Toxic encephalopathy and noise-induced hearing loss

In several laboratory animal studies, it has been documented that the hearing, vision, and brain can be injured due to exposure to organic solvents. This finding formed the background for a pilot study (n=16) aimed at identifying new ways of qualifying diagnostics, treatment, and rehabilitation of patients suffering from brain injury due to exposure to organic solvents, also referred to as toxic encephalopathy. Diagnosing toxic encephalopathy is complicated because the symptoms of this type of diffuse brain injury are non-specific. So, it was initially hypothesised that some of the difficulties involved in diagnosing toxic encephalopathy could be minimized by extending the diagnostic procedure. Apart from clinical interviewing and neuropsychological testing, the diagnosis should include the examination of hearing and vision. This will help in achieving new measures that could improve in diagnosing toxic encephalopathy with more certainty. On the basis of ranking, only one patient in the pilot study was considered to have a normal neuropsychological test profile, which was defined as a test profile without any marked deviations when compared with a normal population. A total of 10 patients were considered to have "discrete problems." These patients had a test profile showing either a few strikingly negative results or an array of results slightly below the expected level when compared with a normal population. A total of four patients were considered to suffer from "moderate problems" and one patient from "severe problems." The patients with "moderate problems" and "severe problems" showed consistent negative results and an unambiguous negative test profile. However, the overall results of all neuropsychological examinations performed revealed a dispersed picture. Quite remarkably, all the 13 patients who had their hearing examined showed a loss of hearing, 7 patients complained about tinnitus, and all patients had a history of exposure to both noise and organic solvents, which had not been observed at the initial examination, but seemed to have serious implications for their prognosis and future life.