Definition of delayed-onset neurologic sequelae: A review article

ABSTRACT Dakessian A, Hagen Z, Rocksmith ER, Sethuraman KN. Definition of delayed-onset neurologic sequelae: A review article. Undersea Hyperb Med. 2025 Second Quarter; 52(2):121-131. Background: Delayed-onset neurologic sequelae (DNS) is a devastating complication of carbon monoxide poisoning. Despite abundant research studies on DNS, the definition remains unclear, with a wide range of symptoms. This review aims to identify the different symptoms and definitions that have been associated with DNS in available research. Methods: For this review, searches were conducted in PubMed and Scopus. Two authors screened research studies by abstract and title, and a third resolved conflicts. After the full-text review, one author extracted the data. Only original full-text research studies in English with a clear definition of DNS were included. Results: This review included 127 studies. Signs and symptoms associated with DNS were categorized into twelve groups. The most used symptom categories to define DNS were general neurological and cognitive/learning dysfunctions. Imaging studies, clinical testing, and neuropsychiatric testing used to define DNS were also documented. Conclusions: The literature did not consistently define DNS attributed to CO toxicity. Standardizing the definition and diagnostic criteria would benefit clinical research. Keywords: carbon monoxide; carbon monoxide poisoning; delayed-onset neurologic sequelae; delayed encephalopathy; delayed encephalopathy after acute carbon monoxide poisoning