Evoked potentials and cerebral blood flow ' in solvent induced psycho - organic syndrome

Epidemiological studies have provided evidence that neuropsychiatric symptoms are induced by long term exposure to solvents; individual diagnosis with psychometric tests, however, is not always possible (for example, when the patient has linguistic difficulties). Therefore evoked potentials and cerebral blood flow were studied in 50 patients occupationally exposed to solvents who were referred to our department and for whom a solvent induced psycho-organic syndrome was suspected. Degree of exposure was evaluated by its duration (mean 13-9, range 1 to 37 years) and its intensity (from an interview). At the group level, P22 and N35 latencies and amplitude N20-P22 of somatosensory evoked potentials were higher in cases than in controls (p < 005), whereas there was no difference for brainstem and visual evoked potentials, nor for hemispheric cerebral blood flow (but a higher distribution in the left occipital region was seen in patients, p < 0.05). Some parameters were linked to degree of exposure (amplitude N20-P22 of somatosensory evoked potentials, interpeak latency I-V of brainstem evoked potentials, distribution of cerebral blood flow in the internal frontal left region). At the individual level, these examinations were not of diagnostic value because sensitivity was low. (British Journal of Industrial Medicine 1993;50:325-330) Service de medecine interne et de toxicologie clinique, H6pital Fernand Widal, 75475 Paris cedex 10, France D Deschamps, L Bertaux, S Dally Centre anti-poisons, H6pital Fernand Widal, 75475 Paris cedex 10, France R Gamier, A Reygagne Centre National de la Recherche Scientifique UA 385, CHU Pitie Salpetriere, 75013 Paris, France F Lille Service d'explorations fonctionnelles du systeme nerveux, H6pital Lariboisiere, 75010 Paris, France Y Tran Dinh 325 Neurobehavioural effects of occupational exposure to organic solvents have given rise to numerous studies in industry.' Although acceptable exposure concentrations have not yet been established, it is admitted that exposure to high concentrations can cause lasting alterations in cognitive function.2 As neurobehavioural impairments are not specific, it is difficult to clinically diagnose a solvent induced psycho-organic syndrome in a patient with subjective symptoms, and for whom being awarded compensation may be a consideration. Many studies have been conducted with psychometric tests. Nevertheless, their results do not confirm the existence of solvent induced psychoorganic syndrome: they are not abnormal at the early stage of the disease, when recovery after removal of exposure occurs in most cases3; so it could be judicious to complement them with research of objective neurological impairments by imaging or electrophysiological methods. Evoked potentials (projections of the action potentials on the cortex) and cerebral blood flows (reflecting cerebral metabolism4) can be perturbed in toxic central neuropathies (for example, from alcohol 5 6) and could be of good diagnostic value in diseases with subjective symptomatology for which the organic cause is difficult to ascertain-for example, migraine7 and perhaps developmental -learning disabilities in children.8 The aims of this study were to compare with controls the measurements of evoked potentials and of cerebral blood flow in 50 patients who were referred to our department and for whom solvent induced psycho-organic syndrome had been suggested, to search for a link between these results and the degree of exposure, and to evaluate their diagnostic interest by comparing them with the results of psychometric tests.