Radiographic Findings of Evolving Sequelae of Cerebellar, Hippocampal, and Basal Nuclei Transient Edema With Restricted Diffusion (CHANTER) Syndrome in a 37-Year-Old Patient

Cerebellar, Hippocampal, and Basal Nuclei Transient Edema with Restricted Diffusion (CHANTER) syndrome is a recently recognized distinct clinicoradiographic pattern of neurologic injury occurring most commonly following polysubstance or opioid abuse. Patients present acutely with unresponsiveness or coma. Magnetic resonance (MR) imaging demonstrates key findings, including bilateral diffusion restriction in the cerebellar cortices and hippocampi and variable diffusion restriction in the basal ganglia. Additionally, cerebellar cytotoxic edema can exert a mass effect on the adjacent fourth ventricle, causing obstructive hydrocephalus and requiring emergent intervention to prevent brain herniation and death. Here, we present a 37-year-old male patient who arrived at the Emergency Department with non-responsiveness in the setting of positive toxicology for cannabis, cocaine, and fentanyl. One day following the presentation, an MRI demonstrated restricted diffusion of the bilateral cerebellar hemispheres and bilateral hippocampi and small foci of restricted diffusion involving the basal ganglia. T2 fluid-attenuated inversion recovery (T2 FLAIR) hyperintensities involving the bilateral precentral gyri were also identified. Additional diagnostic workup, including electroencephalogram (EEG), vessel imaging, and viral panels, effectively ruled out alternative diagnoses, making CHANTER most likely. Following medical treatment without surgical intervention, the patient was discharged to an acute rehab facility with symptoms of impaired judgment, difficulty following commands, and difficulty walking. In the following months, the patient improved in cognitive function and gait. MRI at three months demonstrated interval resolution of previous T2 FLAIR hyperintensities, restricted diffusion zones, and development of new T2 FLAIR hyperintensities in the periventricular and subcortical white matter. This case highlights the need for prompt recognition of radiographic features of CHANTER, as affected patients may demonstrate significant recovery of neurologic status in the months following injury, compared to other patterns of hypoxic brain injury. These patients, therefore, merit more aggressive treatment to maximize recovery.