Presence Of Motor Evoked Potentials Research Articles

Predictors of manual dexterity at 3 and 6 months after stroke: integration of clinical, neurophysiological, and neuroimaging factors.

This retrospective study aimed to predict dexterity at 3 and 6 months post-stroke by integrating clinical, neurophysiological, and neuroimaging factors. We included 126 patients with first-ever, unilateral, and supratentorial stroke. Demographic, stroke characteristics, and initial clinical assessment variables [Mini-mental state examination and Fugl-Meyer Assessment Upper Extremity (FMA-UE)] were evaluated 2 weeks after stroke. Dexterity, measured using the Manual Function Test (MFT) hand subscore, was the primary outcome. The neurophysiological variables, upper limb somatosensory evoked potential (SEP) and motor evoked potential (MEP), were assessed 2 weeks post-stroke. The neuroimaging variable, fractional anisotropy (FA) of the corticospinal tract (CST), was assessed 3 weeks post-stroke. Multiple regression analysis revealed significant predictors for improved dexterity at 3 and 6 months post-stroke, including younger age, higher FMA-UE score, presence of waveforms in the SEP and MEP, and higher FA values in the CST (adjusted R 2 = 0.776, P < 0.001 at 3 months; adjusted R 2 = 0.668, P < 0.001 at 6 months; where MEP, SEP, and FA accounted together for an additional 0.079 and 0.166 of variance beyond age and FMA-UE, respectively). Subgroup analysis was conducted by categorizing the participants based on their initial hand function: those with no hand function (MFT hand subscore = 0) (N = 60) and those with a score >0 (N = 51). Initial FMA-UE was a primary predictive factor regardless of the time point or initial severity, whereas the presence of MEP was a significant predictor only in the group with no initial hand dexterity.

Effect of a tailored upper extremity strength training intervention combined with direct current stimulation in chronic stroke survivors: A Randomized Controlled Trial.

Strengthening exercises are recommended for managing persisting upper limb (UL) weakness following a stroke. Yet, strengthening exercises often lead to variable gains because of their generic nature. For this randomized controlled trial (RCT), we aimed to determine whether tailoring strengthening exercises using a biomarker of corticospinal integrity, as reflected in the amplitude of motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS), could optimize training effects in the affected UL. A secondary aim was to determine whether applying anodal transcranial direct current stimulation (tDCS) could enhance exercise-induced training effects. For this multisite RCT, 90 adults at the chronic stage after stroke (>6 months) were recruited. Before training, participants underwent TMS to detect the presence of MEPs in the affected hand. The MEP amplitude was used to stratify participants into three training groups: (1) low-intensity, MEP <50 μV, (2) moderate-intensity, 50 μV < MEP < 120 μV, and (3) high-intensity, MEP>120 μV. Each group trained at a specific intensity based on the one-repetition maximum (1 RM): low-intensity, 35–50% 1RM; moderate-intensity, 50–65% 1RM; high-intensity, 70–85% 1RM. The strength training targeted the affected UL and was delivered 3X/week for four consecutive weeks. In each training group, participants were randomly assigned to receive either real or sham anodal tDCS (2 mA, 20 min) over the primary motor area of the affected hemisphere. Pre-/post-intervention, participants underwent a clinical evaluation of their UL to evaluate motor impairments (Fugl-Meyer Assessment), manual dexterity (Box and Blocks test) and grip strength. Post-intervention, all groups exhibited similar gains in terms of reduced impairments, improved dexterity, and grip strength, which was confirmed by multivariate and univariate analyses. However, no effect of interaction was found for tDCS or training group, indicating that tDCS had no significant impact on outcomes post-intervention. Collectively, these results indicate that adjusting training intensity based on the size of MEPs in the affected extremity provides a useful approach to optimize responses to strengthening exercises in chronic stroke survivors. Also, the lack of add-on effects of tDCS applied to the lesioned hemisphere on exercise-induced improvements in the affected UL raises questions about the relevance of combining such interventions in stroke.Clinical trial registry numberNCT02915185. https://www.clinicaltrials.gov/ct2/show/NCT02915185.

