['The possible cause of chronic hydrocephalus after subarachnoid hemorrhage (SAH) has been reported to be meningeal fibrosis. We examined whether the induction of tenascin-C (TN-C), an extracellular matrix glycoprotein known to promote tissue fibrosis, was associated with chronic hydrocephalus after SAH.', 'We prospectively measured cerebrospinal fluid TN-C levels in 7 control patients with unruptured cerebral aneurysms and in 29 consecutive patients with aneurysmal SAH on days 1 to 12.', 'Cerebrospinal fluid TN-C levels were less than the diagnostic threshold level in control patients but markedly increased after SAH. Higher TN-C levels were observed in patients with more severe SAH on admission CT, ventricular drainage for acute obstructive hydrocephalus, and a worse outcome. Independent of these factors, however, cerebrospinal fluid TN-C levels were significantly higher in patients with than without subsequent chronic shunt-dependent hydrocephalus on days 1 to 9.'] Does cerebrospinal fluid tenascin-C increase preceding the development of chronic shunt-dependent hydrocephalus after subarachnoid hemorrhage?