Tinnitus- Current concepts in pathophysiology, investigations and treatment modalities

Tinnitus is defined as the perception of sound in the absence of external sound and can manifest itself in variety of ways. The phantom sounds of tinnitus may sound like ringing, clicking or hissing. The disorder is most often caused by damage to the microscopic endings of the hearing nerve in the inner ear, although it can also be attributed to allergies, high or low blood pressure, a tumor, diabetes, thyroid problems, injury to the head or neck, and use of medications such as anti-inflammatories, antibiotics, sedatives, antidepressants, and aspirin.

New research at the University of Michigan Health System suggests over-exposure to noise can actually cause more lasting changes to our auditory circuitry -- changes that may lead to tinnitus, commonly known as ringing in the ears. U-M researchers previously demonstrated that after hearing damage, touch-sensing "somatosensory" nerves in the face and neck can become overactive, seeming to overcompensate for the loss of auditory input in a way the brain interprets -- or "hears" -- as noise that isn't really there. The new study, which appears in the Feb. 1 issue of The Journal of Neuroscience, found that somatosensory neurons maintain a high level of activity following exposure to loud noise, even after hearing itself returns to normal. In normal hearing, a part of the brain called the dorsal cochlear nucleus is the first stop for signals arriving from the ear via the auditory nerve. But it's also a hub where "multitasking" neurons process other sensory signals, such as touch, together with hearing information. During hearing loss, the other sensory signals entering the dorsal cochlear nucleus are amplified, This overcompensation by the somatosensory neurons, which carry information about touch, vibration, skin temperature and pain, is believed to fuel tinnitus in many cases. The involvement of touch sensing (or "somatosensory") nerves in the head and neck explains why many tinnitus sufferers can change the volume and pitch of the sound by clenching their jaw, or moving their head and neck, "This is the first research to show that, in the animals that developed tinnitus after hearing returned to normal, increased excitation from the somatosensory nerves in the head and neck continued.

Prior research has shown that auditory circuits in the brain are more excitable in tinnitus sufferers, but until now it has not been clear whether that is due to hyperactivity of excitatory neural pathways, reduced activity of inhibitory ones, or a bit of both, Thanos Tzounopoulos, Ph.D., assistant professor of otolaryngology and neurobiology, Pitt School of Medicine used a new technique to image auditory circuits using slices of brain tissue in the lab. Dr. Tzounopoulos' team created tinnitus in a mouse model. The scientists then sought to determine what had gone wrong in the balance of excitation and inhibition of the auditory circuits in the affected mice. They established that an imaging technique called flavoprotein autofluorescence (FA) could be used to reveal tinnitus-related hyperactivity in slices of the brain. Experiments were performed in the dorsal cochlear nucleus (DCN), a specialized auditory brain center that is crucial in the triggering of tinnitus. FA imaging showed that the tinnitus group had, as expected, a greater response than the control group to electrical stimulation. Most importantly, despite local stimulation, DCN responses spread farther in the affected mice. Dr. Tzounopoulos' new experimental approach has resolved why tinnitus-affected auditory centers show increased responsiveness. After administering a variety of agents that block specific excitatory and inhibitory receptors and seeing how the brain center responded, his team determined that blocking an inhibitory pathway that produces GABA, an inhibitory neurotransmitter, enhanced the response in the region surrounding the DCN in the control brain slices more so than it did in the tinnitus slices. This means that agents that increase GABA-mediated inhibition might be effective treatments for tinnitus. Dr. Tzounopoulos' team is now trying to identify such drugs.

Because subjective tinnitus is typically localized to the ear with hearing loss, tinnitus was traditionally thought to originate from neural hyperactivity in the damaged ear. However, most studies have found that hearing loss reduces the neural outputs from the damaged cochlea. These negative findings led to the hypothesis that rinnitus arises from aberrant neural activity in the central auditory system. Positron emission tomography imaging studies performed on tinnitus patients that could modulate their tinnitus provide evidence showing that the aberrant neural activity that gives rise to tinnitus resides in the central auditory pathway.

