Cerebellar, hippocampal and basal nuclei transient edema with restricted diffusion (CHANTER) syndrome: a case report

<h3></h3> A 45-year-old male was found obtunded after a suspected mixed overdose of benzodiazepines and pregabalin. He had a past medical history of intravenous heroin use and was on methadone replacement. Admission CT-head demonstrated low attenuation in the cerebellum with evolution over 5 hours to involve the right caudate nucleus. He had a persistent Glasgow Coma Scale score of 3 on attempted extubation. MRI-brain on day 3 demonstrated symmetrical bilateral oedema with restricted diffusion in the cerebellum, hippocampus, and basal ganglia with similar change in the deep white matter of the cerebral hemispheres in the posterior frontal and anterior parietal lobes heralding a diagnosis of CHANTER syndrome. He was supportively managed on intensive care for a month, showed gradual neurological improvement, and was discharged to a neurorehabilitation centre. Repeat MRI two weeks into admission showed significant regression with marked reduction in signal changes in the involved brain regions. CHANTER syndrome was first described in 2019.¹ It afflicts patients with substance misuse disorders and overdose, particularly opiates.² The clinical and radiological presentation can mimic hypoxic ischaemic encephalopathy, but it portends a significantly better prognosis and should be considered within the differential diagnosis in appropriate cases. <h3>References</h3> Jasne, <i>et al.</i> Cerebellar Hippocampal and Basal Nuclei Transient Edema with Restricted diffusion (CHANTER) Syndrome. <i>Neurocritical Care</i>. 2019. Sheehan, <i>et al.</i> Reversible amnesia following opiate overdose: CHANTER syndrome. <i>Practical Neurology</i>. 2023.