Kentaro Naito

Comparison of neuropsychological outcomes after selective amygdalohippocampectomy versus anterior temporal lobectomy

Transsylvian selective amygdalohippocampectomy (TSA) is an operative technique designed to spare unaffected brain tissue during surgical treatment for mesial temporal lobe epilepsy. In contrast to standard anterior temporal lobectomy (ATL), the advantages of TSA with respect to postoperative cognitive outcome are equivocal. We compared cognitive function before and after surgery in 49 patients with unilateral mesial temporal lobe seizures who underwent either ATL (n=17) or TSA (n=32). All patients received neuropsychological testing before and 1 year after surgery. The intelligence quotient (IQ) increased postoperatively in both surgical groups. Memory evaluation in the ATL group revealed a postoperative decline in nonverbal memory after right-sided resection and a postoperative decline in verbal memory after left-sided resection. In the TSA group, there was a slight postoperative decline only in verbal memory after left-sided resection, but other memory function was well preserved. In particular, there was significant postoperative improvement in verbal memory after right-sided resection. Overall, memory function was better preserved in the TSA group than in the ATL group.

Surgical Management of Spinal Intramedullary Tumors: Radical and Safe Strategy for Benign Tumors

Surgery for spinal intramedullary tumors remains one of the major challenges for neurosurgeons, due to their relative infrequency, unknown natural history, and surgical difficulty. We are sure that safe and precise resection of spinal intramedullary tumors, particularly encapsulated benign tumors, can result in acceptable or satisfactory postoperative outcomes. General surgical concepts and strategies, technical consideration, and functional outcomes after surgery are discussed with illustrative cases of spinal intramedullary benign tumors such as ependymoma, cavernous malformation, and hemangioblastoma. Selection of a posterior median sulcus, posterolateral sulcus, or direct transpial approach was determined based on the preoperative imaging diagnosis and careful inspection of the spinal cord surface. Tumor-cord interface was meticulously delineated in cases of benign encapsulated tumors. Our retrospective functional analysis of 24 consecutive cases of spinal intramedullary ependymoma followed for at least 6 months postoperatively demonstrated a mean grade on the modified McCormick functional schema of 1.8 before surgery, deteriorating significantly to 2.6 early after surgery (< 1 month after surgery), and finally returning to 1.7 in the late postoperative period (> 6 months after surgery). The risk of functional deterioration after surgery should be taken into serious consideration. Functional deterioration after surgery, including neuropathic pain even long after surgery, significantly affects patient quality of life. Better balance between tumor control and functional preservation can be achieved not only by the surgical technique or expertise, but also by intraoperative neurophysiological monitoring, vascular image guidance, and postoperative supportive care. Quality of life after surgery should inarguably be given top priority.

Intraoperative assessment of spinal vascular flow in the surgery of spinal intramedullary tumors using indocyanine green videoangiography

Background: The authors demonstrate the utility of indocyanine green videoangiography (ICG-VA) for intraoperative vascular flow assessment in the surgery of a variety of spinal intramedullary tumors to achieve an additional level of safety as well as precision with the surgical procedure. Methods: Fourteen patients with spinal intramedullary tumors (nine cervical and five thoracic) operated on between August 2011 and April 2013 were included in the present study. A fluorescence surgical microscope was used to perform ICG-VA after standard exposure of the lesion to assess the dynamic flow of the spinal microvasculature. Results: Twenty-seven ICG-VA injections were performed in 14 cases. Pathological diagnosis of the tumors included ependymoa, astrocytoma, cavernous malformation, or hemagioblastoma. There were no complications or side-effects related to ICG-VA. Intraoperative ICG-VA provided dynamic flow images of the spinal microvasculature in accordance with the progress of surgical procedures. Angiographic images could be divided into arterial, capillary, and venous phases. All angiographic images were well integrated into the microscopic view. The utility of ICG-VA could be summarized into three categories: (1) Localization of normal spinal arteries and veins, (2) assessment of posterior spinal venous circulation, and (3) differentiation of feeding arteries, tumor, and draining veins. Conclusions: Intraoperative vascular flow assessment using ICG-VA was easy, repeatable, and practical without any significant procedure-related risks. ICG-VA can be used for careful analysis of spinal microvascular flow or anatomical orientation, which is necessary to ensure safe and precise resection of spinal intramedullary tumors.