A study conducted at the University of Arkansas for Medical Sciences (UAMS) has shown potential to markedly improve tinnitus. The study aimed at examining the safety and feasibility of using maintenance sessions of low-frequency repetitive transcranial magnetic stimulation (TMS) to reduce tinnitus loudness and prevent its return over time. TMS involved the placement of a coil on the scalp that creates a magnetic field over the brain’s surface. The magnetic field penetrates up to two or three centimeters from the surface of the coil. An electric current is induced by the magnetic field that either activates or inhibits neural activity. The goal of the study was to inhibit excessive neural activity believed to cause tinnitus. They used a PET scan of the patient’s brain to look for excessive neural activity with increased blood flow in the temporal lobe. They then targetted that area with low-frequency TMS to inhibit the neural activity and decrease the tinnitus.

Researchers Dr. Michael Kilgard and Dr. Navzer Engineer from The University of Texas at Dallas and University-affiliated biotechnology firm MicroTransponder report that stimulation of the vagus nerve paired with sounds eliminated tinnitus in rats. The auditory cortex delegates too many neurons to some frequencies. Because there are too many neurons processing the same frequencies, they are firing much stronger than they should be. In addition, the neurons fire in sync with one another and they also fire more frequently when it is quiet. It's these changing brain patterns that produce tinnitus. Brain changes in response to nerve damage or cochlear trauma cause irregular neural activity believed to be responsible for many types of chronic pain and tinnitus. But when they paired tones with brief pulses of vagus nerve stimulation, they eliminated the physiological and behavioral symptoms of tinnitus in noise-exposed rats. The researchers are, in essence, retraining the brain to ignore the nerve signals that simulate ringing. This minimally invasive method of generating neural plasticity is used to precisely manipulate brain circuits, which cannot be achieved with drugs, "Pairing sounds with VNS provides that precision by rewiring damaged circuits and reversing the abnormal activity that generates the phantom sound.

Scientific Explanation of VNS Paired Stimulation for Tinnitus and Stroke Rehabilitation

Sound masking therapy, a common component of tinnitus treatment, is of uncertain benefit when used on its own, a new evidence review finds. Sound therapy relies on distraction, with an additional noise -- often called white noise -- reducing the contrast between the patient's tinnitus signal and the background noise. This reduces the person's perception of the phantom sounds and the distress they cause. People receive sound therapy in several ways: by devices worn in or on the ear, by headphones connected to an MP3-like device or with an under-the-pillow speaker for night use. the weight of evidence does not support sound therapy as a primary treatment. Sound therapy is useful only when combined with a counseling component to complete a therapeutic process."

Shaowen Bao's experiments with induced hearing loss in rats explain why the neurons in the auditory cortex generate these phantom perceptions. They showed that neurons that have lost sensory input from the ear become more excitable and fire spontaneously, primarily because these nerves have "homeostatic" mechanisms to keep their overall firing rate constant no matter what. With the loss of hearing, you have phantom sounds. Tinnitus resembles phantom limb pain experienced by many amputees, One treatment strategy, then, is to retrain patients so that these brain cells get new input, which should reduce spontaneous firing. This can be done by enhancing the response to frequencies near the lost frequencies. They changed their (brain training) strategy from one where they completely avoided the tinnitus domain to one where they directly engage it and try to redifferentiate or reactivate it, and it seems to be giving better results. Another treatment strategy was to find or develop drugs that inhibit the spontaneous firing of the idle neurons in the auditory cortex. His experiments showed that tinnitus is correlated with lower levels of the inhibitory neurotransmitter GABA (gamma-aminobutyric acid), but not with changes in the excitatory neurotransmitters. Their findings will guide the kind of research to find drugs that enhance inhibition of auditory corti.

Josef P. Rauschecker, PhD, a neuroscientist, says that the absence of sound caused by hearing loss in certain frequencies, due to normal aging, loud-noise exposure, or to an accident, forces the brain to produce sounds to replace what is now missing. But when the brain's limbic system, which is involved in processing emotions and other functions, fails to stop these sounds from reaching conscious auditory processing, tinnitus results. They believe that a dysregulation of the limbic and auditory networks may be at the heart of chronic tinnitus . "A complete understanding and ultimate cure of tinnitus may depend on a detailed understanding of the nature and basis of this dysregulation. Using functional Magnetic Resonance Imaging (fMRI), the Georgetown researchers found that moderate hyperactivity was present in the primary and posterior auditory cortices of tinnitus patients, but that the nucleus accumbens exhibited the greatest degree of hyperactivity, specifically to sounds that were matched to frequencies lost in patients. Based on their findings, the researchers argue that the key to understanding tinnitus lies in understanding how the auditory and limbic systems interact to influence perception -- be it sound, emotions, pain, etc.

