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Three patients, one male and two female, ages 34-58, with substance usage histories presented to a single center from December 2021 to March 2023. Each patient was found unresponsive, given naloxone, and subsequently intubated. Initial labs were notable for rhabdomyolysis and troponemia. Two patients demonstrated cerebellar, hippocampal, and basal ganglia T2/FLAIR signal abnormalities and diffusion restriction resembling the radiographic findings of CHANTER syndrome. MRI of the third patient revealed T2 hyperintensities and diffusion restriction in cerebellar hemispheres, globus pallidus, and corpus callosum, sparing the hippocampus, as well as symmetric bilateral cerebral white matter involvement, sparing U-fibers: suggestive of possibly atypical toxic leukoencephalopathy, possibly superimposed. Urine drug screening was positive for cocaine and methadone in one patient and all three tested negative for opiates. 

Here we present three patients with suspected narcotic overdose who were found to have patterns of MRI findings similar to CHANTER syndrome despite negative urine drugs screens for opiates. The etiologies and pathophysiology of these findings are unknown, but past reports suggest association with synthetic opioid contaminants or other, unidentified toxic metabolites. Without clear opioid use in these patients, it may prove difficult to determine fentanyl or other synthetic opiates as the causing factor. As routine urine drug screens are insufficient, we recommend further studies on presentation, including synthetic opioid and toxicology panels, in order to better determine causality.