Qualitative analysis of spinal intramedullary lesions using PET/CT

OBJECT Although the usefulness of PET for brain lesions has been established, few reports have examined the use of PET for spinal intramedullary lesions. This study investigated the diagnostic utility of PET/CT for spinal intramedullary lesions. METHODS l-[methyl-11C]-methionine (MET)- or [18F]-fluorodeoxyglucose (FDG)-PET/CT was performed in 26 patients with spinal intramedullary lesions. The region of interest (ROI) within the spinal cord parenchyma was placed manually in the axial plane. Maximum pixel counts in the ROIs were normalized to the maximum standardized uptake value (SUVmax) using subject body weight. For FDG-PET the SUVmax was corrected for lean body mass (SULmax) to exclude any influence of the patients body shape. Each SUV was analyzed based on histopathological results after surgery. The diagnostic validity of the SUV was further compared with the tumor proliferation index using the MIB-1 monoclonal antibody (MIB-1 index). RESULTS A total of 16 patients underwent both FDG-PET and MET-PET, and the remaining 10 patients underwent either FDG-PET or MET-PET. Pathological diagnoses included high-grade malignancy such as glioblastoma multiforme, anaplastic astrocytoma, or anaplastic ependymoma in 5 patients; low-grade malignancy such as hemangioblastoma, diffuse astrocytoma, or ependymoma in 12 patients; and nonneoplastic lesion including cavernous malformation in 9 patients. Both FDG and MET accumulated significantly in high-grade malignancy, and the SULmax and SUVmax correlated with the tumor proliferation index. Therapeutic response after chemotherapy or radiation in high-grade malignancy was well monitored. However, a significant difference in SULmax and SUVmax for FDG-PET and MET-PET was not evident between low-grade malignancy and nonneoplastic lesions. CONCLUSIONS Spinal PET/CT using FDG or MET for spinal intramedullary lesions appears useful and practical, particularly for tumors with high-grade malignancy. Differentiation of tumors with low-grade malignancy from nonneoplastic lesions may still prove difficult. Further technological refinement, including the selection of radiotracer or analysis evaluation methods, is needed.

Prediction of the efficacy of surgical intervention in patients with cervical myelopathy by using diffusion tensor 3T-magnetic resonance imaging parameters.

Background: The clinical significance of diffusion tensor (DT) magnetic resonance imaging (MRI) parameters was analyzed to predict postoperative functional recovery in patients with cervical myelopathy. Materials and Methods: Sixteen patients with cervical myelopathy caused by cervical spondylosis, disk herniation or ossification of the posterior longitudinal ligament who underwent surgical intervention in our institute were enrolled in this retrospective study. There were 7 men and 9 women, with a mean age of 62.8 years. Clinical assessment was done before surgery and at least 3 months after surgery. All patients underwent whole-body 3.0-Tesla MRI before surgery. DT images (DTIs) were obtained using a single-shot fast spin-echo-based sequence. Mean values of mean diffusivity (MD) and fractional anisotropy (FA) at 6 disk levels of the cervical spine were measured using manual setting of regions of interest. The MD and FA values at the most compressed part were analyzed. Absolute MD and FA values at the most compressed spinal level in patients were transformed into the normalized values with a z-score analysis. Results: MD-z may decrease with the severity of cervical myelopathy. Receiver operating characteristic analysis of MD-z and FA-z suggested that both MD-z and FA-z have clinical validity for predicting the efficacy of surgical intervention, but MD-z was considered to be the most appropriate value to predict the efficacy of surgery. Conclusions: DTIs may be a promising modality to predict functional recovery after surgery. MD changes may reflect spinal cord condition and its reversibility.

Surgical management of spinal meningiomas: A retrospective case analysis based on preoperative surgical grade.

Background: Although spinal meningiomas respond favorably to surgical excision, their surgical management is impacted by several factors. This study utilized a surgery-based grading system to discuss the optimal surgical strategy. Methods: Twenty-three consecutive patients who underwent surgery for spinal meningiomas were included in this retrospective study. The patients’ neurological condition was assessed using the modified McCormick functional schema (mMFS) and sensory pain scale (SPS), and tumor removal was assessed using Simpson grade. Major factors contributing to surgical difficulty included; tumor size, extent/severity of cord compression, location of tumor attachment, spinal level, and anatomical relationships plus tumor extending in a dumbbell shape and local postoperative recurrence. Results: Fifteen cases were classified as ventral attachment (65.2%). There were two dumbbell-shaped tumors and three local recurrences at the primary site. Simpson grade 1 or 2 resections were performed in 18 of 20 cases (90%) with preoperative surgical grades 0 to 3. Simpson grade 4 resections were achieved in all three cases with preoperative surgical grades 4 to 5. Overall neurological assessment after surgery revealed the satisfactory or acceptable recovery on mMFS and SPS analysis. Conclusions: Lower preoperative grade yielded better results, while the higher the preoperative grade, the more likely tumor was insufficiently removed. A preoperative surgical grading system appeared to be helpful when considering the surgical strategy. Ventral meningiomas could be safely resected via the posterolateral or lateral approach using technical modifications. Recurrent tumors, especially with ventral attachment, were hard to resolve, and primary surgery appears to be important.

Microsurgical Interintimal Dissection in Carotid Endarterectomy

BACKGROUND Safe and complete surgical excision of carotid plaque in carotid endarterectomy (CEA) is essential for preventing postoperative embolic stroke and restenosis. We considered the dissection plane for the plaque according to pathological findings of carotid atherosclerosis. We report our experiences with inner-intimal dissection in CEA. METHODS To obtain complete resection of the plaque with a smooth distal edge and bloodless surface by minimal exposure of the media, the thickened intima was sliced under high-magnification microscopy. The excised specimens were examined pathologically. RESULTS Sixty-three CEAs were performed for 61 patients with carotid stenosis. Complete resection without tacking suture was obtained in all procedures. No mortality was encountered. Minor stroke was recorded in 1 procedure (1.6%). No early restenosis was recorded during follow-up (range, 1-35 months; mean, 15.6 months). Pathological examination revealed interintimal excision of the lesion in each case. CONCLUSION Microsurgical interintimal dissection could accomplish good surgical outcome, including absence of significant early restenosis.

