Thinner abuse alters optokinetic nystagmus parameters

Background. Deliberate self-inhalation of solvents such as thinner is a rec ognized problem in underdeveloped countries, with chronic abuse resulting i n neurological impairment. In this article, we use electronystagmography (E NG) to study optokinetic nystagmus abnormalities (OKN) that may be induced by thinner consumption. Methods. Twenty-five patients exposed to thinner for 5-20 years, in an irre gular fashion of consumption, were recruited from a toxicologic center. Twe nty-five control subjects were invited to participate as volunteers matched by age (+/- 2 years) and gender. At the time of evaluation, all had abstai ned from intoxicants for at least 4 weeks. ENG recordings were performed by clinicians masked to the patient's group. Clockwise and counterclockwise s timulation were performed at 20 and 40 degrees/sec. Results. None of the patients slowed spontaneous nystagmus during the test period. Differences between thinner abusers and controls on clockwise and c ounterclockwise OKN on number of beats of nystagmus elicited on the 40 degr ees/sec velocity were identified. The thinner abusers group showed a lesser number of nystagmus (p level was 0.02 and 0.005, respectively). Conclusions. The present results confirm the sensibility of OKN as an early marker of solvent abuse. These results were obtained in middle-term chroni c exposure to solvent mixtures and are in favor of both cortical and brains tem dysfunction. (C) 2000 IMSS. Published by Elsevier Science Inc.