PATHOPHYSIOLOGY OF TOLUENE BRAIN DAMAGE
The mechanism of brain white matter injury from toluene
is unknown. As mentioned, this solvent, like many
others, is highly lipophilic (1), and in laboratory animals
toluene is preferentially distributed in lipid-rich regions
of the brain (51). These observations support the notion
that myelin, which contains 70% lipid, is targeted for
damage. In an autopsy study of a patient who inhaled
toluene prior to death, tissue concentrations were minimal
in the cerebral cortex and hippocampus and were highest
in the corpus callosum, the largest white matter tract in
the brain (42). MRI also reveals a predilection for damage
to the corpus callosum (Fig. 1B). The pathogenic
action of toluene after localizing in white matter, however,
is uncertain. A contribution by free radical-induced
lipid peroxidation has been suggested by observations
that reactive oxygen species are generated in the CNS by
toluene (52) or possibly benzaldehyde, one of its metabolites
(53).
Since autopsy studies show relatively specific damage
to myelin with axonal sparing (41, 43), the brain damage
induced by toluene may come to be understood as potentially
reversible with abstinence, or even amenable to future
treatments designed to restore the myelin using the
existing scaffolding of preserved axons. Although no data
exist on long-term outcome in toluene abusers who abstain
from inhalant abuse, our experience suggests that
individuals may show partial recovery once the toxic effect
of toluene is no longer present (21).