MRI in chronic paint-thinner intoxication

Decreased thalamic volumes in adolescent inhalant users from Korea and Australia

OBJECTIVES

Research investigating the impact of inhalant misuse on brain structure suggests abnormalities in subcortical regions. We investigated the association between inhalant misuse and subcortical brain volumes in adolescents.

METHODS

Based on a collaborative dataset from South Korea (inhalant users: N = 15, mean age = 16.7, SD = 1.1; controls: N = 15, mean age = 15.4, SD = 1.2) and Australia (inhalant users: N = 7, mean age = 18.2, SD = 1.4; controls: N = 7, mean age = 18.9, SD = 2.6), the volumes of caudate nucleus, putamen, pallidum, amygdala, hippocampus, and thalamus were estimated in adolescent inhalant users and healthy adolescents using FreeSurfer.

RESULTS

The results revealed a significantly decreased right thalamic volume in adolescent inhalant users (P = 0.042), along with a trend-level decrease in left thalamic volume (P = 0.061). A negative correlation (r = -0.544; P = 0.036) between thalamic volume and severity of inhalant use (i.e., reduced volumes associated with greater use) was identified among Korean participants.

CONCLUSIONS

These findings suggest that compared with other subcortical structures, the thalamus is particularly sensitive to damage following chronic inhalant exposure during adolescence.

Neuroprotective strategies in drug abuse-evoked encephalopathy

Encephalopathy is evidenced as an altered mental state with various neurological symptoms, such as memory and cognitive problems. The type of a substance-evoked encephalopathy will depend on the drug, substance, or combination being abused. The categories into which we could place the various abused substances could be tentatively divided into stimulants, amphetamines, hallucinogens, narcotics, inhalants, anesthetics, anabolic steroids, and antipsychotics/antidepressants. Other factors that may underlie encephalopathy, such as infectious agents, environmental, and other factors have also to be taken into account. Drugs of abuse can be highly toxic to the CNS following acute, but more so in chronic exposure, and can produce significant damage to other organs, such as the heart, lungs, liver, and kidneys. The damage to these organs may be at least partially reversible when drug abuse is stopped but CNS damage from repeated or prolonged abuse is often irreversible. The major pathways for the organ and CNS toxicity could be related to ischemic events as well as increased cell damage due to metabolic or mitochondrial dysfunction resulting in increased excitotoxicity, reduced energy production, and lowered antioxidant potential. These susceptibilities could be strengthened by the use of antioxidants to combat free radicals (e.g., vitamin E, lipoic acid); trying to improve energy generation by using mitochondriotropic/metabolic compounds (e.g., thiamine, coenzyme Q10, carnitine, riboflavin); by reducing excitotoxicity (e.g., glutamate antagonists) and other possible strategies, such as robust gene response, need to be investigated further. The drug-abuse-evoked encephalopathy still needs to be studied further to enable better preventative and protective strategies.

Toluene misuse and long-term harms: a systematic review of the neuropsychological and neuroimaging literature

Organic solvent abuse is associated with increased risk for serious medical, neurological, and neuropsychological impairments. While animal research suggests that exposure to organic solvents (especially toluene) may be neurotoxic, much less is known about the consequences of long-term exposure in humans. We reviewed neuroimaging and neuropsychological studies examining chronic toluene misuse in humans. Thirty empirical studies fulfilled the inclusion and exclusion criteria, including case studies (n=9) as well as group studies with (n=11) and without a control group (n=10). Our review indicates that toluene preferentially affects white matter (relative to gray matter) structures and periventricular/subcortical (relative to cortical) regions. The lipid-dependent distribution and pharmacokinetic properties of toluene appears to explain the pattern of MRI abnormalities, as well as the common symptoms and signs of toluene encephalopathy. The commonly observed neuropsychological deficits such as impairments in processing speed, sustained attention, memory retrieval, executive function and language, are also consistent with white matter pathology. We discuss the implications of these findings in the context of a neurodevelopmental framework, as well as the neuropathology and pathophysiology of toluene abuse. We also propose a set of recommendations to guide future research in this area.

Occupational exposure to organic solvents and long-term nervous system damage detectable by brain imaging, neurophysiology or histopathology

The purpose of the present review is to assess the evidence published in scientific literature that industrial organic solvents as a generic group have the ability to induce long-term nervous system damage in workers that can be detected by techniques other than neuropsychological testing. The main body of evidence considered in this review was 40 studies involving the use of brain imaging, neurophysiological testing, gross autopsy or histopathology in groups of workers with long-term solvent exposure. Case reports involving both solvent abuse and occupational exposure, and experimental animal data have also been reviewed as supporting data. A number of the studies in groups of workers provide evidence of the presence of marginal atrophic abnormalities in the brain or deficits in nerve conduction velocity in solvent-exposed workers. However, there are limitations in the design of many of these studies, the strength of association between exposure and effect is not consistently strong, no dose-response relationship can be detected, the reported changes lack specificity and there is no coherence between the human and experimental animal data. Overall, it is not possible to draw reliable conclusions with respect to the presence or absence of nervous system damage related to the common properties of organic solvents.

Neurological complications of drug abuse: pathophysiological mechanisms

Drug abuse is associated with a variety of neurological complications. The use of certain recreational drugs shows a marked temporal association with the onset of both haemorrhagic and ischaemic strokes, the majority of which develop within minutes to 1 h after the administration of the index drug. Delayed onset of stroke has also been observed. Acute, severe elevation of blood pressure, cardiac dysrhythmias, cerebral vasospasm, vasculitis, embolization due to infective endocarditis or dilated cardiomyopathy, embolization due to foreign material injected with the diluents under non-sterile conditions and 'street drug' contaminants with cardiovascular effects have been suggested as possible underlying mechanisms. Rupture of aneurysms and arteriovenous malformations have been detected in up to half of the patients with haemorrhagic stroke due to cocaine abuse. The less common findings reported have included a mycotic cerebrovascular aneurysm in a patient with infective endocarditis and haemorrhagic stroke. In addition to stroke, cocaine seems to provoke vascular headache. Seizures precipitated by recreational drug abuse are usually caused by acute intoxication in contrast to the withdrawal seizures encountered in subjects with alcohol abuse. Movement disorders and cerebral atrophy correlating with the duration of abuse have been described. Snorting of organic solvents may cause encephalopathy. Cases of spongiform leukoencephalopathy in heroin addicts have also been reported. Peripheral neuropathy is occasionally precipitated by drug poisoning after intravenous administration. Impurities of the drug, risky administration techniques, and the use of mixtures of various drugs, frequently with simultaneous alcohol drinking, should be taken into account when assessing the background of the adverse event as well as the overall lifestyle of the addicted subjects.

Interventional neuroradiology

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