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Hiroki Toda, Namiko Nishida, and Koichi Iwasaki

Holmes tremor is often treated with multiple deep brain stimulation (DBS) electrodes. The authors describe a novel technique to suppress the tremors by effectively utilizing a single electrode.

A 16-year-old boy presented with severe right arm tremor following a midbrain injury. A DBS electrode was implanted into the ventral oralis nucleus of the thalamus (VO) and the subthalamic region. While individual stimulation of each target was ineffective, an interleaved dual stimulation of both targets has been effective for 6 years.

Coaxial interleaved stimulation of the VO and the subthalamic region is useful for treating Holmes tremor.

The video can be found here:

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Neuroradiological characteristics of ecchordosis physaliphora

Case report and review of the literature

Hiroki Toda, Akinori Kondo, and Koichi Iwasaki

✓ An extremely rare case of ecchordosis physaliphora is presented in which the authors focus especially on its radiological characteristics. The patient complained of a headache with no other neurological abnormalities. A thorough radiological examination revealed a small intradural prepontine mass with no bone destruction of the clivus. Magnetic resonance imaging was very useful in visualizing this mass as a low signal intensity lesion on T1-weighted images and as a high signal intensity lesion on T2-weighted images without any contrast enhancing effects. At surgery, a cystic gelatinous nodule was found ventral to the pons; the nodule was connected to the dorsal wall of the clivus via a delicate stalk. Histological studies proved that this was an ecchordosis physaliphora. Review of the literature demonstrates that the reported cases of ecchordoses have many common radiological features that would suggest the diagnosis of this rare disease.

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Ichiro Nakano, Koichi Iwasaki, and Akinori Kondo

✓ An unusual case of a metastatic adenocarcinoma located entirely within the trigeminal nerve is reported. The patient, with a history of breast cancer, presented with a pure trigeminal mononeuropathy. The neurological and neuroradiological findings in this patient were quite similar to those of a patient with trigeminal neurinoma. Surgery revealed that the tumor was located within the trigeminal nerve and its appearance was similar to that of a neurinoma. However, histopathological studies proved the tumor to be an adenocarcinoma that was related to the breast cancer treated earlier. A solitary metastatic tumor arising solely in a trigeminal nerve is quite rare; this is the first report of such a case metastasized from breast cancer.

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Koichi Iwasaki, Taichi Ikedo, Hirokuni Hashikata, and Hiroki Toda

A variety of donor-site complications have been reported for anterior cervical discectomy and fusion (ACDF) using autologous iliac bone graft. To minimize such morbidities and to obtain optimal bony fusion at the ACDF surgery, a novel technique was used to harvest cancellous bone from the autologous clavicle instead of the popular iliac crest graft. After a routine cervical discectomy of the affected level, a 1.5-cm linear skin incision was made over the clavicle within 2.5 cm of the sternoclavicular joint on the medial one-third portion. This portion is known as an anatomically safe zone, with no subcutaneous distribution of the supraclavicular nerve. Then, cancellous bone was harvested through a small cortical window developed on the clavicle. Care was taken not to injure the subclavian major vessels and the lung below the clavicle. A box-type titanium cage was packed with the harvested cancellous bone and then inserted into the discectomy-treated space for cervical interbody fusion. From 2009 to 2013, 16 patients with cervical radiculopathy and/or myelopathy underwent single-level ACDF with this method. All but 1 patient experienced significant improvement of clinical symptoms after the surgery and showed radiographic evidence of solid bony fusion and spinal stabilization within 6 months. Further, no peri- and postoperative complications at the clavicular donor site were noted. The mean visual analog scale pain score (range 0 [no pain to 10 [maximum pain]) at 1 year after the surgery was 0.1, and 13 of 14 patients with data at 1-year follow-up were highly satisfied with their donor-site cosmetic outcome. The clavicle is a safe, reliable, and technically easy source of autologous bone graft that yields optimal fusion rates and patient satisfaction with ACDF surgery.

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Noriyoshi Takebe, Koichi Iwasaki, Hirokuni Hashikata, and Hiroki Toda

An intramedullary spinal cord abscess, which is usually associated with discitis, is an uncommon but potentially important complication of vertebral osteomyelitis. The authors describe a rare case of an intramedullary conus medullaris abscess and lumbar osteomyelitis sparing the intervertebral discs and without discitis. The patient also developed a granuloma in the cauda equina during treatment. Diffusion-weighted MRI was useful for differentiating the granulomatous lesion from the relapse of infection.

