The treatment of paraspinal and spinal metastases with spinal radiosurgery represents a natural extension of the principles of intracranial stereotactic radiosurgery. However, spinal radiosurgery is a far more complicated process than intracranial radiosurgery. Larger treatment volumes, numerous organs at risk, and the inability to utilize rigid, frame-based immobilization all contribute to the substantially more complex process of spinal radiosurgery.
Beyond the convenience of a shorter duration of treatment for the patient, spinal radiosurgery affords a greater biological equivalent dose to a metastatic lesion than conventional radiotherapy fractionation schemes. This appears to translate into a high rate of tumor control and fast pain relief for patients. The minimally invasive nature of this approach is consistent with trends in open spinal surgery and helps to maintain or improve a patient's quality of life. Spinal radiosurgery has expanded the neurosurgical treatment armamentarium for patients with spinal and paraspinal metastasis.
Spinal radiosurgery is not considered in the domain of traditional Gamma Knife radiosurgery (GKRS) setup. The major obstacles in GKRS for upper cervical spine lesions remain in difficulty of frame fixation, avoiding collision and maintaining the integrity of the relative position of the lesion from image acquisition to treatment.
The supraorbital margin remains the standard lowest fixation point for Leksell stereotactic frame.
Tripathi et al., describe fixation at the maxilla to target and treat upper cervical spine lesions (up to C3 vertebra) with measures to ensure cervical immobilisation and precision of the GKRS treatment.
They have treated two patients at the upper cervical spine up to C3 vertebra by fixing anterior pillars of the Leksell stereotactic frame at the maxilla. To ensure cervical immobilisation and precision of treatment, the neck was immobilised with a Philadelphia collar. The relative position between the head and sternum with the couch from image acquisition to the radiation delivery was kept constant. Docking angle was kept neutral (90 degrees) throughout the treatment (from image acquisition to actual treatment).
The maxilla is a potential alternative for stereotactic frame fixation. Measures to ensure cervical immobilisation with lower-down frame position permits treatment of lesions as low as C3 vertebra 1).