Ear and hearing

The prevalence of disabling hearing loss is approximately 5% of the gobal population. Noise-induced and drug-induced hearing loss (ototoxicity) are unwanted types of acquired hearing loss. Cisplatin is a mainstay in the treatment of testicular cancer and used as a first-line treatment of a number of different malignant solid tumors. Hearing loss is a major side-effect of cisplatin and may cause treatment interruption. Furosemide is a loop diuretic and can cause synergistic ototoxic effects in combination with aminoglycoside antibiotics or cisplatin. In this research project we are aiming to map drug transport to and within the cochlea and establish methods for otoprotection by performing mechanistic and otoprotective studies. Further insights into the mechanisms of noise-induced and drug-induced hearing loss and how to prevent these will be obtained.

Members of the research group
Göran Laurell, senior professor
Per Olof Eriksson, associate professor
Pernilla Videhult Pierre, PhD student
Jesper Edvardsson Rasmussen, PhD student

Anatomical Studies of the Human Ear – Significance for Cochlear Implants

Anatomical studies of the human inner ear give us a better understanding of how our hearing and cochlear implants (CIs) work. This secretive organ is located inside the body's hardest bone, called the capsula otica. The inner ear is therefore very difficult to study and requires special preparation methods to be successful. Hearing loss is the most common loss of mind.

Cochlear implant is a method of treating deafness caused by an impact on the inner ear and auditory nerve. The surgical method can be used on both children and adults but is particularly successful in children. Cochlear implants are today an established method that involves inserting electrodes into the cochlea, which are stimulated by ordinary sound. Through the operation, many people can regain large parts of their hearing.

Cohlea implants are a huge success in modern medicine. CI electrodes are inserted into the cochlea and their design is usually of two different types. One type is located along the inner wall of the snail (perimodiolar electrode) while the other is located along the outer wall of the cochlea.

Anatomical variations in the cochlea are very pronounced and this affects the final position of the electrode relative to the location/frequency map in the cochlea. Through less invasive surgical techniques and shorter electrodes, it is possible to trace the sensitive structures in the inner ear. Any remaining hearing can be saved and this is today a general goal in surgery. Better knowledge of the anatomical variations and how they can be seen on X-rays is now a common goal in CI surgery and limits any damage to inner ear structures. To help us study these variations, we have the world's largest collection of casts of the human inner ear. This collection contains 325 preparations (Fig. 1). These were prepared in the 70-80s and the technique was described in several works by Wilbrand et al. (Wilbrand et al. 1974) (Wadin 1988) and (Rask-Andersen et al. 1977).

(Fig1) Med hjälp av superupplösande mikroskopi kan man studera proteiner och genuttryck i det mänskliga innerörat. Det görs med fluorescerande antikroppar (immunhistokemi) och superupplösande mikroskopi (structured illumination microscopy eller SIM) . Här ses hörselorganet hos människa (vä) och uttrycket av connexingenen GJB2 (hö) där varje gentranskript (mRNA) lyser som en röd punkt. Mutation i genen är den vanligaste orsaken till medfödd dövhet.

Synchrotron X-ray of the human inner ear. For several years, we have studied the anatomy of the inner ear using high-resolution synchrotron X-ray (SR-PCI). It is being done together with Canadian researchers in London, Ontario, Canada. The investigations are done in a cyclotron located in Saskatoon in Saskatchewan. The technique provides unique information on both bone and soft tissue. It helps us understand how the CI electrode is located in the cochlea and also provides new information about the structure of the cochlea. With this technique, we have also been able to analyze how the different frequencies are located in the cochlea's auditory nerve in different people. We also analyze the cause of Meniere's disease. The results have been widely disseminated around the world.

https://www.entandaudiologynews.com/features/ent-features/post/prof-helge-rask-andersen-on-cell-regeneration-and-treatment-of-human-deafness

We also collaborate with several English institutions including the University of Sheffield, the University of Nottingham and Guy's and St. Thomas' Hospital NHS Foundation Trust in London. Together we try to find new surgical treatment methods for deafness.

With the help of models produced from synchrotron X-rays, we can study a new surgical pathway. This pathway could conceivably be used for injection of, among other things, stem cells to Rosenthal's canal, where our auditory neurons are located. (Li H, Agrawal S, Rohani SA, Zhu N, Cacciabue DI, Rivolta MN, et al. Unlocking the human inner ear for therapeutic intervention. Sci Reports 2022;12(1):1–6

Hearing is one of the cornerstones of communication between people. Impaired hearing has consequences as it becomes difficult to participate in conversations and it is easy to feel left out, cognition can be affected, the effort of listening causes fatigue, and quality of life is affected. In children, language and psychosocial development are also affected. In unilateral or asymmetrical hearing loss, the ability to hear where sounds are coming from and to hear in noisy environments is affected. With adequate hearing rehabilitation, the negative consequences of hearing loss are reduced. We conduct research into the consequences of hearing loss in everyday life and how to make it easier for those affected.

There is an ongoing survey regarding practical aspects of the use of cochlear implants in individuals over 85. Together with Örebro University hospital, a study evaluating the experience of pain on patients with cochlear or brainstem implants and undergoing an MRI examination is conducted. In a journal study, we look at those patients with cochlear implants where they saw an opportunity to use hybrid/electroacoustic stimulation afterwards before surgery. We follow up who has been able to use this combined hearing over time. All children in Region Uppsala are currently offered hearing screening at birth, four years of age and six years of age. In an ongoing journal study, we look at the outcome of the three screening sessions and calculate the prevalence of congenital hearing loss in children. We are part of a Nordic collaboration that deals with children with congenital unilateral hearing loss. Validation studies of various survey instruments are underway to measure, among other things, how children listen in everyday life. These will then be used in a longitudinal multicenter study where children with congenital unilateral or moderate duplex hearing loss will be followed up to the age of four.

Members of the research group

Elsa Erixon, PhD, Senior Consultant
Karin Hallin, PhD, M.Sc.
Ulrika Larsson, Hearing Educator
Fredrik Stillesjö, PhD, Engineer
Nadine Schart-Morén, MD, PhD