Audiological Disturbances Caused by Long-term Exposure to Industrial Solvents. Relation to the Diagnosis of Toxic Encephalopathy

Abstract

Sixty workers, consecutively admitted due to suspicion of solvent-induced chronic toxic encephalopathy (CTE), were investigated with pure-tone audiometry, determination of speech recognition of monosyllabic words and distorted speech and cortical response audiometry (CRA). Eighteen workers not exposed to occupational solvents and noise were also investigated. The scores in the distorted speech test were significantly lower and the CRA latencies were significantly longer in the solvent group than in the control group. There was no difference between the groups in the pure-tone and monosyllabic speech recognition tests. In the solvent group, 19 subjects had one or several pathological audiological test results (values exceeding the mean result of the control group by 2 SD). Independently of the audiological examination all the workers in the solvent group underwent the traditional clinical assessment of CTE, which is based on symptoms, history of exposure, clinical neurological examination and a neuropsychological investigation. They were classified in three groups--CTE, incipient CTE and non-CTE. There was no correlation between these groups and the audiological test results. A previous report on vestibular pathology in the same group of subjects and the present investigation on hearing deficits suggest that long-term exposure to solvents causes disturbances of the central pathways in the otovestibular system. Hitherto, no attention has been paid to these disturbances in the definition of the CTE syndrome.

Chemical exposure and hearing loss

“…[168][169][170][171][172][173] This suggests that hearing loss caused by chemicals can affect a worker's life more extensively than noise-induced hearing loss, because sounds are perceived not only as less loud, but also as distorted. Word recognition may also be compromised.…”

Auditory neuropathy in a patient exposed to xylene: case report

“…For example, impaired speech recognition scores consistent with a retrocochlear pattern and/or abnormal cortical responses and/or abnormal reflex decay have been reported in populations working with toluene, 5 jet fuels, 8 styrene 9 and mixtures of solvents. 8,10 -12 It is now documented that solvents should be considered as individual substances with different specific toxicities, 12 and that solvents may act on transmitters specific for certain neural structures and pathways. 10 For example, significantly delayed auditory brainstem responses (ABRs) were measured in a group of normally hearing workers professionally exposed to toluene.…”

Occupational Chemical-Induced Hearing Loss

“…Many studies have found dysfunction of the central auditory nervous system (CANS) in workers exposed to a mixture of solvents (Fuente et al, 2006;Fuente & McPherson, 2007;Laukli and Hansen, 1995;Moen et al, 1999;Niklasson et al, 1998;Ödkvist et al, 1987;Ödkvist et al,1992;Pollastrini et al, 1994;Varney et al, 1998). Fuente et al (2006), Fuente & McPherson (2007), and Fuente (2008) have shown that workers exposed to a mixture of solvents (toluene, xylene and methyl ethyl ketone) may acquire central auditory dysfunction as evidenced by abnormal results for a set of behavioural central auditory processing tests.…”