武藤 淳

OBJECTIVE Primary spinal cord gliomas are rare, and among these astrocytomas (WHO grade II) are much rarer. The optimal treatment strategy thus remains unclear. The authors conducted a multicenter study led by the Neurospinal Society of Japan (NSJ) to analyze treatment policies and outcomes. The aim was to present optimal treatment methods for spinal cord astrocytoma and to identify predictors of better outcomes. METHODS Among 1033 consecutive cases of spinal cord intramedullary tumors treated surgically at 58 centers affiliated with the NSJ, 57 patients were diagnosed with diffuse astrocytoma (WHO grade II) and were enrolled in the present study. Among these 57 patients, treatment methods, outcomes, and tumor proliferation rate as evaluated by the MIB-1 staining index (SI) were analyzed, and the optimal treatment method for spinal cord astrocytomas (grade II) was determined. In addition, the authors searched for factors predicting better treatment outcomes. RESULTS Treatment for spinal cord astrocytoma comprised three methods: surgery alone in 30 patients, adjuvant radiation therapy in 13 patients, and adjuvant chemoradiotherapy in 13 patients. One patient who did not undergo surgery was excluded from survival analysis. Treatment with surgery alone or surgery with radiotherapy was associated with significantly longer overall and progression-free survivals than that with adjuvant chemoradiotherapy. Patients treated with radiation therapy had a higher MIB-1 SI than those treated with surgery alone. The extent of tumor resection tended to correlate with longer survival. In contrast, postoperative neurological worsening showed the inverse order. Adjuvant chemoradiotherapy was associated with the shortest survival in both total cases and recurrent cases. The optimal cutoff value of MIB-1 SI for predicting longer survival by surgery alone was less than 4.0%. CONCLUSIONS The optimal treatment for spinal cord astrocytoma is maximal tumor resection without neurological impairment. When some tumor remains in patients with an MIB-1 SI less than 4.0%, a wait-and-see approach is optimal. If the MIB-1 SI is higher than 4.0%, local radiation therapy is recommended. Adjuvant chemotherapy is not recommended for the treatment of grade II spinal cord astrocytoma.

Objective: The application of the da Vinci Surgical System in neurosurgery is limited due to technical difficulties requiring precise maneuvers and small instruments. This study details the advantages and disadvantages of robotics in neurosurgery and the reachable range of the transoral approach to lesions of the skull base and upper cervical spine.Methods: In a cadaver study, the da Vinci Xi robot, lacking haptic feedback, was utilized for sagittal and coronal approaches on 5 heads, facilitating dura suturing in 3, with a 30°-angled drill for bone removal.Results: Perfect exposure of all the nasopharyngeal sites, clivus, sellar, and choana, including the bilateral eustachian tubes, was achieved without any external incisions using this palatal split approach of transoral robotic surgery. The time required to perform a single stitch, knot, and complete single suture in robotic suturing of deep-seated were significantly less compared to manual suturing via the endonasal approach.Conclusion: This is the first report to show the feasibility of suturing the dural defect in deep-seated lesions transorally and revealed that the limit of reach in the coronal plane via a transoral approach with incision of the soft palate is the foramen ovale. This preclinical investigation also showed that the transoral robotic approach is feasible for lesions extending from the sellar to the C2 in the sagittal plane. Refinement of robotic instruments for specific anatomic sites and future neurosurgical studies are needed to further demonstrate the feasibility and effectiveness of this system in treating benign and malignant skull base lesions.