Effects of a Robot-Assisted Arm Training Plus Hand Functional Electrical Stimulation on Recovery After Stroke: A Randomized Clinical Trial

ObjectiveTo compare the effects of unilateral, proximal arm robot-assisted therapy combined with hand functional electrical stimulation with intensive conventional therapy for restoring arm function in survivors of subacute stroke. DesignThis was a single-blinded, randomized controlled trial. SettingInpatient rehabilitation university hospital. ParticipantsPatients (N=40) diagnosed as having ischemic stroke (time since stroke <8wk) and upper limb impairment were enrolled. InterventionsParticipants randomized to the experimental group received 30 sessions (5 sessions/wk) of robot-assisted arm therapy and hand functional electrical stimulation (RAT+FES). Participants randomized to the control group received a time-matched intensive conventional therapy. Main Outcome MeasuresThe primary outcome was arm motor recovery measured with the Fugl-Meyer Motor Assessment. Secondary outcomes included motor function, arm spasticity, and activities of daily living. Measurements were performed at baseline, after 3 weeks, at the end of treatment, and at 6-month follow-up. Presence of motor evoked potentials (MEPs) was also measured at baseline. ResultsBoth groups significantly improved all outcome measures except for spasticity without differences between groups. Patients with moderate impairment and presence of MEPs who underwent early rehabilitation (<30d post stroke) demonstrated the greatest clinical improvements. ConclusionsRAT+FES was no more effective than intensive conventional arm training. However, at the same level of arm impairment and corticospinal tract integrity, it induced a higher level of arm recovery.

Predictors for early motor improvement in patients with ischemic stroke

Disability as a stroke consequence is reported by 3% males and 2% females in general population. Motor deficits are common in stroke patients, but their complete recovery is seen only in a minority of cases. Assessment of motor deficits uses clinical methods, especially standardized scales, but also electrophysiological and imagistic methods. The motor recovery is a continuous process, maximal in the first month after stroke, decreasing gradually over the first 6 months. Most powerful predictors for motor recovery are clinical parameters: severity of motor deficit, onset of first voluntary movements after stroke in the first 48-72 hours, a continuous improvement in motor function during the first 8 weeks, a good postural control during the first month, young age, male sex, left hemispheric stroke and absence of other neurological impairments are strong positive predictors. Presence of motor-evoked potentials in paretic muscles and imagistic parameters as location, stroke volume and motor pathways integrity are paraclinical predictors for recovery. There are no specific biomarker which is efficient in predicting recovery. In patients with poor chances for recovery according to actual predictors, the development of more precise algorithms to assess functional outcome is needed, in order to support the choice of appropriate methods and intensity of rehabilitation treatment. Key words: ischemic stroke rehabilitation, functional assessment, motor improvement, recovery predictors, prognostic factors,

Motor Evoked Potentials as Potential Biomarkers of Early Atypical Corticospinal Tract Development in Infants with Perinatal Stroke.

Diagnosis of cerebral palsy (CP) after perinatal stroke is often delayed beyond infancy, a period of rapid neuromotor development with heightened potential for rehabilitation. This study sought to assess whether the presence or absence of motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) could be an early biomarker of atypical development within the first year of life. In 10 infants with perinatal stroke, motor outcome was assessed with a standardized movement assessment. Single-pulse TMS was utilized to assess presence of MEPs. Younger infants (3–6 months CA, n = 5, 4/5 (80%)) were more likely to present with an MEP from the more-affected hemisphere (MAH) compared to older infants (7–12 months CA, n = 5, 0/5, (0%)) (p = 0.048). Atypical movement was demonstrated in the majority of infants with an absent MEP from the MAH (5/6, 83%) compared to those with a present MEP (1/4, 25%) (p = 0.191). We found that age influences the ability to elicit an MEP from the MAH, and motor outcome may be related to MAH MEP absence. Assessment of MEPs in conjunction with current practice of neuroimaging and motor assessments could promote early detection and intervention in infants at risk of CP.

