Application of diffusion tensor imaging for the diagnosis of segmental level of dysfunction in cervical spondylotic myelopathy.

STUDY DESIGN: A retrospective study. OBJECTIVES: Diffusion tensor imaging (DTI) reflects pathological change in the spinal cord more sensitively than conventional magnetic resonance imaging (MRI). Electrophysiological examination enables quantitative assessment of spinal cord function. Few studies have addressed the correlation between intraoperative spinal cord-evoked potentials (SCEPs) and DTI. The purpose of this study was to examine whether DTI is an objective index for the diagnosis of the segmental level of dysfunction in cervical spondylotic myelopathy (CSM). SETTING: Yamaguchi University Graduate School of Medicine, Japan. METHODS: Using 3.0-Tesla MRI, DTI values for the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) were measured at the disc level C2/C3 through C6/C7 in 11 normal subjects and 10 subjects with CSM. Subjects with CSM were divided into two groups based on the extent of compression according to conventional MRI: single level (n=3) and multilevel (n=7). Intraoperative SCEPs were measured in subjects with CSM. For each group, the ADC and FA values were compared with SCEPs with respect to the segmental levels of dysfunction. RESULTS: For all three subjects with single-level compression and six of seven with multilevel compression, the maximal ADC value was observed at the segmental level of dysfunction as per the SCEP. Minimum FA values were observed at those sites in two of three patients with single-level compression and in only two of seven with multi-level compression. CONCLUSION: Our results suggest that ADC might serve as a supplementary diagnostic indicator of the segmental levels of dysfunction in CSM.

Characteristics of C6-7 myelopathy: assessment of clinical symptoms and electrophysiological findings.

STUDY DESIGN: This is a single-center retrospective study. OBJECTIVES: The objective of this study was to study the clinical symptoms and electrophysiological features of C6-7 myelopathy. SETTING: This study was conducted at the Department of Orthopedic surgery, Yamaguchi University Graduate school of medicine, Japan. METHODS: A total of 20 patients with cervical compressive myelopathy were determined by spinal cord-evoked potentials or a single level of obvious magnetic resonance imaging (MRI)-documented cervical spinal cord compression. Neurological examinations included manual muscle testing and investigation of deep tendon reflex, including Hoffmann sign, and of sensory disturbance areas. Motor-evoked potentials (MEPs), compound muscle action potentials (CMAPs) and F-wave were recorded from bilateral abductor digit minim and abductor halluces muscles. Central motor conduction time was calculated as follows: MEPs latency-(CMAPs latency+F latency-1)/2 (ms). RESULTS: Eighteen patients (90%) had negative Hoffmann sign. Eight patients (40%) had no sensory disturbance in the upper limbs and 8 patients (40%) had no muscle weakness in the upper limbs. We determined that patients had cervical myelopathy when their central motor conduction time measured in abductor digit minim was longer than 6.76 ms (+2 s.d.). Using this definition, the sensitivity for myelopathy was 42.8%. CONCLUSION: Patients with C6-7 myelopathy may lack clinical symptoms in their hands and central motor conduction time measured in abductor digit minim tended to be less prolonged, and it only showed symptoms in their lower limbs as gait disturbance. Surgeons should bear in mind the possibility of disorders of caudal C6-7 when they encounter patients with no or few symptoms in their hands and with leg weakness or numbness.

Preoperative diagnosis of the responsible level in CCM using CMAPs: comparison with SCEPs.