A 65-year-old immunocompetent man with moderately controlled diabetes presented with progressive lowerextremity numbness and weakness with urinary dysfunction. He had progressive paraparesis, bilateral leg paresthesia, and sphincter compromise. Magnetic resonance imaging revealed an intramedullary ring-enhanced lesion, which was hyperintense on diffusion-weighted images. The lesion, an intramedullary spinal cord abscess, was surgically drained. During antibiotic treatment, serial MRI showed an enlarging enhanced lesion in the cauda equina, and a recurrent infection was suspected. A second-look surgery confirmed the formation of a granuloma and the absence of a relapse of the abscess. Although the enhanced lesion increased in size, its intensity on diffusion-weighted images remained unchanged. After 3 months of antibiotic treatment, all enhanced lesions were diminished.

An intramedullary spinal cord abscess is a rare but important complication of vertebral osteomyelitis, and it requires immediate treatment. Diffusion-weighted MRI was useful for the initial diagnosis as well as for monitoring treatment efficacy.

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Koichi Iwasaki, Lisa R. Rogers, Gene H. Barnett, Melinda L. Estes, and Barbara P. Barna

✓ In order to investigate the antiproliferative and anti-invasive effects of tumor necrosis factor (TNF)-α on human glioblastoma cells, an in vitro three-dimensional (anchorage-independent) assay was performed using Matrigel, a mixture of extracellular matrix proteins. Four glioblastoma-derived cell lines, including one cloned line, were cultured in Matrigel with or without TNF-α. In the Matrigel containing TNF-α, three of the four cell lines, including the cloned line, showed significant growth inhibition in a dose-dependent manner. Dramatic three-dimensional morphological differences were observed between TNF-treated and untreated glioblastoma cells cultured in Matrigel. Untreated cells formed large and highly branched colonies throughout the gel. In contrast, the majority of TNF-treated cells demonstrated truncated branching processes and, at a high TNF-α dose, an increasing number of cells remained in relatively small spherical aggregates, their cell processes being significantly reduced. Quantitative invasion assay using a micro-Boyden chamber system confirmed that TNF-treated cells lost invasiveness in a dose-dependent manner. These results suggest that TNF-α exerts not only antiproliferative but also anti-invasive effects on human glioblastoma cells in vitro. It is believed that this is the first report showing the anti-invasive effect of TNF-α on tumor cells.

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Hitoshi Kobata, Akinori Kondo, Koichi Iwasaki, Hirofumi Kusaka, Hidefumi Ito, and Shinji Sawada

✓ A case of chordoid meningioma occurring in a 15-year-old girl is presented. The patient manifested seizures as the initial symptom and subsequently exhibited subclinical microcytic hypochromic anemia. The tumor, located in the falcotentorial region and associated with diffuse edema, was totally resected. On histological examination of the surgical specimen, the clustering pattern of partly vacuolated cells in the mucoid stroma mimicked chordoma; however, positive staining of individual cells for vimentin and epithelial membrane antigen led to a diagnosis of meningioma. Interestingly, the tumor cells were surrounded by a periodic acid—Schiff— and type IV collagen—positive substance. Electron microscopy demonstrated a strikingly dense and thick basal lamina. The patient's microcytic hypochromic anemia disappeared after the tumor was removed. Both the clinical and pathological features of this case resemble those of chordoid meningioma, a rare meningioma variant.

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Hiroki Toda, Koichi Iwasaki, Naoya Yoshimoto, Yoshihito Miki, Hirokuni Hashikata, Masanori Goto, and Namiko Nishida


In microvascular decompression surgery for trigeminal neuralgia and hemifacial spasm, the bridging veins are dissected to provide the surgical corridors, and the veins of the brainstem may be mobilized in cases of venous compression. Strategy and technique in dissecting these veins may affect the surgical outcome. The authors investigated solutions for minimizing venous complications and reviewed the outcome for venous decompression.


The authors retrospectively reviewed their surgical series of microvascular decompression for trigeminal neuralgia and hemifacial spasm in patients treated between 2005 and 2017. Surgical strategies included preservation of the superior petrosal vein and its tributaries, thorough dissection of the arachnoid sleeve that enveloped these veins, cutting of the inferior petrosal vein over the lower cranial nerves, and mobilization or cutting of the veins of the brainstem that compressed the nerve roots. The authors summarized the patient characteristics, operative findings, and postoperative outcomes according to the vascular compression types as follows: artery alone, artery and vein, and vein alone. They analyzed the data using chi-square and 1-way ANOVA tests.


The cohort was composed of 121 patients with trigeminal neuralgia and 205 patients with hemifacial spasm. The superior petrosal vein and its tributaries were preserved with no serious complications in all patients with trigeminal neuralgia. Venous compression alone and arterial and venous compressions were observed in 4% and 22%, respectively, of the patients with trigeminal neuralgia, and in 1% and 2%, respectively, of those with hemifacial spasm (p < 0.0001). In patients with trigeminal neuralgia, 35% of those with artery and venous compressions and 80% of those with venous compression alone had atypical neuralgia (p = 0.015). The surgical cure and recurrence rates of trigeminal neuralgias with venous compression were 60% and 20%, respectively, and with arterial and venous compressions the rates were 92% and 12%, respectively (p < 0.0001, p = 0.04). In patients with hemifacial spasm who had arterial and venous compressions, their recurrence rate was 60%, and that was significantly higher compared to other compression types (p = 0.0008).