Differential Poststroke Motor Recovery in an Arm Versus Hand Muscle in the Absence of Motor Evoked Potentials

Background. After stroke, recovery of movement in proximal and distal upper extremity (UE) muscles appears to follow different time courses, suggesting differences in their neural substrates. Objective. We sought to determine if presence or absence of motor evoked potentials (MEPs) differentially influences recovery of volitional contraction and strength in an arm muscle versus an intrinsic hand muscle. We also related MEP status to recovery of proximal and distal interjoint coordination and movement fractionation, as measured by the Fugl-Meyer Assessment (FMA). Methods. In 45 subjects in the year following ischemic stroke, we tracked the relationship between corticospinal tract (CST) integrity and behavioral recovery in the biceps (BIC) and first dorsal interosseous (FDI) muscle. We used transcranial magnetic stimulation to probe CST integrity, indicated by MEPs, in BIC and FDI. We used electromyography, dynamometry, and UE FMA subscores to assess muscle-specific contraction, strength, and inter-joint coordination, respectively. Results. Presence of MEPs resulted in higher likelihood of muscle contraction, greater strength, and higher FMA scores. Without MEPs, BICs could more often volitionally contract, were less weak, and had steeper strength recovery curves than FDIs; in contrast, FMA recovery curves plateaued below normal levels for both the arm and hand. Conclusions. There are shared and separate substrates for paretic UE recovery. CST integrity is necessary for interjoint coordination in both segments and for overall recovery. In its absence, alternative pathways may assist recovery of volitional contraction and strength, particularly in BIC. These findings suggest that more targeted approaches might be needed to optimize UE recovery.

Motor Evoked Potentials Correlate With Magnetic Resonance Imaging and Early Recovery After Acute Spinal Cord Injury.

While the utilization of neurophysiologic intraoperative monitoring with motor evoked potentials (MEPs) has become widespread in surgery for traumatic spine fractures and spinal cord injury (SCI), clinical validation of its diagnostic and therapeutic benefit has been limited. To describe the use of intraoperative MEP at a large level I trauma center and assess the prognostic capability of this technology. The SCI REDCap database at our institution, a level I trauma center, was queried for acute cervical SCI patients who underwent surgery with intraoperative monitoring between 2005 and 2011, yielding 32 patients. Of these, 23 patients had severe SCI (association impairment scale [AIS] A, B, C). We assessed preoperative and postoperative SCI severity (AIS grade), surgical data, use of steroids, and early magnetic resonance imaging (MRI) findings (preoperatively in 27 patients), including axial T2 MRI grade (Brain and Spinal Injury Center score). The presence of MEPs significantly predicted AIS at discharge (P< .001). In the group of severe SCI (ie, AIS A, B, C) patients with elicitable MEPs, AIS improved by an average of 1.5 grades (median = 1), as compared to the patients without elicitable MEP who improved on average 0.5 grades (median = 0, P< .05). In addition, axial MRI grade significantly correlated with MEP status. Patients without MEPs had a significantly higher axial MRI grade in comparison to the patients with MEPs (P< .001). In patients with severe SCI, MEPs predicted neurological improvement and correlated with axial MRI grade. These significant findings warrant future prospective studies of MEPs as a prognostic tool in SCI.

