Helen Adam Keller, an American author and the first deaf-blind person to earn a Bachelor of Arts degree, once noted that while blindness cuts people off from things, deafness cuts victims off from people. Hearing loss is not just an ailment of old age; it can strike at any time and any age, even childhood. For the young, even a mild or moderate case of hearing loss could bring difficulty learning, developing speech and building the important interpersonal skills necessary to foster self-esteem and succeed in school and life.
In Nigeria, the broad consciousness of hearing impairment is low. Lack of resources has resulted in very few screening programs. In Lagos, a recent research has shown that as many as 13.9 per cent of school pupils suffer from hearing loss. Yet, in just 2 per cent of the cases did parents or teachers observe signs of hearing loss. This is the finding of a study examining the incidence of hearing impairment in Nigerian school children. The prevalence of noise pollution is a foremost cause of health concern in Nigeria. The Nigeria Hearing and Speech Association (NIHSA) has linked the growing hearing difficulties being experienced by Nigerians to noise pollution.
The human ear is a complex organ and many scientists consider hearing to be the most complex of the human senses. The brain and auditory system work together to control how we hear and how we balance ourselves. Hearing is our ability to perceive sound by detecting vibrations that travel through our ears. Sound can be detected whether a person is on land, underwater or in the air. The main purpose of the ear is to turn sound waves from the air into electrical signals that are interpreted by the brain. Anatomically, the ear is made up of three parts: the outer, middle, and inner ear. All three parts of the ear are important for detecting sound by working together to move sound from the outer part through the middle and into the inner part of the ear.
Hearing problems can be divided into two, congenital or acquired which can affect the three divisions of the ear. Genetic factors are thought to cause more than 50% of all incidents of congenital hearing loss in children. There are some genetic syndromes, in which, hearing loss is one of the known characteristics. Some examples are Down syndrome (abnormality on a gene) and Usher syndrome (autosomal recessive). Acquired hearing loss is a hearing loss which appears after birth, at any time in one’s life, perhaps as a result of a disease, a condition, or an injury.
Typical problems with the outer ear include ear wax plugs and infections of the auditory canal. Hearing loss caused by an outer or middle ear defect is called conductive hearing loss. Inflammation, fluid behind the eardrum, perforations of the eardrum and otosclerosis (a stiffening of the bones in the middle ear) are the most common problems that impair middle ear function. The bulk of hearing issues concern the inner ear with the most common cause being natural aging process, loud noise, some medications like, Aminoglycoside antibiotics (such as streptomycin, neomycin, or kanamycin,Salicylates (Aspirin) in large quantities. Loop diuretics such as Lasix or ethacrynic acid, drugs used in chemotherapy regimens (cisplatin, carboplatin, or nitrogen mustard can also cause hearing loss. Similarly, skull fractures can also have a negative influence on hearing ability. These influences damage the fine hair cells and affect the transmission of signals to the auditory nerves. Inner ear hearing loss generally cannot be addressed medically; however, in most cases, this type of hearing loss can be corrected with a hearing aid or a hearing implant.
An example of ear impairment which affects the inner ear in adult is the Ménière’s disease. The cause of Ménière’s disease is unknown. It usually begins between the ages of 30 and 50. A person with Ménière’s disease will often have a combination of sensorineural hearing loss, dizziness (vertigo), ringing in the ear (tinnitus) and sensitivity to loud sounds.
This type of hearing loss is managed by a doctor and audiologist. Some people with Ménière’s disease report mild symptoms, but for others the symptoms are much worse. The hearing loss comes and goes, but over time some loss becomes permanent.
In the time past, people with permanent hearing loss usually resign to fate, but succour has now come the way of this group of people through cochlear implant, an intricate, medical electronic device that is surgically implanted behind the ear to treat hearing loss. A cochlear implant improves hearing by representing sounds better. Patients may not get back normal hearing but they will be able to hear sounds more clearly and will have an improved understanding of speech in environments filled with noise.
A cochlear implant consists of internal parts that are implanted beneath the skin and external parts that are worn by the patient. The external part has a speech processor that helps in creating the sensation of sound. The external microphone and processor gathers the sounds in the environment and converts them into electrical impulses. The cochlear implant sends impulses to the auditory nerve that transmits the signals to the brain. It can bypass the non-functional portions of the ear and provide a direct stimulation to the auditory nerve. These signals are then transmitted by the auditory nerve to the brain that perceives the signals as sound.
It is heart-warming that the first- ever home grown cochlear implantation surgery was recently performed in the country by a team of medical experts at the Lagos State University Teaching Hospital, LAUSTH. Similar feat was achieved last year by a team of medical personnel from the hospital in collaboration with Germany based Cochlear Foundation. Consequently, people with hearing impairments otherwise considered to be permanent can now enjoy an improvement in their quality of life and be able to connect with fellow human beings better.
•Bakare writes from Alausa, Ikeja