Motor Evoked Potentials Studies Research Articles

Task-related modulation of motor response to emotional bodies: A TMS motor-evoked potential study

Exposure to emotional body postures during perceptual decision-making tasks has been linked to transient suppression of motor reactivity, supporting the monitoring of emotionally relevant information. However, it remains unclear whether this effect occurs implicitly, i.e., when emotional information is irrelevant to the task. To investigate this issue, we used single-pulse transcranial magnetic stimulation (TMS) to assess motor excitability while healthy participants were asked to categorize pictures of body expressions as emotional or neutral (emotion recognition task) or as belonging to a male or a female actor (gender recognition task) while receiving TMS over the motor cortex at 100 and 125 ms after picture onset. Results demonstrated that motor-evoked potentials (MEPs) were reduced for emotional body postures relative to neutral postures during the emotion recognition task. Conversely, MEPs increased for emotional body postures relative to neutral postures during the gender recognition task. These findings indicate that motor inhibition, contingent upon observing emotional body postures, is selectively associated with actively monitoring emotional features. In contrast, observing emotional body postures prompts motor facilitation when task-relevant features are non-emotional. These findings contribute to embodied cognition models that link emotion perception and action tendencies.

Neurophysiological Evaluation of Neural Transmission in Brachial Plexus Motor Fibers with the Use of Magnetic versus Electrical Stimuli.

The anatomical complexity of brachial plexus injury requires specialized in-depth diagnostics. The clinical examination should include clinical neurophysiology tests, especially with reference to the proximal part, with innovative devices used as sources of precise functional diagnostics. However, the principles and clinical usefulness of this technique are not fully described. The aim of this study was to reinvestigate the clinical usefulness of motor evoked potential (MEP) induced by a magnetic field applied over the vertebrae and at Erb's point to assess the neural transmission of brachial plexus motor fibers. Seventy-five volunteer subjects were randomly chosen to participate in the research. The clinical studies included an evaluation of the upper extremity sensory perception in dermatomes C5-C8 based on von Frey's tactile monofilament method, and proximal and distal muscle strength by Lovett's scale. Finally, 42 healthy people met the inclusion criteria. Magnetic and electrical stimuli were applied to assess the motor function of the peripheral nerves of the upper extremity and magnetic stimulus was applied to study the neural transmission from the C5-C8 spinal roots. The parameters of compound muscle action potential (CMAP) recorded during electroneurography and MEP induced by magnetic stimulation were analyzed. Because the conduction parameters for the groups of women and men were comparable, the final statistical analysis covered 84 tests. The parameters of the potentials generated by electrical stimulus were comparable to those of the potentials induced by magnetic impulse at Erb's point. The amplitude of the CMAP was significantly higher following electrical stimulation than that of the MEP following magnetic stimulation for all the examined nerves, in the range of 3-7%. The differences in the potential latency values evaluated in CMAP and MEP did not exceed 5%. The results show a significantly higher amplitude of potentials after stimulation of the cervical roots compared to potentials evoked at Erb's point (C5, C6 level). At the C8 level, the amplitude was lower than the potentials evoked at Erb's point, varying in the range of 9-16%. We conclude that magnetic field stimulation enables the recording of the supramaximal potential, similar to that evoked by an electric impulse, which is a novel result. Both types of excitation can be used interchangeably during an examination, which is essential for clinical application. Magnetic stimulation was painless in comparison with electrical stimulation according to the results of a pain visual analog scale (3 vs. 5.5 on average). MEP studies with advanced sensor technology allow evaluation of the proximal part of the peripheral motor pathway (between the cervical root level and Erb's point, and via trunks of the brachial plexus to the target muscles) following the application of stimulus over the vertebrae.

Effects of trunk neuromuscular electrical stimulation on the motor circuits of able-bodied individuals

Upper- and lower-limb neuromuscular electrical stimulation (NMES) is known to modulate the excitability of the neural motor circuits. However, it remains unclear whether short-duration trunk muscle NMES could achieve similar neuromodulation effects. We assessed motor evoked potentials (MEPs) elicited through transcranial magnetic stimulation of the primary motor cortex representation of the trunk extensor muscles to evaluate corticospinal excitability. Moreover, cervicomedullary motor evoked potentials (CMEPs) were assessed through cervicomedullary junction magnetic stimulation to evaluate subcortical excitability. Twelve able-bodied individuals participated in the MEP study, and another twelve in the CMEP study. During the interventions, NMES was applied bilaterally to activate the erector spinae muscle and produce intermittent contractions (20 s ON/20 s OFF) for a total of 20 min while participants remained seated. Assessments were performed: (i) before; (ii) during (in brief periods when NMES was OFF); and (iii) immediately after the interventions to compare MEP or CMEP excitability. Our results showed that MEP responses were not affected by trunk NMES, while CMEP responses were facilitated for approximately 8 min during the intervention, and returned to baseline before the end of the 20 min stimulating period. Our findings therefore suggest that short-duration NMES of the trunk extensor muscles likely does not affect the corticospinal excitability, but it has a potential to facilitate subcortical neural circuits immediately after starting the intervention. These findings indicate that short-duration application of NEMS may be helpful in rehabilitation to enhance neuromodulation of the trunk subcortical neural motor circuits.