Abstract 101: Predicting Motor Recovery at One Week After Ischemic Stroke: a Combined Transcranial Magnetic Stimulation and MRI Study

Introduction: The failure of numerous stroke clinical trials partially lies in the difficulty in predicting motor recovery in the acute phase. Because of the interindividual variability in subsequent recovery, better prediction of motor prognosis and earlier patient stratification are required to design a promising protocol for clinical trials. Recently, an algorithm to predict motor recovery at 2 weeks after stroke has been reported by combining diffusion-weighted MRI and transcranial magnetic stimulation (TMS); however, 2 weeks may be too late for therapeutic intervention. The aim of this study was therefore to explore how to predict motor recovery even earlier at 1 week after ischemic stroke. Subjects and Methods: Twenty-five patients with acute ischemic stroke (67.9±10.5 years old) who showed supratentorial lesions and hemiparesis of the upper extremity were prospectively enrolled. Integrity of the corticospinal tract was assessed structurally with MRI and functionally with TMS within 7 days after onset (acute phase), at 10-20 days (subacute), and at 6 months (chronic). The fractional anisotropy (FA) asymmetry index (FAcontra-FAipsi)/(FAcontra+FAipsi) at the level of the cerebral peduncle was calculated on MRI, while motor evoked potential (MEP) was recorded on TMS. The Fugl-Meyer scale was used to evaluate upper limb impairment in the subacute and chronic phase. Results: Patients with detectable MEP at 1 week after onset showed significantly higher Fugl-Meyer score at 6 months compared to those without MEP (65.4 versus 33.6, p=0.011). Those with FA asymmetry index of less than 0.024 at 1 week showed significantly higher Fugl-Meyer score at 6 months compared to those with the index above 0.024 (64.2 versus 40.1, p=0.037). Conclusion: Presence of MEP and smaller asymmetry of FA at 1 week after ischemic stroke could be a useful biomarker for predicting better motor recovery. This finding can be useful in earlier patient stratification in future clinical trials.

Spared Primary Motor Cortex and The Presence of MEP in Cerebral Palsy Dictate the Responsiveness to tDCS during Gait Training

The current priority of investigations involving transcranial direct current stimulation (tDCS) and neurorehabilitation is to identify biomarkers associated with the positive results of the interventions such that respondent and non-respondent patients can be identified in the early phases of treatment. The aims were to determine whether: (1) present motor evoked potential (MEP); and (2) injuries involving the primary motor cortex, are associated with tDCS-enhancement in functional outcome following gait training in children with cerebral palsy (CP). We reviewed the data from our parallel, randomized, sham-controlled, double-blind studies. Fifty-six children with spastic CP received gait training (either treadmill training or virtual reality training) and tDCS (active or sham). Univariate and multivariate logistic regression analyses were employed to identify clinical, neurophysiologic and neuroanatomic predictors associated with the responsiveness to treatment with tDCS. MEP presence during the initial evaluation and the subcortical injury were associated with positive effects in the functional results. The logistic regression revealed that present MEP was a significant predictor for the six-minute walk test (6MWT; p = 0.003) and gait speed (p = 0.028), whereas the subcortical injury was a significant predictor of gait kinematics (p = 0.013) and gross motor function (p = 0.021). In this preliminary study involving children with CP, two important prediction factors of good responses to anodal tDCS combined with gait training were identified. Apparently, MEP (integrity of the corticospinal tract) and subcortical location of the brain injury exerted different influences on aspects related to gait, such as velocity and kinematics.

The Predictive Value of Motor-Evoked Potentials and the Silent Period on Patient Outcome after Acute Cerebral Infarction

The predictive value of neurophysiologic assessment on patients' outcome after acute cerebral infarction is poorly understood. The aim of this study was to investigate the prognostic value of motor-evoked potentials (MEPs) and the silent period (SP) on clinical outcome. A total of 202 patients with acute cerebral infarction were prospectively recruited. MEP and SP were recorded from the abductor pollicis brevis of the affected side within 10 days after stroke onset. Patient outcome was measured as the dependency rate. Cortical MEP was induced in 78 patients whereas it was absent in 82 patients. The initial NIHSS (National Institutes of Health Stroke Scale) score was significantly lower in patients with MEP than in those without MEP (P < .001). Regression analysis demonstrated that a left-sided lesion (OR = .391, 95% CI .178-.858, P = .019), NIHSS at admission (OR = .826, 95% CI .744-.917, P < .001), and presence of MEP (OR = 3.918, 95% CI 1.770-8.672, P < .001) were independent predictors of outcome 3 months after stroke. Among patients with MEP, only the contralateral cortical SP value was significantly shorter in the good outcome subgroup (t = 2.541, P = .013). Receiver operating characteristic curve analysis demonstrated that SP was able to predict patients at higher risk of unfavorable outcome 3 months after stroke onset (area under the curve .721, 95% CI .58-.86, P = .008). These data suggested that MEP and SP were useful tools to predict patients' acute outcomes following cerebral infarction.

