CHANTER (Cerebellar, Hippocampal ANd Basal Nuclei Transient oEdema with Restricted Diffusion) Syndrome was recently described as a constellation of clinical and imaging findings different from from ischemic, anoxic or toxic brain injury, mainly occurring in association with drug abuse, most commonly opioids.

POUNCE (Paediatric Opioid Use Associated Neurotoxicity with Cerebellar oEdema) Syndrome presents similarly in paediatric patients treated with opioids. 

CHANTER Syndrome is characterised by diffusion restriction bilaterally in the hippocampus, cerebellum and basal nuclei due to cytotoxic oedema. In some cases, early obstructive hydrocephalus may develop. The cerebral cortex, thalamus and subcortical white matter are commonly spared. 

Despite the initial presentation with stupor or coma, the majority of the patients recover almost completely, in case of an early clinical intervention and once substance exposure is discontinued. Rarely, this entity might also lead to irreversible brain damage.