Hearing loss is very common and has a significant impact on the day to day lives of millions of people across the world. The World Health Organisation estimate that there are 26 million years worth of activity lost globally as a result of hearing loss. In the UK, and other developed countries, there is access to numerous options for the restoration of hearing but, nevertheless, hearing loss remains a significant issue, particularly in the elderly, many of whom do not pursue a solution to their hearing difficulties.
The hearing mechanism consists of three parts, the part the carries sound to the inner ear (conductive system), the hearing organ itself (the cochlea) and the hearing pathways of the brain that interpret the sound so that we can understand it. The picture below shows the different parts of the ear.
The conductive system consists of the pinna, ear canal, the ear drum and the hearing bones. Sound travels down the ear canal and hits the ear drum. The sound waves are then carried through the hearing bones to the inner ear. The cochlea is a fluid filled tube with a membrane spanning across it that runs the length of the tube. On the membrane there are many microscopic hairs. The sound waves pass into the cochlea and are carried by the fluid inside resulting in deflection of the membrane. This deflection activates the hair cells that then activate hearing nerves. These then send impulses to the hearing centres in the brain to enable interpretation of the sound.
Causes of Hearing Loss
The causes of hearing loss are numerous but can be divided into 2 groups. The first results from problems with the conductive system i.e. sound does not reach the inner ear effectively. This is called conductive hearing loss. The second results from problems with the cochlea itself or with the hearing pathways inside the brain. This is called sensorineural hearing loss. The list below shows the common causes of hearing loss. It is by no means exhaustive.
|Conductive hearing loss||Sensorineural hearing loss|
|Ear drum perforations||Excessive noise exposure|
|Acute and chronic ear inflammation||Drugs toxic to the ear|
|Hearing bone damage or stiffness||Vestibular schwannomas|
Diagnosis of hearing loss
In adults, hearing loss is something that is noticed either by the individual or the individual’s family. It is not uncommon for people to say that they can’t hear so well in a noisy room or that they require the television up loud. More severe hearing losses make it difficult to have a conversation when the person is not looking at the face of the person they are talking to or if they are talking on the phone. In some cases there may also be other symptoms like tinnitus or, more rarely, dizziness. There might also be a previous history of ear infections, in which case there may be pain or discharge from the ear. There may also be a history of operations or injuries to the ear.
In children, diagnosing hearing loss can be more difficult because they cannot describe the difficulties that they are having. The most common way for hearing loss in children to come to light is because of the speech and language developmental delay that results from the hearing loss. In older children, their parents or teachers might notice difficulties hearing day to day.
The team at the Ear and Hearing clinic will talk to you about the problems you have had in order to make a rapid and accurate diagnosis.
The main stay of diagnosis of hearing loss is, however, a hearing test. There are several different types of hearing test but the most common one is called a pure tone audiogram. In this test, tones are played in to each ear at different frequencies (measured in hertz) and the intensity of the sound (in decibels) is gradually reduced until the level at which the sound can only just be heard is determined. This is called the hearing threshold. The hearing thresholds for each ear are then recorded on an audiogram. An example of a normal audiogram is shown below.
A normally hearing person can hear the tones as quiet as 20dB or quieter.
The team at the Ear and Hearing Clinic are very experienced at carrying out all types of hearing test and will be able to explain the findings of the test to you. Most types of hearing test can be done at the same time as your initial consultation. For very young children, it is not possible to carry out the tests in the same way but the full range of children’s hearing tests are available through the Ear and Hearing Clinic.
Examining the Ear
An important element of any hearing assessment is examination of the ear. Professor Lloyd will make a detailed assessment of your/your child’s ear, often using a high powered microscope. The pictures below show a normal ear drum (A) and an ear drum with a hole or perforation (B).
It is sometimes necessary to clean the ears in order to clearly view structures such as the eardrum or relieve discomfort or loss of hearing caused by excess wax. At the clinic we use a suction device to remove wax under the microscope. This method of clearance is much safer than traditional syringing techniques.
Treatment of Hearing Loss
The treatment for hearing loss very much depends on the cause.
Sensorineural Hearing Loss
For sensorineural hearing loss, hearing aids are the only way of augmenting hearing unless the hearing loss is very severe, in which cochlear implants can be used to restore hearing (see later).
There is a wide variety of traditional hearing aids on the market but there are also a number of implantable hearing aids available that open up a wider range of options for hearing loss. The current range of traditional hearing aids are very effective. They are all digital and offer significant improvements in quality over older, analogue aids. Broadly speaking the aids may be worn behind the ear or in the ear. The latter are so discreet that it is difficult to see that the wearer even has a hearing aid in place. There are also lots of options for different programmes for different environments, Bluetooth and wireless connectivity and remote control capabilities. The picture below shows a typical behind the ear hearing aid.
A modern behind the ear digital hearing aid. They are now much more discreet and comfortable than their older analogue predecessors.
The team at the Ear and Hearing Clinic are able to offer the full range of hearing aids and will be able to talk you through the options available.
For people with profound hearing loss, a normal hearing aid is not usually powerful enough. In this situation, hearing can be restored using a cochlear implant. This is an electrical device that is inserted into the cochlea and stimulates the nerves of hearing electrically when the hair cells are no longer capable of picking up sounds.
A cochlear implant in situ is shown in this diagram. There are two parts to a cochlear implant, the processor and its coil (A and B) and the implanted portion (C). (1) The hook holding the processor to the ear. (2) The electronics package for the implantable portion. (3) The electrode array that is placed within the cochlea. (4) The cochlear nerve that carries electrical impulses from the cochlea to the brain.
