General description

Toluene, also known as methylbenzene, is an aromatic hydrocarbon commonly found in solvents such as paint thinners, lacquers, glues, and adhesives. Widely used in various industries, including rubber, lumber, dry cleaning, and aviation, it is also a primary component in spray paints, making it one of the most commonly abused inhalants due to its intoxicating and hallucinogenic effects when inhaled in high concentrations. Abuse of toluene often involves prolonged exposure to paint fumes, which has led to extensive clinical, neuroimaging, and neuropathological studies on its neurotoxic effects.

The primary target of toluene toxicity is the central nervous system (CNS), particularly the white matter in the brain, cerebellum, brainstem, and optic nerves, where it induces demyelination and neuronal cell loss. Acute effects include hallucinations and euphoria, while chronic exposure is associated with lasting neuropsychiatric impairments such as cognitive and memory deficits, dysarthria, cerebellar ataxia, and vision impairment. Neuropsychological and MRI studies in long-term users reveal consistent damage to white matter, leading to a permanent and disabling form of chronic encephalopathy.

Following inhalation, toluene accumulates in fat-rich tissues, including the CNS, spinal cord, and adrenal glands. It is metabolized in the body into hippuric acid and cresol, primarily excreted through urine. Diagnosis of toluene exposure is often confirmed by elevated urinary levels of hippuric acid.

Radiographic features

MRI shows symmetric bilateral T2WI and FLAIR hyperintensity in the deep cerebral white matter, posterior limb of the internal capsule, middle cerebellar peduncle, and corticospinal tract of the brainstem. T2WI and FLAIR also reveal bilateral hypointensity in the thalamus and globus pallidus, reflecting toluene uptake. Hypointensity on T2WI and FLAIR may also be observed in the subcortical white matter, particularly in chronic abusers. Chronic toluene abuse can lead to dementia, with associated bilateral atrophy of the cerebral cortex in the frontal and parietal lobes.