Tatsuro Hayashida

Evaluation of lumbosacral nerve root lesions using evoked potentials recorded by a surface electrode technique.

Study Design Patients with lumbar disc herniation were studied with lumbosacral evoked potentials (EPs). Objectives. To evaluate lumbosacral EPs for the functional diagnosis of nerve root lesions in patients with lumbar disc herniation. Summary of Background Data. No clinical studies have been conducted using lumbosacral EPs elicited by body surface leads. Methods. Lumbosacral EPs elicited by stimulating the posterior tibial nerve were recorded using surface electrodes placed over the interspinous processes of T12-S1. By subtracting the waveform recorded at NT12 (T12/L1 potential) from that at NL3 (L3/L4 potential), NL3′ (residual potential) potentials were clearly identified. NT12 and NL3′ potentials were classified into four groups based on the degree of the reduction of amplitude and/or the prolongation of latency. Results. Significant correlations were found between the NL3′ score and the straight-leg raising test score (r = 0.36, P < 0.05) and between the NT12 amplitude and sensory disturbance (r = 0.37, P < 0.02). The NL3′ score was 1.2 ± 0.5 points before surgery, and it significantly improved to 2.5 ± 0.5 points 2 months after surgery (P < 0.05). Short-term, the NT12 amplitude did not change significantly. Twelve months after surgery, the NT12 amplitude improved significantly to 1.1 ± 0.5 &mgr;V (P < 0.05). Conclusions. The results of this study indicated that the NL3′ score may reflect impairment of the impulse traversing the nerve root in the acute clinical stage, whereas the NT12 amplitude reflects a neurologic deficit. The postoperative clinical course can be estimated by observing recovery of the NL3′ score and NT12 amplitude.

Disassembly of a Modular Femoral Component After Femoral Head Prosthetic Replacement

We report a rare case of a taper-locked femoral inner head that have been completely separated from the stem neck. A 76-year-old man who had hip fracture of the right hip had disassembly of inner head and stem neck after revision of bipolar hip prosthesis. This force could have been amplified by the pumping phenomenon generated after the revised inner head. We suspect the sealed air pushes back the stem neck, and unlocks the taper lock of the inner head, causing separation of the stem neck from the inner head. To prevent pumping phenomenon, we recommend manual testing of the taper lock to confirm that it has been assembled correctly and its integrity before implantation when the bloody and fatty membrane is adequately removed from stem neck.

Clinical study of a modified Brooks technique for atlanto-axial subluxation using polyethylene tape.

Forty-four patients, 15 males and 29 females (3-71 years old; mean age, 52.9), were treated for the control of cervical instability with a modified Brooks operation using Tekmilon tape (an ultrahigh molecular weight polyethylene tape) instead of metal wires. Forty of the patients had rheumatoid arthritis (RA) with atlanto-axial subluxation (AAS), three patients had os odontoideum, and one patient had a cervical spine injury. The mean follow-up period was 8 years and 4 months. These patients were divided into three groups: 30 years or less, 31 to 60 years, and over 60 years. Atlanto-dental interval (ADI), inclination angle of atlanto-axial vertebrae (A-A angle), and bone fusion were examined on plain radiographs. The proportion of patients with reduced neck pain (Ranawats grade 0 or grade 1) increased from 42.5% to 97.9% at the time of postoperative evaluation. Surgical complications, such as dural tear, lamina fracture, and spinal cord injury did not occur in any cases. Thirty-nine patients (88.6%) achieved bone union. ADI in the maximum flexed position improved from 10.3 to 2.5 mm. There was no statistical difference between ADI in males and females. ADI did not change in any age group both before and after surgery. A-A angle also improved from 9.4 to 24.4 degrees. The polyethylene tapes, used for internal fixation, caused no neurologic complications during sublaminar wiring and produced no MR artifacts. This modified Brooks technique using Tekmilon tape was proved to be a simple and safe treatment of AAS.

Estimation of cervical cord dysfunction by somatosensory evoked potentials

The purpose of this study was to examine the relationship of abnormal short‐latency somatosensory evoked potentials (SSEPs) recorded by a noncephalic reference montage with clinical variables in cervical myelopathy patients and to reexamine the diagnostic utility of SSEPs in such patients. We studied cervical SSEPs elicited by stimulating the median and ulnar nerves in 87 patients. Our grade classification of spinal N13, which is based on the normal limits of latencies or amplitudes, corresponded well with the clinical variables and is of value when trying to localize the cervical lesion segmentally. The N9–P14 interpeak latency in response to ulnar nerve stimulation correlated well with lower extremity function (r = −0.440, P <0.0001). We suggest a combined assessment of N13 amplitude, and N9–N13 and N9–P14 interpeak latencies to estimate dorsal column and dorsal horn function separately in patients with cervical myelopathy.

