PET scan findings in a patient with a remote history of exposure to organic solvents.

This is a single-case study employing positron emission tomography (PET) scanning and neuropsychological assessment on a 47-year-old male with a 15-year history of repeated respiratory and dermal exposure to high levels of organic solvents with at least 750 peak exposures (i.e., solvent "intoxication"). At age 43, he presented with neuropsychological symptoms of a solvent encephalopathy and multiple abnormalities in his peripheral neurological examination but had normal MRI and EEG findings. Four years after cessation of exposure to degreasing and solvent chemicals, the patient produced a grossly abnormal PET scan in which frontal, hippocampal, and parietal hypometabolism were particularly noteworthy. During this same 4-year period of nonexposure, modest improvements in neuropsychological testing were noted, along with substantial improvements in partial seizurelike symptoms. Frontal lobe deficits elicited in testing and from collateral interview, however, did not change. Findings suggest that repeated peak exposures to organic solvents m y result in a neurobehaviorally complex solvent syndrome caused by central nervous system damage that is readily apparent on PET scan, even though it is not evident in either imaging technologies. In addition, the case is the first reported in which functional neuroimaging was employed to study a patient with chronic solvent encephalopathy many years after cessation of solvent exposure.