Sponsored by brainstem. The brain is like two large mushrooms side by side with a single stalk. The stalk of the 'mushrooms' is called the brainstem, and it controls many vital functions such as blood pressure and breathing. Sound signals pass from the cochlea along the auditory nerve to the brainstem, where they activate other nerve cells that transmit the message higher up the brain. If deafness is caused by damage to the cochlea or the auditory nerve, it may be possible to restore some perception of sound by carefully stimulating the correct region of the brainstem.
Conductive deafness occurs when something prevents the sound vibrations from reaching the inner ear.
This could merely be wax in the ear canal, but it could also occur if infection has caused the ear drum to become perforated so that it does not resonate normally with the vibration. Alternatively, the ossicles might become stiff so that they lose their 'lever' action. With conductive deafness, the hearing organ is basically normal, and the problem lies in getting sound to the cochlea. In sensori-neural deafness , the defect lies in either the cochlea or the transmission of the sound signals to the brain once they have left the cochlea. This form of deafness tends to occur with age, and is accelerated by exposure to loud sounds, perhaps at a disco, perhaps from a ghetto blaster, but also from construction projects.