PTK2 and obstructive hydrocephalus: Whether some of the same intracellular signaling pathways involved in cancer progressions such as the focal adhesion kinase (FAK) pathway or the p38 mitogen-activated protein kinase (MAPK) pathway [47] are likewise activated in obstructive hydrocephalus, but not communicating hydrocephalus, remains unclear, and whether this single protein might be clinically useful as a biomarker to select patients with obstructive hydrocephalus and ETV as the primary treatment option needs to be investigated further.