Hearing starts when oscillating molecules of air vibrate the ear drum or tympanic membrane. The vibrations are then transmitted into the inner ear via the middle ear bones known as the ossicles. This part of the hearing apparatus, from the outer ear to the cochlea, is the conductive component of the hearing and any damage to this mechanism will cause conductive hearing loss. Once the vibrations are transmitted into the inner ear they will oscillate the fluid inside the cochlea which is then converted to electrical nerve impulse via the hair cells. The impulse is then sent to the brain through a complex neuronal pathway. Any disruption from the inner ear to brain cortex would cause a sensorineural hearing loss. When both conductive and sensorineural components are affected then it becomes a mixed hearing loss.
Conductive hearing loss:
The most common cause by far is wax or cerumen impaction. The other common cause is fluid in the middle ear or serous otitis media. Other causes of conductive hearing loss include otosclerosis, ossicular chain abnormality, chronic ear disease and tympanosclerosis.
Sensorineural hearing loss:
This type of hearing loss, as caused by aging or loud noise exposure, is usually due to hair cell death in the cochlea. Other causes include hearing nerve agenesis, trauma and skullbase tumors the most common of which are acoustic neuromas.
Sudden hearing loss:
When the sudden hearing loss is conductive it is rarely an emergency. Particularly it if is not accompanied by pain, it is usually not due to an infection. However, a sudden sensorineural hearing loss is an emergency and you should be seen by an otolaryngologist within a few days. Your doctor can distinguish the two by using a tuning fork or performing an audiogram. If it is not possible for you to see your doctor urgently, you can tell the difference by doing a simple test. Making a loud humming noise with your mouth closed. If you hear the noise better in the ear you suddenly lost your hearing in, you have a conductive hearing loss. However, if you hear the sound better in your hearing ear, then you have a sensorineural loss. For example, if you have diminished hearing in the right ear and when you hum you hear the sound better in that ear (in your head), then you have a conductive loss. However, if you hear better in the left ear, then you have a sensorineural hearing loss.