Proportional recovery after stroke depends on corticomotor integrity.

For most patients, resolution of upper limb impairment during the first 6 months poststroke is 70% of the maximum possible. We sought to identify candidate mechanisms of this proportional recovery. We hypothesized that proportional resolution of upper limb impairment depends on ipsilesional corticomotor pathway function, is mirrored by proportional recovery of excitability in this pathway, and is unaffected by upper limb therapy dose. Upper limb impairment was measured in 93 patients at 2, 6, 12, and 26 weeks after first-ever ischemic stroke. Motor evoked potentials (MEPs) and motor threshold were recorded from extensor carpi radialis using transcranial magnetic stimulation, and fractional anisotropy (FA) in the posterior limbs of the internal capsules was determined with diffusion-weighted magnetic resonance imaging. Initial impairment score, presence of MEPs and FA asymmetry were the only predictors of impairment resolution, indicating a key role for corticomotor tract function. By 12 weeks, upper limb impairment resolved by 70% in patients with MEPs regardless of their initial impairment, and ipsilesional rest motor threshold also resolved by 70%. Resolution of impairment was insensitive to upper limb therapy dose. These findings indicate that upper limb impairment resolves by 70% of the maximum possible, regardless of initial impairment, but only for patients with intact corticomotor function. Impairment resolution seems to reflect spontaneous neurobiological processes that involve the ipsilesional corticomotor pathway. A better understanding of these mechanisms could lead to interventions that increase resolution of impairment above 70%.

Electrophysiological prognostic factors of aphasia recovery

Aphasia is the main cause of communication disorders following stroke. The individual prognosis of aphasia recovery remind difficult to establish in the acute phase. The aim of this study was to investigate whether the motor evoked potentials (MEP) of the hand and the orbicularis oris in the acute phase of stroke could predict aphasia recovery. This study is ongoing at the University Hospital of Bordeaux. All consecutive patients with aphasia, first left hemispheric stroke confirmed by imaging, right-handed, non-demented, have been proposed for inclusion. MEPs were collected after stimulation of M1 the abductor pollicis and the orbicularis oris, right and left. The assessment of language performed in the acute phase was composed of: Language Screening Test (LAST) and the aphasia severity rating scale (ASRS) of the Boston Diagnostic Aphasia Examination (BDAE). Three and six months later, the language assessment was composed by: LAST, ASRS and BDAE. Good recovery from aphasia was defined as a score of ASRS 4 or 5. The association between the presence of a MEP after stimulation and good recovery was studied by Fischer exact tests. In our interim analysis, 46 patients were followed at 3 months, and 23 at 6 months. The presence of MEP of the right hand (left cortical stimulation) was significantly associated with good recovery 3 months ( P = 0.003) and 6 months ( P = 0.003) after a stroke. The presence of MEP of the right orbicularis oris (left cortical stimulation) was significantly associated with good recovery 3 months ( P = 0.003) and 6 months ( P = 0.011). MEP of hand and lips predict recovery from aphasia. This results suggest the importance of production systems in the recovery of language, suggesting a new approach compared semantic core highlighted in the old classic models such as Lichtheim.

Predictability of Motor Outcome According to the Time of Motor Evoked Potentials From the Onset of Stroke in Patients With Putaminal Hemorrhage.

