Masayuki Ohashi

Can prophylactic bilateral C4/C5 foraminotomy prevent postoperative C5 palsy after open-door laminoplasty?: a prospective study.

Study Design. A prospective study. Objective. To evaluate the effectiveness of prophylactic C4/C5 microforaminotomy with open-door laminoplasty for cervical myelopathy in preventing postoperative C5 palsy. Summary of Background Data. Postoperative C5 palsy is a common complication of cervical laminoplasty. Although the etiology of C5 palsy and preventive measures remain unclear, we hypothesize that C5 palsy is caused by C5 nerve root impairment induced by potential C4/C5 foraminal stenosis and posterior shifting of the spinal cord after laminoplasty. Methods. The study included 141 consecutive patients with cervical myelopathy (103 men and 38 women) who underwent open-door laminoplasty with prophylactic bilateral C4/C5 foraminotomy between 2009 and 2010. These were designated as the foraminotomy group (FG). One hundred forty-one consecutive patients (100 men and 41 women) who underwent open-door laminoplasty without prophylactic foraminotomy during 2006 to 2008 served as a control group. This was the nonforaminotomy group (NFG). The incidence of C5 palsy, operation time, blood loss, and the number of decompressed disc levels were recorded. Results. The incidence of C5 palsy was 1.4% (2 of 141 cases) in the FG, and 6.4% (9 of 141 cases) in the NFG. The mean operation times were 129 and 102 minutes, respectively. There were significant differences in the incidence of C5 palsy and operation time (both comparisons, P < 0.05). There were no significant differences in blood loss or the number of decompressed disc levels (both comparisons, P > 0.05). Conclusion. Prophylactic bilateral C4/C5 microforaminotomy significantly decreased the incidence of postoperative C5 palsy. These results suggest that the main etiology of C5 palsy was C5 root impairment. However, 2 patients experienced C5 palsy despite undergoing prophylactic foraminotomy, which indicated that other factors including spinal cord impairment after acute decompression against cervical canal stenosis may also be considered as minor etiologies of C5 palsy. We conclude that prophylactic C4/C5 foraminotomy was an effective preventive measure against postoperative C5 palsy after laminoplasty.

Analysis of C5 palsy after cervical open-door laminoplasty: relationship between C5 palsy and foraminal stenosis.

Study Design: A retrospective study. Objective: To determine the clinical and imaging characteristics of postoperative C5 palsy after cervical open-door laminoplasty. Summary of Background Data: Postoperative C5 palsy is a common complication of cervical laminoplasty, and although there are several hypotheses regarding its etiology, the pathogenesis and preventive measures remain unidentified and many controversies remain. Methods: A total of 141 consecutive patients (100 men and 41 women) who had undergone open-door laminoplasty for cervical myelopathy between 2006 and 2009 were included in this study. Postoperative C5 palsy was defined as deltoid muscle weakness of a grade <3 in manual muscle test. The patients were divided into 2 groups: 1 that had experienced C5 palsy (PG; the palsy group) and the other that had not (NPG; the nonpalsy group). The parameters evaluated were the incidence of C5 palsy, the level at which spinal cord compression appeared preoperatively, the spinal cord level showing a T2 high-signal intensity lesion on magnetic resonance imaging, T2 high-signal intensity lesions newly appearing postoperatively, and the diameters of the C4/5 and C5/6 foramens. Results: The incidence of C5 palsy was 6.4% (9/141 cases). There were no significant differences between the 2 groups in sex, age, diagnosis, operation time, blood loss, level of spinal cord compression, level of T2 high-signal lesion, or new T2 high-signal lesions. The average diameter of the C4/5 foramen was 1.99 mm in the PG and 2.76 mm in the NPG (P<0.005). In contrast, the average diameter of the C5/6 foramen was 2.35 mm in PG and 2.50 mm in the NPG. Conclusions: There was a significant difference in the diameter of the C4/5 foramen between the PG and the NPG. The results suggest that the main etiology of C5 palsy is impairment of the C5 nerve root induced by preexisting C4/5 foraminal stenosis.

