Visual evoked potentials in workers with chronic solvent encephalopathy

Abstract

Objectives: Two promising variations of visual evoked potentials (VEPs) were studied in solvent-exposed workers: the effect of a low-contrast stimulus in comparison with the usually applied high contrast, and the ability of pattern-onset VEP to reveal damage to specific visual cortical areas. In addition, we studied disturbances of a visual event-related potential (P300). Methods: Thirty male patients (48±9 years of age) with solvent-induced chronic encephalopathy, and 41 controls (46±8 years) without solvent exposure, participated. Pattern-reversal checkerboards with low (11%) contrast and with high (93%) contrast between the checks were used. For onset VEPs two dedicated stimulus patterns were used. P300 was elicited with an ''oddball'' paradigm. Results: At low contrast the N75-P100 peak-to-peak amplitude in the controls was 9.6±4.9 lV, i.e. 57% of the amplitude at high contrast (16.3±7.2 lV). In the patients the response at low contrast was only 48% of that at high contrast; the corresponding amplitudes were 7.5±3.5 lV and 15.8±4.9 lV. For the pattern-onset VEPs no effect of exposure was found. With regard to the P300, the patients missed more targets (average 3.6%) than did the controls (average 0.5%). Patients had a smaller P300 amplitude (8.8±4.5 lV) than the controls (11.5±5.3 lV), and a longer latency (390±34 ms compared to 376±24 ms). Conclusion: The results point to a physiological basis for the solvent-induced decrease of visual contrast sensitivity as found by others by means of psychophysical methods. The results also suggest that the neurophysiological examination of the visual system in persons who have undergone exposure to toxins might be benefited by the addition of low-contrast stimuli.

Visually-evoked P300 and NOGO potentials as indicators of central nervous system function in patients with vibration syndrome

“…Various studies of the eVects of occupational factors on central nervous system (CNS) function using event-related potential (ERP) recording have been performed, in clinical cases of exposure to organic solvents (Morrow et al 1992;Chuwers et al 1995;Lindgren et al 1997;Verberk et al 2004) or hydrogen sulphide (Wasch et al 1989;Hirsch 2002), vibration syndrome (VS) (Hirata et al 1995), surveys on lead exposure Murata et al 1993;Hirata et al 2004), survey on manganese exposure (Wennberg et al 1991(Wennberg et al , 1992 survey on solvent exposure (Estrin et al 1990;Lundberg et al 1995;Vrca et al 1997;Morrow et al 1998), shift work (Yasukouchi et al 1995), vibroacoustic disorder (Martinho andCastelo 1999), and cervico-brachial disorders . Hirata et al (1995) reported that the P300 latencies of vibration syndrome (VS) patients were delayed compared with those of healthy control subjects.…”

Exposição ocupacional a ruído e solventes e alterações auditivas periféricas e centrais

“…, 1999;GONG et aI. , 2003;SEEBER et aI., 2004 (MORATA et aL, 1993;MORATA et aL, 1997;THUOMAS et aL, 1996;VRCA et aL,1997;NIKLASSON et aL, 1998;MOEN et aL, 1999 (NYLEN e HAGMAN, 1994;LAUKLI e HANSEN 1995;SLlWINSKA-KOWALSKA, et aL, 2005; (MORROW et ai, 1998;MOEN et aL, 1999;VERBERK et aL, 2004;SEEBER et aL, 2004). Embora pesquisas tenham indicado que algumas dessas habilidades possam estar comprometidas também pela exposição isolada a ruído (COSTA et aL, 1992), neste estudo as repercussões da exposição a solventes sobre a função auditiva central medidas pelo teste do PEALL-P300 foram bem mais evidentes em relação à exposição a ruído.…”