Abstract

BACKGROUND: Opioid-dependent patients have been shown to have structural brain alterations. This study focuses on magnetic resonance imaging (MRI) measurements of brain and their correlation with the onset age and the duration of opioid abuse.
METHODS: Brain MRI was obtained from 17 opioid-dependent patients (mean age 34 years, SD 7 years) and 17 controls. Compulsive opioid use had begun between ages 15 and 31 (mean 20) and had continued from 5 to 26 years. All patients were tobacco smokers, six had also abused amphetamines and 11 benzodiazepines. Relative volumes of cerebral white matter (WM), gray matter (GM), and cerebrospinal fluid (CSF) spaces were measured. In addition, Sylvian fissure ratio (SFR), bifrontal ratio, and midsagittal cerebellar vermian area were correlated with the onset age and the duration of opioid abuse.
RESULTS: The total volume (GM + WM + CSF) of the cerebrum was significantly smaller in patients than in controls (Mann-Whitney U-test, p = 0.026) as well as the absolute volumes of GM and WM (p = 0.014 and p = 0.007, respectively). There was no significant difference in GM and WM volumes normalized with total cerebral volume. In contrast, the absolute volume of CSF did not significantly differ between the groups, but the relative volume of CSF was significantly higher in opioid dependents (p = 0.029). SFR and bifrontal ratio were larger in opioid dependents than in controls (p = 0.005 and p = 0.013). The SFR correlated negatively (p = 0.017, r = - 0.569) and the area of vermis cerebelli correlated positively (p = 0.043, r = 0.496) with the onset age of opioid abuse. The length of opioid abuse and the area of vermis cerebellum had a negative correlation (p = 0.038, r = - 0.523) even though the areas of cerebellar vermis did not significantly differ between opioid dependents and controls. The authors speculate that the onset of substance abuse in adolescence or early adulthood may have in part disturbed the late brain maturation process, as in normal development, the dorsolateral frontal cortex and superior parts of the temporal lobes are the last to maturate. Also, the cerebellar vermis may be affected by early onset substance abuse. It is possible that the brain is more vulnerable to substance abuse at a young age than later in life.