ENPP2 and hematoma: In addition to VEGF, Ang/Tie2, and MMPs, Autotaxin (ATX)–lysophosphatidic acid (LPA) signaling is newly implicated: a prospective clinical study demonstrated ∼3-fold higher ATX catalytic activity in hematoma fluid vs. paired serum, directly implicating the ATX–LPA axis in cSDH pathophysiology.