Radiobiological effects of photon radiosurgery on choroid plexus cells in vitro

The standard surgical treatment of hydrocephalus by cerebrospinal fluid (CSF) shunt is accompanied by numerous complications. The search for alternative treatment methods includes resection, coagulation and irradiation of part of the plexus choroideus. The reduction of CSF secretion after choroid plexus (CP) irradiation has been investigated only on the experimental level. The new Photon Radiosurgery System (PRS) now also provides clinically the opportunity to induce selective radionecrosis on the CP with high efficiency and safety. In order to achieve a basic understanding of the reaction of CP cells after PRS irradiation, we investigated the cell death after different irradiation doses using TB dye-exclusion and MTT assay on sheep choroid plexus (SCP) cells. We observed a dose-dependent decrease in cell survival with increasing doses of irradiation (9, 18, 27 and 36 Gy). Lower irradiation doses (9, 18 Gy) induced an initial decrease of cell survival. Cells were able to recover from day 6 on and achieved a similar cell viability compared to non-irradiated cells on day 12. In contrast, higher doses (27 and 36 Gy) of irradiation induced a constant decrease of the cell survival over 12 days. These results clearly demonstrate that PRS irradiation is able to induce radionecrosis of CP cells which are responsible for the secretion of CSF. Interstitial photon radiosurgery can provide the opportunity to deliver the irradiation dose locally to CP with minimal exposure of surrounding tissue. Our basic data support further studies investigating this concept in animal models and clinically.