Somatosensory evoked potential studies in internal capsule and corona radiata infarction

To document the somatosensory evoked potential (SEP) changes in capsular and corona radiata infarction and correlate these with clinical and radiological findings, 15 patients with corona radiata and 16 with internal capsular infarction were studied. The mean age of the patients was 55 years (range 26–80), and 6 of them were female. In the patients with corona radiata infarction, median N9–N20 conduction time was abnormal in 4 cases, which correlated with sensory abnormalities in 1. In 3 of these patients, infarction was located in the anterior two-thirds and in 1 there was total corona radiata infarction. The amplitude of N20 potential on the affected side was reduced in 1 patient. In the capsular infarction group, N9–N20 conduction time was abnormal in 1 patient only who had total involvement of the posterior limb of the internal capsule. The amplitude of N20 was reduced in another patient. There were 4 patients who had abnormal sensory findings, but their SEPs were normal. At 3 months, the SEP changes remained stable in all of the patients who were followed up. The SEP changes did not correlate with changes in sensation or 3-month outcome as assessed by the Barthel index score. The lack of clinicoradiological and SEP correlation may be owing to variation on the organisation of sensory pathways in the corona radiata and internal capsule. Received: 3 July 1997 Received in revised form: 15 January 1998 Accepted: 27 January 1998     

Central motor conduction in cervical dystonia with cervical spondylotic myelopathy

OBJECTIVES: It has been known that cervical dystonia develops secondarily to spinal cord injuries as secondary dystonia. However, little is known about the pathophysiological mechanism. PATIENTS AND METHODS: We examined motor and sensory conduction in six patients with symptomatic cervical dystonia by transcranial magnetic stimulation (TMS). All of the patients exhibited unilateral head rotation. They had symptoms corresponding to cervical myelopathy and felt discomfort in the neck, shoulders or arms before involuntary movement occurred. RESULTS: Although the overall central motor conduction time (CMCT) was not different from that of normal controls, contralateral CMCT was significantly delayed compared to ipsilateral CMCT (p<0.05). The results of somatosensory evoked potential study demonstrated that contralateral central conduction time (CCT) was not significantly different from ipsilateral CCT. CONCLUSION: These findings indicate that there is a selective interference with the contralateral corticospinal tract in patients with symptomatic cervical dystonia.     

Central motor conduction as a measure of disease progression in early multiple sclerosis

We monitored disease progression in 27 patients with clinically or laboratory-supported definite multiple sclerosis by means of clinical assessments [expanded disability status scale (EDSS), and the neurologic rating scale (NRS)] repeated at 6 month intervals for 2 years. Each clinical assessment was accompanied by evoked potentials (EP; visual, brain stem auditory, and somatosensory evoked potentials), motor evoked potentials elicited by magnetic stimulation, and magnetic resonance imaging of the brain and brain stem. Central conduction indices were calculated for each central pathway. According to the EDSS 18 patients deteriorated, eight were unchanged and one improved. The central motor conduction index (CMCI) was the only conduction parameter which correlated significantly with both EDSS and NRS at baseline [rho=0.51 (EDSS); -0.65 (NRS)], at final investigation, and when individual changes from baseline to final investigation were addressed (rho=0.38; -0.38). Individual deteriorations or improvements of the CMCI during the 2 years correlated with changes in both EDSS and NRS (rho = 0.51; -0.38). The MRI parameters did not correlate with the clinical scores. The concordance between MRI and CMCI in detection of disease activity was 63%. We conclude that the CMCI stands out as an objective, accurate and easily obtained outcome parameter.     

Serial changes in motor and somatosensory evoked potentials in putaminal haemorrhage

Little is known about evoked potential changes in putaminal haemorrhage. In this study, somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs) have been serially evaluated and their role in the prognosis of putaminal haemorrhage is now reported. Nineteen patients with CT- or MRI-proven putaminal haemorrhage were examined after a mean duration of 13 days (range 2–30); there were 4 females and 9 males, ranging in age between 25 and 70 years. The haematomas were of medium size in 13 and large or small in 3 patients each. The changes in the clinical picture and the SEPs and MEPs were evaluated on admission, and after 30 and 90 days. Central motor conduction time (CMCT) could not be recorded in 13, but was prolonged in 2 and normal in 4 patients. Median SEPs revealed the absence of near field potentials in 11 and prolongation of N9–N20 conduction time in 1 patient. In the follow-up period MEP and SEP abnormalities only changed in 5 patients; MEPs changed in 4 and SEPs in 2. The period of normalisation of MEPs ranged between 1 and 6 months. CMCT correlated with motor and N9–N20 conduction time with sensory impairment. Eight patients had poor, 6 partial and 5 complete recovery. Power, sensation, CMCT, and size and location of haematoma made positive contributions to recovery.     