Dissection of the arachnoid sleeve that envelops the superior petrosal vein may help to reduce venous complications in surgery for trigeminal neuralgia. Venous compression may correlate with worse prognosis even with thorough decompression, in both trigeminal neuralgia and hemifacial spasm.

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Hitoshi Fukuda, Alexander I. Evins, Koichi Iwasaki, Itaro Hattori, Kenichi Murao, Yoshitaka Kurosaki, Masaki Chin, Philip E. Stieg, Sen Yamagata, and Antonio Bernardo


Occipital artery–posterior inferior cerebellar artery (OA-PICA) bypass is a technically challenging procedure for posterior fossa revascularization. The caudal loop of the PICA is considered the optimal site for OA-PICA anastomosis, however its absence can increase the technical difficulty associated with this procedure. The use of the far-lateral approach for accessing alternative anastomosis sites in OA-PICA bypass in patients with absent or unavailable caudal loops of PICA is evaluated.


A morphometric analysis of OA-PICA bypass with anastomosis on each segment of the PICA was performed on 5 cadaveric specimens through the conventional midline foramen magnum and far-lateral approaches. The difficulty level associated with anastomoses at each segment was qualitatively assessed in each approach for exposure and maneuverability by multiple surgeons. A series of 8 patients who underwent OA-PICA bypass for hemodynamic ischemia or ruptured dissecting posterior fossa aneurysms are additionally reviewed and described, and the clinical significance of the caudal loop of PICA is discussed.


Anastomosis on the caudal loop could be performed more superficially than on any other segment (p < 0.001). A far-lateral approach up to the medial border of the posterior condylar canal provided a 13.5 ± 2.2–mm wider corridor than the conventional midline foramen magnum approach, facilitating access to alternative anastomosis sites. The far-lateral approach was successfully used for OA-PICA bypass in 3 clinical cases whose caudal loops were absent, whereas the midline foramen magnum approach provided sufficient exposure for caudal loop bypass in the remaining 5 cases.


The absence of the caudal loop of the PICA is a major contributing factor to the technical difficulty of OA-PICA bypass. The far-lateral approach is a useful surgical option for OA-PICA bypass when the caudal loop of the PICA is unavailable.

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Yasuchika Aoki, Masatsune Yamagata, Fumitake Nakajima, Yoshikazu Ikeda, Koh Shimizu, Masakazu Yoshihara, Junichi Iwasaki, Tomoaki Toyone, Koichi Nakagawa, Arata Nakajima, Kazuhisa Takahashi, and Seiji Ohtori


Because the authors encountered 4 cases of hardware migration following transforaminal lumbar interbody fusion, a retrospective study was conducted to identify factors influencing the posterior migration of fusion cages.


Patients with lumbar degenerative disc disease (125 individuals; 144 disc levels) were treated using transforaminal lumbar interbody fusion and followed for 12–33 months. Medical records and pre- and postoperative radiographs were reviewed, and factors influencing the incidence of cage migration were analyzed.


Postoperative cage migration was found in 4 patients at or before 3 months. Because all the cages that migrated postoperatively were bullet-shaped (Capstone), only these cages were analyzed. The analysis of preoperative radiographs revealed that higher posterior disc height ([PDH] ≥ 6 mm) significantly increased the incidence of postoperative cage migration, but percent slippage, translation, range of motion, and Cobb angle did not. The incidence of cage migration in patients with unilateral fixation (3 [8.3%] of 36) was not significantly different from that in patients with bilateral fixation (1 [2.1%] of 48). Patients who had scoliotic curvature with a Cobb angle > 10° when treated with unilateral fixation demonstrated a tendency to have more frequent postoperative cage migration than patients treated with bilateral fixation.

To examine the influence of the height of fusion cages, a value obtained by subtracting preoperative anterior disc height (ADH) or PDH from cage height was defined as “Cage height – ADH” (or “Cage height –PDH”). The analysis revealed that the value for “Cage height –ADH” as well as “Cage height –PDH” was significantly lower in migrated levels than in nonmigrated levels, suggesting that the choice of undersized cages may increase the incidence of cage migration.


The results suggest that the use of a bullet-shaped cage, higher PDH, the presence of scoliotic curvature, and undersized fusion cages are possible risk factors for cage migration. One patient with postoperative cage migration following bilateral screw fixation underwent revision surgery, and the pedicle screw fixation was found to be disrupted. Other than in this patient, cage migration occurred only in those treated by unilateral fixation. The potential for postoperative cage migration and limitations of unilateral fixation should be considered by spine surgeons.