Mechanism of prolonged central motor conduction time in compressive cervical myelopathy

Kaneko, Kazuo; Taguchi, Toshihiko; Morita, Hideki; Yonemura, Hiroshi; Fujimoto, Hideaki; Kawai, Shinya

doi:10.1016/s1388-2457(01)00533-8

Cited by 59 publications

(36 citation statements)

References 13 publications

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“…Our results showed that functional recovery in the corticospinal tract following cervical laminoplasty in patients with CCM can be quantitatively assessed and that the corticospinal conduction block improvements due to the increase in the number of axons that propagate the evoked potentials were one of the causes of improved JOA scores. The CMCT values did not completely improve to the normal range, which has been reported previously, 10,28 and the mean CMCT recovery rate and (JOA score) RR in our series were 0.91 and 0.43, respectively. The data should be important information on the pathophysiology of recovery following surgery.…”

Section: Discussionsupporting

confidence: 75%

“…Kaneko and colleagues examined CMCT following TMS, as well as spinal cord evoked potentials (SCEPs) following transcranial electric stimulation (TES), in patients with CCM and normal subjects. 10 Their results showed that CMCT was prolonged in such patients and that the patients exhibited significant attenuation in their SCEP amplitudes following TES but no significant delay in their SCEP latencies. The authors concluded that impaired temporal summation of multiple descending potentials following TMS produces delays in motor neuron firing that contribute to the prolongation of CMCT.…”

Section: Discussionmentioning

confidence: 97%

“…9,19 Central motor conduction time (CMCT) can be measured to evaluate corticospinal function in cervical myelopathy. 2,10,25,36 In fact, there is an excellent correlation between MRI findings and CMCT in patients with cervical myelopathy. 17 Central motor conduction time is more prolonged in patients with more severe cervical spinal cord compression, according to MRI analysis.…”

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confidence: 98%

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Electrophysiological evidence of functional improvement in the corticospinal tract after laminoplasty in patients with cervical compressive myelopathy

Nakanishi¹,

Tanaka²,

Kamei³

et al. 2014

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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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Section: Discussionsupporting

confidence: 75%

Section: Discussionmentioning

confidence: 97%

mentioning

confidence: 98%

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Electrophysiological evidence of functional improvement in the corticospinal tract after laminoplasty in patients with cervical compressive myelopathy

Nakanishi¹,

Tanaka²,

Kamei³

et al. 2014

SPI

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“…Moreover, CMCT was found to be more prolonged in patients who had more severe cervical spinal cord compression as determined by MRI analysis [17]. Because of this delayed CMCT, it is suggested that CMCT prolongation is primarily due to corticospinal conduction block, rather than conduction delay [18][19][20]. On the other hand, there is no correlation in elderly patients over 70 years between CMCT and the Japanese Orthopaedic Association (JOA) score, which reflects the severity of clinical disability [21].…”

Section: Discussionmentioning

confidence: 99%

Quantitative assessment of myelopathy patients using motor evoked potentials produced by transcranial magnetic stimulation

et al. 2009

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Motor evoked potentials (MEPs) study using transcranial magnetic stimulation (TMS) may give a functional assessment of corticospinal conduction. But there are no large studies on MEPs using TMS in myelopathy patients. The purpose of this study is to confirm the usefulness of MEPs for the assessment of the myelopathy and to investigate the use of MEPs using TMS as a screening tool for myelopathy. We measured the MEPs of 831 patients with symptoms and signs suggestive of myelopathy using TMS. The MEPs from the abductor digiti minimi (ADM) and abductor hallucis (AH) muscles were evoked by transcranial magnetic brain stimulation. Central motor conduction time (CMCT) is calculated by subtracting the peripheral conduction time from the MEP latency. Later, 349 patients had surgery for myelopathy (operative group) and 482 patients were treated conservatively (nonoperative group). CMCTs in the operative group and nonoperative group were assessed. MEPs were prolonged in 711 patients (86%) and CMCTs were prolonged in 493 patients (59%) compared with the control patients. CMCTs from the ADM and AH in the operative group were significantly more prolonged than that in the nonoperative group. All patients in the operative group showed prolongation of MEPs or CMCTs or multiphase of the MEP wave. MEP abnormalities are useful for an electrophysiological evaluation of myelopathy patients. Moreover, MEPs may be effective parameters in spinal pathology for deciding the operative treatment.