The imaging technique, magnetoencephalography (MEG), can determine the site of perception of tinnitus in the brain, which could in turn allow physicians to target the area with electrical or chemical therapies to lessen symptoms. Since MEG can detect brain activity occurring at each instant in time, it is possible to detect brain activity involved in the network or flow of information across the brain over a 10-minute time interval," Using MEG, the areas in the brain that are generating the patient's tinnitus can actually be visulaized, which then cab be precisely targetted for treating tinnitus. MEG is an effective clinical tool for localizing the probable source of tinnitus in patients' brains. It also has the potential to assist with the development of future interventional strategies to alleviate tinnitus.

                    Magnetic Source Imaging & Magnetoencephalography

                                      

Hilke Bartels of the University Medical Center Groningen, has revealed that a remarkable number of tinnitus patients are depressed and have a negative attitude towards life. They do not dare to share these feelings with others, which means they experience little social support, which in turn leads to withdrawal behaviour. This is also described as the so-called ‘type D personality’. Anxiety and depression appear to strengthen the effect of tinnitus. People with a type D personality in particular should undergo treatment that concentrates on the reduction of anxiety and depression. UMCG started an experimental treatment regime whereby the relevant brain areas were continuously stimulated with the help of a pulse generator, a sort of pacemaker. The patients indicated that the ‘noise’ was reduced to manageable levels.

In the times to come  there is a  lot of hope for those patients suffering from tinnitus.  In the future, those patients who don't respond to sound therapy and counselling might need to go for further investigations like fMRI or Magneto-encephalography.  Transcranial magneto therapy or vagus nerve paired stimulation appears to be promising in those cases  refractory to conventional treatment  modalities.

Source:

1. University of Michigan Health System (2012, February 1). Tinnitus: New evidence touch-sensing nerve cells may fuel 'ringing in the ears'.ScienceDaily. Retrieved December 10, 2012, from http://www.sciencedaily.com­/releases/2012/02/120201092301.htm
2. University of Pittsburgh Schools of the Health Sciences (2011, April 19). Tinnitus caused by too little inhibition of brain auditory circuits, study finds. ScienceDaily. Retrieved December 10, 2012, from http://www.sciencedaily.com­/releases/2011/04/110418152322.htm
3. Semin Hear 2008 Nov;29(4):333-349.Human Brain Imaging of Tinnitus and Animal Models.Lobarinas E, Sun W, Stolzberg D, Lu J, Salvi R.Source Center for Hearing & Deafness, University at Buffalo, Buffalo, New York.
4. University of Arkansas for Medical Sciences (2008, July 11). New Tinnitus Treatment: Potential To Greatly Diminish Ringing In The Ears. ScienceDaily. Retrieved December 10, 2012, from http://www.sciencedaily.com­/releases/2008/07/080709125626.htm
5. University of Texas at Dallas (2011, January 13). Tinnitus treatment: Rebooting the brain helps stop the ring of tinnitus in rats.ScienceDaily. Retrieved December 10, 2012, from http://www.sciencedaily.com­/releases/2011/01/110112132130.htm
6. Health Behavior News Service, part of the Center for Advancing Health (2010, December 12). 'White-noise' therapy alone not enough to curb tinnitus. ScienceDaily. Retrieved December 10, 2012, from http://www.sciencedaily.com­/releases/2010/12/101210095530.htm
7. University of California - Berkeley (2011, September 13). Tinnitus discovery could lead to new ways to stop the ringing: Retraining the brain could reanimate areas that have lost input from the ear. ScienceDaily. Retrieved December 10, 2012, from http://www.sciencedaily.com­/releases/2011/09/110912144247.htm?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+sciencedaily%2Fmind_brain%2Ftinnitus+%28ScienceDaily%3A+Mind+%26+Brain+News+--+Tinnitus%29
8. Georgetown University Medical Center (2011, January 15). Tinnitus is the result of the brain trying, but failing, to repair itself. ScienceDaily. Retrieved December 10, 2012, from http://www.sciencedaily.com­/releases/2011/01/110112122504.htm
9. Henry Ford Health System (2009, October 5). Non-invasive Imaging Technique Can Help Diagnose Tinnitus. ScienceDaily. Retrieved December 10, 2012, from http://www.sciencedaily.com­/releases/2009/10/091004141223.htm
10. University of Groningen (2008, November 24). Tinnitus: Psychological Treatment And Neurostimulation Offer Hope. ScienceDaily. Retrieved December 11, 2012, from http://www.sciencedaily.com­/releases/2008/11/081120175851.htm?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+sciencedaily%2Fmind_brain%2Ftinnitus+%28ScienceDaily%3A+Mind+%26+Brain+News+--+Tinnitus%29

