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Takeshi Oichi, Yasushi Oshima, Hiroyuki Oka, Yuki Taniguchi, Hirotaka Chikuda, Yoshitaka Matsubayashi, Katsushi Takeshita and Sakae Tanaka

OBJECTIVE

Several investigators have reported the occurrence of interlaminar bony fusion after cervical laminoplasty, which is reportedly associated with reduced postoperative cervical range of motion (ROM). However, to the authors’ knowledge, no previous study has investigated the characteristics of patients who were likely to develop interlaminar bony fusion after cervical laminoplasty. Therefore, the objective of this study was to investigate the risk factors for interlaminar bony fusion in patients with cervical spondylotic myelopathy (CSM) following cervical laminoplasty and to investigate the effect of interlaminar bony fusion on surgical outcomes.

METHODS

The authors retrospectively reviewed data from 92 patients with CSM (63 men and 29 women) after cervical laminoplasty. The presence of interlaminar bony fusion was evaluated by functional radiographs 2 years after surgery. The patients were divided into 2 groups according to the presence of postoperative interlaminar bony fusion: a fusion group (at least 1 new postoperative interlaminar bony fusion) and a nonfusion group (no new interlaminar bony fusion). Potential risk factors for postoperative interlaminar bony fusion were assessed, including diabetes mellitus, smoking status, whether the C-2 lamina was included in the surgical treatment, C2–7 Cobb angle in each cervical position, preoperative cervical ROM, and T-1 slope. The differences in each variable were compared between the fusion and nonfusion groups. Thereafter, multivariate logistic regression analysis was performed to identify the risk factors for postoperative interlaminar bony fusion. For surgical outcomes, the recovery rate based on Japanese Orthopaedic Association scores and the reduction rate of cervical ROM were evaluated 2 years after surgery.

RESULTS

Interlaminar bony fusion was observed in 60 cases, 52 of which were observed at the C2–3 level. Patients in the fusion group were significantly older, had a significantly larger C2–7 angle in flexion, and had a significantly lower preoperative cervical ROM than those in the nonfusion group. A high T-1 slope was significantly more frequent in the fusion group. Multivariate analysis revealed that the significant risk factors for postoperative interlaminar bony fusion were high T-1 slope (odds ratio 4.81; p = 0.0015) and older age (odds ratio 1.05; p = 0.025). The Japanese Orthopaedic Association recovery rate in patients with interlaminar bony fusion did not differ significantly from those without bony fusion (45% vs 48%; p = 0.73). However, patients with bony fusion showed significantly reduced postoperative cervical ROM compared with those without bony fusion (50% vs 25%; p < 0.001).

CONCLUSIONS

High T-1 slope and older age were significant risk factors for developing interlaminar bony fusion after cervical laminoplasty in patients with CSM. Interlaminar bony fusion was associated with reduced postoperative cervical ROM, but it did not affect neurological outcomes.

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Takeshi Oichi, Hirotaka Chikuda, Teppei Morikawa, Harushi Mori, Daisuke Kitamura, Junya Higuchi, Yuki Taniguchi, Yoshitaka Matsubayashi, Yasushi Oshima and Sakae Tanaka

Dumbbell-shaped tumors consisting of 2 different tumors are extremely rare. Herein, the authors present a case of concurrent spinal schwannoma and meningioma mimicking a single cervical dumbbell-shaped tumor. A 64-year-old man presented with a 5-year history of gradually exacerbating left occipital pain without clinical evidence of neurofibromatosis. Magnetic resonance imaging showed an extradural tumor along the left C-2 nerve root with a small intradural component. The tumor was approached via a C-1 hemilaminectomy. The intradural tumor was resected together with the extradural tumor after opening the dura mater. The intradural tumor was attached to the dura mater around the exit point of the C-2 nerve root. Intraoperative biopsy revealed that the extradural tumor was a schwannoma and that the intradural tumor was a meningioma. The dura mater adjacent to the tumor was then coagulated and resected. Postoperative pathological examination confirmed the same diagnoses with no evidence of continuity between the intra- and extradural components. The patient’s postoperative clinical course was uneventful. Clinicians should be aware that cervical dumbbell-shaped tumors can consist of 2 different tumors.