Early Right Motor Cortex Response to Happy and Fearful Facial Expressions: A TMS Motor-Evoked Potential Study.

The ability to rapidly process others’ emotional signals is crucial for adaptive social interactions. However, to date it is still unclear how observing emotional facial expressions affects the reactivity of the human motor cortex. To provide insights on this issue, we employed single-pulse transcranial magnetic stimulation (TMS) to investigate corticospinal motor excitability. Healthy participants observed happy, fearful and neutral pictures of facial expressions while receiving TMS over the left or right motor cortex at 150 and 300 ms after picture onset. In the early phase (150 ms), we observed an enhancement of corticospinal excitability for the observation of happy and fearful emotional faces compared to neutral expressions specifically in the right hemisphere. Interindividual differences in the disposition to experience aversive feelings (personal distress) in interpersonal emotional contexts predicted the early increase in corticospinal excitability for emotional faces. No differences in corticospinal excitability were observed at the later time (300 ms) or in the left M1. These findings support the notion that emotion perception primes the body for action and highlights the role of the right hemisphere in implementing a rapid and transient facilitatory response to emotional arousing stimuli, such as emotional facial expressions.

The Long-Term Effect of Treatment Using the Transcranial Magnetic Stimulation rTMS in Patients after Incomplete Cervical or Thoracic Spinal Cord Injury.

Repetitive transcranial magnetic stimulation (rTMS) may support motor function recovery in patients with incomplete spinal cord injury (iSCI). Its effectiveness mainly depends on the applied algorithm. This clinical and neurophysiological study aimed to assess the effectiveness of high-frequency rTMS in iSCI patients at the C2–Th12 levels. rTMS sessions (lasting 3–5 per month, from 2 to 11 months, 5 months on average) were applied to 26 iSCI subjects. The motor cortex was bilaterally stimulated with a frequency at 20–25 Hz and a stimulus strength that was 70–80% of the resting motor threshold (15.4–45.5% maximal output) during one therapeutic session. Surface electromyography (sEMG) recordings at rest and during maximal contractions and motor evoked potential (MEP) recordings were performed from the abductor pollicis brevis (APB) and the tibialis anterior (TA) muscles. The same neurophysiological studies were also performed in patients treated with kinesiotherapy only (K group, n = 25) and compared with patients treated with both kinesiotherapy and rTMS (K + rTMS). A decrease in sEMG amplitudes recorded at rest from the APB muscles (p = 0.001) and an increase in sEMG amplitudes during the maximal contraction of the APB (p = 0.001) and TA (p = 0.009) muscles were found in the K + rTMS group. A comparison of data from MEP studies recorded from both APB and TA muscles showed significant changes in the mean amplitudes but not in latencies, suggesting a slight improvement in the transmission of spinal efferent pathways from the motor cortex to the lower spinal centers. The application of rTMS at 20–25 Hz reduced spasticity in the upper extremity muscles, improved the recruitment of motor units in the upper and lower extremity muscles, and slightly improved the transmission of efferent neural impulses within the spinal pathways in patients with C2–Th12 iSCI. Neurophysiological recordings produced significantly better parameters in the K + rTMS group of patients after therapy. These results may support the hypothesis about the importance of rTMS therapy and possible involvement of the residual efferent pathways including propriospinal neurons in the recovery of the motor control of iSCI patients.

Spinal Cord Infarction: A Single Center Experience and the Usefulness of Evoked Potential as an Early Diagnostic Tool.

