Diffusion weighted imaging in heroin-associated spongiform leukoencephalopathy

Background: Heroin-associated spongiform leukoencephalopathy (HASL) is a rare complication of heroin abuse. We report a case that highlights the increased sensitivity of diffusion weighted imaging (DWI) compared with T2-weighted imaging in the acute setting of HASL. Methods: Single case report. Results: A 36-year-old male with a history of heroin abuse (snorting) presented with a 3-day history of lethargy. MRI brain revealed restricted diffusion involving the globus pallidum and cerebral cortex bilaterally that was not seen on fluid-attenuated inversion recovery (FLAIR) images. The patient was diagnosed with acute HASL. Repeated MRI FLAIR at 3 months confirmed the development of atrophy and T2 hyperintensity in the subcortical white matter, consistent with leukoencephalopathy. Neurological exam at 3-month follow-up was nonfocal. Conclusions: Restricted diffusion, which likely corresponds to electron microscopic findings of fluid entrapment between the myelin lamellae, may be detectable earlier than changes on FLAIR. Clinicians should be aware of the neuroimaging findings of HASL and the increased sensitivity of MRI DWI over T2-weighted images in detecting HASL acutely.