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Kazuyoshi Nakanishi, Nobuhiro Tanaka, Naosuke Kamei, Toshio Nakamae, Bun-ichiro Izumi, Ryo Ohta, Yuki Fujioka and Mitsuo Ochi

Object

The pathophysiology of occult tethered cord syndrome (OTCS) with no anatomical evidence of a caudally shifted conus and a normal terminal filum is hard to understand. Therefore, the diagnosis of OTCS is often difficult. The authors hypothesized that the posterior displacement of the terminal filum may become prominent in patients with OCTS who are in a prone position if filum inelasticity exists, and they investigated prone-position MRI findings.

Methods

Fourteen patients with OTCS and 12 control individuals were examined using T2-weighted axial MRI with the patients in a prone position on a flat table. On each axial view, the distance between the posterior and anterior ends of the subarachnoid space (A), the distance between the posterior end of the subarachnoid space and the terminal filum (B), the distance between the posterior end of the subarachnoid space and the dorsal-most nerve among the cauda equina (C), and the distance between the posterior end of the subarachnoid space and the ventral-most nerve (D) were measured. The location ratios of the terminal filum, the dorsal-most nerve, and the ventral-most nerve were calculated by the ratio of A to B (defined as TF = B/A), A to C (defined as DN = C/A), and A to D (defined as VN = D/A), respectively. Patients underwent sectioning of the terminal filum with the aid of a surgical microscope. The low-back pain Japanese Orthopaedic Association score was obtained before surgery and at the final follow-up visit.

Results

On prone-position axial MRI, the terminal filum was separated from the cauda equina and was shifted caudally to posterior in the subarachnoid space in all patients with OTCS. The locations of the caudal cauda equina shifted to ventral in the subarachnoid space. The TF values in the OTCS group were significantly lower than those in the control group at the L3–4 (p = 0.023), L-4 (p = 0.030), L4–5 (p = 0.002), and L-5 (p < 0.001) levels. In contrast, the DN values in the OTCS group were significantly higher than those of the control group at the L-2 (p = 0.003), L2–3 (p = 0.002), L-3 (p < 0.001), L3–4 (p < 0.001), L-4 (p = 0.007), L4–5 (p = 0.003), and S-1 (p = 0.014) levels, and the VN values in the OTCS group were also significantly higher than those of the control group at the L2–3 (p = 0.022), L-3 (p = 0.027), L3–4 (p = 0.002), L-4 (p = 0.011), L4–5 (p = 0.019), and L5–S1 (p = 0.040) levels. Sections were collected during surgery for histological evaluation, and a decreased elasticity within the terminal filum was suggested. Improvements in the Japanese Orthopaedic Association score were observed at the final follow-up in all patients.

Conclusions

The authors' new method of using the prone position for MRI shows that the terminal filum is located significantly posterior and the cauda equina is located anterior in patients with OTCS, suggesting a difference in elasticity between the terminal filum and cauda equina.

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Toru Doi, Hideki Nakamoto, Koji Nakajima, Shima Hirai, Yusuke Sato, So Kato, Yuki Taniguchi, Yoshitaka Matsubayashi, Ko Matsudaira, Katsushi Takeshita, Sakae Tanaka and Yasushi Oshima

OBJECTIVE

Preoperative mood disorders such as depression and anxiety are known to be associated with poor health-related quality of life (HRQOL) outcomes after lumbar spine surgery. However, the effects of preoperative depression and anxiety on postoperative HRQOL outcomes and patient satisfaction in cervical compressive myelopathy are yet to be clarified. This study aimed to investigate the effect of depression and anxiety on HRQOL outcomes and patient satisfaction following surgery for cervical compressive myelopathy.

METHODS

The authors reviewed the cases of all consecutive patients with cervical compressive myelopathy who had undergone surgical treatment in the period between January 2012 and March 2017 at their institution. Using the Hospital Anxiety and Depression Scale (HADS), the authors classified patients as depressed (HADS-D+) or not depressed (HADS-D−) and anxious (HADS-A+) or not anxious (HADS-A−). Patient HRQOL was evaluated preoperatively and at the end of at least 1 year after surgery using the physical and mental component summaries of the SF-12 Health Survey, EQ-5D (EuroQol health survey of five dimensions), Neck Disability Index, and Japanese Orthopaedic Association scale. Patient satisfaction was evaluated on the basis of a seven-item questionnaire and divided into two categories: satisfied and dissatisfied. Preoperative HRQOL statuses, postoperative improvements in HRQOL outcomes, and patient satisfaction were compared between the groups.