Background: Spinal cord infarction (SCI) is a rare disease and its early diagnosis is challenging. Here, we described the clinical features and imaging findings of SCI, and assessed the results of evoked potential (EP) studies to elucidate their diagnostic role in the early stage of SCI.Methods: We retrospectively analyzed 14 patients who had spontaneous SCI. The demographic, neurological, and temporal profiles of the SCI patients were identified. We reviewed the imaging findings and assessed the changes in them over time. To review EP, central motor conduction time (CMCT) and somatosensory evoked potential (SEP) values were obtained. We also enrolled 15 patients with transverse myelitis (TM), and compared the clinical, radiological and electrophysiological features between SCI and TM patients.Results: The ages of the SCI patients ranged from 54 to 73 years. Nine patients (64.3%) showed nadir deficits within 6 h. The most common type of clinical visit was via the emergency center. Nine patients (64.3%) presented with peri-onset focal pain. The median initial modified Rankin scale score was 3. For 9 patients (64.3%), initial T2 imaging findings were negative, but subsequent diffusion weighed imaging (DWI) showed diffusion restriction. Vertebral body infarction was observed in 5 patients (35.7%). EP data were available for 10 SCI patients. All 8 patients who had their CMCT measured showed abnormalities. Among them, motor evoked potentials were not evoked in 6 patients at all. SEP was measured in 10 patients, and 9 of them showed abnormalities; one of them showed no SEP response. For 5 patients, the EP studies were done prior to DWI, and all the patients showed definite abnormalities. The abnormalities in the EP findings of the SCI patients were more profound than those of the TM patients, even though the duration from the onset to the start of the study was much shorter for SCI patients.Conclusion: SCI can be diagnosed based on typical clinical manifestations and appropriate imaging studies. Our study also indicates that immediate sensory and motor EP study can have an adjuvant diagnostic role in the hyperacute stage of SCI, and can improve the accuracy of diagnosis.

Functional Recovery Following the Transplantation of Olfactory Ensheathing Cells in Rat Spinal Cord Injury Model.

Study DesignOlfactory ensheathing cells (OECs) from rat olfactory mucosa were cultured, characterized, and transplanted into a rat model of spinal cord injury (SCI).PurposeTo evaluate different doses of OECs in a rat model of SCI.Overview of LiteratureSCI causes permanent functional deficit because the central nervous system lacks the ability to perform spontaneous repair. Cell therapy strategies are being explored globally. The clinical use of human embryonic stem cell is hampered by ethical controversies. Alternatively, OECs are a promising cell source for neurotransplantation. This study aimed to evaluate the efficacy of different doses of allogenic OEC transplantation in a rat model of SCI.MethodsOECs were cultured from the olfactory mucosa of Albino Wistar rats; these cells were characterized using immunohistochemistry and flow cytometry. Rats were divided into five groups (n=6 rats each). In each group, different dosage (2×105, 5×105, 10×105, and >10×105) of cultured cells were transplanted into experimentally injured spinal cords of rat models. However, in the SCI group, only DMEM (Dulbecco’s modified Eagle's medium) was injected. Rats were followed up upto 8 weeks post-transplantation. The outcome of transplantation was assessed using the Basso, Beattie, Bresnahan (BBB) scale; motor-evoked potential studies; and histological examination.ResultsCultured cells expressed 41% of p75NTR, a marker for OEC, and 35% of anti-fibronectin, a marker for olfactory nerve fibroblast. These cells also expressed S100β and glial fibrillary acid protein of approximately 75% and 83%, respectively. All the transplanted groups showed promising BBB scores for hind-limb motor recovery compared with the SCI group (p<0.05). A motor-evoked potential study showed increased amplitude in all the treated groups compared with the SCI. Green fluorescent protein-labeled cells survived in the injured cord, suggesting their role in the transplantation-mediated repair. Transplantation of 5×105 cells showed the best motor outcomes among all the doses.ConclusionsOECs demonstrated a therapeutic effect in rat models with the potential for future clinical applications.

MOTOR EVOKED POTENTIAL IN PATIENTS WITH PARKINSON’S DISEASE: A TRANSCRANIAL MAGNETIC STIMULATION STUDY

Background: Parkinson’s disease (PD) is a neurodegenerative condition of the central nervous system, which is accompanied by the impairment of the cortico-subcortical excitation and inhibition systems. It is characterized by motor and non-motor symptoms, having both hypokinetic and hyperkinetic features. Objective: To investigate the integrity of the central motor pathways by studying the motor evoked potential (MEP) latencies, amplitudes and central conduction time (CMCT) of the median nerve in patients with PD as compared to healthy controls. Methods: Twenty-five patients with documented PD were studied; with a mean age of (63.16±5.49 years) as compared to 25 age and sex matched apparently healthy controls. All subjects were instructed about the examination and informed consent was provided. Transcranial magnetic stimulation TMS-MEP study of the right median nerve was done. Cortical and cervical latencies and amplitudes of the MEP study were determined. The responses were recorded with both relaxed and slightly contracted target muscle. CMCT calculation was done by subtraction of the latency of peripheral segment of the motor pathway (spinal motor root to muscle) from that of the entire motor pathway (motor cortex to muscle) or by calculation of the CMCT with the F-wave method. Results: The means of the cortical latencies of PD patients during relaxation and facilitation states were lower than controls; and the differences were significant for both (P=0.03 and 0.02; respectively). In both relaxed and facilitation states, the means of CMCT in PD patients were lower than in control and the difference was significant during contraction (P=0.02), and near statistical significance during relaxation (P=0.08). CMCT calculations by the estimation of F wave and distal motor latency (DML) were equivocal between relaxation and facilitation states. Nevertheless, the differences were not statistically significant (P=0.45; P=0.62; respectively). The means of the MEP amplitude of PD patients were lower than controls (4.21±1.94 versus 4.28± 1.84 mV; respectively). Nevertheless, the differences were not significant (P=0.89). Conclusion: Single-pulse TMS is a valuable study to investigate central motor dysfunction in PD. CMCT measurement of the median nerve or any nerve in the upper limb is a potential marker for the evaluation of the severity of PD; especially in the facilitated state. Keywords: Parkinson’s disease, TMS, MEP, CL, CMCT Citation: Ahmed HR, Al-Hashimi AF. Motor evoked potential in patients with Parkinson’s Disease: a transcranial magnetic stimulation study. Iraqi JMS. 2018; Vol. 16(1): 14-21. doi: 10.22578/IJMS.16.1.4