STUDY DESIGN: A retrospective study. OBJECTIVE: To elucidate the correlation between compound muscle action potentials (CMAPs) amplitudes and responsible level of compressive cervical myelopathy (CCM), and the accuracy of level diagnosis by using CMAPs. SETTING: This study was conducted at the Department of Orthopedic surgery, Yamaguchi University Graduate School of Medicine, Japan. METHOD: A total of 28 patients with CCM were investigated in this study. Erb's point-stimulated CMAPs were measured from deltoid, biceps, triceps in all patients as compared with 88 healthy subjects. We performed a level diagnosis on the basis of CMAPs amplitudes. We performed a level diagnosis on the basis of CMAPs amplitudes and using an index that measures the deviation of CMAPs amplitudes between triceps and deltoid or biceps. RESULTS: Significant correlations between the mean CMAPs amplitudes and responsible level were showed for deltoid (6.82±2.33 mV) at C3/4 (P<0.01) and biceps (8.75±4.42 mV) at C4/5 (P=0.015). Despite considerable individual variability in CMAP amplitudes, there were correlations among CMAPs amplitudes for deltoid, biceps and triceps in the same individual. The sensitivity was 75.0%, specificity 75.0% in the index for diagnosis of C3/4. The sensitivity was 75.0%, specificity 66.7% in the index for diagnosis of C4/5. CONCLUSION: This study showed small CMAPs amplitudes in the deltoid indicated a C3/4 level of myelopathy and in biceps at the C4/5 level and could help exclude clinically silent cord compression and determine the surgical procedure to the suitable level of concern.

Relative vulnerability of various spinal tracts in C3-4 cervical spondylotic myelopathy: multi-modal spinal cord evoked potentials.

STUDY DESIGN: Retrospective study. OBJECTIVE: To investigate the progression of spinal tract lesions in cervical spondylotic myelopathy (CSM) at C3-4 intervertebral level using spinal cord-evoked potensials (SCEPs). SETTING: This study was conducted at the Department of Orthopaedic Surgery, Yamaguchi University Graduate School of Medicine, Japan. METHODS: A total of 30 patients with CSM were investigated in this study. In all patients, only the C3-4 intervertebral level was symptomatic, as shown by examination of SCEPs. SCEPs were recorded following median nerve stimulation (MN-SCEPs), transcranial electric stimulation (TES-SCEPs) and spinal cord stimulation (spinal-SCEPs). RESULTS: The incidence of abnormalities varied in the order of MN-SCEPs (100%), TES-SCEPs (90%) and spinal-SCEPs (67%). Patients were grouped into three types according to SCEPs: transverse (all SCEPs abnormal), post-erolateral (abnormalities in the MN-SCEPs and TES-SCEPs) and upper limbs sensory (abnormal only for MN-SCEPs). In all, 20 of the 30 patients (67%) were the transverse type, 7 (23%) the post-erolateral type and 3 (10%) the upper limbs sensory type. CONCLUSION: The present study showed the lateral part of the posterior funiculus mediating upper limb sensory function was more vulnerable than the lateral corticospinal tract, which is consistent with numbness tending to appear at an early stage of mild CSM.

A new rabbit model for the study on cervical compressive myelopathy.

Development process and pathology of myelopathy due to chronic spinal cord compression have not been fully elucidated. This study was conducted in order to establish an experimental model which can efficiently produce myelopathy and be useful in the studies on myelopathy due to chronic spinal cord compression. Under electrophysiological monitoring of the spinal cord, anterior compression was produced on C5 using a plastic screw. Two weeks later, a plastic plate was inserted under the C5 arch. For the subsequent 10 months on average, walking pattern and MR images were periodically monitored. Before the sacrifice, electrophysiological test was performed and then histopathological examination was done. Palsy appeared at 5 months on average after the addition of posterior compression. Mean compression ratio of the spinal cord calculated on MR images was 34%. All animals with compression showed a high intramedullary signal intensity, and the mean contrast-to-noise ratio (CNR) in the compressed area was 49%. Electrophysiological test showed a significant decrease in the amplitude of spinal cord evoked potentials (SCEPs) at the given compression level. Histology showed flattening of the anterior horn, disappearance and necrosis of anterior horn cells in the gray matter; and demyelination and axonal degeneration in the white matter. The antero-posterior compression produces the condition of spinal canal stenosis. Repeated antero-posterior compression to the spinal cord is important in establishing myelopathy. The present animal model was evaluated to be useful in the studies on myelopathy.