RESULTS

Among the 121 patients eligible for inclusion in the study, there were 69 patients (57.0%) without depression (HADS-D−) and 52 (43.0%) with depression (HADS-D+) and 82 patients (67.8%) without anxiety (HADS-A−) and 39 (32.2%) with anxiety (HADS-A+). All patients who completed both the preoperative and postoperative questionnaires had significant postoperative improvements in all HRQOL outcomes. The HADS-D+ and HADS-A+ patients had poorer preoperative HRQOL statuses than the HADS-D− and HADS-A− patients, respectively. However, statistically significant improvements in all HRQOL outcomes were observed in both HADS-D+ and HADS-A+ patients. Patient satisfaction was comparable between the HADS-D or HADS-A groups.

CONCLUSIONS

Cervical compressive myelopathy patients with preoperative depression or anxiety according to the HADS tool had worse preoperative HRQOL statuses. However, patients with cervical compressive myelopathy showed significant improvements in HRQOL outcomes and had sufficient levels of satisfaction after surgery regardless of the presence of preoperative depression or anxiety.

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Kazuyoshi Nakanishi, Nobuhiro Tanaka, Naosuke Kamei, Ryo Ohta, Yuki Fujioka, Takeshi Hiramatsu, Satoshi Ujigo and Mitsuo Ochi

Object

Cervical laminoplasty is a surgical procedure for cervical compressive myelopathy (CCM), and satisfactory outcomes have been reported. However, few reports have examined the pathophysiology of improvements in spinal cord function. The aim of this study was to investigate the variation in central motor conduction time (CMCT) before and after cervical laminoplasty in patients with CCM.

Methods

Motor evoked potentials (MEPs) following transcranial magnetic stimulation and compound muscle action potentials (CMAPs) and F-waves following electrical stimulation of the ulnar and tibial nerves at the wrist and ankle were measured from the abductor digiti minimi muscle (ADM) and abductor hallucis muscle (AH) in 42 patients with CCM before and 1 year after cervical laminoplasty. The peripheral conduction time (PCT) was calculated as follows: (latency of CMAPs + latency of F-waves − 1)/2. The CMCT was calculated by subtracting the PCT from the onset latency of the MEPs. The CMCT recovery ratio was defined and calculated as the ratio of CMCT values 1 year after surgery to those before surgery. The CMCT data were analyzed as longer or shorter CMCT between the patients' right and left ADMs and AHs. The Japanese Orthopaedic Association (JOA) score for cervical myelopathy was obtained as a clinical outcome before and 1 year after surgery. The recovery rate (RR) 1 year after surgery was calculated using the following formula: (postoperative JOA score 1 year after surgery – preoperative JOA score)/(17 – preoperative JOA score) × 100. Correlations among CMCT parameters, patient age, JOA score, and RR were determined.

Results

The longer and shorter CMCTs from the ADM (longer, p = 0.000; shorter, p = 0.008) and the longer CMCT from the AH (longer, p = 0.000) before surgery decreased significantly 1 year after surgery; the shorter CMCT from the AH did not significantly differ (shorter, p = 0.078). The mean JOA score before surgery was 10.1 ± 3.0 and improved significantly to 12.9 ± 2.7 at 1 year after surgery (p = 0.000). The mean CMCT recovery ratio and RR were 0.91 ± 0.18 and 0.43 ± 0.27, respectively. The longer/shorter CMCT parameters in the ADM and AH before or 1 year after surgery correlated significantly with the JOA score both before and 1 year after surgery. The CMCT recovery ratio from the longer CMCT in the ADM correlated significantly with the RR (r = − 3090, p = 0.011). There were no significant correlations between age and any CMCT parameters or CMCT recovery ratios.

Conclusions

These results suggest that cervical laminoplasty improves corticospinal tract function 1 year after surgery, which may be one of the reasons for the JOA score improvements in patients with CCM. The degree of improvement in corticospinal tract function did not correlate with patient age in this case series. The results demonstrated quantitative evidence of the pathophysiology of functional recovery in the corticospinal tract following cervical laminoplasty in patients with CCM.

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Daiki Uchida, Yuki Amano, Hirokazu Nakatogawa, Takayuki Masui, Naoto Ando, Teiji Nakayama, Haruhiko Sato, Tetsuro Sameshima and Tokutaro Tanaka

OBJECTIVE

Adjustable shunt valves that have been developed for the management of hydrocephalus all rely on intrinsically magnetic components, and artifacts with these valves on MRI are thus inevitable. The authors have previously reported that the shapes of shunt artifacts differ under different valve pressures with the proGAV 2.0 valve. In the present study the authors compared the size and shape of artifacts at different pressure settings with 4 new-model shunt valves.

