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  • Author or Editor: Naoki Ishiguro x
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Yukihiro Matsuyama, Yoshihito Sakai, Yoshito Katayama, Shiro Imagama, Zenya Ito, Norimitsu Wakao, Koji Sato, Mitsuhiro Kamiya, Yasutsugu Yukawa, Tokumi Kanemura, Makoto Yanase and Naoki Ishiguro

Object

The authors investigated the outcome of intramedullary spinal cord tumor surgery, focusing on the effect of preoperative neurological status on postoperative mobility and the extent of tumor excision guided by intraoperative spinal cord monitoring prospectively.

Methods

Intramedullary spinal cord tumor surgery was performed in 131 patients between 1997 and 2007. The authors compared the pre- and postoperative neurological status and examined the type of surgery in 106 of these patients. A modified McCormick Scale (Grades I–V) was used to assess ambulatory ability (I = normal ambulation; II = mild motor sensory deficit, independent without external aid; III = independent with external aid; IV = care required; and V = wheelchair required). The type of surgery was classified into 4 levels: total resection, subtotal resection, partial resection, and biopsy.

Results

The 106 patients consisted of 47 females and 59 males, whose average age was 42.5 years (range 6–75 years). The mean follow-up period was 7.3 years (range 2.5 months–21 years). The tumor types included astrocytoma (12 cases), ependymoma (46 cases), hemangioblastoma (16 cases), cavernous hemangioma (17 cases), and others (15 cases overall: gangliocytoma, 1; germ cell tumor, 1; lymphoma, 3; neurinoma, 1; meningioma, 1; oligodendroglioma, 1; sarcoidosis, 2; glioma, 1; and unknown, 4). Initial total excision, subtotal resection, partial resection, biopsy, and duraplasty were performed in 59, 12, 22, 12, and 1 patients, respectively. According to the preoperative McCormick Scale, ambulatory status was classified as Grades I, II, III, IV, and V in 41(38%), 30 (28%), 14 (13%), 19 (19%), and 2 (2%) patients, respectively. Thirty-three (31%) of 106 patients suffered postoperative neurological deterioration. The number of patients who did not lose ambulatory ability or who achieved an ambulatory status of Grade I or II postoperatively was 33 (80%), 21 (70%), 10 (71%), 8 (42%), and 1 (50%) in patients with preoperative Grades I, II, III, IV, and V, respectively. Total excision was performed in 31 (79%) of 39 patients with preoperative Grade I, 12 (40%) of 30 patients with Grade II, 7 (50%) of 14 patients with Grade III, and 9 of 21 patients (38%) with Grade IV or V, indicating that the rate of total excision was significantly higher in patients with Grade I status.

Conclusions

The postoperative ambulatory ability was excellent in patients with a good preoperative neurological status. Total excision in patients with Grade I or II ambulation was associated with a good prognosis for postoperative mobility. However, the rate of postoperative deterioration was 31.5%, which is relatively high, and patients should be fully informed of this concern prior to intramedullary spinal cord tumor surgery.

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Shiro Imagama, Yukihiro Matsuyama, Yoshihito Sakai, Hiroshi Nakamura, Yoshito Katayama, Zenya Ito, Norimitsu Wakao, Koji Sato, Mitsuhiro Kamiya, Fumihiko Kato, Yasutsugu Yukawa, Yasushi Miura, Hisatake Yoshihara, Kazuhiro Suzuki, Kei Ando, Kenichi Hirano, Ryoji Tauchi, Akio Muramoto and Naoki Ishiguro

Object

The purpose of this study was to provide the first evidence for image classification of idiopathic spinal cord herniation (ISCH) in a multicenter study.

Methods

Twelve patients who underwent surgery for ISCH were identified, and preoperative symptoms, severity of paralysis and myelopathy, disease duration, plain radiographs, MR imaging and CT myelography findings, surgical procedure, intraoperative findings, data from spinal cord monitoring, and postoperative recovery were investigated in these patients. Findings on sagittal MR imaging and CT myelography were classified into 3 types: a kink type (Type K), a discontinuous type (Type D), and a protrusion type (Type P). Using axial images, the location of the hiatus was classified as either central (Type C) or lateral (Type L), and the laterality of the herniated spinal cord was classified based on correspondence (same; Type S) or noncorrespondence (opposite; Type O) with the hiatus location. A bone defect at the ISCH site and the laterality of the defect were also noted.

