By Kent Knickol and Michael Seidman
The human ear is an intricate and delicate part of our bodies. Exactly how does it work? How does it transmit sound?
A normally functioning ear transmits sound in the following way:
1. Sound is transmitted as sound waves through the ear canal to the eardrum.
2. The sound waves cause the eardrum to vibrate, which in turn, causes the three tiny bones (hammer,anvil and stirrup) in the middle ear to vibrate.
3. These sound vibrations continue through the middle ear bones and across a tiny membrane to the fluid in the snail- shaped inner ear called the cochlea.
4. Fluid movement causes thousands of tiny hair cells in the cochlea to move.
5. The movement of the hair cells converts the fluid movement into electric energy.
6. The electrical energy is transmitted by the hair cells to the hearing (auditory)nerve.
7. The auditory nerve sends the electrical impulses to the brain where they are interpreted as sound information.
Unfortunately, "normal" hearing function is not the standard for a large percentage of our population. Hearing impairment affects about one in 10 Americans. Hearing loss can be conductive (due to faulty transmission of sound waves) or sensorineural (faulty sound reception by nerve cells), or both. Common causes of conductive hearing loss are wax blocking the ear, a perforated eardrum, or fluid in the ears. Common reasons for sensorineural deafness are noise exposure, age-related changes, and ototoxic drugs (that damage hearing).
Hearing impairment is measured by the amount of level of loss in what are called decibels (dB) hearing level (HL). Decibels are like degrees of a thermometer. As temperature increases, so do the number of degrees. As the volume of sound increases, so do the number of decibels. Normal conversation is usually between 45 - 55 dB. A baby crying hovers around 60 dB and downtown traffic can blister the ear at 90 dB.
Hearing loss can be:
- Mild (a loss up to 40 dB) - with trouble in hearing ordinary conversation
- Moderate (40-60 dB) - where voices must be raised to be heard
- Severe (over 60 dB loss) - where people must shout to be heard
According to the World Health Organization, the term "deaf" should only be applied to individuals with hearing impairment so severe that they cannot benefit from sound amplification or hearing aid assistance.
Causes, Risk Factors and Treatment Options
Hearing loss may be congenital (present at birth) caused by:
- Use of ototoxic drugs during pregnancy
- Prenatal rubella in expectant mothers
- Infections during pregnancy
- Perinatal anoxia (fetal oxygen lack)
- Rh blood disease
Hearing loss may be acquired by:
- Noise exposure
- Presbycusis (age-related loss)
- Infections that affect the middle ear and inner ear such as mumps, measles and influenza
- Ototoxicity (drugs that harm the inner ear)
- Head injuries
- Benign tumors of the hearing nerve (acoustic neuroma)
- Cancer (rare)
Appropriately chosen, properly fitted, and regularly checked hearing aids can greatly improve the quality of life for hearing-impaired persons. They are prescribed according to the type and severity of hearing loss, how well someone can manipulate the aid, and the condition of the ear canal.
The treatment for sensorineural hearing loss is often the use of hearing aids or cochlear implants. A cochlear implant is an electronic device implanted behind the ear. Unlike a hearing aid that amplifies sounds, cochlear implants directly stimulate the auditory nerve fibers in the cochlea.
Dr. Michael Seidman, from the Henry Ford Department of Otolaryngology, has studied specific compounds for reversing nerve-related hearing loss. A patent was awarded to Dr. Seidman for the development of supplements (particularly the Anti-Age/Energy Formula-Body Language Vitamin Co), which are available on the web, Henry Ford pharmacies and at some of the finest health food stores.
Vestibular Schwanomma (Acoustic Neuroma)
A vestibular schwanomma (also referred to as an acoustic neuroma) is a slow growing tumor of the hearing or balance nerve. It is the most common benign growth seen by otolaryngologists at Henry Ford. This tumor occurs in about three out of every 100,000 people, and there are about 2,000 3,000 new patients with this problem each year.