METHODS

The authors attached 4 new models of MRI-resistant shunt valve to the temporal scalp of a healthy volunteer: the proGAV 2.0; Codman Certas Plus; Polaris; and Strata MR. They set 3 different scales of pressures for each valve, depending on magnet orientation to the body axis. Artifacts were evaluated and compared among all valves on a 3.0-T GE scanner and 2 valves were also evaluated on a Philips scanner and a Siemens scanner. In-plane artifact sizes were evaluated as the maximum distance of the artifact from the expected scalp.

RESULTS

The sizes and shapes of artifacts changed depending on valve pressure for all valves on the 3 different MRI scanners. Artifacts were less prominent on spin echo sequences than on gradient echo sequences. For diffusion-weighted imaging and time-of-flight MR angiography, the authors matched image numbers within the same sequence and compared appearances of artifacts. For all valves, the number of images affected by artifacts and the image number showing the largest artifact differed among valve settings.

CONCLUSIONS

Artifacts of all adjustable shunt valves showed gross changes corresponding to pressure setting. Not only the maximum distance of artifacts but also the shape changed significantly. The authors suggest that changing pressure settings offers one of the easiest ways to minimize artifacts on MRI.

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Daiki Uchida, Yuki Amano, Hirokazu Nakatogawa, Takayuki Masui, Naoto Ando, Teiji Nakayama, Haruhiko Sato, Tetsuro Sameshima and Tokutaro Tanaka

OBJECTIVE

Adjustable shunt valves that have been developed for the management of hydrocephalus all rely on intrinsically magnetic components, and artifacts with these valves on MRI are thus inevitable. The authors have previously reported that the shapes of shunt artifacts differ under different valve pressures with the proGAV 2.0 valve. In the present study the authors compared the size and shape of artifacts at different pressure settings with 4 new-model shunt valves.

METHODS

The authors attached 4 new models of MRI-resistant shunt valve to the temporal scalp of a healthy volunteer: the proGAV 2.0; Codman Certas Plus; Polaris; and Strata MR. They set 3 different scales of pressures for each valve, depending on magnet orientation to the body axis. Artifacts were evaluated and compared among all valves on a 3.0-T GE scanner and 2 valves were also evaluated on a Philips scanner and a Siemens scanner. In-plane artifact sizes were evaluated as the maximum distance of the artifact from the expected scalp.

RESULTS

The sizes and shapes of artifacts changed depending on valve pressure for all valves on the 3 different MRI scanners. Artifacts were less prominent on spin echo sequences than on gradient echo sequences. For diffusion-weighted imaging and time-of-flight MR angiography, the authors matched image numbers within the same sequence and compared appearances of artifacts. For all valves, the number of images affected by artifacts and the image number showing the largest artifact differed among valve settings.

CONCLUSIONS

Artifacts of all adjustable shunt valves showed gross changes corresponding to pressure setting. Not only the maximum distance of artifacts but also the shape changed significantly. The authors suggest that changing pressure settings offers one of the easiest ways to minimize artifacts on MRI.

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Toru Doi, Ryuji Sakamoto, Chiaki Horii, Naoki Okamoto, Koji Nakajima, Shima Hirai, Fumihiko Oguchi, So Kato, Yuki Taniguchi, Yoshitaka Matsubayashi, Naoto Hayashi, Sakae Tanaka and Yasushi Oshima

OBJECTIVE

The incidence and risk factors for the progression of ossification of the posterior longitudinal ligament (OPLL) have been previously reported in surgically and nonsurgically treated symptomatic patients. However, the correlates of OPLL progression in asymptomatic subjects with OPLL are not well characterized. This study aimed to clarify the incidence and risk factors for OPLL progression in asymptomatic subjects based on whole-body CT.

METHODS

The authors retrospectively reviewed 2585 healthy subjects who underwent whole-body CT at a single health center from September 2007 to December 2011. This study included asymptomatic subjects with OPLL who underwent CT scans twice with an interval of at least 5 years. Progression of OPLL was assessed based on initial and final CT scan. Subjects were divided into two groups: nonprogression (OPLL-NP) and progression (OPLL-P) groups. Clinical characteristics, bone mineral density status, OPLL types, and OPLL involvement of multiple vertebral levels between the two groups were compared. Risk factors for progression of OPLL were identified by logistic regression analysis after propensity score adjustment.