Results

Patients with Type P herniation had a good postoperative recovery, and those with a Type C location had significant severe preoperative lower-extremity paralysis and a significantly poor postoperative recovery. Patients with a bone defect had a significantly severe preoperative myelopathy, but showed no difference in postoperative recovery.

Conclusions

The authors' results showed that a Type C classification and a bone defect have strong relationships with severity of symptoms and surgical outcome and are important imaging and clinical features for ISCH. These findings may allow surgeons to determine the severity of preoperative symptoms and the probable surgical outcome from imaging.

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Kei Ando, Shiro Imagama, Norimitsu Wakao, Kenichi Hirano, Ryoji Tauchi, Akio Muramoto, Fumihiko Kato, Yasutsugu Yukawa, Noriaki Kawakami, Koji Sato, Yuji Matsubara, Tokumi Kanemura, Yukihiro Matsuyama and Naoki Ishiguro

Object

The purpose of this study was to provide the first evidence for the influence of an ossified anterior longitudinal ligament (OALL) on the clinical features and surgical outcomes in an ossified ligamentum flavum (OLF) in the thoracic region.

Methods

Sixty-three patients who underwent surgery for a 1-level thoracic OLF were identified, and preoperative symptoms, severity of symptoms and myelopathy, disease duration, MR imaging and CT findings, surgical procedure, intraoperative findings, complications, and postoperative recovery were investigated in these patients. Entities of OALLs were found on sagittal CT images to be adjacent to or at the same vertebral level as the OLF were classified into 4 types: no discernible type (Type N), one-sided (Type O), discontinuous (Type D), and continuous (Type C).

Results

The duration of symptoms was especially long for Types D and C OALLs. Patients with Type D OALLs had a significantly worse percentage of recovery, as well as worse preoperative JOA scores.

Conclusions

The authors' results showed that a Type D OALL had strong associations with preoperative severity of symptoms and surgical outcomes. These findings may allow surgeons to determine the severity of preoperative symptoms and the probable surgical outcomes from the OALL classifications. Moreover, surgery with instrumentation for Type D OALLs may produce better surgical outcomes.

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Hiroaki Nakashima, Yasutsugu Yukawa, Shiro Imagama, Tokumi Kanemura, Mitsuhiro Kamiya, Makoto Yanase, Keigo Ito, Masaaki Machino, Go Yoshida, Yoshimoto Ishikawa, Yukihiro Matsuyama, Naoki Ishiguro and Fumihiko Kato

Object

The cervical pedicle screw (PS) provides strong stabilization but poses a potential risk to the neurovascular system, which may be catastrophic. In particular, vertebrae with degenerative changes complicate the process of screw insertion, and PS misplacement and subsequent complications are more frequent. The purpose of this study was to evaluate the peri- and postoperative complications of PS fixation for nontraumatic lesions and to determine the risk factors of each complication.

Methods

Eighty-four patients who underwent cervical PS fixation for nontraumatic lesions were independently reviewed to identify associated complications. The mean age of the patients was 60.1 years, and the mean follow-up period was 4.1 years (range 6–168 months). Pedicle screw malpositioning was classified on postoperative CT scans as Grade I (< 50% of the screw outside the pedicle) or Grade II (≥ 50% of the screw outside the pedicle). Risk factors of each complication were evaluated using a multivariate analysis.

Results

Three hundred ninety cervical PSs and 24 lateral mass screws were inserted. The incidence of PS misplacement was 19.5% (76 screws); in terms of malpositioning, 60 screws (15.4%) were classified as Grade I and 16 (4.1%) as Grade II. In total, 33 complications were observed. These included postoperative neurological complications in 11 patients in whom there was no evidence of screw misplacement (C-5 palsy in 10 and C-7 palsy in 1), implant failure in 11 patients (screw loosening in 5, broken screws in 4, and loss of reduction in 2), complications directly attributable to screw insertion in 5 patients (nerve root injury by PS in 3 and vertebral artery injury in 2), and other complications in 6 patients (pseudarthrosis in 2, infection in 1, transient dyspnea in 1, transient dysphagia in 1, and adjacent-segment degeneration in 1). The multivariate analysis showed that a primary diagnosis of cerebral palsy was a risk factor for postoperative implant failure (HR 10.91, p = 0.03) and that the presence of preoperative cervical spinal instability was a risk factor for both Grade I and Grade II screw misplacement (RR 2.12, p = 0.03), while there were no statistically significant risk factors for postoperative neurological complications in the absence of evidence of screw misplacement or complications directly attributable to screw insertion.

