Immune Cells Discovered in a Group of CSDH Patients: A Pilot Study With Immunophenotypic Profiling

Introduction: The unpredictability of recurrence of chronic subdural hematoma (CSDH) and in parallel its steady increase in incidence represents a global challenge. In this regard, recent evidence suggests the involvement of immune cells in the pathophysiology of CSDH, however, little is known about the composition and relevance of individual immune compartments in the natural history of the entity

Methods: In this single-center pilot study, five CSDH patients underwent mini-craniotomy. Peripheral blood and hematoma fluid samples were collected, with additional peripheral blood drawn from three healthy volunteers. Mononuclear cells from the samples were isolated by density gradient centrifugation and analyzed via flow cytometry. Inflammatory mediators (IL-6, IL-8, TNF-α) and fractalkine (CX3CL1) were measured using multiplex ELISA.

Results: The average age of the five patients was 66 years (range 54–81), with an average GCS score of 13.4 upon admission. Immune profiling of the CSDH fluid revealed a predominance of T lymphocytes (CD45+CD3+), which constituted 53.49% ± 21.9% of the immune cells, of which 22% ± 11.59% were cytotoxic T lymphocytes (CD8+). The innate immune cells included NK cells (CD45+CD3- CD56+), and NK-T. Monocytes (CD45+CD14+) accounted for 5.8% ± 0.8%. A novel erythro-myeloid progenitor population (CD45+CD31+) was identified. These progenitors were absent in healthy controls and correlated positively with peripheral platelet count (p=0.009). NK cells were significantly reduced in both hematoma fluid and peripheral blood of CSDH patients compared to controls (p=0.0014 and p=0.0021, respectively), while NK-T cells were elevated in both compartments (p=0.0347 and p=0.07, respectively). Inflammatory cytokines IL-6 and IL-8 were significantly higher in hematoma fluid compared to peripheral blood (2814 ±1539 pg/ml and 2481 ±796 pg/ml, respectively), while TNF-α levels were reduced (2.5 ±0.7 pg/ml in hematoma fluid vs. 11.2 ±6.06 pg/ml in peripheral blood, p=0.005). CX3CL1 levels were significantly elevated in hematoma fluid compared to both peripheral blood and healthy controls (p < 0.0001).

Conclusion : This study identifies key immune populations within CSDH, notably erythro-myeloid progenitors and NK-T cells, offering new insights into its pathophysiology and potential biomarkers for clinical outcomes.