侧脑室体旁放射冠区脑梗塞的临床和CT对照分析

报告经头颅CT扫描证实的侧脑室体旁放射冠区脑梗塞84例,其中腔隙性脑梗塞(Lacunae infarction,LI)59例,分水岭梗塞(Watershed infarction,WI)25例。结合文献就两者的病因,临床特征和放射冠区传导束的排列情况进行了讨论,结果发现高血压是二者共同的、主要的病因,放射冠区锥体束的排列顺序与躯体存在定位关系。     

Peripheral motor nerve conduction abnormality,muscle strength,and muscle wasting in patients with acute stroke: A pilot study

IntroductionStroke-related muscle wasting are important therapeutic targets to reduce disability in patients with stroke. Peripheral nerve conduction impairment is one reported factor that causes muscle wasting in these patients, but muscle strength, muscle wasting, and peripheral nerve conduction abnormality have not been examined in patients with acute stroke. We therefore investigated changes in lower-leg motor nerve conduction, muscle strength, and muscle wasting in patients with acute stroke.MethodsPatients with acute stroke were recruited. Their motor conduction velocity (MCV) and compound motor action potential (CMAP) amplitude in both sides of the common peroneal nerve, and lower paretic leg muscle strength by the Motricity Index (MI) and quadriceps muscle thickness (QMT) on both sides were measured at the time of admission and again 2 weeks later.ResultsEighteen patients with acute stroke (median [interquartile range], age = 68 [14] years; female = 4 [22%]) were enrolled. The MCV and CMAP amplitude were not significantly different between limbs. The QMT was significantly reduced in paretic (P = 0.014) and non-paretic (P = 0.003) limbs, but the lower paretic leg MI was increased (P = 0.0.001). There was a significant correlation between % differences in CMAP amplitude and % differences in QMT in the paretic limb (R = 0.604, P = 0.008), but not in the non-paretic limb (R = 0.225, P = 0.369).ConclusionsLower-leg muscle wasting was associated with the change in CMAP amplitude in paretic limbs, but not in non-paretic limbs, in patients with acute stroke.     

Pure dysarthria due to anterior internal capsule and/or corona radiata infarction: a report of five cases.

Five cases with a sudden onset of dysarthria in the setting of hypertension are presented. No case had limb weakness or other neurological deficits. Computed tomographic scan demonstrated a small low density lesion in the anterior part of the internal capsule or the adjacent corona radiata. All cases showed a good recovery from dysarthria within two to four weeks.     

Dissociation of motor symptoms during deep brain stimulation of the subthalamic nucleus in the region of the internal capsule

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) can be an effective treatment for the motor symptoms of Parkinson's disease. The therapeutic benefits are voltage-dependent and, in many cases, limited by the appearance of side effects, including muscle contractions. We have observed a number of clinical cases where improvements in rigidity were accompanied by a worsening of bradykinesia. Considering the anatomic position of STN and current approaches to implantation of the DBS lead, we hypothesized that this dissociation of motor symptoms arises from activation of pyramidal tract fibers in the adjacent internal capsule. The objective of this study was to assess the physiological basis for this dissociation and to test our hypothesis that the underlying etiology of this paradox is activation of fibers of the internal capsule. The effect of STN DBS at 80% of motor threshold for each of the four contacts was evaluated for its effect on rigidity, bradykinesia, and akinesia in a single primate with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced parkinsonism. Consistent with our observations in humans, this near-threshold stimulation was found to improve rigidity while bradykinesia and akinesia worsened. Worsening bradykinesia in the face of improvement of other motor signs in Parkinson's disease (PD) patients is suggestive of activation of pyramidal tract (PT) fibers during stimulation. This phenomenon may occur without overt muscle contraction and improved rigidity.     