A correlation between magnetic resonance imaging and electrophysiological findings in cervical spondylotic myelopathy.

STUDY DESIGN: Correlation between compressed spinal cords on magnetic resonance imaging (MRI) and electrophysiological findings in cervical spondylotic myelopathy patients. OBJECTIVE: To clarify the correlation between spinal-cord-evoked potentials and MRI measurements of compressed spinal cords in patients with cervical spondylotic myelopathy. SUMMARY OF BACKGROUND DATA: Compression of the spinal cord does not always cause clinical symptoms and it is difficult to infer the degree of dysfunction of the spinal cord from MRI findings. METHODS: Seventeen patients with cervical spondylotic myelopathy were examined with MRI and spinal-cord-evoked potentials before surgery. Using abnormality in spinal-cord-evoked potentials as indicators of spinal cord morphology, spinal-cord transverse area and compression ratios (central and 1/4-lateral) were measured on T1-weighted axial imaging. The correlations between these dimensions and electrophysiological findings were investigated. RESULTS: The mean preoperative transverse area of the spinal cord was 47.13 mm2. The mean preoperative central compression ratio of the spinal cord was 34.4%. The mean preoperative 1/4-lateral compression ratio of the spinal cord was 27.5%. A correlation (Spearman r=0.65, P < 0.01) was observed between the 1/4-lateral compression ratio of the spinal cord and the amplitude ratio of spinal-cord-evoked potentials after electric stimulation of the brain (Br(E)-SCEPs). CONCLUSIONS: The preoperative 1/4-lateral compression ratio of the spinal cord was found to reflect the degree of dysfunction of the corticospinal tracts.

Neuromuscular stimulation therapy after incomplete spinal cord injury promotes recovery of interlimb coordination during locomotion.

The mechanisms underlying the effects of neuromuscular electrical stimulation (NMES) induced repetitive limb movement therapy after incomplete spinal cord injury (iSCI) are unknown. This study establishes the capability of using therapeutic NMES in rodents with iSCI and evaluates its ability to promote recovery of interlimb control during locomotion. Ten adult female Long Evans rats received thoracic spinal contusion injuries (T9; 156 +/- 9.52 Kdyne). 7 days post-recovery, 6/10 animals received NMES therapy for 15 min/day for 5 days, via electrodes implanted bilaterally into hip flexors and extensors. Six intact animals served as controls. Motor function was evaluated using the BBB locomotor scale for the first 6 days and on 14th day post-injury. 3D kinematic analysis of treadmill walking was performed on day 14 post-injury. Rodents receiving NMES therapy exhibited improved interlimb coordination in control of the hip joint, which was the specific NMES target. Symmetry indices improved significantly in the therapy group. Additionally, injured rodents receiving therapy more consistently displayed a high percentage of 1:1 coordinated steps, and more consistently achieved proper hindlimb touchdown timing. These results suggest that NMES techniques could provide an effective therapeutic tool for neuromotor treatment following iSCI.

Vascularized fibular graft after excision of giant cell tumor of the distal radius. A case report.

Although hemiarthroplasty of the wrist using vascularized proximal fibula has been described often, long term results with documentation of results are insufficient. A case of giant cell tumor of the distal radius with remarkable extraskeletal extension is reported. Vascularized fibula including its proximal head was used to replace the defect created after en bloc resection of the tumor. There was no deterioration in radiographic findings or function of the new joint at the time of the 10-year followup. Satisfactory range of motion of the wrist and the forearm was maintained. There was no instability in the joint, and grip strength measured 65% of the opposite side. Postoperative magnetic resonance imaging showed survival of the whole graft, including the subchondral portion. In addition to thorough revascularization of the graft, appropriate soft tissue reconstruction using dynamic tendon transfer contributed to the success. When these requirements are fulfilled, the graft can provide a functional and durable result. Although this is a single experience, the authors recommend wrist arthroplasty, rather than arthrodesis, in carefully selected patients.