What matters deafness of the ear, when the mind hears. The one true deafness, the incurable deafness, is that of the mind.
Around 1 in 1,000 newborns present with profound hearing impairment with genetic factors possibly accounting for as many as half. At present 120 genes have been found, that when mutated, are responsible for deafness. However, more than half of all recessively inherited deafness results from mutations in only one gene, known as connexion 26.
In addition to single gene defects affecting only deafness there also nearly 400 syndromes in which deafness is a feature. Waardenburg Syndrome is one of the most common.
Some individiuals develop a progressive deafness occurring in adulthood, such as due to abnormal growth of bone in the inner ear characteristic of otosclerosis.
Around 24,000 people in the UK are both deaf and blind with the majority losing their senses later in life from infections such as rubella. The major genetic cause for deaf blindness is Usher syndrome.
Some autoimmune disorders can also effectthe workings of the inner ear, such as Vogt-Koyanagi-Harada syndrome that can result in permanent deafness and balance/coordination problems
The balance organs in the inner ear basically consist of tubes and cavities containing fluid and small hairs which are moved in response to motion of the head. Spinning around, can cause the fluid to keep sloshing around long after motion has ceased, with the hair cells still informing the brain that the body is still moving, even after it has stopped – this causes the dizziness. A similar situation can occur whilst reading in a moving car - the inner ear senses the movement of the vehicle, but the eyes see only the book which is not moving. The resulting sensory conflict can lead to the typical symptoms of motion sickness, such as nausea. Nausea in Greek means seasickness (Gr. naus; ship).
Defects in the regulation of the fluid in the tubes of the inner ear causes Ménière's disease, while another disorder effecting balance is the rare inherited condition, known as Joubert's syndrome results from defects in regions of the brain involved in processeing signals involved in balance regulation.