Cortico-conus motor conduction time (CCCT) for leg muscles

Objective

To measure the conduction time from the motor cortex to the conus medullaris (cortico-conus motor conduction time, CCCT) for leg muscles using magnetic stimulation.

Methods

Motor evoked potentials (MEPs) were recorded from tibialis anterior muscles in 51 healthy volunteers. To activate spinal nerves at the most proximal cauda equina level or at the conus medullaris level, magnetic stimulation was performed using a MATS coil. Transcranial magnetic stimulation of the motor cortex was also conducted to measure the cortical latency for the target muscle. To obtain the CCCT, the latency of MEPs to conus stimulation (conus latency) was subtracted from the cortical latency.

Results

MATS coil stimulation evoked reproducible MEPs in all subjects, yielding CCCT data for all studied tibialis anterior muscles.

Conclusions

MATS coil stimulation provides CCCT data for healthy subjects.

Significance

This novel method is useful for evaluation of corticospinal tract function for leg muscles because no peripheral component affects the CCCT.     

Localization of orofacial representation in the corona radiata,internal capsule and cerebral peduncle in Macaca mulatta

Subcortical white matter injury is often accompanied by orofacial motor dysfunction, but little is known about the structural substrates accounting for these common neurological deficits. We studied the trajectory of the corticobulbar projection from the orofacial region of the primary (M1), ventrolateral (LPMCv), supplementary (M2), rostral cingulate (M3) and caudal cingulate (M4) motor regions through the corona radiata (CR), internal capsule (IC) and crus cerebri of the cerebral peduncle (ccCP). In the CR each pathway was segregated. Medial motor area fibers (M2/M3/M4) arched over the caudate and lateral motor area fibers (M1/LPMCv) curved over the putamen. At superior IC levels, the pathways were widespread, involving the anterior limb, genu and posterior limb with the M3 projection located anteriorly, followed posteriorly by projections from M2, LPMCv, M4 and M1, respectively. Inferiorly, all pathways maintained this orientation but shifted posteriorly, with adjacent fiber bundles overlapping minimally. In the ccCP, M3 fibers were located medially and M1 fibers centromedially, with M2, LPMCv, and M4 pathways overlapping in between. Finally, at inferior ccCP levels, all pathways overlapped. Following CR and superior IC lesions, the dispersed pathway distribution may correlate with acute orofacial dysfunction with spared pathways contributing to orofacial motor recovery. In contrast, the gradually commixed nature of pathway representation inferiorly may enhance fiber vulnerability and correlate with severe, prolonged deficits following lower subcortical and midbrain injury. Additionally, in humans these findings may assist in interpreting orofacial movements evoked during deep brain stimulation, and neuroimaging tractography efforts to localize descending orofacial motor pathways.     

早期立体定向置管引流治疗内囊区小血肿的临床研究

目的比较内囊区小血肿早期立体定向治疗与保守治疗的临床疗效。方法选择肌力在1~2级的60例内囊区小血肿患者按入院先后顺序随机分两组,每组30例,分别行早期立体定向血肿排空术和保守治疗。结果按日常生活能力(ADL)分级:立体定向组Ⅰ级19例,Ⅱ级8例,Ⅲ级3例,无死亡病例。保守治疗组Ⅰ级8例,Ⅱ级9例,Ⅲ级7例,Ⅳ级5例,死亡1例(3.3%),随访1~6个月,立体定向组恢复良好率90%,致残率10%。保守治疗组恢复良好率58.6%,致残率41.4%。两组ADL能力、致残率方面差异有显著统计意义,P<0.01。结论立体定向治疗内囊区小血肿,定位准确,创伤小,神经功能恢复快,其临床疗效明显优于内科保守治疗,可以降低致残率,提高患者生存质量。     

Estimate of motor conduction in human spinal cord: slowed conduction in spinal cord injury

By using motor evoked potential (MEP) created by transcranial electric stimulation over the motor cortex and F-wave measurement from the peripheral nerve stimulation, it is possible to estimate the spinal cord motor conduction velocity (SCMCV) in the diseased state. Twenty-four patients with spinal cord injury (SCI) between T1 and T11 neurological levels participated in this study. MEP in leg muscle was absent in all neurologically complete paraplegics. In 16 patients with neurologically incomplete SCI, MEP was obtained in 13 patients. The SCMCV estimated from C7 to T12 spinal levels was 32.1 (SD = 9.4) m/s. This was significantly slower than 63.3 (SD = 8.6) m/s in 40 normal controls. This noninvasive, indirect method is measurable, and can provide valuable electrophysiological data in the assessment of motor function in patients with SCI.     

