Single-voxel proton MR spectroscopy in toluene abuse.

Inhalation of toluene, which is an organic solvent, causes toxic encephalopathy characterized by cognitive impairment, cerebellar and extra-pyramidal symptoms. We studied cranial MR images and single-voxel MR spectroscopy of 22 toluene abusers and age-matched control subjects. The mean age of the abusers and mean duration of abuse were 18,1 years and 47 months, respectively. We got three MR spectra from the centrum semiovale, cerebellum and thalamus by using STEAM sequence with a TE value of 30 ms. N-acetyl aspartate (NAA)/Creatine (Cr), Choline (Cho)/Cr, myo-inositol (mI)/Cr peak integral ratios were calculated. NAA/Cr in the cerebellum and centrum semiovale of the abusers were significantly lower than those of the control subjects. mI/Cr in centrum semiovale and cerebellum were higher in toluene abusers. No significant difference was found in the metabolite ratios of the thalami. The association of NAA/Cr and mI/Cr ratios in cerebellum and centrum semiovale with the duration of abuse was significant. Normal level of NAA in thalamus, which was a neuron rich gray matter structure, might imply that toluene inhalation did not cause direct neuronal injury. Selective reduction of NAA and increased level of mI in white matter supported the theory of that axonopathy and gliosis were the main mechanisms of pathophysiology in chronic toluene encepholopathy. Insignificance of elevation of Cho/Cr ratios demonstrated that toluene inhalation did not cause active demyelination.

Cranial MR findings in chronic toluene abuse by inhalation.

BACKGROUND AND PURPOSE: Chronic abuse of toluene by inhalation causes variable white matter changes and thalamic hypointensity on T2-weighted MR images. The purpose of our study was to assess cranial MR findings in a large series of patients who chronically abuse toluene-containing solvents to investigate the factors causing the qualitative variability of white matter changes and thalamic hypointensity. METHODS: We studied the neurologic signs, symptoms, and cranial MR findings in 41 patients who chronically abused thinner, a toluene-containing solvent. We classified white matter changes as diffuse or restricted. We tested the associations of the development of white matter lesions and thalamic hypointensity with patient age at onset of abuse and duration of abuse. RESULTS: MR images revealed white matter lesions in 46% of the patients, atrophic dilatation of ventricles and sulci in 27%, and thalamic hypointensity in 20%. White matter changes were restricted in 53% and diffuse in 47%. The development of white matter changes and thalamic hypointensity were significantly associated with duration of abuse longer than 4 years (P <.05 and P <.01, respectively). CONCLUSION: White matter changes seem to start in the deep periventricular white matter, and they spread into peripheral white matter, causing the loss of gray matter-white matter differentiation with continued toluene abuse. The deposition of iron due to demyelination and axonal loss is the most probable mechanism for the thalamic hypointensity found in solvent abusers.