Acoustic neuromas are thought to arise from a genetic change that occurs in our chromosomes. It has been determined that the long arm of chromosome 22 incurs a loss in a tumor suppressor gene. Essentially, this means that there is a change in the genetic code. The reason that this happens is not understood. Some patients get this on both sides, and this means that they have neurofibromatosis type 2. If a patient has tumors on both sides, then other family members should be checked with an MRI as well.
The typical symptoms of acoustic neuromas are hearing loss and/or tinnitus (ringing or buzzing)in one ear. Sometimes there are also balance problems or facial spasms, weakness or paralysis.
Initial evaluation for this type of tumor includes a complete history and physical in relation to the ear, nose, throat and skull base region. A hearing test is imperative, and sometimes we will perform an auditory brainstem response test (ABR). This is a fairly accurate screening test, but it is not perfect. The best test for making the diagnosis is an MRI. As part of the preoperative evaluation, an otolaryngologist may also request an Electronystagmogram (ENG), which is a special balance test to discover how much the balance nerve is involved.
Dr. Seidman offers several approaches for the removal of acoustic neuromas:
- Translabyrinthine: This is the standard way that most Neurotologic surgeons remove these tumors. The disadvantage to this approach is that the patient is guaranteed to have complete loss of hearing in the operated ear. Even a hearing aid will not help. The advantage is that it has, theoretically, the least risk to causing facial paralysis.
- Retrolabyrinthine: This is typically used for tumors that are closer to the brainstem and more in the area called the cerebellar pontine angle. This approach has the positive aspect of being able to possibly save hearing, but hearing preservation with this approach or with the middle cranial approach range from 0-75% and really depends upon the size of the tumor.
- Middle Cranial Fossa approach: This is the preferred method of removal for tumors that are primarily in the internal auditory canal and for those growths that are less than 10-15 mm in size. This surgery also has the possibility of saving hearing, again with hearing preservation up to 75-80% of patients with 90-95% chance of saving the facial function, all with complete tumor removal.
Usually after surgery, patients will complain of some headaches, but these rapidly improve. The most common problems deal with facial weakness or paralysis, eye closure, burning of the eye (because it is not tearing normally), balance problems and generalized fatigue. These are all normal findings after surgery and will improve with time. If a patient should have permanent facial paralysis, which usually occurs with larger tumors there is a chance for re-animation procedures, but typically we wait for at least one year to see how much function returns.
Tinnitus, from the Latin word "tinnire," which means "to ring or tinkle like a bell," is a hearing ailment that affects over 35 million Americans. Most often, it affects people over the age of 40, but it is now being seen more frequently in young people who are exposed to loud, amplified music.
Tinnitus is characterized by annoying ear noises -- ringing, buzzing, whistling, hissing or other noises heard in the ear in the absence of environmental -- which can be soft or loud enough to be completely debilitating. Tinnitus can also cause sleep disturbance and interfere with concentration.
Tinnitus is not a disease in itself, but a symptom that something is wrong in the auditory system. While theories exist, the actual mechanism responsible for tinnitus remains unknown, as does the origin of the ear noises. Tinnitus is not just in the patient's imagination. Although there is no known cure for tinnitus, Dr Seidman is considered a world expert in the management of this particular problem and can offer many methods for coping with the condition.
Tinnitus can occur in a single episode, for a few days or weeks, or permanently. It can occur in one ear (unilaterally) or both ears (bilaterally). While more common in both ears, the rare unilateral ailment can be more serious.
What can cause tinnitus?
- Acoustic trauma from noises such as loud music, concerts and gunshots
- Long-term exposure to noises from welding equipment, power saws, jackhammers, vacuum cleaners, power mowers, snow blowers and some kitchen appliances
- High cholesterol
- High blood pressure
- Earwax buildup
- Meniere's disease
- Medications (sometimes too much aspirin)
- Old age (the natural degeneration of hearing)
When specialists can identify the cause of tinnitus (e.g., earwax buildup, high cholesterol or the presence of a tumor), relief may be possible through treatment available for those conditions. In addition to taking a complete medical history, your physician will do a physical exam that will include screening for hearing loss or other deficiencies. You also may be referred for formal hearing tests.
