Burden of and risk factors for neurological complications in critical illness

Neurological complications are common in critical illness and are increasingly recognized as major contributors to morbidity, mortality, and long-term disability among patients admitted to an intensive care unit (ICU). Even in the absence of a primary neurological diagnosis, systemic critical illness can exert substantial physiological stress on the brain through hypoxemia, hemodynamic instability, inflammation, and metabolic derangements. Delirium, stroke, seizures, and neuromuscular disorders represent frequent neurological manifestations of multi-organ dysfunction and are associated with prolonged ICU stay, persistent cognitive deficits, and impaired neuropsychological and functional recovery. Recognition of modifiable risk factors has led to targeted strategies such as standardized delirium screening, judicious sedative use, and mitigation of environmental contributors including immobility, sleep disruption, and sensory impairment. However, variability in definitions, surveillance practices, and outcome measures limits precise estimation of the true burden and may contribute to ongoing underrecognition. In addition, an incomplete understanding of the mechanisms of neurological injury and recovery involving the brain, peripheral nerves, and skeletal muscle further hinders progress in this field. This review synthesizes current evidence on the epidemiology, phenotypes, and risk factors of neurological complications in critical illness, highlighting key knowledge gaps and the current limitations in causal inference and therapeutic evidence, and identifying priorities for future research.