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The Physicians and Audiologists at Let Them Hear Foundation (LTHF) and California Ear Institute (CEI) are involved in a large number of research projects. Researchers meet monthly to update one another, and to offer constructive feedback on research projects and objectives. Below is a sampling of current projects:
Accuracy of ASSR in Pediatric CI Evaluation
The Auditory Steady-State Response (ASSR) is an auditory evoked potential elicited with modulated tones that can be used to predict hearing sensitivity in patients of all ages – even newborns! ASSR is a “cutting edge” tool that is being used regularly by our Diagnostic Audiology Department. The ASSR system's primary advantage over the standard evoked potential test is the ability to differentiate between severe and profound hearing loss, as well as distinguishing between levels of profound hearing losses, e.g. the difference between a 90 dB and a 110 dB hearing loss. This ability is crucial in instances where a cochlear implant is being considered, as well as to accurately fit amplification. Unlike ABR testing, which does not differentiate the severe and profound levels, the ASSR evaluation, in combination with behavioral testing, makes earlier identification of hearing loss even more accurate. With this study we compare the accuracy of the ASSR Equipment to other testing techniques, to ensure that appropriate decisions are being made for each patient.
Allergy to Cochlear Implants
5 cases of allergy to cochlear implant casing materials have been reported in the world literature. LTHF/CEI has 2 more cases to add! We have outlined an important protocol for testing and diagnosis when allergy to CI is suspected, course of treatment, and the mechanism to make a CI without those components that create the allergy in the patient.
Auto-Neural Response Telemetry Programming of Cochlear Implants
New equipment can potentially automate the CI programming process. In young children this is extremely important as they do not have the language to help us program their device. Working with Cochlear Corporation, we are refining the equipment, software, and automated programming technique. It is our hope that this programming tool can be extended to others, especially to those working with implant recipients in developing nations.
Bilateral Cochlear Implants Adults and Children
In the past 3 years bilateral cochlear implants have come into clinical use as the result of the work at LTHF and a few other centers around the world. Less than 1% of CI patients worldwide have implants in both ears. Let Them Hear is one of the leading centers in the country when it comes to bilateral cochlear implants! Our findings have been consistent with research being conducted elsewhere. The advantages of bilateral implants include improved directional hearing capabilities, increased understanding in noise, and improved speech understanding. Clinically we have noticed a faster response rate in patients using 2 implants vs. 1. We are currently involved in a number of bilateral cochlear implant studies.
Bilateral Cochlear Implant and Sound Localization
A special laboratory at UC Berkeley is expanding upon research previously conducted at LTHF. This study looks at the ability of patients with bilateral CIs to localize a sound source. The laboratory at UC Berkeley has sophisticated psychoacoustic measurement capabilities such as 3D instead of 2D special relations measurements. Previous work in the laboratory has shown that patients with CIs do not rely on timing cues (like the person with normal hearing), but rely on other qualities of sound in order to localize. Results will ideally lead to creation and production of a better cochlear Implant, produced in conjunction with manufacturers.
Botox for Migraine Associated Dizziness
Patients with migraines frequently suffer dizziness as the dilated blood vessels in the brain responsible for the headache steal blood from the inner ear. This leads to dysfunction and unpleasant symptoms. Treatment of migraines with Botox may alleviate the dizziness associated with the underlying cause. Only recently recognized, migraine associated dizziness may account for over 50% of those cases of dizziness previously beyond the limits of medical understanding, giving hope to a segment of patients with a very disabling problem.
Botox for Tinnitus
Botox injections, frequently used for wrinkle reduction, have also been found to successfully stop chronic pain syndromes such as migraines. Tinnitus, very similar to chronic pain, is the target of this investigation. In the first work ever conceived or done on the subject, CEI/LTHF has shown a 20% response rate from tinnitus sufferers in a small group of patients. This study broadens the # of people and sites that will treat tinnitus sufferers with Botox injections while following the tinnitus in each subject to define effects of the intervention.
