To report a case of Cerebellar, Hippocampal, and Basal Nuclei, Transient Edema and Restricted Diffusion (CHANTER) after opioid use, and provide histopathologic data to aid in characterization of pathophysiologic mechanisms.

CHANTER is an entity that appears to have distinct radiographic appearances in cases of coma and stupor in the setting of opioid use. However, little is known about its pathophysiology and histologic processes. 

A 63-year-old right-handed male presented to the emergency department after a sudden, witnessed loss of consciousness and subsequent coma, on a background of atrial fibrillation, prescription opioid use, hypertension, and obstructive sleep apnea. Magnetic Resonance Imaging (MRI) subsequently demonstrated restricted diffusion in the bilateral cerebral hemispheres, hippocampi, and basal ganglia, among other smaller watershed territory infarctions. The pattern of diffusion restriction and edema appeared consistent with a radiologic entity known as Cerebellar, Hippocampal, and Basal Nuclei, Transient Edema and Restricted Diffusion (CHANTER). While neurologic recovery is variable but skews towards full recovery, we present a case with complications of continued coma. Here, we also provide post-mortem histopathologic data in support of this diagnosis, including internal granular cell necrosis, neuronal necrosis, and extravasating red blood cells, along with reactive astrocytes and numerous spheroids. 

Both hypoxic-ischemic and toxic-metabolic mechanisms are theorized in CHANTER, with only one other case report providing histopathologic information. Here, we offer a concurring report of the histologic processes that may be taking place in CHANTER, in an effort to understand its pathophysiology better. However, further research and studies are required to delineate more specific cellular pathways and pathologic mechanisms, ultimately leading to potential therapeutic targets.