Motor evoked potentials during revascularization in ischemic stroke predict motor pathway ischemia and clinical outcome

ObjectiveThe relevance of motor evoked potential (MEP) recovery during mechanical endovascular thrombectomy (MT) in patients with ischemic stroke is unclear. We correlated MEP recovery during MT to symptom improvement and to ischemia in eloquent motor areas on magnetic resonance imaging (MRI) and compared the predictive value of MEPs to visual angiographic reperfusion status, classified by modified Thrombolysis in Cerebral Infarction grading (mTICI).MethodsPatients with hemisyndrome and large-vessel occlusion undergoing MT were included (n35, 49% females; 73.9 ± 14.5 years; n31 anterior circulation). MEPs were elicited transcranially and recorded at the abductor pollicis brevis muscle bilaterally throughout the procedure. An MRI was acquired within 7 days after MT.ResultsThe median door-to-needle time was 3.5 hours. Median National Institutes of Health Stroke Scale at presentation was 16 (7 – 37). Median Modified Rankin Scale score was 4 at day 7 and 3 months. After MT, MEP-recovery occurred in 21 cases after a median time span of 4.5 min [range 2 – 11 min]. Symptom improvement at day 7 (3 months) was noted in 22 (21) cases. Absence of ischemia on postinterventional MRI was noted in 21 cases, 19 of whom showed MEP-recovery. Stratified for symptom improvement at day 7, sensitivity (specificity) of MEP-recovery was 86% (85%) and of mTICI ≥ 2b was 95% (23%). Stratified for absence of ischemia on postinterventional MRI, sensitivity (specificity) of MEP-recovery was 90% (86%) and of mTICI ≥ 2b was of 95% (21%).ConclusionsMEP recovery occurs early after successful endovascular mechanical revascularization and is superior to mTICI grading in predicting postoperative neurological outcome and postoperative motor-pathway ischemia.SignificanceThis is a new, significant and clinically important study since it emphasizes the additional value of MEP monitoring in a field, which has been traditionally unaffiliated with neurophysiological monitoring.     

Diagnostic significance of motor evoked potentials in space-occupying lesions of the brain stem and spinal cord

Summary Motor evoked potentials (MEP) were examined in 50 patients with space-occupying lesions of the brain stem and spinal cord. MEP findings were correlated with the motor status as established by clinical examination. The results clearly show the high sensitivity of MEP for detection of motor deficits: 17 recordings (77%) from the thenar muscle and 42 (84%) from the anterior tibial muscle correlated correctly with the clinical motor status. False-positive results were found in 5 (23%) thenar recordings and 8 (16%) and anterior tibial recordings. False-negative correlation was not observed. The high rate of false-positive results appears to indicate that MEP detect subclinical motor deficits. This electrophysiological test is therefore recommended, especially when involvement of the descending pathways is suspected and clinical examination reveals no abnormality.     

Medial reorganization of motor function in corona radiata following middle cerebral artery infarction A case report

Peri-lesional reorganization is one of the motor recovery mechanisms following stroke. A 23-year-old female who presented with complete paralysis of the right extremities at the onset of infarct in the left middle cerebral artery territory was included. She slowly recovered some function, and could extend the affected knee with resistance after 9 months. Diffusion tensor tractography, functional MRI, and transcranial magnetic stimulation testing were performed at 7 years after onset. Results showed that diffusion tensor tractography of the affected （left） hemisphere passed through the medial corona radiata at, or around, the wall of the lateral ventricle. The contralateral primary sensorimotor cortex was activated during affected knee movements. The motor-evoked potential, which was obtained from the affected leg, exhibited corticospinal tract characteristics. Results indicated that motor function of the affected leg recovered via the corticospinal tract, which descended through the corona radiata medial to the infarct. The motor function of the affected leg was reorganized to the medial corona radiata following infarct to the middle cerebral artery territory.     

