Cerebellar, hippocampal, and basal nuclei transient edema with restricted diffusion (CHANTER) syndrome

Cerebellar, hippocampal, and basal nuclei transient edema with restricted diffusion (CHANTER) syndrome is a recently described constellation of imaging findings in adults with opioid neurotoxicity. It is characterized by cytotoxic edema in the bilateral hippocampi and cerebellar cortices, and variably in the basal ganglia .

This entity likely falls within a pathophysiologic spectrum with chasing the dragon leukoencephalopathy (which predominantly affects white matter and occurs after inhalational heroin use), pediatric opioid use‐associated neurotoxicity with cerebellar edema (POUNCE) syndrome (which occurs in children), and opioid-associated amnestic syndrome (which involves the hippocampi alone).

Epidemiology

A single case series of 6 patients has been reported .

Clinical presentation

Patients present with decreased level of consciousness .

Radiographic features

Imaging shows cerebellar edema, which progresses to cause hydrocephalus. MRI demonstrates bilateral, symmetric restricted diffusion in the grey matter of the cerebellum and hippocampi, as well as asymmetric involvement of the basal ganglia . The cerebral cortex is spared.

Differential diagnosis

• hypoxic-ischemic encephalopathy can also cause restricted diffusion in the hippocampus, cerebellar cortex, and deep grey nuclei, but cerebral cortex should also be involved