Neutrophil-to-Lymphocyte Ratio in Acute Cerebral Hemorrhage: a System Review

Infections are a leading cause of morbidity and mortality in patients with acute CNS injury. It has recently become clear that CNS injury significantly increases susceptibility to infection by brain-specific mechanisms: CNS injury induces a disturbance of the normally well balanced interplay between the immune system and the CNS. As a result, CNS injury leads to secondary immunodeficiency - CNS injury-induced immunodepression (CIDS) - and infection. CIDS might serve as a model for the study of the mechanisms and mediators of brain control over immunity. More importantly, understanding CIDS will allow us to work on developing effective therapeutic strategies, with which the outcome after CNS damage by a host of diseases could be improved by eliminating a major determinant of poor recovery.

The neutrophil/lymphocyte ratio (NLR) has recently been described as a predictor of mortality in patients who undergo percutaneous coronary intervention. The aim of this study was to investigate the utility of admission NLRs in predicting outcomes in patients with acute coronary syndromes (ACS). A total of 2,833 patients admitted to the University of Michigan Health System with diagnoses of ACS from December 1998 to October 2004 were followed. Patients were divided into tertiles according to NLR. The primary end point was all-cause in-hospital and 6-month mortality. The ACS cohort comprised 564 patients with ST-segment elevation myocardial infarctions and 2,269 patients with non-ST-segment elevation ACS. Patients in tertile 3 had higher in-hospital (8.5% vs 1.8%) and 6-month (11.5% vs 2.5%) mortality compared with those in tertile 1 (p <0.001). After adjusting for Global Registry of Acute Coronary Events risk profile, patients in the highest tertile were at an exaggerated risk for in-hospital (odds ratio 2.04, p = 0.013) and 6-month (odds ratio 3.88, p <0.001) mortality. Admission NLR is an independent predictor of in-hospital and 6-month mortality in patients with ACS. This relatively inexpensive marker of inflammation can aid in the risk stratification and prognosis of patients diagnosed with ACS.

Intracerebral hemorrhage (ICH) accounts for 10-15% of all strokes and is associated with high mortality and morbidity. Currently, no effective medical treatment is available to improve functional outcomes in patients with ICH. Potential therapies targeting secondary brain injury are arousing a great deal of interest in translational studies. Increasing evidence has shown that inflammation is the key contributor of ICH-induced secondary brain injury. Inflammation progresses in response to various stimuli produced after ICH. Hematoma components initiate inflammatory signaling via activation of microglia, subsequently releasing proinflammatory cytokines and chemokines to attract peripheral inflammatory infiltration. Hemoglobin (Hb), heme, and iron released after red blood cell lysis aggravate ICH-induced inflammatory injury. Danger associated molecular patterns such as high mobility group box 1 protein, released from damaged or dead cells, trigger inflammation in the late stage of ICH. Preclinical studies have identified inflammatory signaling pathways that are involved in microglial activation, leukocyte infiltration, toll-like receptor (TLR) activation, and danger associated molecular pattern regulation in ICH. Recent advances in understanding the pathogenesis of ICH-induced inflammatory injury have facilitated the identification of several novel therapeutic targets for the treatment of ICH. This review summarizes recent progress concerning the mechanisms underlying ICH-induced inflammation. We focus on the inflammatory signaling pathways involved in microglial activation and TLR signaling, and explore potential therapeutic interventions by targeting the removal of hematoma components and inhibition of TLR signaling. Copyright © 2013 Elsevier Ltd. All rights reserved.