Neurophysiological studies in acute transverse myelitis

A systematic evaluation of anterior horn cell, motor and sensory pathways is possible by electromyography (EMG), motor (MEPs) and somatosensory (SEPs) evoked potentials, respectively, which may provide valuable information on acute transverse myelitis (ATM). In a prospective hospital-based study, EMG, MEP and SEP studies were carried out on admission and after 3 months in 39 patients with ATM. All the patients also underwent detailed clinical evaluation, and spinal magnetic resonance imaging (MRI) was performed in 28. Outcome was defined at the end of 3 months as poor, partial or complete recovery on the basis of functional status. Spinal MRI revealed hyperintense signal changes in T2 extending for two segments to the entire spinal cord. Central motor conduction time to tibialis anterior (CMCT-TA) was more frequently abnormal (90%), followed by tibial SEP (77%). CMCT to abductor digiti minimi (ADM) was abnormal in 30% and median SEP in 15% of patients. Evidence of denervation on EMG was present in 51% of patients. The CMCT-TA improved in 48% patients and tibial SEP in 32%. Median SEP improved in all patients, and CMCT-ADM remained prolonged in two. At 3 months 2 patients had died, and 18 had poor, 10 partial and 9 complete recovery. CMCT was correlated with miscle power, tone, reflec and MRI changes. Patients' outcome of was correlated with CMCT, SEP and EMG. These results are consistent with pronounced involvement of dorsal region of spinal cord in ATM. MEP is more frequently abnormal than SEP. Received: 31 August 1999 / Received in revised form: 12 June 2000 / Accepted: 28 June 2000     

Decreased cortical excitability during motor imagery after disuse of an upper limb in humans

OBJECTIVE: The present study investigated the effect of joint immobilization on corticomotoneuronal excitability to only intracortical input from a hierarchical level above the primary motor cortex. METHODS: Motor evoked potentials (MEPs) and H-reflexes in the flexor carpi radialis muscle were elicited from 8 orthopedic patients with splints and 8 healthy volunteers. Each patient was examined on the day of splint removal (disuse stage) and 2 months after that day (recovery stage). Both potentials were recorded under 3 conditions: at rest, while imagining motor movement (during motor imagery), and during 10% of maximum voluntary contraction (10% MVC). RESULTS: In the patient group, the amplitude of surface electromyography during voluntary maximum wrist flexion was lower at the disuse stage than at the recovery stage, although the supra-maximum M-wave amplitude did not change between stages. Compared to both the patient group at the recovery stage and the control group, patients at the disuse stage recorded significantly lower MEPs, but only during motor imagery. In contrast, the H-reflex amplitudes were not significantly changed under any of the 3 conditions for both patients and control. CONCLUSIONS: The present results indicated a strict parallelism between motor execution (the reduction of electromyography during mvc after immobilization) and motor imagery (the reduction of MEP-amps after immobilization). This parallelism suggests that a functional reorganization or decreased excitability in the cerebral cortex area involved in executing movement likely decreases the motor capability to produce voluntary muscular output after immobilization.     

Evoked potential studies in thalamic hemorrhage

Due to paucity of a comprehensive study on somatosensory and motor evoked potentials in thalamic hemorrhage, the present study has been undertaken. Clinical examination, motor evoked potential (MEP) and median somatosensory evoked potential (SEP) studies were performed on 22 consecutive patients with CT-proven thalamic hemorrhage. The clinical and evoked potential studies were carried out on admission and repeated at the end of 3 months. The hematomas were classified as type A (with posterolateral extension) and type B (without posterolateral extension). The hematomas were of type A and type B in 11 patients each. The patients with type A hematomas had persistent inexcitability of motor pathways and SEPs were unrecordable. In type B, MEP was not recordable in three, prolonged in five and normal in three patients; in all these patients, MEP returned to normal in the follow-up study. The cortical potential;; of median SEP were normal in four and unrecordable in five patients with type B hematoma. In the follow-up study, SEPs became recordable in all, although central sensory conduction time (CSCT) was prolonged in three patients. MEP and SEPs were related to the respective motor and sensory dysfunction and to posterolateral extension of hematoma. Patients with type A hemorrhage had worse prognosis compared to type B, emphasising the importance of posterolateral extension. A persistently unrecordable MEP and SEP in thalamic hemorrhage suggests a posterolateral extension which predicts a poor outcome.