Pediatric opioid use‐associated neurotoxicity with cerebellar edema (POUNCE) syndrome

Pediatric opioid use‐associated neurotoxicity with cerebellar edema (POUNCE) syndrome is a toxic encephalopathy in children with opioid overdose that features prominent cerebellar edema. Cerebellar predominance, along with variable supratentorial involvement, appears to be a distinct pattern of opioid neurotoxicity in children ^1,2. However, it is likely part of a pathophysiologic spectrum that also includes adult cases of chasing the dragon leukoencephalopathy (which occurs specifically after heroin vapor inhalation) and cerebellar edema (cerebellar, hippocampal, and basal nuclei transient edema with restricted diffusion (CHANTER) syndrome).

Epidemiology

About 20 cases in the English literature have been reported as of 2020 ¹.

Clinical presentation

Affected children are usually accidentally exposed to prescription or illicit opioids ¹. They present with respiratory depression and decreased level of consciousness ¹. Other common clinical findings include mutism and ataxia ¹.

Radiographic features

Imaging shows bilateral cerebellar edema and a variable degree/distribution of supratentorial white matter lesions (hyperintense on T2-weighted MRI, hypodense on CT) ^1-7. Diffusion restriction has been reported in some cases ^2,5-7.

Mass effect can result in hydrocephalus and tonsillar herniation.

Differential diagnosis

• acute cerebellitis
• hypoxic-ischemic encephalopathy