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Heroin-induced leukoencephalopathy, also known as heroin-associated spongiform leukoencephalopathy, is a toxic leukoencephalopathy caused by the inhalation of heroin fumes, which is called "chasing the dragon."
Three stages are recognized:
cerebellar signs and motor restlessness
pyramidal and pseudobulbar signs
spasms, hypotonic paresis, and ultimately death
Only a minority of patients progress through all three.
There may be a latent period with a subclinical evolution of white matter degeneration. Progression of the disease continues even after cessation of the toxin for up to 6 months.
There is symmetric spongiform degeneration, specifically in the cerebral and cerebellar white matter as well as the corticospinal and solitary tracts.
These are similar to other toxic leukoencephalopathies with widespread white matter hyperintensity on T2/FLAIR sequences involving both supra- and infratentorial compartments, but with a characteristic distribution:
symmetrical involvement of the posterior limb of the internal capsules extending inferiorly into the pontine corticospinal tracts, and superiorly into the perirolandic subcortical white matter
symmetrical butterfly wing pattern involvement of the cerebellar white matter and middle cerebellar peduncles (one of the causes of the so-called MCP sign)
sparing of adjacent grey matter structures and subcortical U-fibers
Typically regions demonstrate high DWI signal, which only sometimes represents true diffusion restriction.
MR spectroscopy may show abnormally elevated intracerebral lactate in the affected white matter as well as decreased levels of N-acetylaspartate (NAA) in the white matter, gray matter, and cerebellum.
Treatment and prognosis
Treatment is generally supportive.
History and etymology
The following passage is from the original description in the American Journal of Roentgenology by Ciaran F Keogh 1:
"The term “chasing the dragon” appears to have originated in China in the 1920s and became a popular mechanism of heroin administration in the 1950s in Hong Kong because the drug was cheap but impure. A small quantity of powder is placed on aluminum foil, which is then heated underneath with a lighter or matches. The heroin liquefies into a reddish-brown glob, which moves around on the foil and emits a white vapor. The glob or “dragon” is “chased” with the lighter underneath while the vapor is sucked through a straw or pipe..."
- 1. Keogh CF, Andrews GT, Spacey SD et-al. Neuroimaging features of heroin inhalation toxicity: "chasing the dragon". AJR Am J Roentgenol. 2003;180 (3): 847-50. AJR Am J Roentgenol (full text) - Pubmed citation
- 2. Brain imaging in substance abuse. Humana Press. ISBN:0896037703. Read it at Google Books - Find it at Amazon