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“…6,15,33,40 In addition, F-wave studies have been reported to be able to detect diabetic neuropathy. 1,20,34 Motor conduction latencies are increased in patients with diabetic neuropathy.…”

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confidence: 99%

Electrophysiological assessments of the motor pathway in diabetic patients with compressive cervical myelopathy

Nakanishi¹,

Tanaka²,

Kamei³

et al. 2015

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OBJECT The occurrence of compressive cervical myelopathy (CCM) increases in adults over 50 years of age. In addition, diabetes mellitus (DM) is a frequent comorbidity for people of this age and may impact the severity of CCM. The authors assessed motor pathway function in diabetic patients with CCM to investigate the correlation between electrophysiological parameters and clinical symptoms. METHODS Motor evoked potentials (MEPs) were measured from the abductor digiti minimi muscle (ADM) and the abductor hallucis muscle (AH) following transcranial magnetic stimulation, as were M- and F-waves following electrical stimulation of the ulnar and tibial nerves, in 22 patients with CCM and diabetes mellitus (DM) who had not experienced symptomatic diabetic neuropathy (CCM-DM group), in 92 patients with CCM alone (CCM group), and in 24 healthy adults (control group). The peripheral conduction time (PCT; measured from the ADM and AH) was calculated as follows: (M-wave latency + F-wave latency −1)/2. The central motor conduction time (CMCT; measured from the ADM and AH) was calculated by subtracting the PCT from the onset latency of the MEPs. The Japanese Orthopaedic Association (JOA) score for cervical myelopathy was obtained before and 1 year after surgery as a clinical outcome measure. RESULTS MEP, PCT, and CMCT parameters in the CCM-DM and CCM groups were significantly longer than those in the control group (p = 0.000−0.007). The PCTs in the CCM-DM group were significantly longer than those in the CCM group (p = 0.001−0.003). No significant differences were detected in the MEP and CMCT parameters between the CCM-DM and CCM groups (p = 0.080–1.000). The JOA score before surgery in the CCM-DM group was 10.7 ± 2.0 points and was significantly lower than that in the CCM group (12.2 ± 2.5 points, p = 0.015). In the CCM-DM group, JOA scores before surgery correlated with MEP-AH (r = −0.610, p = 0.012) and PCT-AH (r = −0.676, p = 0.004) values, but not with CMCT values, while the JOA scores were related to both MEP and CMCT parameters in the CCM group. The JOA scores improved to 13.8 ± 2.2 points after surgery (p = 0.001) and correlated with MEP-AH (r = −0.667, p = 0.005) and PCT-AH (r = −0.611, p = 0.012) in the CCM-DM group. CONCLUSIONS The results suggest that MEP, PCT, and CMCT parameters each reveal abnormalities in the upper and lower motor neurons even in patients with DM. The results also show a prolonged PCT in CCM-DM patients, despite having no history of diabetic neuropathy. Corticospinal tract impairments are similar between CCM and CCM-DM patients, while the JOA score of the CCM-DM patients is lower than that in the CCM patients. The JOA score in CCM-DM patients may be influenced by additional impairments in peripheral nerves or other diabetic complications. These electrophysiological studies may be useful for screening motor pathway function for CCM in patients with DM.

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Mechanism of prolonged central motor conduction time in compressive cervical myelopathy

Cited by 59 publications

References 13 publications

Electrophysiological evidence of functional improvement in the corticospinal tract after laminoplasty in patients with cervical compressive myelopathy

Electrophysiological evidence of functional improvement in the corticospinal tract after laminoplasty in patients with cervical compressive myelopathy

Quantitative assessment of myelopathy patients using motor evoked potentials produced by transcranial magnetic stimulation

Electrophysiological assessments of the motor pathway in diabetic patients with compressive cervical myelopathy

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