ObjectiveTo determine the predictability of motor evoked potentials (MEP) in patients with putaminal hemorrhage (PH) according to the time of MEP from the onset of stroke.MethodsSixty consecutive patients with PH from January 2006 to November 2013 were retrospectively reviewed. Motor function of affected extremities was measured at onset time and at six months after the onset. Patients were classified into two groups according to the time of MEP from the onset of stroke: early MEP group (within 15 days from onset) and late MEP group (16-30 days from onset). Patients were also classified into two groups according to the presence of MEP on the affected abductor pollicis brevis (APB): MEP (+) group-patients (showing MEP in the affected APB) and MEP (-) group-patients (no MEP in the affected APB). Motor outcome was compared between the two early and late MEP groups or between the presence and absence of MEP in the affected APB groups.ResultsFor patients with MEP (+), a larger portion in the late MEP group showed good prognosis compared to the early MEP group (late MEP, 94.4%; early MEP, 80%). In contrast, in patients with MEP (-), a larger portion of patients in the late MEP group showed bad prognosis compared to the early MEP group (late MEP, 80%; early MEP, 71.4%). No significant improvement of MI between MEP (+) and MEP (-) was observed when MEP was performed early or late.ConclusionOur results revealed that the predictability of motor outcome might be better if MEP is performed late compared to that when MEP is performed early in patients with PH.

Corticospinal Integrity and Motor Impairment Predict Outcomes After Excitatory Repetitive Transcranial Magnetic Stimulation: A Preliminary Study

ObjectiveTo identify the effective predictors for therapeutic outcomes based on intermittent theta-burst stimulation (iTBS). DesignA sham-controlled, double-blind parallel study design. SettingA tertiary hospital. ParticipantsPeople with stroke (N=72) who presented with unilateral hemiplegia. InterventionsTen consecutive sessions of real or sham iTBS were implemented with the aim of enhancing hand function. Patients were categorized into 4 groups according to the presence (MEP+) or absence (MEP−) of motor-evoked potentials (MEPs) and grip strength according to the Medical Research Council (MRC) scale. Main Outcome MeasuresCortical excitability, Wolf Motor Function Test (WMFT), finger-tapping task (FT), and simple reaction time were performed before and after the sessions. ResultsMEPs and the MRC scale were predictive of iTBS therapeutic outcomes. Group A (MEP+, MRC>1) exhibited the greatest WMFT change (7.6±2.3, P<.001), followed by group B (MEP−, MRC>1; 5.2±2.2 score change) and group C (MEP−, MRC=0; 2.3±1.5 score change). These improvements were correlated significantly with baseline motor function and ipsilesional maximum MEP amplitude. ConclusionsThe effectiveness of iTBS modulation for poststroke motor enhancement depends on baseline hand grip strength and the presence of MEPs. Our findings indicate that establishing neurostimulation strategies based on the proposed electrophysiological and clinical criteria can allow iTBS to be executed with substantial precision. Effective neuromodulatory strategies can be formulated by using electrophysiological features and clinical presentation information as guidelines.

Functional implications of corticospinal tract impairment on gait after spinal cord injury

Maximum toe elevation during walking is an objective measure of foot drop and reflects the impairment of the corticospinal tract (CST) in persons with spinal cord injury (SCI). To determine if this measurement is functionally relevant to ambulatory abilities, we correlated maximum toe elevation with clinical physiotherapy tests. Cross-sectional study, laboratory and clinical settings. A total of 24 individuals with SCI (American Spinal Injury Association (ASIA) Impairment Scale D) were recruited. Maximum toe elevation during the swing phase of treadmill gait was measured with a kinematic system. CST function was assessed in a sitting position by measuring the motor-evoked potentials (MEPs) induced in tibialis anterior muscle with transcranial magnetic stimulation over the motor cortex. Clinical tests performed were 10-m and 6-min walk test (6MWT), Timed-Up and Go (TUG), Walking Index for Spinal Cord Injury, Berg Balance Scale, Lower Extremity Motor Score (LEMS) and sensory score of the L4, L5 and S1 dermatomes. Participants with lower toe elevation during gait walked at a slower speed, took more time to perform the TUG test, and covered a shorter distance in the 6MWT. They also scored lower on the LEMS and showed impaired superficial sensitivity of the dermatomes around the ankles. Few correlations were observed between CST function and clinical tests, but the presence of MEP at rest was indicative of faster speed and longer distance in the 6MWT. These results indicate that maximum toe elevation, which is directly correlated with CST impairment, is functionally relevant as it also correlates with timed clinical tests, LEMS and sensory scores.

