The Crucial Role of Eosinophils in the Life Cycle, Radiographical Architecture, and Risk of Recurrence of Chronic Subdural Hematomas

Preoperative elevated eosinophils in peripheral blood for prediction of postoperative recurrence of chronic subdural hematoma

OBJECTIVE

Chronic subdural hematoma (CSDH) is a common neurological disease with a significant postoperative recurrence rate. There are numerous reported studies of the development of CSDH. In recent years, fibrinolysis, angiogenesis, and inflammation have all been identified as relevant factors in the development of CSDH. While several authors have reported risk factors associated with CSDH recurrence, differential blood count of leukocytes has not yet been discussed. Therefore, in this study the authors aimed to retrospectively investigate the association between differential blood leukocyte count and the rate of CSDH recurrence.

METHODS

The authors retrospectively reviewed 476 patients with 529 CSDHs who underwent surgery at a single institution between January 2011 and December 2021. After exclusion of patients who had not undergone a differential blood test of leukocytes preoperatively, CSDHs in 517 cerebral hemispheres of 466 patients were included in the study. Peripheral blood eosinophil counts ≥ 100/µL were considered eosinophil rich.

RESULTS

CSDHs in 494 cerebral hemispheres of 445 patients were followed up postoperatively for at least 3 months or until resolution indicated by CSDH disappearance. Postoperative recurrence of CSDH was observed in 46 cerebral hemispheres (9.3%). Among the preoperative differential blood counts of all leukocytes, eosinophils alone were significantly associated with CSDH recurrence (median [IQR] 76/µL [30-155/µL] vs 119/µL [39-217/µL]; p = 0.03). Multivariable regression analysis showed thrombocytopenia (adjusted OR [aOR] 5.23, 95% CI 1.85-14.79; p = 0.002), use of anticoagulant drugs (aOR 2.51, 95% CI 1.17-5.38; p = 0.02), hematoma volume (10 mL per increase) (aOR 1.08, 95% CI 1.00-1.16; p = 0.04), and eosinophil-rich peripheral blood (aOR 2.22, 95% CI 1.17-4.23; p = 0.02) were all independent predictors for CSDH recurrence.

CONCLUSIONS

This study showed that preoperative peripheral blood eosinophil count was an independent risk factor for CSDH recurrence. Therefore, patients with CSDH who have elevated eosinophils preoperatively in peripheral blood require careful follow-up.

Biofluid Biomarkers in the Prognosis of Chronic Subdural Hematoma: A Systematic Scoping Review

The present systematic scoping review aimed at mapping and analyzing the available literature on biological fluid (biofluid) biomarkers showing promise in the prediction of chronic subdural hematoma (cSDH) recurrence and the prognosis of neurological/functional patient outcome. Twenty-three studies published between 2003 and 2023 investigating a diverse range of biomarkers in hematoma fluid and/or the circulation in 3749 patients were included. Immune cell populations and inflammatory/anti-inflammatory cytokines comprised the most studied category of biomarkers displaying significant findings. A notable time trend in biomarker studies was a recent shift in research focus towards the analysis of circulating biomarkers. Several biomarkers were indicated as independent predictors of cSDH recurrence and/or functional/neurological outcome, including circulating fibrinogen degradation products (FDP), brain natriuretic peptide (BNP-1) and high-density lipoprotein (HDL), as well as blood urea nitrogen (BUN) and the ratios of blood neutrophil to lymphocyte (NLR) or red blood cell distribution width to platelet count (RPR). While studies on cSDH prognostic biomarkers have gained, in recent years, momentum, additional multicenter prospective studies are warranted to confirm and extend their findings. The identification of prognostic biofluid biomarkers in cSDH is an active field of research that may provide future tools, guiding clinical decisions and allowing for the design of treatments based on risk stratification.

Subdural Lesions Linking Additional Intracranial Spaces and Chronic Subdural Hematomas: A Narrative Review with Mutual Correlation and Possible Mechanisms behind High Recurrence

The purpose of this study was two-fold. The first was to investigate the pathologic mechanisms underlying the formation of subdural fluid collection, an umbrella term referring to a condition commonly seen in the clinical setting. Accumulation of the cerebrospinal fluid (CSF) in the subdural space can be referred to in this disease category, disregarding the underlying source of the subdural fluid. However, in these two clinical situations, especially after trauma or brain surgery, fluid collection from the subarachnoid space (subdural hygroma) or from the ventricle to the subarachnoid space and infusion into the subdural space (external hydrocephalus), surgical management of critical patients may adopt the strategies of burr-hole, subduroperitoneal shunt, or ventriculoperitoneal shunt, which present distinctly different thoughts. Crucially, the former can be further transformed into chronic subdural hematoma (CSDH). The second significant theme was the pathogenesis of CSDH. Once the potential dural border cell (DBC) layer is separated such as if a wound is formed, the physiological mechanisms that seem to promote wound healing will resume in the subdural space as follows: coagulation, inflammation, fibroblast proliferation, neovascularization, and fibrinolysis. These aptly correspond to several key characteristics of CSDH formation such as the presence of both coagulation and fibrinolysis signals within the clot, neomembrane formation, angiogenesis, and recurrent bleeding, which contribute to CSDH failing to coagulate and absorb easily. Such a complexity of genesis and the possibility of arising from multiple pathological patterns provide a reasonable explanation for the high recurrence rate, even after surgery. Among the various complex and clinically challenging subdural lesions, namely, CSDH (confined to the subdural space alone), subdural hygroma (linked in two spaces), and external hydrocephalus (linked in three spaces), the ability to fully understand the different pathological mechanisms of each, differentiate them clinically, and devote more interventional strategies (including anti-inflammatory, anti-angiogenic, and anti-fibrinolysis) will be important themes in the future.

Peripheral blood eosinophil and classification of residual hematoma help predict the recurrence of chronic subdural hematoma after initial surgery

Chronic subdural hematoma (CSDH) is a common type of intracranial hemorrhage in neurosurgical practice, whose incidence has increased markedly in recent years. However, CSDH still troubles clinicians with a high postoperative recurrence rate. The presence of eosinophils has been confirmed in some CSDH surgical specimens. Furthermore, postoperative residual hematoma has not been classified, and its association with the recurrence of CSDH remains unknown. The present study aimed to test the hypothesis that the peripheral blood eosinophils and the classification of postoperative residual hematoma are significant for the prediction of CSDH recurrence after burr-hole surgery. A retrospective review of 258 CSDH patients who received burr-hole surgery was performed. A complete blood picture with differential count was taken before surgery. Clinical, laboratory, and radiographic factors predicting CSDH recurrence were identified in univariable and multivariable analyses. Univariable analysis showed that the percentage of eosinophils, peripheral blood eosinophil count <0.15 × 10⁹/L, gradation and separated types, postoperative volume of the residual cavity ≥70 ml, residual air volume ≥28 ml, residual hematoma volume ≥55 ml, residual hematoma width ≥1.4 cm, postoperative midline shift ≥5.6 mm, postoperative brain re-expansion rate <41%, postoperative low-density type, and postoperative high-density type correlated with the recurrence of CSDH. Multivariable analysis, however, showed that peripheral blood eosinophil count <0.15 × 10⁹/L, gradation and separated types, preoperative midline shift ≥9.5 mm, postoperative brain re-expansion rate <41%, postoperative low-density type, and postoperative high-density type are independent predictors for the recurrence of CSDH. We expect that peripheral blood eosinophils and the classification of postoperative residual hematoma may facilitate our understanding of the recurrence of CSDH after initial surgery.