Robotic surgery in Otolaryngological practice

Robotic surgery is the use of robots in performing surgery. Three major advances aided by surgical robots have been remote surgery, minimally invasive surgery, and unmanned surgery. Major potential advantages of robotic surgery are precision and miniaturization. Further advantages are articulation beyond normal manipulation and three-dimensional magnification.

A minimally invasive medical procedure is defined as one that is carried out by entering the body through the skin or through a body cavity or anatomical opening, but with the smallest damage possible to these structures.

Robotically-assisted surgery was developed to overcome the limitations of minimally-invasive surgery and to enhance the capabilities of surgeons performing open surgery. In the case of robotically-assisted minimally-invasive surgery, instead of directly moving the instruments, the surgeon uses one of two methods to control the instruments; either a direct telemanipulator or through computer control. A telemanipulator is a remote manipulator that allows the surgeon to perform the normal movements associated with the surgery whilst the robotic arms carry out those movements using end-effectors and manipulators to perform the actual surgery on the patient. In computer-controlled systems the surgeon uses a computer to control the robotic arms and its end-effectors, though these systems can also still use telemanipulators for their input. One advantage of using the computerised method is that the surgeon does not have to be present. but can be anywhere in the world, leading to the possibility for remote surgery.

da Vinci Robotic system at the 2012 Academy meeting

The da Vinci Surgical System comprises three components: a surgeon’s console, a patient-side robotic cart with 4 arms manipulated by the surgeon (one to control the camera and three to manipulate instruments), and a high-definition 3D vision system. Articulating surgical instruments are mounted on the robotic arms which are introduced into the body through cannula's. The original telesurgery robotic system that the da Vinci was based on was developed at SRI International in Menlo Park with grant support from DARPA and NASA. Although the telesurgical robot was originally intended to facilitate remotely performed surgery in battlefield and other remote environments, it turned out to be more useful for minimally invasive on-site surgery. The patents for the early prototype were sold to Intuitive Surgical in Mountain View, California.

The da Vinci senses the surgeon’s hand movements and translates them electronically into scaled-down micro-movements to manipulate the tiny proprietary instruments. It also detects and filters out any tremors in the surgeon's hand movements, so that they are not duplicated robotically. The camera used in the system provides a true stereoscopic picture transmitted to a surgeon's console.

Drs. Gregory S. Weinstein and Bert W. O'Malley, Jr. of the University of Pennsylvania School of Medicine's Department of Otorhinolaryngology: Head and Neck Surgery founded the world's first TransOral Robotic Surgery (TORS) program at Penn Medicine in 2004, where they developed and researched the TORS approach for a variety of robotic surgical neck approaches for both malignant and benign tumors of the mouth, voice box, tonsil, tongue and other parts of the throat. TORS has dramatically improved the way head and neck cancers are treated, by achieving complete tumour removal while preserving speech and swallowing. It is a game changer for the way oropharyngeal tumors will be treated in the years to come. Head and neck tumor treatments often involve a combination of surgery, radiation therapy, and chemotherapy. In many cases, surgery offers the greatest chance of cure; yet conventional surgery may require an almost ear-to-ear incision across the throat or splitting the jaw, resulting in speech and swallowing deficits for patients. In comparison, the minimally invasive TORS approach, which accesses the surgical site through the mouth, has been shown to improve long term swallowing function and reduce risk of infection while speeding up the recovery time. When compared to traditional surgeries, after their cancers have been removed successfully, patients have been able to begin swallowing on their own sooner and leave the hospital earlier. TORS outcomes are markedly improved when compared to standard chemotherapy, radiation or traditional open surgical approaches for oropharyngeal cancer.