Henry Ford Health System runs the only well established clinic for bothersome tinnitus in Michigan, which has been operating for nearly a decade. For more information, please contact Tinnituscenter@hfhs.org
Meniere's disease or syndrome is a condition characterized by hearing impairment, ringing in the ears (tinnitus), and periodic vertigo (disturbance of balance and equilibrium). The disease results from distention of the endolymphatic compartment of the inner ear referred to as endolymphatic hydrops. A precise cause of hydrops cannot be found in most cases.
A reliable diagnosis can be made from history alone when there is a clear-cut symptom triad: characteristic vertigo; tinnitus; and fluctuating, unilateral hearing loss. Approximately 75% of patients also report a sensation of fullness in the affected ear or ears.
The specialists at Henry Ford Health System, under the direction of Dr. Seidman typically recommend a multifactorial approach to treating Meniere's disease, with general attention given to overall physical and mental well being, proper diet, salt restriction (less than 2 grams of sodium daily), avoidance of known triggers, and stress management. Some patients may require diuretics ("water pills") to help control symptoms by reducing pressure in the ear.
Various symptomatic approaches are used, depending on the severity of the patient's vertigo and nausea. For mild symptoms when the person tries to continue normal activities, dimenhydrinate (Dramamine) or meclizine HCI (Antivert) may be used. Various other medications may also be used for symptomatic relief, although not specifically indicated for Meniere's disease. These include transdermal scopolamine patches (Transderm Scop); promethazine HCI (Phenergan), an antihistaminic, antivertiginous medication used for more severe attacks, and diazepam (Valium).
Surgery is generally reserved for patients with intractable, intolerable vertigo or tinnitus, or to slow the progression of hearing loss. The decision to operate depends on the severity of the patient's symptom and the lack of efficacy of medical management. That is when the conventional medical management is not effective at symptom relief and the person is significantly affected, they essentially ask the surgeon to do something more.
Treatments and Options for Hearing Impairment (Hearing Aid Program)
Obtaining hearing aids involves a five-step process:
- Hearing Test: The evaluation involves testing the ear's sensitivity for different frequencies of sound, hearing for speech and the function of the middle ear. Afterward, an audiologist determines whether hearing aids are necessary.
- Medical Clearance: The hearing test results are forwarded to the patient's physician, who must provide a medical evaluation and clearance before hearing aids are ordered. This clearance is assurance that a physician evaluated the patient and test results, considered treatment options and agrees that hearing aids are appropriate.
- Hearing Aid Selection: An audiologist will review the hearing test results and perform additional assessment and counseling. The different styles and technologies of hearing aids will also be discussed. A non-refundable fee is required at this appointment. This is applied toward the total cost of the hearing aids. Patients may pay for the hearing aids with cash, personal check or credit cared.
- Hearing Aid Orientation & Counseling: The hearing aids are delivered at this appointment, during which the audiologist discusses their use, care and maintenance. Patients are welcome to bring a family member or friend to understand how the hearing aids operate.
- Hearing Aid Recheck: During the 30-day trial period, patients meet with an audiologist to ensure they are adjusting well to their hearing aids.
Most patients who have hearing loss benefit significantly from hearing aids. The ability to understand speech varies, depending on the nature of the hearing problem. The best time to begin wearing hearing aids is as soon as hearing loss becomes apparent. Hearing aids cannot stop the progression of hearing loss or return hearing to normal. The goal of hearing aids is to make sounds easier to hear and improve the level of communication. It takes time to get accustomed to hearing aids and learn how to achieve their maximum performance.
Are two hearing aids better than one?
Most patients with equal hearing loss in both ears can enhance their hearing quality by wearing two hearing aids. The brain processes sound more efficiently when it receives sound from both ears. Two hearing aids provide the best advantage for hearing in noise and improve the ability to localize sound direction, thus making listening more comfortable. Patients who wear two hearing aids also find they can be set at a lower volume than a single hearing aid.