Prevention of neurological complications using a neural monitoring system with a finger electrode in the extreme lateral interbody fusion approach

OBJECTIVE Extreme lateral interbody fusion (XLIF) is a minimally disruptive surgical procedure that uses a lateral approach. There is, however, concern about the development of neurological complications when this approach is used, particularly at the L4-5 level. The authors performed a prospective study of the effects of a new neural monitoring system using a finger electrode to prevent neurological complications in patients treated with XLIF and compared the results to results obtained in historical controls. METHODS The study group comprised 36 patients (12 male and 24 female) who underwent XLIF for lumbar spine degenerative spondylolisthesis or lumbar spine degenerative scoliosis at L4-5 or a lower level. Using preoperative axial MR images obtained at the mid-height of the disc at the treated level, we calculated the psoas position value (PP%) by dividing the distance from the posterior border of the vertebral disc to the posterior border of the psoas major muscle by the anteroposterior diameter of the vertebral disc. During the operation, the psoas major muscle was dissected using an index finger fitted with a finger electrode, and threshold values of the dilator were recorded before and after dissection. Eighteen cases in which patients had undergone the same procedure for the same indications but without use of the finger electrode served as historical controls. Baseline clinical and demographic characteristics, PP values, clinical results, and neurological complications were compared between the 2 groups. RESULTS The mean PP% values in the control and finger electrode groups were 17.5% and 20.1%, respectively (no significant difference). However, 6 patients in the finger electrode group had a rising psoas sign with PP% values of 50% or higher. The mean threshold value before dissection in the finger electrode group was 13.1 ± 5.9 mA, and this was significantly increased to 19.0 ± 1.5 mA after dissection (p < 0.001). A strong negative correlation was found between PP% and threshold values before dissection, but there was no correlation with threshold values after dissection. The thresholds after dissection improved to 11 mA or higher in all patients. There were no serious neurological complications in any patient, but there was a significantly lower incidence of transient neurological symptoms in the finger electrode group (7 [38%] of 18 cases vs 5 [14%] of 36 cases, p = 0.047). CONCLUSIONS The new neural monitoring system using a finger electrode may be useful to prevent XLIF-induced neurological complications.

Diagnostic utility of waveform analysis of compound muscle action potentials for carpal tunnel syndrome

Purpose. To determine the diagnostic utility of waveform analysis of compound muscle action potentials (CMAP) for carpal tunnel syndrome (CTS). Methods. A total of 131 hands in 71 patients diagnosed with CTS (grouped according to severity) and 80 hands in 44 normal subjects were evaluated using nerve conduction test through the carpal tunnel combined with waveform analysis of CMAP. Results. Compared to normal subjects, the sensory nerve conduction velocity and mean frequency of the CMAP waveform were significantly reduced in patients with CTS. Compared with distal motor latency and sensory nerve conduction velocity, the mean frequency of the CMAP decreased significantly with increasing clinical severity. Conclusion. This study suggests that waveform analysis of CMAP is of diagnostic value in CTS, and is also of value in objective evaluation of postoperative recovery of carpal median nerve dysfunction.

Effect of three-dimensional rotational deformity correction in surgery for adult degenerative scoliosis using lumbar lateral interbody fusion and posterior pedicle screw fixation

Introduction Corrective surgery for adult degenerative scoliosis using lateral interbody fusion (LIF) and additional posterior fixation is an efficient procedure. However, it is unclear how this procedure affects rotational deformity correction. Therefore, the goal of the present study was to use three-dimensional (3D) images, taken during surgery, to investigate rotational deformity correction in the treatment of adult degenerative scoliosis using LIF and posterior fixation using a pedicle screw system. Methods The subjects were 12 females who were treated using LIF and posterior fixation for adult degenerative scoliosis. The patients had a mean age of 72 (65-76) years. 3D images were acquired before surgery, after LIF, and after additional posterior fixation. Rotational angles of the upper vertebra with respect to the lower vertebra of each fixed segment were measured in 3 planes. Correction factors for rotational deformity were investigated after LIF and additional posterior fixation. Results There were significant improvements in radiographical parameters for global spinal balance. The correction angles per segment were 4.7° for lateral bending, 6.9° for lordosis, and 4.5° for axial rotation. LIF was responsible for correction of four-fifths of lateral bending and axial rotation, and two-thirds of lordotic changes. Conclusions Lateral bending, axial rotational deformities, and lordosis were primarily corrected by LIF. Further lordosis correction was achieved using additional posterior fixation. These results indicate that corrective surgery for adult degenerative scoliosis using these procedures is effective for rotational deformity correction and leads to an ideal global spinal alignment.

