In a normal ear, the sound hits on an intact eardrum. Three small bones work as a lever mechanism to increase the movement, and the third bone (stapes) works as a piston to convey this amplified vibrations to the fluid system of the inner ear. Some mechanical problem, such as fluid in the ear, perforation of the eardrum, or damage to the lever mechanism of the three bones which amplify the sound, or fixity of the eardrum or the bones or piston or new bone formation may result in a hearing loss, where the amplified sound is not reaching the inner ear. However, if the inner ear is stimulated directly by the bone, the nerves, hearing organ and hearing is normal. This is called conductive hearing loss. This is often reversible, and may be corrected by surgery.
Here there is a damage to the inner ear (sense organ), or damage to the auditory nerve which conducts the signals to the brain (Neural Hearing Loss). These occur when there is physical or other damage to the end organ or the nerve. Mostly sensory-neural hearing loss is not reversible (except for sudden onset hearing loss due to certain causes). No surgery can correct this loss and a hearing aid is the only solution. Sudden onset sensory-neural hearing loss can be due to a viral infection, or a “mini stroke”: blockage of blood supply. This can be reversed by urgent medical management.
Is a combination of conductive loss, with sensory-neural loss also present. The conductive part may be correctable. Screening for hearing loss is now recommended in all newborns. In children, hearing problems may cause speech to develop slowly, along with other learning handicaps. By early screening, congenital hearing loss (sensory-neural hearing loss present from birth) can be detected early and suitable measures like Hearing aids, or cochlear implantation can be done at an early age, so that the child does not also become mute. In childhood, ear infections are the most common cause of temporary hearing loss. Fluid can linger in the ear following an ear infection. Although this fluid can go unnoticed, it can cause significant hearing and learning problems. Any fluid that lasts longer than 8-12 weeks is cause for concern, and needs to be treated by a minor surgery to drain the fluid. In this surgery, electrodes are inserted into the inner ear, and the hearing aid (speech processor) fitted behind the ear thus sends electrical signals straight to the hearing nerves. This is not suitable if the nerve itself is damaged. The implant is very expensive and has its own share of complications.