High-tech Hearing Aids
The type and degree of hearing loss, as well as environment are all among the many factors considered when choosing a high-tech hearing aid over a traditional one. The choices of more advanced technology include:
- Multi-channel hearing aids: These allow sounds to pass through separate amplifiers so lower frequencies receive less amplification than higher frequencies. Remote controls can be used to adjust the volume for different environments.
- Dual-microphone hearing aids: These have microphones that selectively amplify sounds facing the wearer instead of sounds at the side or from behind. Multiple listening programs are available in the remote control that will change the amplification frequency to suit the wearer's listening environment.
- Digital hearing aids: These provide a clearer, crisper sound quality than traditional hearing aids. These automatically adjust amplification to the listening environment.
- Semi implantable aids: These require an outpatient surgical procedure, cost approximately $15,000-20,000.00 and generally speaking provide significantly better hearing results than the most powerful and high tech hearing aids currently available on the market
- Bone Anchored Hearing Aid (BAHA): This also requires a surgical procedure, and while some insurance companies may cover this, most cover a small part and the patient is required to cover approximately $3,500-5,000.00 in costs. The BAHA is used for patients with either a severe conductive type of hearing loss or single sided nerve deafness. Examples might be people who are born with a severely deformed ear (aural atresia), patients with previous ear bone surgery that was ineffective and for patients with deafness in one ear (they are not cochlear implant candidates)
A cochlear implant is an electronic device that restores partial hearing to the deaf. When the hearing impairment is due to a problem in the inner ear, a sensorineural impairment (nerve deafness) results. In most cases of sensorineural hearing loss, the hair cells have been damaged and do not function. Although many of the auditory nerve fibers may be intact and capable of transmitting electrical impulses to the brain, without functioning hair cells the nerve fibers remain unstimulated. It has been thought that sensorineural hearing loss cannot be corrected medically. However, the research by Dr. Seidman, who has studied specific nutritional supplements, may be able to slow and in some cases improve upon nerve related hearing loss.
How Cochlear Implants Work
Part of a cochlear implant is surgically implanted in the ear (temporal bone) and part is worn externally like a hearing aid. However, a cochlear implant is not a hearing aid in the sense of making sound louder or clearer. It is a medical device that bypasses damaged parts of the inner ear and electronically stimulates the nerve of hearing.
Cochlear implants are designed to bypass the hair cells that are not functioning and provide stimulation directly to the auditory nerve.
There are a number of different cochlear implants currently available. All systems consist of a microphone, a signal processor, a signal coupler (transmitter and receiver), and one or more electrodes that are implanted in or around the cochlea.
The microphone and signal processor are worn outside the body, like a hearing aid. Either a transmitter outside the body with a receiver inside, or a connector that protrudes through the skin just behind the ear, can be used. Both provide a direct connection between the signal processor and electrodes.
The electrical stimuli are sent inside the body to the implanted electrodes. The electrical signals stimulate the auditory nerve fibers, and the signal is then sent to the brain.
The cochlear implant is designed only for individuals who receive little benefit from hearing aids. Candidates are usually two years of age or older.
Cochlear Implant Surgery
Dr. Seidman at the Henry Ford Health System's Department of Otolaryngology specialize in cochlear implant procedures. The procedure is performed under general anesthesia. An incision is made behind the ear. The mastoid bone is opened, leading to the middle ear. The operation takes several hours depending on the specific cochlear implant used. The vast majority of procedures are done on an outpatient basis.
Benefits of the Cochlear Implant
Cochlear implants do not provide normal hearing. The majority of totally deaf patients who receive a cochlear implant are able to detect medium-to-loud sounds, including speech at comfortable listening levels. Many patients can learn to recognize some familiar sounds.
For many patients, cochlear implants aid in communication by improving lip-reading ability. They are able to use clues from the sounds and rhythms of speech and combine these with what they see.
Results vary for different individuals, depending on factors such as age at time of deafness, age at implant surgery, duration of deafness, status of the remaining auditory nerve fibers, and training.