Brain damage in a large cohort of solvent abusers

The neuropathology of solvent inhalation consists of patchy myelin loss with white matter macrophages that contain granular inclusions. It has been described only in a small number of cases. We sought to characterize the abnormalities in greater detail. In a retrospective study from 1995 to 2009, we encountered 88 autopsy cases with documented history of solvent abuse by inhalation and 1 with industrial exposure. Among these are 6 fetuses and infants with maternal exposure, 23 children (12–17 years), and 60 adults (18–66 years). Available brain samples from 75 cases were stained with solochrome cyanin (to demonstrate myelin) and periodic acid–Schiff (PAS) (to highlight the inclusions). Forty brains of ethanol and/or illicit drug exposed individuals and ten cases of multiple sclerosis were examined as controls. We found that 16 cases (age 23–49, median 37 years) had well-established leukoencephalopathy with multifocal myelin loss and abundant macrophages that stain with PAS and which contain birefringent inclusions. Six cases (age 15–55, median 27 years) had early leukoencephalopathy with scattered macrophages but no obvious myelin changes. Clusters of PAS-staining but non-birefringent macrophages were seen in 2/10 cases of (active) multiple sclerosis and in none of the ethanol/drug exposed brains. Ultrastructurally, inclusions from solvent cases differed from multiple sclerosis cases. Although exposure to solvents is impossible to quantify, there appears to be a duration-dependent effect. Brain damage related to solvent abuse can begin within only a few years of the onset. In the context of substance abuse, the changes are relatively specific for solvent inhalation and do not appear to result from demyelination alone. Interaction with ethanol cannot be excluded as a compounding risk factor.