Conclusions

In the present study, misplacement of cervical PSs and associated complications occurred more often than in previous studies. The rates of screw-related neurovascular complications and neurological deterioration unrelated to PSs were high. Insertion of a PS for nontraumatic lesions is surgically more challenging than that for trauma; consequently, experienced surgeons should use PS fixation for nontraumatic cervical lesions only after thorough preoperative evaluation of each patient's cervical anatomy and after considering the risk factors specified in the present study.

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Hiroaki Nakashima, Shiro Imagama, Yasutsugu Yukawa, Tokumi Kanemura, Mitsuhiro Kamiya, Makoto Yanase, Keigo Ito, Masaaki Machino, Go Yoshida, Yoshimoto Ishikawa, Yukihiro Matsuyama, Nobuyuki Hamajima, Naoki Ishiguro and Fumihiko Kato

Object

Postoperative C-5 palsy is a significant complication resulting from cervical decompression procedures. Moreover, when cervical degenerative diseases are treated with a combination of decompression and posterior instrumented fusion, patients are at increased risk for C-5 palsy. However, the clinical and radiological features of this condition remain unclear. Therefore, the purpose of this study was to clarify the risk factors for developing postoperative C-5 palsy.

Methods

Eighty-four patients (mean age 60.1 years) who had undergone posterior instrumented fusion using cervical pedicle screws to treat nontraumatic lesions were independently reviewed. The authors analyzed the medical records of some of these patients who developed postoperative C-5 palsy, paying particular attention to their plain radiographs, MRI studies, and CT scans. Risk factors for postoperative C-5 palsy were assessed using multivariate logistic regression analysis. The cutoff values for the pre- and postoperative width of the intervertebral foramen (C4–5) were determined by receiver operating characteristic curve analysis.

Results

Ten (11.9%) of 84 patients developed postoperative C-5 palsy. Seven patients recovered fully from the neurological complications. The pre- and postoperative C4–5 angles showed significant kyphosis in the C-5 palsy group. The pre- and postoperative diameters of the C4–5 foramen on the palsy side were significantly smaller than those on the opposite side in the C-5 palsy group and those bilaterally in the non–C5 palsy group. Risk factors identified by multivariate logistic regression analysis were as follows: 1) ossification of the posterior longitudinal ligament (relative risk [RR] 7.22 [95% CI 1.03–50.55]); 2) posterior shift of the spinal cord (C4–5) (RR 1.73 [95% CI 1.00–2.98]); and 3) postoperative width of the C-5 intervertebral foramen (RR 0.33 [95% CI 0.14–0.79]). The cutoff values of the pre- and postoperative widths of the C-5 intervertebral foramen for C-5 palsy were 2.2 and 2.3 mm, respectively.

Conclusions

Patients with preoperative foraminal stenosis, posterior shift of the spinal cord, and additional iatrogenic foraminal stenosis due to cervical alignment correction were more likely to develop postoperative C-5 palsy after posterior instrumentation with fusion. Prophylactic foraminotomy at C4–5 might be useful when preoperative foraminal stenosis is present on CT. Furthermore, it might be useful for treating postoperative C-5 palsy. To prevent excessive posterior shift of the spinal cord, the authors recommend that appropriate kyphosis reduction should be considered carefully.

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Zenya Ito, Shiro Imagama, Yoshihito Sakai, Yoshito Katayama, Norimitsu Wakao, Kei Ando, Kenichi Hirano, Ryoji Tauchi, Akio Muramoto, Hany El Zahlawy, Yukihiro Matsuyama and Naoki Ishiguro

Object

The purpose of this study was to review the present criteria for the compound muscle action potential (CMAP) alert and for safe spinal surgery.

Methods

The authors conducted a retrospective study of 295 patients in whom spinal cord monitoring had been performed during spinal surgery. The waveforms observed during spinal surgery were divided into the following 4 grades: Grade 0, normal; Grade 1, amplitude decrease of 50% or more and latency delay of 10% or more; Grade 2, multiphase pattern; and Grade 3, loss of amplitude. Waveform grading, its relationship with postoperative motor deficit, and CMAP sensitivity and specificity were analyzed. Whenever any wave abnormality occurred, the surgeon was notified and the surgical procedures were temporarily suspended. If no improvements were seen, the surgery was terminated.

