CRS has been controlled by universal vaccination (MMR or MMRV vaccine). Cytomegalovirus (CMV) infection is the most common cause of progressive sensorineural hearing loss in children. It is a common viral infection contracted by contact with infected bodily fluids such as saliva or urine and easily transmitted in nurseries and thus from toddlers to expectant mothers. CMV infection during pregnancy can affect the developing foetus and lead to learning difficulties as well as hearing loss. Toxoplasmosis, a parasitic disease affecting 23% of the population in the U.S., can cause sensorineural deafness to the fetus in utero. Hypoplastic auditory nerves or abnormalities of the cochlea. Abnormal development of the inner ear can occur in some genetic syndromes such as LAMM syndrome (labyrinthine aplasia, microtia and microdontia), Pendred syndrome, branchio-oto-renal syndrome, CHARGE syndrome
GATA2 deficiency, a grouping of several disorders caused by common defect, viz., familial or sporadic inactivating mutations in one of the two parental GATA2 genes. These autosomal dominant mutations cause a reduction, i.e. a haploinsufficiency, in the cellular levels of the genes product, GATA2. The GATA2 protein is a transcription factor critical for the embryonic development, maintenance, and functionality of blood-forming, lympathic-forming, and other tissue-forming stem cells. In consequence of these mutations, cellular levels of GATA2 are deficient and individuals develop over time hematological, immunological, lymphatic, and/or other disorders. GATA2 deficiency-induced abnormalities in the lymphatic system are proposed to be responsible for a failure in generating the perilymphatic space around the inner ears semicircular canals, which in turn underlies the development of sensorineural hearing loss.
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pregnancy and childbirth information
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Otoscopy
Direct examination of the external canal and tympanic membrane (ear drum) with an otoscope, a medical device inserted into the ear canal that uses light to examine the condition of the external ear and tympanic membrane, and
middle ear through the semi-translucent membrane. Differential testing
Differential testing is most useful when there is unilateral hearing loss, and distinguishes conductive from sensorineural loss. These are conducted with a low frequency tuning fork, usually 512 Hz, and contrast measures of air and bone conducted sound transmission. Weber test, in which a tuning fork is touched to the midline of the forehead, localizes to the normal ear in people with unilateral sensorineural hearing loss. Rinne test, which tests air conduction vs. bone conduction is positive, because both bone and air conduction are reduced equally. less common Bing and Schwabach variants of the Rinne test. absolute bone conduction (ABC) test.Table 1. A table comparing sensorineural to conductive hearing loss

Other, more complex, tests of auditory function are required to distinguish the different types of hearing loss. Bone conduction thresholds can differentiate sensorineural hearing loss from conductive hearing loss. Other tests, such as oto-acoustic emissions, acoustic stapedial reflexes, speech audiometry and evoked response audiometry are needed to distinguish sensory, neural and auditory processing hearing impairments. Tympanometry
A tympanogram is the result of a test with a tympanometer. It tests the function of the middle ear and mobility of the eardrum.