Studies On Hearing Loss Discovers New Causes

New researches identify two causes that can cause hearing loss in people apart from the all other existing causes, greying hereditary syndrome and type 1 diabetes. The researches are featured in the July edition of Otolaryngology—Head and Neck Surgery.

In the first study researchers have found a previously unreported hereditary syndrome composed of sensorineural hearing loss (a form of hearing loss due to a lesion of the auditory division of the eight cranial nerve or the inner ear), early greying of scalp hair, and adult-onset essential tremor.

A team of researchers from Tufts University, Stanford University, and New York University examined three families with combinations of early hair greying, sensorineural hearing loss, and essential tremor that seem to be reproducible at varying levels from generation to generation. A retrospective chart review was performed on the three patients with sensorineural hearing loss, early greying of scalp hair, and tremor, each with family members with similar features. In each case, a family history had also been carefully obtained. Two additional siblings with significant findings from one family were also presented.

The study’s patients were a 65-year-old man and two women in their 40s. Two noted hearing loss in adulthood, one as a child. All had complete greying in their 20s. The women developed essential tremor in their 20s, and the man in his 50s. All of the individuals had blue eyes without heterochromia (a difference in coloration in two structures which are normally alike in color.)

Molecular genetic studies failed to link these patients with mutations known to be associated with Waardenburg syndrome, an inherited disorder often characterized by varying degrees of hearing loss and changes in skin and hair pigmentation. A literature search of the English language has failed to reveal previous reports of similar syndromes.

In the second study, the relationship between diabetes mellitus and sensorineural hearing loss (SNHL) has been studied for more than a century. In order to examine the effects of diabetes on the cochlea, researchers have conducted the first study to quantitatively analyze the changes in the cochlea due to type 1 diabetes mellitus.

The researchers studied the temporal bones from patients with juvenile onset diabetes (insulin-dependent.) The results show that type 1 diabetes mellitus results in changes of the cochlea which are likely to result in hearing loss. This study suggests that type 1 diabetes mellitus can subsequently cause the degeneration of cochlear lateral walls and outer hair cells.

Source: Newswise

Medindia on Hearing Loss: Further information

Hearing loss: Losing the ability to hear sounds may be due to infection, blockage or damage to the ear. Other kinds of hearing loss may be due to damage to the pathway through which the sound waves travel from the hair cells of the inner ear to the auditory nerves. The probable causes of this may be age, disease, infections, tumor or stroke.

Diabetes: Diabetes affects the population in terms of affecting the metabolism of blood glucose and impaired function of the insulin that helps in controlling the blood sugar levels. The main risk factors for diabetes are obesity, physical inactivity, genetic influence and age related factors. Recent studies have shown that low birth weight is also another risk factor for the disease.