Results

Compound muscle action potential wave changes occurred in 38.6% of cases. With Grade 1 or 2 changes, no paresis was detected. Postoperative motor deficits were seen in 8 patients, all with Grade 3 waveform changes. Among the 287 patients without postoperative motor deficits, CMAP changes were not seen in 181, with a specificity of 63%. The false-positive rate was 37% (106 of 287). However, when a Grade 2 change was set as the alarm point, sensitivity was 100% and specificity was 79.4%. The false-positive rate was 20% (59 of 295).

Conclusions

Neither the Grade 1 nor the Grade 2 groups included patients who demonstrated a motor deficit. All pareses occurred in cases showing a Grade 3 change. Therefore, the authors propose a Grade 2 change (multiphasic waveform) as a new alarm point. With the application of this criterion, the false-positive rate can be reduced to 20%.

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Ryoji Tauchi, Shiro Imagama, Hidefumi Inoh, Yasutsugu Yukawa, Tokumi Kanemura, Koji Sato, Yoshihito Sakai, Mitsuhiro Kamiya, Hisatake Yoshihara, Zenya Ito, Kei Ando, Akio Muramoto, Hiroki Matsui, Tomohiro Matsumoto, Junichi Ukai, Kazuyoshi Kobayashi, Ryuichi Shinjo, Hiroaki Nakashima, Masayoshi Morozumi and Naoki Ishiguro

Object

Cervical spondylosis that causes upper-extremity muscle atrophy without gait disturbance is called cervical spondylotic amyotrophy (CSA). The distal type of CSA is characterized by weakness of the hand muscles. In this retrospective analysis, the authors describe the clinical features of the distal type of CSA and evaluate the results of surgical treatment.

Methods

The authors performed a retrospective review of 17 consecutive cases involving 16 men and 1 woman (mean age 56.3 years) who underwent surgical treatment for the distal type of CSA. The condition was diagnosed on the basis of cervical spondylosis in the presence of muscle impairment of the upper extremity (intrinsic muscle and/or finger extension muscles) without gait disturbance, and the presence of a compressive lesion involving the anterior horn of the spinal cord, the nerve root at the foramen, or both sites as seen on axial and sagittal views of MRI or CT myelography. The authors assessed spinal cord or nerve root impingement by MRI or CT myelography and evaluated surgical outcomes.

Results

The preoperative duration of symptoms averaged 11.8 months. There were 14 patients with impingement of the anterior horn of the spinal cord and 3 patients with both anterior horn and nerve root impingement. Twelve patients were treated with laminoplasty (plus foraminotomy in 1 case), 3 patients were treated with anterior cervical discectomy and fusion, and 2 patients were treated with posterior spinal fixation. The mean manual muscle testing grade was 2.4 (range 1–4) preoperatively and 3.4 (range 1–5) postoperatively. The surgical results were excellent in 7 patients, good in 2, and fair in 8.

Conclusions

Most of the patients in this series of cases of the distal type of CSA suffered from impingement of the anterior horn of the spinal cord, and surgical outcome was fair in about half of the cases.

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Kei Ando, Shiro Imagama, Zenya Ito, Kazuyoshi Kobayashi, Hideki Yagi, Tetsuro Hida, Kenyu Ito, Mikito Tsushima, Yoshimoto Ishikawa and Naoki Ishiguro

OBJECT

Little is known about the progression of spinal schwannomas. The aim of this study was to determine the natural progression of spinal schwannomas and establish the risk of tumor growth.

METHODS

This study retrospectively analyzed data from 23 patients (12 men and 11 women, 40–89 years old) with schwannomas detected by MRI. The mean follow-up period was 5 years (range 2–10 years). The absolute and relative growth rates of the tumors were calculated.

RESULTS

The average tumor size was 1495 mm3 at the initial visit and 2224 mm3 at the final follow-up. The average absolute growth rate was 139 mm3 per year, and the average relative growth rate was 5.3% per year. Tumors were classified into 3 groups based on enhancement patterns: isointense/hyperintense (iso/high; 11 cases), rim enhancement when enhancement was peripheral (high/rim; 5 cases), and heterogeneous/heterogeneous (hetero/hetero; 7 cases) based on Gd-enhanced T2-weighted MRI. The average absolute growth rates of the 3 lesion groups were 588 mm3, 957 mm3, and 3379 mm3, respectively (p < 0.01).

CONCLUSIONS

Although the tumors classified as iso/high and high/rim on T2-weighted Gd-enhanced MR images were small and grew very little, most tumors with hetero/hetero classification increased in size. Hetero/hetero-type tumors should be followed closely and may require surgery.

