasour single control with normal audiogramsand speech perception and no impairmentscompared to adults on any of the psychophysicaltasks. Even with all of this biologicaldata consistent with a disorder of auditorytemporal processing, some still questionedwhether the disorder was “psychologically”based. Eve’s speech was unaffected withde<strong>la</strong>yed auditory feedback while her sister’sspeech rhythms were adversely impacted.All of this work could not have done this workwithout support from the National Institutes ofHearing and Communications Disorders whohad funded for 10 years our investigations ofneural mechanisms of auditory brain stempotentials in neurological disorders. I consideredEve’s appearance an essential key forunderstanding central auditory processes andtheir re<strong>la</strong>tion to ABR measures.We wrote a paper about Eve entitled “Absenceof both auditory evoked potentials and auditorypercepts dependant on timing cues” thatwas published in BRAIN in 1991 and suggestedthat the temporal processing disorderreflected a deficit either in the nerve or in thesynapses between nerve and inner hair cells(Starr A, McPherson D, Patterson J, Don M,Luxford W, Shannon R, Sininger Y,Tonakawa L,Waring M.). At this time, Eve had normalneurological and peripheral nerve studies.So we were able to get on with our lives againsimi<strong>la</strong>r to what Anthony Quinn says at the endof the movie “Zorba the Greek“ of the survivorsof Greek tragedies “then all went to theseashore. ”And we did go to the seaside, but not for long,as other patients with this special hearing disordercame to light. In particu<strong>la</strong>r Charles Berlinand Linda Hood in New Orleans, TerencePicton in Toronto, and Yvonne Sininger and Ifound other patients with the same paradox(absent ABRs and re<strong>la</strong>tively preserved hearingthresholds) indicating that Eve was not aloneand we had a problem to really solve. Wegathered together in New Orleans at theKresge Hearing Institute where Berlin workedalong with several of the patients together inNew Orleans. We met with the patients andreviewed their audiological and neurological findings.We were considering alternative andoften-conflicting hypotheses. It was apparentthat several of the patients had <strong>neuropathie</strong>seither sporadic or as part of an inheritedneurological disorders, and it seemed likely thatfor those patients, the disorder was also involvingthe auditory nerve.We (Starr A, Picton TW,Sininger Y, Hood LJ, Berlin CI.) published a 1996paper describing “Auditory Neuropathy”, also7Les Cahiers de l’Audition - Vol. 20 - n°6 - Novembre/Décembre 2007