Photodynamic therapy (PDT) is a promising tool for least-invasive alternative methods for the treatment of brain tumors. The newly discovered PDT-induced opening of the blood–brain barrier (BBB) permeability open novel strategies for drug-brain delivery during post-surgical treatment of glioblastoma GBM. Here we discuss mechanisms of PDT-mediated opening of the BBB and age differences in PDT-related increase in BBB permeability, including with formation of brain edema. The meningeal lymphatic system plays a crucial role in the mechanism of brain drainage and clearance from metabolites and toxic molecules. We discuss that noninvasive photonic stimulation of fluid clearance via meningeal lymphatic vessels, and application of optical coherence tomography (OCT) for bed-side monitoring of meningeal lymphatic drainage has the promising perspective to be widely applied in both experimental and clinical studies of PDT and improving guidelines of PDT of brain tumors.