Case Report: Carcinoid of the Tympanic Membrane
Report of a case of a patient with an extremely rare tumor of the eardrum that was treated at CEI.
Case Report: Ependymoma of the Internal Auditory Canal (IAC)
Report of a case of a patient with an extremely rare tumor of the brain that involved the canal between the brain and the inner ear. This tumor was removed surgically, curing the patient.
Case Report – lightning strike hearing impairment
One of our patients was struck by lightning 16 years ago. This patient has been deaf ever since. Her hearing has been restored thanks to bilateral CI’s implanted at CEI/LTHF. This is a one-of-a-kind story, and this report details her case.
CI Surgical Findings and Perioperative Outcomes <18 months
CI surgery has become the standard of care for deaf children at younger and younger ages. At LTHF, we have a very high number of young children with CI’s. The results of cochlear implant surgery in children down to 5 months of age is being studied. Studies such as this are necessary, in order to petition the FDA to lower the allowed age of implantation below the current 12 month limit. Our experience makes us believe that implantation at a younger age is the best option for some implant candidates.
Cochlear Implant FDA Sanctioned Trials
All new Cochlear Implant technology is evaluated with FDA trials to determine safety and effectiveness of these new devices. CEI/LTHF has been the site of all FDA sponsored clinical trials for CIs in Northern California since the early 1990’s. LTHF and CEI perform research for all three CI manufacturers: Cochlear Corporation (Australia), Advanced Bionics Corporation (USA), and MedEl Corporation (Austria). We offer all devices to our patients. Dr. Roberson and Lisa Tonokawa serve as advisors on the Surgeon’s Advisory Board and the Audiology Advisory Board for manufacturers.
Adult Bilateral CI Advanced Bionics Corporation:
Bilateral CI study in Adults with the Advanced Bionics 90k Cochlear Implant/Bionic Ear.
System 4 Cochlear Implant Cochlear Corporation: Study of the Cochlear Corporation Freedom CI, the newest Cochlear Implant on the market.
Hybrid CI Cochlear Corporation: A short electrode CI can be implanted into the inner ear without damage to the limited hearing that remains there. Hybrid patients can then use both a hearing aid and a CI to produce a combination of sound that is proving to be superior to sound from a Hearing Aid or CI alone.
Dural Exposure in CI Surgery
CI surgery in very young children involves placement of a device that measures 5 mm or so in thickness. This device is placed in a depression created in the skull surgically. The average skull thickness in children is less than 2 mm. Full thickness removal of the skull and placement of the CI on the underlying fibrous lining of the skull, called the dura, is the safest technique in the very young. This study looks at the frequency of the need to expose dura and the safety of it, while defining surgical techniques for less experienced surgeons to follow.
Genetic Sequencing in Hearing Loss
Working cooperatively with Dr. Iris Schrijver in the Pathology Department at Stanford, and a “start-up” genetics testing laboratory, LTHF/CEI patients have the option to have testing performed on the genes that code for the structures in their ears. Approximately 300 genes and the proteins that come from them are needed to form a human ear. This “gene chip” technology could, for the first time, allow doctors in the clinic to test over half of these genes at a single time! We are very enthusiastic that this work will have immense impact on the treatment of the hearing impaired.
Hearing Preservation in CI
Surgeons at CEI/LTHF are able to insert CI electrodes into the inner ear of some patients without losing the hearing that is present in the ear. This study seeks to understand the surgical technique needed to perform hearing preservation CI surgery, potentially opening a new frontier for cochlear implants and the hearing impaired.
iPod Project – Sound exposure with personal music players
A generation of young people are using personal music players very frequently. In many cases, sound exposure is intense. LTHF worries that children and young adults are damaging their hearing from chronic exposure to damaging sound energy. From industrial exposure experiments, we know that noise exposure over a lifetime gives a cumulative effect. Our youth may be setting themselves up for hearing loss later in life. By measuring the Sound Pressure Levels from individual personal music players and the amount of weekly exposure, we seek to quantify this risk before it is too late for some individuals.