Clinical outcomes of posterior lumbar interbody fusion for lumbar foraminal stenosis: preoperative diagnosis and surgical strategy.

Study Design A retrospective case study of the use of posterior lumbar interbody fusion (PLIF) to treat lumbar foraminal stenosis (LFS). Objectives To characterize the features of clinical symptoms, radiographic evaluation, and surgical outcomes of PLIF in LFS. Summary of Background Data There is no gold standard for the surgical treatment of foraminal stenosis, which occurs in 8% to 10% of surgical cases of lumbar degenerative disease. Methods Data from 31 patients (33 segments) who underwent PLIF from 2001 to 2005 at our institution were analyzed. Exclusion criteria included the patients having both LFS and central canal stenosis, plus extraforaminal or intraforaminal disc herniation. There were 22 males and 9 females, with an average age of 61 (31∼78 y). The affected levels were as follows: L3/4 in 1 patient, L4/5 in 4, and L5/S1 in 28. All patients underwent PLIF with the combination of segmental pedicle screws, interbody cages, and autogenous local bone graft. Results The frequencies of Kemp sign (+), intermittent claudication, leg pain in a sitting position, and leg pain at night, were high. Radiographic evaluation showed severe disc degeneration such as loss of disc height, massive osteophyte formation, and transverse offset angles of the nerve root at the corresponding level. Magnetic resonance imaging and 3D-reconstraction computed tomography clearly showed intraforaminal stenosis in sagittal, axial, and coronal planes. The PLIF procedure provided complete root decompression, restoration of disc height, and preservation of lumbar lordosis at final follow-up. The Japanese Orthopedic Association score improved from 17.1 points preoperatively to 24.9 points at final follow-up, and the overall fusion rate was 100%. Conclusion Lumbar foraminal stenosis could be reliably diagnosed by distinctive clinical symptoms, and various radiographic examinations such as plain x-ray, Magnetic resonance imaging, and 3D-reconstraction computed tomography. The PLIF procedure, in combination with segmental pedicle screws, interbody cages, and autogenous local bone graft provides excellent clinical outcomes, and is a rational and useful surgical option for lumbar foraminal stenosis.

Two-year clinical and radiological outcomes of open-door cervical laminoplasty with prophylactic bilateral C4-C5 foraminotomy in a prospective study.

Study Design. A prospective study. Objective. To evaluate the 2-year outcomes of open-door cervical laminoplasty with prophylactic bilateral C4–C5 foraminotomy. Summary of Background Data. A prospective trial of prophylactic bilateral C4–C5 foraminotomy with open-door laminoplasty for cervical compression myelopathy showed a significant efficacy for preventing postoperative C5 palsy. However, in bilateral foraminotomy, there are concerns such as postoperative instability, hinge fracture, or nonunion, which may cause deterioration of neurological symptoms and neck pain. Methods. A prospective trial was performed in 141 patients between 2009 and 2010 (group F). A group of 141 patients who underwent open-door laminoplasty without prophylactic foraminotomy from 2006 to 2008 served as a control group (group NF). Here, we report 2-year radiological and clinical data for 121 patients (follow-up rate: 85.8%) in group F and 115 patients (81.6%) in group NF. The 2 groups were demographically similar, except for the operation time. Results. In group F, the mean rate of facet joint preservation was 71.4%. C2–C7 and C4–C5 lordosis and C4 translational movement were maintained postoperatively in both groups. The range of motion of C2–C7 and C4–C5 significantly decreased to about 80% of the preoperative values in both groups (P < 0.01). These radiological parameters and the incidence of hinge fracture and nonunion did not differ significantly between the groups. Visual analogue scale scores for neck pain were unchanged and significant recoveries (P < 0.001) in Japanese Orthopaedic Association scores were found in both groups. There were no significant differences in these clinical scores between the groups. The incidences of C5 palsy were 1.7% and 7.0% in groups F and NF, respectively (P = 0.043). Conclusion. Prophylactic bilateral C4–C5 foraminotomy did not adversely affect the 2-year radiological and clinical outcomes. Therefore, we conclude that this approach is an effective and desirable procedure for preventing postoperative C5 palsy. Level of Evidence: 3