Transcranial Magnetic Stimulation Predicts Functional Recovery after Botulinum Toxin Treatment in Stroke Patients

Spasticity is a disabling stroke complication. Despite the ascertained efficacy of botulinum toxin A (BoNT-A) in reducing spasticity, only few patients improve in upper limb active function and it is not possible on clinical basis to predict the response to treatment (1). Motor-evoked potential (MEP) recording after transcranial magnetic stimulation (TMS) of motor cortex may provide noninvasive evaluation of central motor pathways (2). We performed a prospective study in 14 chronic stroke patients with upper limb spasticity to assess the efficacy of TMS to predict upper limb functional response to one-time injections of BoNT-A. MEP findings were correlated with the change in the Action Research Arm Test (ARAT) score at one-month. Twelve patients (85·7%) had a reduction of spasticity and five of these patients (35·7%) also improved in the ARAT score. The presence of MEP in the affected hand had a positive predictive power of 57·1% and a negative predictive power of 85·7% of a functional improvement; thus, it is very unlikely that patients who have no MEP in affected hand respond to BoNT-A. These results confirm that BoNT-A reduces spasticity in stroke patients, and in some of them can also improve upper limb function. TMS may be useful in selecting the patients that are more likely to improve in upper limb function because it is more specific than clinic evaluation in assessing corticospinal pathway responsible for fine manipulatory finger movements (3). Fioravante Capone, Paolo Profice, Fabio Pilato, Anna Rita Bentivoglio, Tamara Ialongo, Raffaella Di Giacopo, Federico Ranieri, and Vincenzo Di Lazzaro* Institute of Neurology, Campus BioMedico University, Rome, Italy Fondazione Alberto Sordi – Research Institute for Ageing, Rome, Italy Department of Neurosciences, Universita Cattolica, Rome, Italy CeRiN (Center for Neurocognitive Rehabilitation), CIMeC (Center for Mind/Brain Sciences), University of Trento, Rome, Italy

Motor Evoked Potentials and Somatosensory Evoked Potentials of Upper and Lower Extremities for Prediction of Functional Recovery in Stroke

Objective: The aim of this study was to evaluate the relationship between motor evoked potentials (MEPs) or somatosensory evoked potentials (SSEPs) and the recovery of function in acute or subacute stroke patients. Method: Twenty one hemiplegic stroke patients were examined with MEPs of extensor carpi radialis, abductor pollicis brevis, tibialis anterior and abductor hallucis and SSEPs of median and tibial nerves. A separate score was defined for upper and lower extremities wi thin the Fugl-Meyer assessment and Korean-modified Barthel index. Motor performances were evaluated simultaneously with the evoked potential assessments and at 2 weeks after the first examination. Results: The second motor function of upper extremity was significantly higher in patients with the presence of MEP or SSEP (p＜0.05). The improvement of self care was correlated with the responsiveness in SSEP. Motor function of lower extremity was significantly associated with the responsiveness in MEP or SSEP (p＞0.05). MEP in tibialis anterior or tibial SSEP were correlated with the mobility. Conclusion: MEP in tibialis anterior is useful in predicting in mobility after stroke. SSEP is predictive for activities in daily living after stroke. (Brain & NeuroRehabilitation 2012; 5: 24-31)

Disinhibition in the Unaffected Hemisphere Is Related with the Cortical Involvement of the Affected Hemisphere

