P3C399: Pediatric Opioid Use-associated Neurotoxicity with Cerebellar Edema (POUNCE) Syndrome After Accidental Fentanyl Ingestion: A Case Report

Introduction: Pediatric opioid use-associated neurotoxicity with cerebellar edema (POUNCE) syndrome is a rare but severe side effect of opioid overdose in children. Opioid overdose typically presents with decreased responsiveness, bradycardia and respiratory depression. These symptoms are usually reversable with the administration of naloxone, an opioid receptor antagonist. Rarely, more severe effects, such as POUNCE syndrome, can occur. We present the manifestations of acute neurological decline and cerebellar edema as a result of opioid toxicity.

Case Description: A previously healthy 23 month old male presented to the emergency room unresponsive. On arrival, the patient was tachycardic (200s bpm), hypertensive, tachypneic and found to have pinpoint pupils on initial assessment. The patient reportedly had an accidental ingestion of approximately one gram of fentanyl prior to onset of symptoms. Naloxone was administered with mild improvement in mental status. The patient did remain altered, tachycardic and tachypneic. They were given a total of five doses of Naloxone prior to being placed on a naloxone drip. The patient had continued hemodynamic instability and developed seizure-like activity. After stabilization with intubation, a head CT scan was performed. They were then placed on continuous EEG. On review of EEG, no epilepiform activity was noted. Drug testing was positive for fentanyl and cocaine. The initial CT was limited due to motion artifact, but did not display any acute changes. However, a repeat head CT 12 hours later due to continued symptoms showed bilateral diffuse cerebellar hypodensity and obstructive hydrocephalus. A third CT 24 hours later showed continued diffuse cerebellar hypodensity and obstructive hydrocephalus and cerebellar tonsillar herniation. Brain MRI performed also showed bilateral cerebellar infarction. The decision was made by Neurosurgery to emergently divert cerebral spinal fluid with an external ventricular drain (EVD). The following morning, the patient had a craniectomy for posterior fossa decompression. The patient’s EVD was removed after seven days and he was discharged to an inpatient rehab facility after 14 days with significant neurological recovery.

Discussion: Fatal and near fatal opioid ingestions in children under the age of five years of age have significantly increased over the last decade. Although most opioid ingestions can be managed with opioid receptor antagonists and supportive care, this rare neurological outcome requires emergent neurosurgical intervention to minimize long term neurological sequelae. POUNCE syndrome is unique in that it is the result of a neurological toxicity and not due to a hypoxic injury, which can result from respiratory depression or failure due to opioids.

Conclusion: POUNCE syndrome is exceedingly rare, as fewer than 20 cases have been reported. Cases which have been described follow similar clinical courses. All reported cases have needed emergent neurosurgical intervention. With recognition of symptoms and swift action, most children ultimately have good outcomes.