Middle Ear Mechanics Laboratory
A large number of studies are ongoing in a laboratory located onsite at LTHF. These studies allow for measurement of the effects of intervention and device application to the human middle ear. Human cadaver bones are being used to test new prostheses, adjustable prostheses for surgical reconstruction, implantable hearing devices, and hearing preservation CI surgical techniques. Several pieces of equipment have been built for Dr. Roberson that allow LTHF to perform experiments not possible anywhere else in the world.
Pediatric Cholesteatoma
Surgeons at CEI have performed surgery for a non-cancerous, destructive tumor of the middle ear on over 3,000 patients. This tumor, called a cholesteatoma, is the most common tumor of the ear. Several unique techniques for removal and reconstruction of the damaged hearing mechanism are practiced at our institution. This very large study seeks to understand the success of certain procedures, allowing for refinement in surgical technique. These findings will be shared with Ear Surgeons around the world, in order to improve the standard of outcomes for Pediatric Patients.
Posturography and Cochlear Implantation
Posturography is a very sophisticated and sensitive testing mechanism for the balance system. We know cochlear implant patients do very well without balance problems following surgery. We also know the inner ear, where the electrode is placed, contains both balance and hearing function. By applying this test we will define any subtle balance changes that have previously gone undetected. This will be particularly important with bilateral CI’s to determine if two devices place patients at higher risk for balance dysfuction.
Premature Presbycusis and Connexin Gene
Genetic transmission of hearing impairment is the most common cause of hearing loss and our ability to understand it, define the gene responsible, and screen patients is exploding. This extremely exciting and ground-breaking study looks at the most common gene for unexplained causes of hearing loss and its effect on the aging ear.
Revision of Stapedectomy vs. Revision of Stapedotomy
Surgery for a condition called Otosclerosis involves removing all of the stapes (called a Stapedectomy) or a portion of it (called a Stapedotomy) and replacement with a prosthesis. You may not know that Stapedotomy Surgery performed with a laser was first described and performed at the California Ear Institute (CEI). You may also not know that Dr. Roberson designed the prosthesis we currently use for the procedure. In a small number of patients, revision surgery is needed. This study compares revision surgery performed on patients who had stapedectomy to revision surgery performed on patients who had stapedotomy. Results favor stapedotomy and should prompt all surgeons to abandon the older technique of stapedotomy replacing it with the surgical technique described at CEI – the laser stapedotomy.
23 - Secreting Glomus Tumor / Alpha Blockade Surgical Management
A Glomus Tumor is a rare tumor of the blood vessels, which involves the base of the skull in the ear. Surgical removal is frequently necessary. A small percentage of these tumors produce a chemical – adrenaline - that can make surgery dangerous. Specifically, removal of a secreting tumor can suddenly decrease the amount of adrenaline in the bloodstream, causing blood pressure to drop. This drop in blood pressure is non-responsive to medications and may lead to the death of the patient in the operating room. This work details the pre-operative recognition, preparation for the removal of the adrenaline source (the tumor), and the intra-operative treatment of such tumors based on our experience with several such cases.
Stacked ABR and Meniere’s Database
Using commonly available equipment, a new test protocol has been formulated to test for Meniere’s Disease and the associated elevated fluid pressures in affected ears. Working with the House Ear Clinic, we are gathering data to determine the accuracy and sensitivity of this test protocol. This test is not yet available to the public.
Stapedius Resection in CI < 12 months
Very small children have middle ears that are correspondingly small. Placement of cochlear implant electrodes through the middle ear must avoid structures such as the facial nerve. In order to accomplish this safely in children under one year of age, removal of a small muscle attached to the middle ear bones has been performed. Since very few children under one year of age have received implants, this surgical technique is novel. This report seeks to describe use of this technique for the benefit of other patients and their surgeons.
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