Obstructive sleep apnea (“sleep apnea”) is a disorder in which the soft tissues of the throat collapse on inhalation during sleep, causing disruption in the normal breathing process. Uvulo-palato-pharyngoplasty has been used to treat the palatal and pharyngeal collapse component of OSA. Tackling the tongue base component of the collapse was not always successful. Now TORS has been employed to successfully reduce the tongue base with considerably less morbidity. 
(TORS - Tongue base reduction)

Robotic surgery though the mouth is a safe and effective way to remove tumors of the throat and voice box, The preliminary study examined the outcomes of 13 head and neck cancer patients with tumors located in the region of the throat between the base of the tongue and just above the vocal cords, an area known as the supraglottic region.  The study found that the use of robot-assisted surgery to remove these tumors through the mouth took about 25 minutes on average, and that blood loss was minimal -- a little more than three teaspoons, or 15.4 milliliters, on average, per patient. No surgical complications were encountered and 11 of the 13 patients could accept an oral diet within 24 hours.  If, on the other hand, these tumors are removed by performing open surgery on the neck, the operation can take around 4 hours to perform, require 7 to 10 days of hospitalization on average and require a tracheostomy tube and a stomach tube, the researchers say.

As the rate of thyroid cancer continues to climb, doctors are urging patients to be more cautious about thyroid nodules, a common disorder that is responsible for a small but growing number of thyroid cancer cases. Until recently, the only way to remove nodules and rule out cancer was through surgery that required a five centimeter incision across the front of the neck.Today however, a new option exists that allows surgeons to access the neck through the armpit, allowing for a biopsy of tissue with no visible scar. The procedure, transaxillary robotic thyroid surgery, utilizes 3D cameras and specially designed robotic arms to create a small incision within the armpit, the mechanical arms work just like hands allowing the specialized surgeon to operate remotely with precise control and movements to remove suspicious nodules. The underarm area has fewer nerve endings than the anterior neck area, so there's less pain, no scarring on the neck, and the incision heals faster. 

                                          (Robotic thyroidectomy)
Georgia Health Sciences University surgeons successfully performed a robotic submandibular salivary gland excision through the face lift incision in the hairline. A facelift incision and robotics can help surgeons safely remove a portion of a diseased thyroid from some patients without the characteristic neck scar. "It is outpatient, it doesn't require a surgical drain and it has the advantage of no neck scar," said Dr. David Terris, Chairman of the GHSU Department of Otolaryngology-Head and Neck Surgery. The goal was a no-neck-scar technique that's as safe as conventional thyroidectomy, which involves an incision at the base of the neck to gain immediate access to the thyroid, the surgeons report in The Laryngoscope. The benefits for robotic thyroid surgery include shorter recovery period, less pain in neck following surgery and better preservation of the laryngeal nerves and the parathyroid glands.

Doctors at AIIMS claimed to have performed  the first robotic surgery for throat cancer in India,  in May 2011.   The doctors from AIIMS had been to University of Pennsylvania Hospital, Philadephia,  for training in TORS.   Similar surgeries were performed at Manipal hospital, Bangalore. 

Source:

1)Science Daily

2) Wikipedia

3) Penn Medicine, Dept of Otorhinolaryngology Head & Neck  surgey website
4) U tube

Biologically chargeable ear implants- A major breakthrough

The chip is small enough to fit in the cavity of the middle ear. (Credit: Patrick P. Mercier)

  In a recent issue of the journal Nature Biotechnology, a team of researchers from MIT, the Massachusetts Eye and Ear Infirmary (MEEI) and the Harvard-MIT Division of Health Sciences and Technology (HST) demonstrated for the first time that cochlear potentials could power implantable electronic devices without impairing hearing. This has far reaching potential in the areas of diagnostics, and other implantable devices like cochlear implants and fully implantable hearing aids.  Today the cochlear  implants is powered by an external power source.  

