Neuroimaging in Drug and Substance Abuse

Recreational drug abuse represents a serious public health problem. Worldwide, the predominant abused illicit drugs include cannabis, opiates, cocaine, amphetamine, and other new psychoactive substances. Overall, cannabis is the most commonly consumed drug. Heroin or diacetylmorphine is the most commonly consumed illegal compound within the opiate group. Alcohol is a legally and socially accepted drug; however, its chronic and abusive consumption is associated with increased morbidity. The most common central nervous system (CNS) complications of illicit drug abuse are cerebrovascular diseases or hypoxic-ischemic injuries. On imaging, common findings include stroke, intracranial hemorrhage, infectious changes, chronic leuko-encephalopathy, or atrophic changes. However, recent postmortem detailed examinations have shown a more extensive damage in the CNS. The damage seems relevant and more diffuse in the gray and white matter, the vasculature and also the neurovascular unit (blood-brain barrier), either by direct or indirect toxic or metabolic drug effect. Some neurodegenerative processes such as Parkinson’s disease can also be associated with chronic drug abuse. Given that in many cases, there is polysubstance abuse, it is difficult to ascribe the abnormalities to a single substance. Neuroimaging traditionally played a secondary role in this scenario, where it was limited to detect acute events. However, thanks to advances in pathological knowledge and improvements in morphological and functional imaging techniques, radiologists have now become very important in the diagnosis of acute and chronic neurological complications of recreational drug abuse.