Valgus Slipped Capital Femoral Epiphysis in Patient with Hypopituitarism

Slipped capital femoral epiphysis (SCFE) is a common disease of adolescent and the epiphysis is positioned more posteromedially in relation to the femoral neck shaft with varus SCFE; however, posterolateral displacement of the capital epiphysis, valgus SCFE, occurs less frequently. We report a case of valgus SCFE in a 17-year-old boy with hypopituitarism. After falling down, he experienced difficulty in walking. The radiographs were inconclusive; however three-dimensional computed tomography images showed lateral displacement of the epiphysis on the right femoral head. Valgus SCFE was diagnosed. The patient underwent in situ pinning of both sides. In situ pinning on the left side was performed as a prophylactic pinning because of endocrine abnormalities. At the 1-year follow-up, he could walk without any difficulty and there were no signs of pain. The epiphysis is commonly positioned more posteromedially in relation to the femoral neck shaft with most SCFE, but, in this case, the epiphysis slipped laterally. Differential diagnosis included femoral neck fracture (Delbet-Colonna type 1); however, this was less likely due to the absence of other clinical signs. Therefore, we diagnosed the patient as SCFE. When children complain of leg pain and limp, valgus SCFE that may not be visualized on anteroposterior radiographs needs to be considered.

P30.11 Descending spinal cord tract in patients with cervical and thoracic spinal stenosis using motor evoked potentials recorded from paravertebral muscles

yet. Aim: In this study, our aim was to reveal these effects to investigate whether the change of stimulus frequencies could be of convenient use in obtaining more accurate CCT estimations in SEP studies of these patients. Patients and methods: We performed median SEPs of 14 patients with NB and 15 healthy volunteers. We changed the stimulus frequency as 2 Hz, 4 Hz, 6 Hz and 9 Hz in successive recordings and compared the changes on SEP potentials and peak and onset CCT in the Neuro-Behcet (NB) group and the normal group statistically. Results: Our results indicated that the onset CCT values of the NB group were higher than the normal group in 4 Hz and 9 Hz stimulations. However, the comparison of peak CCT in the NB group and the normal group did not show any statistically meaningful differences in all stimulation frequencies. Conclusion: Onset CCT has not been measured before in former SEP studies of patients with NB. We highly recommend measuring onset CCT at higher stimulation frequencies in order to reveal central conduction time pathologies in these patients.

P15.24 Evaluation of sensory function after splint fixation in carpal tunnel syndrome using the current perception threshold test

Objectives: To determine whether the alteration of proximal conduction velocity (CV) really occurs in patients with carpal tunnel syndrome (CTS) whose abductor pollicis brevis (APB) muscle showed either with or without axonal degeneration. Background: Retrograde conduction slowing (RCS) did occur in axotomic rat and cat model in which the proximal part of axotomic axons showed 40% reduction of CV and 7% decrease of CV in the remaining intact axons. However, whether or not RCS will occur in human is not sure. Subjects and methods: Consecutive CTS patients (n = 150) were enrolled in this study. Fifty CTS patients were confirmed by electrodiagnosis and had denervation of APB muscles in needle examination, comprised of Group 1 and the others (n = 100) with normal needle examination (Group 2). One hundred volunteers served as controls (n = 100). We measured median and ulnar distal motor latencies (DML), forearm motor CV (FMCV), compound muscle action potential (CMAP) amplitudes and furthermore, median wrist–palm CV (W–P MCV) was measured. Results: The mean ± standard deviation (SD) of the W– P MCV for Group 1, Group 2 and controls were 19.73 ± 7.65, 32.7 ± 6.83 and 52.75 ± 6.4 m/s and those of median FMCV were 48.63 ± 8.32, 54.42 ± 2.11 and 57.86 ± 4.24 m/s, respectively. There was a significant reduction in the W–P MCV (62.6%) and a decrease in the median FMCV (15.95%) in Group 1 and 38% reduction in W–P MCV and 5.9% decrease in median FMCV in Group 2. Conclusion: A marked decrease of the proximal CV really occurs in CTS patients with axonal degeneration, and a mild decrease in CTS patients with demyelination. It is against the conventional wisdom that alteration of nerve function exclusively occurs in distal nerve segments; however, the alteration of proximal conduction property, especially in CV, does concomitantly appear, suggesting neuroplasticity really occurs in proximal nerve part.