RESULTS

Of the 109 subjects with OPLL (91 men and 18 women), 20 (18.3%) exhibited OPLL progression (OPLL-P group). Subjects in the OPLL-P group were significantly younger (p = 0.031), had higher prevalence of multilevel OPLL involvement (p = 0.041) and continuous type of OPLL (p = 0.015), and had higher uric acid (UA) levels (p = 0.004) at the time of initial CT examination compared to the OPLL-NP group. Younger age (adjusted odds ratio [aOR] 0.95, 95% CI 0.90–0.99), OPLL involvement of multiple vertebral levels (aOR 2.88, 95% CI 1.06–7.83), continuous type of OPLL (aOR 4.21, 95% CI 1.35–13.10), and higher UA levels (aOR 2.09, 95% CI 1.24–3.53) were significant risk factors for OPLL progression.

CONCLUSIONS

Younger age, OPLL involvement of multiple vertebral levels, continuous type of OPLL, and higher UA levels are significant risk factors for OPLL progression in asymptomatic subjects.

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Keisuke Takai, Toshiki Endo, Takao Yasuhara, Toshitaka Seki, Kei Watanabe, Yuki Tanaka, Ryu Kurokawa, Hideaki Kanaya, Fumiaki Honda, Takashi Itabashi, Osamu Ishikawa, Hidetoshi Murata, Takahiro Tanaka, Yusuke Nishimura, Kaoru Eguchi, Toshihiro Takami, Yusuke Watanabe, Takeo Nishida, Masafumi Hiramatsu, Tatsuya Ohtonari, Satoshi Yamaguchi, Takafumi Mitsuhara, Seishi Matsui, Hisaaki Uchikado, Gohsuke Hattori, Nobutaka Horie, Hitoshi Yamahata and Makoto Taniguchi

OBJECTIVE

Spinal arteriovenous shunts are rare vascular lesions and are classified into 4 types (types I–IV). Due to rapid advances in neuroimaging, spinal epidural AVFs (edAVFs), which are similar to type I spinal dural AVFs (dAVFs), have recently been increasingly reported. These 2 entities have several important differences that influence the treatment strategy selected. The purposes of the present study were to compare angiographic and clinical differences between edAVFs and dAVFs and to provide treatment strategies for edAVFs based on a multicenter cohort.

METHODS

A total of 280 consecutive patients with thoracic and lumbosacral spinal dural arteriovenous fistulas (dAVFs) and edAVFs with intradural venous drainage were collected from 19 centers. After angiographic and clinical comparisons, the treatment failure rate by procedure, risk factors for treatment failure, and neurological outcomes were statistically analyzed in edAVF cases.

RESULTS

Final diagnoses after an angiographic review included 199 dAVFs and 81 edAVFs. At individual centers, 29 patients (36%) with edAVFs were misdiagnosed with dAVFs. Spinal edAVFs were commonly fed by multiple feeding arteries (54%) shunted into a single or multiple intradural vein(s) (91% and 9%) through a dilated epidural venous plexus. Preoperative modified Rankin Scale (mRS) and Aminoff-Logue gait and micturition grades were worse in patients with edAVFs than in those with dAVFs. Among the microsurgical (n = 42), endovascular (n = 36), and combined (n = 3) treatment groups of edAVFs, the treatment failure rate was significantly higher in the index endovascular treatment group (7.5%, 31%, and 0%, respectively). Endovascular treatment was found to be associated with significantly higher odds of initial treatment failure (OR 5.72, 95% CI 1.45–22.6). In edAVFs, the independent risk factor for treatment failure after microsurgery was the number of intradural draining veins (OR 17.9, 95% CI 1.56–207), while that for treatment failure after the endovascular treatment was the number of feeders (OR 4.11, 95% CI 1.23–13.8). Postoperatively, mRS score and Aminoff-Logue gait and micturition grades significantly improved in edAVFs with a median follow-up of 31 months.

CONCLUSIONS

Spinal epidural AVFs with intradural venous drainage are a distinct entity and may be classified as type V spinal vascular malformations. Based on the largest multicenter cohort, this study showed that primary microsurgery was superior to endovascular treatment for initial treatment success in patients with spinal edAVFs.