Hydrogen peroxide modulates synaptic transmission in ventral horn neurons of the rat spinal cord

Excessive production of reactive oxygen species (ROS) is implicated in many central nervous system disorders; however, the physiological role of ROS in spinal ventral horn (VH) neurons remains poorly understood. We investigated how pathological levels of H2O2, an abundant ROS, regulate synaptic transmission in VH neurons of rats using a whole‐cell patch clamp approach. H2O2 increased the release of glutamate and GABA from presynaptic terminals. The increase in glutamate release involved N‐type voltage‐gated calcium channels (VGCCs), ryanodine receptors (RyRs), and inositol trisphosphate receptors (IP3Rs); the increase in GABA release, which inhibited glutamatergic transmission, involved IP3R. Inhibiting N‐type VGCCs and RyRs attenuates excitotoxicity resulting from increased glutamatergic activity while preserving the neuroprotective effects of GABA, and may represent a novel strategy for treating H2O2‐induced motor neuron disorders resulting from trauma or ischaemia–reperfusion injury.

Hydrogen peroxide modulates neuronal excitability and membrane properties in ventral horn neurons of the rat spinal cord

Hydrogen peroxide (H2O2), a reactive oxygen species, is an important signaling molecule for synaptic and neuronal activity in the central nervous system; it is produced excessively in brain ischemia and spinal cord injury. Although H2O2-mediated modulations of synaptic transmission have been reported in ventral horn (VH) neurons of the rat spinal cord, the effects of H2O2 on neuronal excitability and membrane properties remain poorly understood. Accordingly, the present study investigated such effects using a whole-cell patch-clamp technique. The bath-application of H2O2 decreased neuronal excitability accompanied by decreased input resistance, firing frequency, and action potential amplitude and by increased rheobase. These H2O2-mediated changes were induced by activation of extrasynaptic, but not synaptic, GABAA receptors. Indeed, GABAergic tonic currents were enhanced by H2O2. On the other hand, the amplitude of medium and slow afterhyperpolarization (mAHP and sAHP), which plays important roles in controlling neuronal excitability and is mediated by small-conductance calcium-activated potassium (SK) channels, was significantly decreased by H2O2. When extrasynaptic GABAA receptors were completely blocked, these decreases of mAHP and sAHP persisted, and H2O2 increased excitability, suggesting that H2O2 per se might have the potential to increase neuronal excitability via decreased SK channel conductance. These findings indicate that activating extrasynaptic GABAA receptors or SK channels may attenuate acute neuronal damage caused by H2O2-induced hyperexcitability and therefore represent a novel therapeutic target for the prevention and treatment of H2O2-induced motor neuron disorders.

Tranexamic acid evokes pain by modulating neuronal excitability in the spinal dorsal horn.

Tranexamic acid (TXA) is an antifibrinolytic agent widely used to reduce blood loss during surgery. However, a serious adverse effect of TXA is seizure due to inhibition of γ-aminobutyric acid (GABA) and glycine receptors in cortical neurons. These receptors are also present in the spinal cord, and antagonism of these receptors in spinal dorsal horn neurons produces pain-related phenomena, such as allodynia and hyperalgesia, in experimental animals. Moreover, some patients who are injected intrathecally with TXA develop severe back pain. However, the effect of TXA on spinal dorsal horn neurons remain poorly understood. Here, we investigated the effects of TXA by using behavioral measures in rats and found that TXA produces behaviors indicative of spontaneous pain and mechanical allodynia. We then performed whole-cell patch-clamp experiments that showed that TXA inhibits GABAA and glycine receptors in spinal dorsal horn neurons. Finally, we also showed that TXA facilitates activation of the extracellular signal-regulated kinase in the spinal cord. These results indicated that TXA produces pain by inhibiting GABAA and glycine receptors in the spinal dorsal horn.

