Hyperthermia therapy using Nd-YAG Laser for the treatment of malignant brain tumors have recently developed in neurosurgical field. We have developed new thermal probes for localized laser hyperthermia to the peripheral or infiltrating malignant brain tumor cells immediately after the tumor debulking during the surgery. (1) We have made different sizes of expermental ballon probes, which consisted of laser photofiber covered with photo-scattering materials, latex rubber and thermal sensor. The air injection in the balloon was better than soy bean oil injection. An adequate linear correlation was obtained between the temperature of the probe and that of the balloon surface. (2) In the experiment of local laserthermia applied to swine & rat brains, the temperature of the surrounding brain attached to the balloon could be easily controlled at 42.543.5°C by changing the output power between 5W and 15W. In histological examination, remarkable necrosis and multiple small bleeding as well as autolysis were noticed in the peripheral brain tissue attached to the balloon in the acute stage. The peripheral brain tissue consisted of coagulation necrosis and scattered gliosis in the chronic stage. (3) In the cases of hyperthermia for human glioma xenografts in athymic nude mice at 43.5°C for 20 minutes, remaining tumor tissue attached to the balloon revealed masssive necrosis with small hemorrhage and infiltrating inflammatory cells in the peripheral portion. Although there was no viable tumor cells within 5mm distance from the balloon, tumor necrosis was limited and scattered viable tumor cells were found after hyperthermia at 41.5°C for 20 minutes. (4) Intraoperative laserthermia therapies using balloon probes with Nd : YAG laser for 7 patients with malignant gliomas, 12 patients with metastatic brain tumors and 1 patient with primary malignant lymphoma were successfully performed without any complication during past 2 years. Post operative CT and/or MRI revealed no tumor enhancement or poor enhancement of tumor border. Although follow up of our cases is not so long, this local laserthermia is effective and easy to handle, it might be useful in the treatment of malignant brain tumors including metastatic tumors during surgery.