There are 2 parts. The implantable part has an electronics package that is placed under the skin just above and behind the ear and an electrode array that is inserted into the cochlea which has a series of small electrodes along its length that electrically stimulates different areas of the cochlea. This part requires an operation to implant. The operation is, however, usually straightforward in experienced hands and can be performed as a day case for most people. The second part is the sound processor. This is the part that picks up sound and converts it to an electrical signal that can be interpreted by the implanted portion. This part has the battery pack and a round ‘coil’ that transfers the signal electromagnetically to the implanted portion. If you would like to see a cochlear implant operation please click here.
Link to COCHLEAR IMPLANT VIDEO
Outcomes from Cochlear Implantation
Cochlear implantation is one of the greatest advances in medicine in the last 50 years. In adults who was deafened later in life, a cochlear implant usually enables them to have a normal conversation and, in some cases, use the telephone and often means they can go back to a normal job and enjoy normal everyday relationships again. In children who are born profoundly deaf, a cochlear implant allows them to develop normal speech and language and enables them to go to a mainstream school and have all the opportunities that a normally hearing person would have. Professor Lloyd is a very experienced cochlear implant surgeon and works with a team of dedicated audiologists and speech therapists at the Richard Ramsden Auditory Implant Centre in Manchester, one of the busiest units of its kind in the UK. Together, the team are able to achieve results comparable to those of other leading units across the world.
Conductive Hearing Loss
In contrast to sensorineural hearing loss, conductive hearing loss is often amenable to surgical correction. Blockages of the ear canal are usually easily removed using microsuction. If there is hearing loss because of a hole in the ear drum then it is possible to repair the hole and potentially improve the hearing.
Ossicular Repair Surgery
If there is damage to the hearing bones then this can often be corrected. For example, if the middle hearing bone is damaged, it can be replaced with an artificial hearing bone by carrying out a small procedure. This is called an ossiculoplasty. The diagram below shows how this can be carried out:
A. The middle hearing bone is absent and the hearing bones are no longer in continuity. B. An artificial hearing bone has been used to bridge the gap between the remaining hearing bones.
If you would like to see an ossiculoplasty procedure please click on the link below (ADD VIDEO).
Professor Lloyd is able to offer the full range of ossiculoplasty procedures. His results are comparable to those of other leading otologists. His results are shown in the table below compared to some of the results from other leading hearing restoration surgeons.
INSERT OUTCOME TABLE.
Table showing Professor Lloyd’s ossiculoplasty outcomes compared to those published by other surgeons around the world.
Correction of Fixation of the Hearing Bones
Fixation of the hearing bones most commonly occurs at the inner most bone called the stapes. The fixation is usually because of new bone formation around the stapes in a condition called otosclerosis. This results in a conductive hearing loss. It is possible to augment the hearing in this condition using a hearing aid. Alternatively, there is an operation, called a stapedectomy, that is a very effective way of correcting the hearing loss in this condition. In this operation the outer part of the stapes (the arch) is removed and a tiny hole, usually a fraction of a millimeter across is made in the remaining part of the bone that is in contact with the inner ear. Through this hole, a tiny piston is passed and the other end of the piston is hooked around the middle hearing bone. Sound can then pass through the hearing bones and piston to the inner ear, therefore bypassing the fixed stapes.
Professor Lloyd is able to offer this type of surgery as a day case procedure. He uses the latest laser techniques to minimize the risk of the surgery and optimize the hearing outcome. This type of surgery has an 85% chance of reducing the conductive hearing loss to a level where it is not noticeable.
Implantable Hearing Aids
Conductive hearing loss is also amenable to rehabilitation using implantable bone conducting hearing aids. The implantable hearing aid options include devices such as Bone Anchored Hearing Aids (BAHA), Bonebridge and Soundbridge devices all of which are available through Professor Lloyd. The principle by which the BAHA and the Bonebridge work is similar. Both consist of an implantable device that is able to vibrate. Sound is detected by the device and converted to vibrations that are transferred through the bone of the skull to the inner ear. In so doing, any problems with the conduction of sound from the outside world are bypassed. The diagrams below show how a BAHA and a Bonebridge device work.
Both the BAHA and the Bonebridge enhance hearing by picking up sounds, converting them into vibrations that are then transferred through the skull directly to the inner ear. They therefore bypass a conductive hearing loss. In the BAHA (A) the vibrations are generated in a hearing aid that clips onto a screw that is implanted into the skull. With the Bonebridge (B) the sound is picked up by a processor that attaches to the implantable part by magnetism. There is no break in the skin with this type of implant and it is therefore a more cosmetically acceptable procedure. The signal that the processor picks up is transferred by electromagnetism to the implantable part. Within the implantable part is a small crystal that vibrates and it is this that allows sound to be transferred to the inner ear.
The operations for the BAHA and the Bonebridge are straightforward and can be undertaken as a day case.
Risks of Hearing Surgery
Operations to restore hearing loss are generally very safe. As with any operation, however, there are certain risks. The commonest complaint after hearing restoration surgery is change in the sense of taste on the operated side. This is because the taste nerve runs through the ear and may be stretched or bruised during the operation. This can occur in up to 25% of patients but is almost always temporary although it can take up to 6 weeks for the change in taste to recover. With any hearing operation, there is a risk that it will not work. The risk of no noticeable hearing improvement following ossiculoplasty are shown above. The risk of no noticeable hearing improvement after stapedectomy is 15%. There is also a risk that the hearing could be worse in the operated ear after surgery and in the worst case scenario the hearing could go altogether (a dead ear). With ossiculoplasty the risk of this is under 1%. With stapedectomy the risk of this is 2%. It is also possible to develop dizziness and tinnitus after this type of surgery. It is also possible to cause a hole in the ear drum following this type of surgery but the risk of this is also under 1%. Finally, there is a risk of bleeding and infection as there is with any operation although these are unusual with this type of surgery.