(1) All three cases have MR findings suggestive of spongiform leukoencephalopathy. MRS may help differentiate toxicity due to inhaled heroin from other non-heroin related toxicities. (2) Discordance between perfusion and spectroscopy in one chasing patient adds evidence that the disease is due to impaired energy metabolism at the cellular level. (3) MR findings of spongiform leukoencephalopathy secondary to chasing heroin can progress despite apparent abstinence of the drug and during clinical improvement, suggesting the MR changes may represent an evolving injury.

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BACKGROUND AND PURPOSE:Acute hyperammonemic encephalopathy has significant morbidity and mortality unless promptly treated. We describe the MR imaging findings of acute hyperammonemic encephalopathy, which are not well-recognized in adult patients.