The prevalence of genetic deafness has been calculated at about 1: 2000. The hereditary causes of deafness are constantly increasing and have practically tripled in the last thirty years (today, one case of infantile deafness in three is of genetic origin).

In any case, we can reasonably assume that a good part of the increase in this percentage is due not so much to an absolute increase, but rather to the improved methods of diagnosis and recognizing the various syndromes.

Hereditary deafness is divided into:
Recessive

Dominant

Tied to sex

Acquired deafness

Acquired deafness, in turn, is divided into three types:

Pre-natal deafness. The pre-natal causes of deafness are mostly due to infections caught during pregnancy (German measles, infections from cytomegalovirus, toxoplasmosis, AIDS, etc.).
Even the use of medicines (salicylates, quinine and its synthetic similars, aminoglycoside antibiotics, some diuretics) and drugs (cocaine, alcohol) has shown to be harmful to the hearing system of the foetus.
Some conditions tied to pregnancy pathologies, such as gestosis and renal insufficiency, can create the conditions for foetal suffering and thus secondarily cause hypoacusis.

Perinatal. Among the perinatal causes of deafness, an important role is played by hypossia⁽¹⁾ and jaundice⁽²⁾. Late or insufficient breathing at the moment of birth can be the cause of hypossia, often with very serious local and general consequences. The seriousness of the injuries caused mainly depends on the degree and duration of the hypossia.
Jaundice (altered colour of the skin and mucous membrane due to the accumulation of bilirubin) is a physiological event that only in rare cases becomes very serious pathologically (haemolytic illness of the newborn baby) with the presence of bilirubin, a highly neurotoxic substance, in the encephalon.

In recent years it has been seen how the ever wider distribution of Neonatal Intensive Care Centres has improved the survival rate in high-risk newborns, but a concomitant increase in the probabilities of developing deafness is also induced.

Postnatal. Meningoencephalitis, together with parotitis (mumps), is by far the most frequent cause of deafness in infancy and early childhood.
The inner ear can be affected both by specific viruses (parotitis, measles) and by aspecific viruses. The measles virus usually causes mild to serious bilateral hearing loss, whereas parotitis causes a completely one-sided deafness.
Even various kinds of mechanical trauma can be among the cases of acquired postnatal deafness.


⁽¹⁾ The lack of or reduced oxygen supply to tissues

⁽²⁾ Pathological condition due to the accumulation of bilirubin in the blood