Photodynamic therapy of malignant brain tumors: clinical results of, difficulties with, questions about, and future prospects for the neurosurgical applications.

Photodynamic therapy (PDT) has been applied in a variety of oncological fields with good results. In neurosurgery, the clinical series are limited and the number of treated patients is not statistically significant. This work examines the results of PDT performed in our clinic and discusses some difficulties and causes of failure of this method in neurosurgical patients. Eight patients with malignant brain tumors underwent PDT. All had been treated previously by operation and radiation therapy and one patient had also received chemotherapy. At 24 hours after the i.v. injection of hematoporphyrin (5 mg/kg body weight), the tumor was removed as radically as possible and the residual tumor bed was exposed to either 630-nm light from an argon-dye laser or 600- to 680-nm light isolated from the emission of a quartz-halogen lamp. The type of sensitizer, the irradiation methods, and the peculiarities of glial tumors are examined as possible causes of failure. The longer survivals of some patients with glial tumors treated by PDT may make this treatment suitable when traditional therapies fail.

Physiological function after middle cerebral artery occlusion in rabbits with neovascularization of the brain by transposed omentum.

The effect of brain neovascularization by omental transposition on somatosensory evoked potentials and on regional cerebral blood flow (rCBF) measured by hydrogen clearance was evaluated in rabbits exposed to experimental ischemia after occlusion of the middle cerebral artery (MCA). After MCA occlusion, the animals with brains neovascularized by transposed omentum showed a mild drop of rCBF accompanied by normal patterns of somatosensory evoked potentials elicited by sciatic stimulation. In the control animals, the evoked cortical electrical activity drastically decreased in amplitude immediately after arterial occlusion and fell to zero one-half hour later. The decay of bioelectrical activity in these rabbits was associated inevitably with a major drop in the rCBF. Morphological examination, as well as the functional data, indicate that omental transposition in animals exposed to experimental ischemia minimizes the occurrence of cerebral infarction because the neovascularization is capable of maintaining the local blood flow for at least 1 hour; therefore, the cortical electrical activity is preserved totally. In the light of these results, the authors suggest that this surgical technique can also be utilized in human beings who are affected by transient ischemic attacks to prevent more serious consequences.

Local cerebral blood flow after middle cerebral artery occlusion in rabbits following transposition of omentum to the brain.

Transposition of pedicled omental grafts to the brain has been shown to minimize the effects of cerebral infarction in dogs and monkeys. An experimental study in which pedicled omental grafts and free non-revascularized omental grafts were placed on the brains of rabbits is reported. With the use of a modified inhaled hydrogen clearance technique to measure blood flow in the brain tissue, it was determined that the pedicled omental graft minimized the effects of middle cerebral artery occlusion by maintaining a collateral blood supply and limiting the decline of local cerebral flow. Super-position of free omental grafts on the brain had no effect on the threshold for infarction.