Delayed Neuropsychiatric Syndrome Due to Unrecognized Carbon Monoxide Toxicity: A Case Report.

Introduction: Carbon monoxide (CO) is a leading cause of poison-related deaths in children and frequently results in nonspecific neurological symptoms and imaging findings. Rarely, pediatric patients develop a delayed neuropsychiatric syndrome (DNS) following a lucid interval. Although imaging findings of early bilateral globi pallidi injury and white matter demyelination in association with DNS are most common, these findings are not always present. It is important to consider CO toxicity in patients found unresponsive without a clear etiology. Patient Presentation: This 16-year-old boy was found unresponsive at his workplace with initial labs notable for end-organ injury. After stabilization, he had deficits in language, attention, memory, and left-sided dysmetria on neurological assessment. Imaging demonstrated injury in the bilateral caudate, putamen, hippocampi, and cerebellum, concerning for anoxic injury. His symptoms initially improved, but he developed new agitation and dyskinetic movements 6 days after presentation. His imaging continued to evolve with late enhancement in areas of prior injury and the bilateral globi pallidi. Ultimately, it was discovered that he had CO toxicity from a leaky workplace water heater. Discussion and Conclusions: We highlight a rare presentation of DNS in a pediatric patient with CO toxicity. Our patient demonstrates the spectrum of clinical and imaging findings associated with CO toxicity and DNS. The clinical and neuroimaging features of CO toxicity are variable, making diagnosis challenging without a known exposure. It is important to maintain CO toxicity on the differential for patients presenting with unexplained neurological symptoms.