Apparent diffusion coefficients distinguish amyotrophic lateral sclerosis from cervical spondylotic myelopathy

OBJECTIVE Fifty percent of patients with amyotrophic lateral sclerosis (ALS) have cervical spondylotic myelopathy (CSM) as a complication. Because patients with ALS do not develop bulbar signs and symptoms at onset, differentiating them from patients with CSM is sometimes difficult. We aimed to determine whether the apparent diffusion coefficients (ADCs) of intracranial corticospinal tracts can be used to distinguish between patients with ALS and those with CSM. METHODS We evaluated 19 consecutive patients with ALS who did not have CSM by cervical MRI, 16 patients with CSM, and 11 healthy controls. We examined the mean ADCs in the precentral gyrus, the corona radiata, the posterior limbs of the internal capsule (PLIC), and the cerebral peduncle by 3T magnetic resonance imaging (MRI). The mean ADCs in the intracranial corticospinal tracts in patients with ALS were compared with those in patients with CSM. RESULTS The mean ADCs in the intracranial corticospinal tracts in patients with ALS were compared with those in patients with CSM (p<0.05). Additionally, the mean ADCs in the precentral gyrus, the PLIC, and the cerebral peduncle in the patients with ALS, including the patients who were initially diagnosed as having clinically possible ALS on the basis of the revised El Escorial criteria and did not develop bulbar symptoms at onset, were also higher than those in patients with CSM (p<0.05). CONCLUSIONS Elevated ADCs in the intracranial corticospinal tracts might be useful for distinguishing ALS from CSM in the early stage of the disease.

One-stage surgery in combination with thoracic endovascular grafting and resection of T4 lung cancer invading the thoracic aorta and spine

A novel strategy of one-stage surgery in combination with thoracic endovascular grafting and resection for T4 lung cancer invading the thoracic aorta and spine is described. A 56-year-old man with locally advanced lung cancer infiltrating the aortic wall and spine underwent neoadjuvant chemotherapy and thoracic irradiation, followed by en bloc resection of the aortic wall and spine with thoracic endovascular grafting. He developed postoperative chylothorax, but there were no stent graft-related events. After 3 months, computed tomography (CT) did not show aortic stent graft stenosis, migration, or deformation.

Variation of the position of the aorta relative to a kyphotic thoracic spine: safety margin for pedicle screw placement in the adult Japanese population.

Study Design. An analysis of computed tomography images of the spine in adult Japanese patients. Objective. To evaluate the variation of the position of the aorta relative to a spine with a thoracic kyphotic angle and to verify the safety margin for transpedicular screw fixation. Summary of Background Data. Recent studies have suggested that the aorta is positioned more laterally and posteriorly in patients with idiopathic scoliosis than in normal patients; however, variation of the position of the aorta in thoracic sagittal alignment has not been performed. Methods. T4–T12 vertebrae were studied using computer tomography images in 58 Japanese patients (aged 31–90 years) with normal coronal alignment of the spine. Pedicle diameter, pedicle length, chord length, closest distance from the aorta, and pedicle-aorta angle (PAA) were evaluated using a Mann-Whitney U test and Spearman rank correlation analysis. Results. Pedicle diameter showed an increase in size from T4 (4.7 mm) to T12 (8.2 mm), pedicle length had an almost constant size of about 20 mm, and chord length increased from T4 (37.7 mm) to T12 (47.2 mm). Closest distance from the aorta decreased from T4 (29.6 mm) to T6 (24.6 mm) and then increased to T12 (49.3 mm). PAA increased from T4 (31.5°) to T6 (38.6°) and then decreased to T12 (5.0°). Sagittal curvature showed a correlation with PAA, with an increasing sagittal thoracic Cobb angle related to decreases in PAA at the T5 (r = −0.31, P = 0.034), T6 (r = −0.37, P = 0.008), and T7 (r = −0.29, P = 0.036) levels. Conclusion. The descending aorta is positioned more medially at the T5, T6, and T7 levels in patients with a kyphotic spine. These spatial relationships should be considered when planning pedicle screw insertion for a kyphotic spine.