Benefits and Limitations of Indocyanine Green Fluorescent Image-Guided Surgery for Spinal Intramedullary Tumors

BACKGROUND Intraoperative image guidance using near-infrared indocyanine green videoangiography (ICG-VA) has been used to provide real-time angiographic images during vascular or brain tumor surgery, and it is also being used for spine surgery. OBJECTIVE To further investigate the benefits and limitations of ICG-VA image-guided surgery for spinal intramedullary tumors through retrospective study. METHODS ICG-VA was used in 48 cases that were treated surgically over the past 5 yr. The pathological diagnoses of the tumors included astrocytic tumor, ependymal tumor, cavernous malformation, and hemangioblastoma. RESULTS Localization of normal spinal arteries and veins on the dorsal surface of the spinal cord helped the surgeons determine the length or point of myelotomy. Well-demarcated tumor stain was recognized in limited cases of anaplastic or highly vascularized tumors, whereas the location of cavernous malformation was recognized as an avascular area on the dorsal surface of the spinal cord. Feeding arteries and tumor stain were well differentiated from draining veins in dorsal hemangioblastomas, but not in intramedullary deep-seated or ventral tumors. The preservation of small perforating branches of the anterior spinal artery after successful resection of the tumor could be well visualized. CONCLUSION ICG-VA can provide real-time information about vascular flow dynamics during the surgery of spinal intramedullary tumors, and it may help surgeons localize the normal circulation of the spinal cord, as well as the feeding arteries and draining veins, especially in highly vascular tumors. However, the benefits of intraoperative ICG-VA might be limited for intramedullary deep-seated or ventral tumors.

Posterolateral approach for spinal intradural meningioma with ventral attachment

Background: Spinal meningioma with ventral attachment is a challenging pathology. Several technical modifications have been proposed to secure safe and precise resection of these tumors. Materials and Methods: This retrospective study focused on the precise and safe surgery of spinal meningiomas with strictly ventral attachment of cervical or thoracic spine. The surgical technique included a lateral oblique position for the patient, laminectomy with unilateral medial facetectomy on the tumor side, and spinal cord rotation with the dentate ligament. The neurological status of patients was assessed using the modified McCormick functional schema (mMFS) and sensory pain scale (SPS) before and at least 3 months after surgery. Patients were followed-up for a mean of 23.7 months. Tumor removal was graded using the Simpson grade for removal of meningiomas, and the extent of excision was confirmed using early postoperative magnetic resonance imaging. Results: Simpson grade 1 or 2 resections were achieved in all cases. No major surgery-related complications were encountered, postoperatively. The mean mMFS score before surgery was 3.1, improving significantly to 1.7 after surgery (P < 0.05). The mean SPS score before surgery was 2.4, improving significantly to 1.6 after surgery (P < 0.05). Conclusions: This surgical technique offers a posterolateral surgical corridor to the ventral canal of both cervical and thoracic spine. The present preliminary analysis suggests that functional outcomes were satisfactory with minimal surgery-related complications, although considerable surgical experience is needed to achieve a high level of surgical confidence.

C2 Nerve Root Resection to Achieve Safe and Wide Exposure of Lateral Atlantoaxial Joints in Posterior C1-2 Instrumented Fixation: Technical Note

Posterior atlantoaxial (C1-2) fixation with individual screw placement in C1 and C2 has been one of the technical options to treat C1-2 subluxation or instability. In the present study, we demonstrate the surgical technique of C2 nerve root resection to avoid the troublesome bleeding from the perivertebral venous plexus and achieve full exposure of the lateral C1-2 joints. The present study includes a series of 16 consecutive patients who underwent posterior C1-2 instrumented fixation with individual screw placement in C1 and C2. All patients underwent unilateral or bilateral C2 nerve root resection at the sensory ganglion. Screw malposition resulting in vascular or neural injury was not encountered. Sensory pain scale analysis indicated that the mean score before surgery was 2.4, which significantly improved to 1.4 after surgery. No patients reported allodynia or C2 distribution neuropathic pain during the follow-up. C2 nerve root resection resulted in early postoperative dysesthesia in all 16 patients; however, neurological examination during the follow-up revealed that only 12.5% of all analyzed patients did not demonstrate satisfactory recovery of C2 sensory disturbance. Postoperative radiologic analysis revealed solid osseous or partial fusion at the lateral C1-2 joints in all cases during the follow-up. No case demonstrated non-union with pseudoarthrosis. Although C2 nerve root resection is still under debate and not fully justified, the present study suggests that C2 nerve root resection does not always result in significant morbidity and can be an option for surgical resolution to achieve safe and wide exposure of lateral C1-2 joints.