38 year-old female with altered mental status after recent heroin overdose.
1. Diffuse supratentorial white matter disease with sparing of the grey structures with known clinical history suggest heroin-induced leukoencephalopathy.
Heroin-induced leukoencephalopathy is a form of toxic leukoencephalopathy secondary to inhalation of heroin fumes, known as "chasing the dragon".
This results in symmetric spongiform degeneration, often of both supratentorial and infratentorial white matter and the corticospinal solitary tracts.
The above-mentioned subcortical U-fibers, also known as short association fibers, are connections between adjacent gyri along the very outer aspect of the subcortical white matter. These fibers are among the last parts of the brain to myelinate with very slow myelin turnover. Diseases altering myelin metabolism/turnover will therefore affect these last, resulting in relative "sparing" of the U-fibers.
Different imaging presentations of common drug-induced encephalopathies
https://pubs.rsna.org/doi/10.1148/rg.323115115