Konstantina Stankovic, an otologic surgeon at MEEI, and HST graduate student Andrew Lysaght implanted electrodes into the cochlea of guinea pigs' ears. Attached to the electrodes were low-power electronic devices developed by MIT's Microsystems Technology Laboratories (MTL). After the implantation, the guinea pigs responded normally to hearing tests, and the devices were able to wirelessly transmit data about the chemical conditions of the ear to an external receiver.  .  

The cochlea is the auditory portion of the inner ear. The cochlea is a spiralled, hollow, conical chamber of bone.It houses three chambers or scalae within,  which are as follows: 

• the scala vestibuli (containing perilymph), which lies superior to the cochlear duct and abuts the oval window
• the scala tympani (containing perilymph), which lies inferior to the scala media and terminates at the round window
• the scala media (containing endolymph), or cochlear duct, a region of high potassium ion concentration that the cilia of the hair cells project into.

    This ionic gradient generates  the endocochlear potentials.  Endocochlear potential (EP) is a battery-like electrochemical gradient found in and actively maintained by the inner ear. The scala vestibuli and scala tympani has a high concentration of Na+ ions, while the scala media higher concentration of K+ ions,  The difference in gradients generate  this EP.    Anantha P Chandrakasan and fellow scientists demonstrated that the mammalian EP can be used as a power source for electronic devices. They achieved this by designing an anatomically sized, ultra-low quiescent-power energy harvester chip integrated with a wireless sensor capable of monitoring the EP itself.  The  voltage generated by these EP is very low.  A device powered by this biological battery can harvest only a small fraction of its power. Low-power chips, however, are precisely the area of expertise of Anantha Chandrakasan's group at MTL.  Saurav Bandyopadhyay, a graduate student in Chandrakasan's group, equipped their chip with an ultralow-power radio transmitter: After all,  an implantable medical monitor wouldn't be much use if there were no way to retrieve its measurements. The MTL chip also includes power-conversion circuitry in order to amass enough charge to power the radio.   In the experiments, the chip itself remained outside the guinea pig's body, but it's small enough to nestle in the cavity of the middle ear.

What does it mean for the speciality? This means that we will be able to monitor voltage changes in the endolymph and perilymph on real time basis in patients.   This could shed more  light in understanding the different stages of Meniere's disease.    Imagine being able to know what happens when we perfuse gentamycin or dexamethasone in those patients with Meniere's disease or with Sudden hearing loss.  Newer inner ear drugs could be developed in the future using this technology.  You could have a fully implantable cochlear implant and a totally implantable hearing aid of a different design in the near future.  This technology has tremendous potential for not only otology but even for other branches of modern medicine.

Source:

1)Patrick P Mercier, Andrew C Lysaght, Saurav Bandyopadhyay, Anantha P Chandrakasan, Konstantina M Stankovic. Energy extraction from the biologic battery in the inner ear. Nature Biotechnology, 2012; DOI:10.1038/nbt.2394.

2)Massachusetts Institute of Technology (2012, November 8). Medical devices powered by the ear itself. ScienceDaily. 

Esteem - The first totally implantable hearing aid

One of the highlights of the  ISCON 2012 conference was the lecture by Prof Ricardo Bento, Sao Paulo,  Brazil about his experience with Esteem- the first totally implantable hearing aid.  Initially we wondered as  to  why one  would go through the trouble of going through a surgical procedure,  instead of just popping a very tiny concealed completely in the canal hearing aid into your ear canal and be done with it.  But after hearing Prof. Bento, we came to know as to some people will go through all the trouble. One of the famous implantees is none other than the renowned Otologist, Dr. Michael Glasscock.  Prof. Bento showed us the clippings of the procedure and I should say that it is not a easy surgery at all.  The FDA took all of five years to approve this implant.  He explained how using a conventional canal hearing aid cuts off the resonance created by  the external auditory canal,  before it strikes the tympanic membrane.  It is unique in that it is powered by a battery, which has a life from  about 3 to 9 years.  This device is  also powered by a piezo device which uses the vibration of the tympanic membrane to generate its charge.  Since it has no external parts, the user can swim or have a bath and still hear.  The device can be controlled with a remote control, and if you take the trouble to turn it off at night, the battery will last even longer.  The battery can be changed with a small incision under local anaesthesia.

