Audiological Screening in People with Diabetes. First Results

The relationship between diabetes mellitus (DM) and hypoacusia has been discussed since the work of Jordao, in 1857. Type II diabetes was considered a prevalent age-related medical condition, resulting in subclinical pathological changes. It was estimated that the incidence is about 9.6% of people in USA. (Cowie et al. 2006). Some studies has shown that the magnitude of hearing loss in patients with DM is related to the duration of the disease, age, and affects the auditory threshold to high frequencies. (Frisina et al. 2006). In a study of Tay HL et al. (1995) was found that there is a possible correlation between the duration of diabetes and hearing loss. The auditory system requires glucose and high-energy utilization for its complex signal processing. This suggests that the cochlea may also be a target organ for the ill effects of hyperglycemias. (Cullen and Cinnamond, 1993). Increased glucose exposure, even for short periods, initiates a metabolic cascade that could disrupt the cochlea both anatomically and physiologically (Jorgensen, 1961). Hearing depends on small blood vessels and nerves of the inner ear that are affected by high blood sugar level in diabetic patients. Outer hair cells modulate auditory reception in the inner ear: consequently, OAEs are commonly considered a useful index of cochlear function (Martin et al., 1990). Well-established complications of diabetes, such as retinopathy, nephropathy, and peripheral neuropathy involve pathogenic changes to the microvasculature and sensory nerves (Acuña García, 1997). This conditions lead to a common symptoms in diabetic people that are tinnitus, dizziness and sensorineural hearing impairment, typically bilateral and progressive. Moreover, the specific pathologic effects of hyperglycemias and the complication associated with diabetes such as microvascular and neuropathic sorrows affecting also the ear including sclerosis of the internal auditory artery, thickened capillaries of the stria vascularis, atrophy of the spiral ganglion, and demyelination of the eighth cranial nerve, has been described among autopsied patients with diabetes (Lisowska et al., 2001). Several studies are present in the international literature and the results are not unique. Compromised cochlear function has been measured using evoked otoacoustic emissions, a non-invasive method to assess damage to the outer hair cells of the cochlea, among patients with diabetes relative to healthy controls (Lisowska et al., 2002). The aim of our study is to evaluate the topography of sensorineural hearing loss induced by diabetes, checking the sensitivity of audiological investigation to probe the damage.