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Kazuyoshi Kobayashi, Shiro Imagama, Zenya Ito, Kei Ando, Tetsuro Hida, Kenyu Ito, Mikito Tsushima, Yoshimoto Ishikawa, Akiyuki Matsumoto, Yoshihiro Nishida and Naoki Ishiguro

OBJECTIVE

Corrective surgery for spinal deformities can lead to neurological complications. Several reports have described spinal cord monitoring in surgery for spinal deformity, but only a few have included patients younger than 20 years with adolescent idiopathic scoliosis (AIS). The goal of this study was to evaluate the characteristics of cases with intraoperative transcranial motor evoked potential (Tc-MEP) waveform deterioration during posterior corrective fusion for AIS.

METHODS

A prospective database was reviewed, comprising 68 patients with AIS who were treated with posterior corrective fusion in a prospective database. A total of 864 muscles in the lower extremities were chosen for monitoring, and acceptable baseline responses were obtained from 819 muscles (95%). Intraoperative Tc-MEP waveform deterioration was defined as a decrease in intraoperative amplitude of ≥ 70% of the control waveform. Age, Cobb angle, flexibility, operative time, estimated blood loss (EBL), intraoperative body temperature, blood pressure, number of levels fused, and correction rate were examined in patients with and without waveform deterioration.

RESULTS

The patients (3 males and 65 females) had an average age of 14.4 years (range 11–19 years). The mean Cobb angles before and after surgery were 52.9° and 11.9°, respectively, giving a correction rate of 77.4%. Fourteen patients (20%) exhibited an intraoperative waveform change, and these occurred during incision (14%), after screw fixation (7%), during the rotation maneuver (64%), during placement of the second rod after the rotation maneuver (7%), and after intervertebral compression (7%). Most waveform changes recovered after decreased correction or rest. No patient had a motor deficit postoperatively. In multivariate analysis, EBL (OR 1.001, p = 0.085) and number of levels fused (OR 1.535, p = 0.045) were associated with waveform deterioration.

CONCLUSIONS

Waveform deterioration commonly occurred during rotation maneuvers and more frequently in patients with a larger preoperative Cobb angle. The significant relationships of EBL and number of levels fused with waveform deterioration suggest that these surgical invasions may be involved in waveform deterioration.

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Kazuyoshi Kobayashi, Kei Ando, Ryuichi Shinjo, Kenyu Ito, Mikito Tsushima, Masayoshi Morozumi, Satoshi Tanaka, Masaaki Machino, Kyotaro Ota, Naoki Ishiguro and Shiro Imagama

OBJECTIVE

Monitoring of brain evoked muscle-action potentials (Br[E]-MsEPs) is a sensitive method that provides accurate periodic assessment of neurological status. However, occasionally this method gives a relatively high rate of false-positives, and thus hinders surgery. The alarm point is often defined based on a particular decrease in amplitude of a Br(E)-MsEP waveform, but waveform latency has not been widely examined. The purpose of this study was to evaluate onset latency in Br(E)-MsEP monitoring in spinal surgery and to examine the efficacy of an alarm point using a combination of amplitude and latency.

METHODS

A single-center, retrospective study was performed in 83 patients who underwent spine surgery using intraoperative Br(E)-MsEP monitoring. A total of 1726 muscles in extremities were chosen for monitoring, and acceptable baseline Br(E)-MsEP responses were obtained from 1640 (95%). Onset latency was defined as the period from stimulation until the waveform was detected. Relationships of postoperative motor deficit with onset latency alone and in combination with a decrease in amplitude of ≥ 70% from baseline were examined.

RESULTS

Nine of the 83 patients had postoperative motor deficits. The delay of onset latency compared to the control waveform differed significantly between patients with and without these deficits (1.09% ± 0.06% vs 1.31% ± 0.14%, p < 0.01). In ROC analysis, an intraoperative 15% delay in latency from baseline had a sensitivity of 78% and a specificity of 96% for prediction of postoperative motor deficit. In further ROC analysis, a combination of a decrease in amplitude of ≥ 70% and delay of onset latency of ≥ 10% from baseline had sensitivity of 100%, specificity of 93%, a false positive rate of 7%, a false negative rate of 0%, a positive predictive value of 64%, and a negative predictive value of 100% for this prediction.

CONCLUSIONS

In spinal cord monitoring with intraoperative Br(E)-MsEP, an alarm point using a decrease in amplitude of ≥ 70% and delay in onset latency of ≥ 10% from baseline has high specificity that reduces false positive results.