 The Esteem® system includes three implantable components (Sound Processor, Sensor, and Driver), and external testing and programming instruments.  The Esteem Totally Implantable Hearing System by Envoy Medical Corporation (St. Paul, MN) is a fully implantable system that uses piezoelectric transducers.  It uses the eardrum as the microphone.  The mechanical signal is detected by a piezoelectric transducer at the head of the incus (the sensor) and converted to an electrical signal that is amplified, filtered, and converted back to a vibratory signal.  The processed vibratory signal is then delivered by another piezoelectric transducer (the driver) to the stapes capitulum.  The Esteem hearing implant is different from all other microphone-based hearing devices (e.g., hearing aids, other middle ear implants or cochlear implants) because it uses the eardrum to process the incoming sound and thus preserves a natural way of hearing.  The Esteem is implanted under the skin behind the ear and in the middle ear space, and therefore invisible.


https://www.youtube.com/watch?v=xdBzjR-i9E0
(How the Esteem works- Animation)

https://www.youtube.com/watch?v=XdKVaW8krOY
(Esteem testimonial-Dr.Glasscock)

The Esteem® device is intended to reduce the effect of moderate to severe hearing loss in patients 18 years of age or older. The Esteem® is used in patients with hearing loss that meet the following criteria:

• Stable hearing loss caused by defective hair cells in the inner ear (sensorineural loss) in both ears
• Moderate to severe sensorineural hearing loss as defined by Pure Tone Average (PTA) at 500, 100, and 2000 hertz (Hz)
• Ability to understand what is heard (speech discrimination test score) greater than or equal to 40% of the words heard during the test.
• Normally functioning middle ear (Eustachian) tube
• Normal middle ear anatomy
• Normal tympanic membrane
• Adequate space for the Esteem® implant determined through a high resolution Computed Tomography (CT) scan
• Minimum 30 days of experience with appropriately fitted hearing aids.

The Esteem® device should not be used under the following conditions: History of:

• post-adolescent chronic middle ear infections
• inner ear disorders or recurring vertigo requiring treatment
• disorders such as an infection of the mastoid bone (mastoiditis)
• swelling in the inner ear (hydrops)
• Meniere’s disease (a condition characterized by a ringing sound in the ear(s) or head [tinnitus], hearing loss, vertigo and a feeling of fullness in the ear)
• disabling tinnitus which requires treatment
• fluctuating air conduction and/or bone conduction hearing loss over the past one year period of 15 decibels (dB) in either direction at two or more hearing frequencies (from 500 to 4000 Hz)
• swimmer’s ear (otitis externa) or eczema of the outer ear canal
• destructive middle ear disease (cholesteatoma)
• central auditory disorders (retrocochlear)
• thick scar tissue that continues to grow (keloid formation)
• excessive sensitivity to silicone rubber, polyurethane, stainless steel, titanium and/or gold

A clinical study of this device involved 60 subjects at 3 investigational centers (57 were implanted with the device). The side-effects observed in the clinical study included:

• Taste disturbance: 42% of subjects (14% ongoing after 1 year)
• Facial paresis (partial paralysis) / paralysis: 7% of subjects (1% ongoing after 1 year)
• Tinnitus: 18% of subjects* (5% ongoing after 1 year) * Some subjects reported having tinnitus prior to the Esteem® implant.

The surgical procedure involved a wide mastoidectomy,  a posterior tympanotomy, resection of the long process  of the incus, and fixing the driver and the overall system within the middle ear cleft.  The tricky part is stripping off the entire mucosa from the stapes superstructure.  This is a very delicate maneuver and subluxation of the footplate could be a  disaster.  This stripping is essential in order to fix  the driver  to the stapes superstructure using cement.  Specific surgical training is needed to accommodate routine surgical steps along with less familiar steps, such as placement of cement material and overall fixation of the system.  

It is certain that these hearing aids are expensive and requires a lot of expertise in implanting them.  It will be preferred b y certain individuals like doctors, musicians and sports persons for whom wearing a conventional hearing aid could be a hindrance in their day to day lives.   It will be interesting to see  how popular these  type of hearing aids will become in the future.