ABSTRACTTo investigate whether the disinhibition of the unaffected hemisphere (UH) is related with the lesion location or integrity of the corticospinal tract, we evaluated the intracortical excitability of hand motor cortex in the UH using a paired-pulse transcranial magnetic stimulation paradigm short intracortical inhibition (sICI) and intracortical facilitation (ICF) in 30 subacute stroke survivors. The participants were then classified according to the lesion locations (cortical versus subcortical) and the presence of motor-evoked potential (MEP) response on the paretic hand (MEP+ versus MEP−). The sICI and ICF in the UH were compared according to lesion location and presence of paretic MEP. The sICI and ICF in the UH were comparable between MEP+ and MEP− groups. However, in terms of lesion location, intracortical inhibition was present in patients with subcortical lesions, whereas the patients with cortical lesions showed significant disinhibition in the UH. In conclusion, these findings support that the disinhibition of UH in subacute stage is related to the location of lesion rather than the integrity of the corticospinal tract.

Efficacy of EMG-triggered electrical arm stimulation in chronic hemiparetic stroke patients

EMG-triggered electrostimulation (EMG-ES) may improve the motor performance of affected limbs of hemiparetic stroke patients even in the chronic stage. This study was designed to characterize cortical activation changes following intensified EMG-ES in chronic stroke patients and to identify predictors for successful rehabilitation depending on disease severity. We studied 9 patients with severe residual hemiparesis, who underwent 8 weeks of daily task-orientated multi-channel EMG-ES of the paretic arm. Before and after treatment, arm function was evaluated clinically and cortical activation patterns were assessed with functional MRI (fMRI) and/or transcranial magnetic stimulation (TMS). As response to therapy, arm function improved in a subset of patients with more capacity in less affected subjects, but there was no significant gain for those with Box & Block test values below 4 at inception. The clinical improvement, if any, was accompanied by an ipsilesional increase in the sensorimotor cortex (SMC) activation area in fMRI and enhanced intracortical facilitation (ICF) as revealed by paired TMS. The SMC activation change in fMRI was predicted by the presence or absence of motor-evoked potentials (MEPs) on the affected side. The present findings support the notion that intensified EMG-ES may improve the arm function in individual chronic hemiparetic stroke patients but not in more severely impaired individuals. Functional improvements are paralleled by increased ipsilesional SMC activation and enhanced ICF supporting neuroplasticity as contributor to rehabilitation. The clinical score at inception and the presence of MEPs have the best predictive potential.

Estimulación eléctrica del nervio facial con función pronóstica en la cirugía de parótida

Continuous electromyography during parotidectomies and direct stimulation of the facial nerve as an intraoperative identification technique significantly lower the rate of post-operative morbidity.To determine the usefulness of intra-operative neurophysiological parameters registered by means of electrical stimulation of the facial nerve as values capable of predicting the type of lesion and the functional prognosis.Our sample consisted of a correlative series of 20 cases of monitored parotidectomies. Post-operative facial functioning, type of lesion and its prognosis were compared with the variations in latency/amplitude of the muscle response between two stimulations of the facial nerve before and after resection, as well as in the absence or presence of muscle response to stimulation after resection.All the patients except one presented motor evoked potentials (MEP) to stimulation after resection. There was no facial damage following the operation in 55% of patients and 45% presented some kind of paresis. The 21% drop in the amplitude of the intra-operative MEP and the mean increase in latency of 13.5% correspond to axonal and demyelinating insult, respectively, with a mean recovery time of three and six months. The only case of absence of response to the post-resection stimulation presented permanent paresis.The presence of MEP following resection does not ensure that functioning of the nerve remains undamaged. Nevertheless, it can be considered a piece of data that suggests a lower degree of compromise, if it is present, and a better prognosis. The variations in latency and amplitude of the MEP tend to be intra-operative parameters that indicate the degree of compromise and functional prognosis.