To highlight an increasingly important clinical syndrome characterized by acute toxic encephalopathy secondary to opioid overdose in pediatric patients. We present a case of Pediatric Opioid Use-associated Neurotoxicity with Cerebellar Edema (POUNCE) syndrome.

POUNCE syndrome is a rare condition postulated to be caused by a direct neurotoxic effect to cerebellar opioid receptors leading to cytotoxic edema. Clinical presentation may include encephalopathy, respiratory depression, mutism, ataxia, and dystonia in the setting of opioid overdose. Imaging findings can show bilateral cerebellar involvement.

A 16-year-old female presented with altered mental status and extreme electrolyte derangements after multiple days of vomiting, difficulty talking and walking, and poor oral intake. Family reported a history of regular Percocet abuse. Initially, she was obtunded but followed some commands. She was mute, had an upward gaze preference, and low tone. Despite correction of other metabolic derangements, her neurologic exam did not initially improve. A brain MRI was obtained and demonstrated areas of restricted diffusion in the bilateral cerebellar dentate nuclei, adjacent cerebellar white matter, and middle cerebellar peduncles with faint edema, and without intracranial mass effect. Her exam evolved throughout her hospitalization to have scanning speech, bilateral dysmetria, and truncal titubation. She was ultimately discharged to an inpatient rehab facility.

POUNCE syndrome is a rare condition that should be considered in cases of acute encephalopathy in children with history of opioid exposure. Given the unprecedented opioid abuse epidemic, this is an important clinical entity to identify. Accidental ingestion leading to this syndrome has been reported in younger children. This syndrome likely has a spectrum in pathophysiology, with similarities to CHANTER syndrome and chasing the dragon encephalopathy described in adults. Outcomes have ranged from complete resolution to brain herniation, thus clinicoradiological monitoring is critical. Recovery can be prolonged in some patients.