Case Presentation: A 28-year-old woman with bipolar disorder and polysubstance use was found unresponsive at home and achieved return of spontaneous circulation after 9 minutes of CPR. On arrival she had a GCS of 3, evidence of aspiration, and urine studies positive for fentanyl and benzodiazepines. CT chest confirmed large-volume aspiration, and CT head showed possible early cerebral edema without hemorrhage. She was admitted to the ICU for vasoplegic shock and initiated on targeted temperature management, antibiotics, and supportive care. MRI obtained for suspected anoxic injury instead demonstrated restricted diffusion in the cerebellum, hippocampi, and bilateral globus pallidi—findings more consistent with CHANTER syndrome, with superimposed hypoxic-ischemic changes. Her course was notable for prolonged ventilation requiring tracheostomy and PEG placement, but she demonstrated steady neurologic improvement. At approximately one month, she was liberated from mechanical ventilation, tolerating oral intake, and her remaining deficits were limited to mild–moderate speech latency. 3 months following discharge, the patient was noted to have made continued neurologic recovery with removal of PEG tube prior to being lost to continued follow-up.
Discussion: Recognizing CHANTER syndrome is essential because its imaging distribution and clinical implications differ from global hypoxic injury. While anoxic encephalopathy predominantly affects cortical and watershed regions, CHANTER involves deep gray nuclei and cerebellar structures with relative cortical sparing—features that can preserve the potential for meaningful neurologic recovery despite dramatic MRI findings. Distinguishing CHANTER early can prevent inappropriate continuation of hypothermia protocols, guide monitoring for cerebellar edema or hydrocephalus, and refine neuroprognostication. This case underscores CHANTER syndrome as an underrecognized cause of coma following opioid-associated cardiac arrest. Awareness of its distinct imaging pattern and management considerations can support accurate diagnosis and improve patient care in a growing high-risk population.
Conclusions: The opioid epidemic has produced novel neurologic complications beyond classic hypoxic injury. Cerebellar-Hippocampal-Basal Nuclei Transient Edema (CHANTER Syndrome), first described in 2019, presents with altered mental status and characteristic MRI abnormalities involving the cerebellum, hippocampus, and basal ganglia. Early recognition is critical because management and prognosis differ significantly from other anoxic or toxic encephalopathies.