The growth in this percentage being due not to a real increase but rather to an improvement in diagnostic capabilities.

Acquired deafness is subdivided in three different types:

Prenatal deafness, caused by an infection or the use of medicines or drugs during pregnancy or by illnesses such as renal insufficiency.

Perinatal deafness, mainly caused by hypoxia (oxygen deprivation) or jaundice (an illness resulting from an accumulation of bilirubin in the blood).

Postnatal deafness, caused by meningoencephalitis, mumps or certain viruses but also as a result of mechanical trauma.

Types of deafness

Hearing deficit can be classified according to several criteria. Quantitative criteria result in the following classification:

• Normal hearing (hearing threshold less than 20dB)
• Slight deafness (hearing threshold between 20 and 40 dB)
• Medium deafness (hearing threshold between 40 and 70 dB)
• Serious deafness (hearing threshold between 70 and 90 dB)
• Severe deafness (hearing threshold between 90 and 120 dB
• Total hearing loss (hearing threshold over 120 dB)

Hypoacusis is divided, on the basis of the site of the problem, into:

• Transmissive or related to conduction
• Neurosensorial or related to perception
• Mixed