Burden of and risk factors for neurological complications in critical illness

Neurological complications contribute substantially to morbidity, mortality, and long-term disability in patients admitted to intensive care units (ICUs) for non-neurological conditions. Although these complications have been recognized for several decades, with early descriptions dating back to the formative years of intensive care medicine in the mid-to-late twentieth century, they remain incompletely characterized and inconsistently addressed in modern critical care practice [ 1 , 2 ]. In this context, burden encompasses not only the incidence and prevalence of neurological complications, but also their downstream clinical impact, including prolonged ICU stay, increased healthcare utilization, and long-term functional and cognitive impairment. Delirium, stroke, seizures, and neuromuscular disorders are common yet frequently underrecognized manifestations of critical illness. These complications are consistently associated with longer ICU stays, greater resource utilization, and worse functional outcomes after discharge [ 1 , 3 , 4 , 5 ]. Historically, critical care has prioritized support of the cardiovascular, respiratory, and renal systems. However, growing evidence underscores the brain’s particular vulnerability to the physiological stresses of critical illness, including hypoxemia, hypotension, inflammation, metabolic derangements, and iatrogenic factors such as mechanical ventilation and sedation-related coma and immobility. Even in the absence of a primary neurological insult, these systemic and treatment-related factors can precipitate acute brain injury. Given the breadth of neurological complications encountered in the ICU, prior literature has often focused on individual entities in isolation. In contrast, this review aims to integrate contemporary evidence on the overall burden, shared and distinct risk factors, and clinical management considerations of neurological complications in critically ill patients without primary neurological disease. Our goal is not to exhaustively re-review the pathophysiology of each condition, but rather to synthesize epidemiologic data, identify common mechanistic themes, highlight modifiable contributors, and outline opportunities for neuroprotective care within the ICU. Heterogeneity in case definitions, diagnostic criteria, and surveillance practices across studies and institutions limits comparability and may obscure the true scope of neurological injury in critical illness, potentially contributing to underdetection, particularly in patients with subtle or fluctuating manifestations. This variability reinforces the need for standardized phenotyping and more consistent reporting. By examining neurological complications within a unified framework, we aim to better define their clinical impact, identify gaps in detection and risk stratification, and inform strategies to mitigate long-term neurological sequelae.