A Recurrent Cervical Neurenteric Cyst Treated Anteriorly: Safe, Gross-Total Excision Facilitated by Prophylactic Unilateral Vertebral Artery Exposure, Microdissection, and Spinal Cord Monitoring—A Case Report and Technical Note

This study reports on a 67-year-old woman with partial Brown-Séquard syndrome due to a recurrent cervical neurenteric cyst at C3 to C4. The myelopathic symptoms reappeared 22 years after a previous shunting operation performed posteriorly with a silicone tube connecting the intradural cervical cyst cavity to the subarachnoid space. We have now succeeded in removing the cyst nearly completely with the anterior approach. The surgical procedure consisted of right vertebral artery exposure at C3 and C4 and a subtotal corpectomy of C3 followed by microdissection of the cyst, duraplasty, and iliac strut graft fusion. Spinal cord monitoring with motor-evoked potential studies helped us safely dissect the cyst wall tightly adhering to the spinal cord. Duraplasty with Gore-Tex patch-grafting in conjunction with postoperative lumbar subarachnoid drainage worked well in preventing a spinal fluid fistula. At two years after surgery, the patient showed a nearly complete return of function without any recurrence of the cyst.

Automatic Recruitment of the Motor System by Undetected Graspable Objects: A Motor-evoked Potential Study.

Previous behavioral and neuroimaging studies have suggested that the motor properties associated with graspable objects may be automatically accessed when people passively view these objects. We directly tested this by measuring the excitability of the motor pathway when participants viewed pictures of graspable objects that were presented during the attentional blink (AB), when items frequently go undetected. Participants had to identify two briefly presented objects separated by either a short or long SOA. Motor-evoked potentials were measured from the right hand in response to a single TMS pulse delivered over the left primary motor cortex 250 msec after the onset of the second target. Behavioral results showed poorer identification of objects at short SOA compared with long SOA, consistent with an AB, which did not differ between graspable and nongraspable objects. However, motor-evoked potentials measured during the AB were significantly higher for graspable objects than for nongraspable objects, irrespective of whether the object was successfully identified or undetected. This provides direct evidence that the motor system is automatically activated during visual processing of objects that afford a motor action.

Neuroplasticity and Brachial Plexus Injury

Traumatic damage to the brachial plexus is associated with temporary or permanent motor and sensory dysfunction of the upper extremity. It may lead to the severe disability of the patient, often excluded from the daily life activity. The pathomechanism of brachial plexus injury usually results from damage detected in structures taking origin in the rupture, stretching or cervical roots avulsion from the spinal cord. Often the complexity of traumatic brachial plexus injury requires a multidisciplinary diagnostic process including clinical evaluation supplemented with clinical neurophysiology methods assessing the functional state of its structures. Their presentation is the primary goal of this paper.The basis for the diagnosis of brachial plexus function is a clinical examination and neurophysiology studies: electroneurography (ENG), needle electromyography (EMG), somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs) assessing the function of individual brachial plexus elements.The ENG and EMG studies clarify the level of brachial plexus damage, its type and severity, mainly using the Seddon clinical classification. In contrast to F-wave studies, the use of the MEPs in the evaluation of traumatic brachial plexus injury provides valuable information about the function of its proximal part. MEPs study may be an additional diagnostic in confirming the location and extent of the lesion, considering the pathomechanism of the damage. Clinical neurophysiology studies are the basis for determining the appropriate therapeutic program, including choice of conservative or reconstructive surgery which results are verified in prospective studies.

The uses and interpretations of the motor-evoked potential for understanding behaviour.

The motor-evoked potential (MEP) elicited in peripheral muscles by transcranial magnetic stimulation (TMS) over human motor cortex is one of the hallmark measures for non-invasive quantification of cortical and spinal excitability in cognitive and clinical neuroscience. In the present article, we distinguish three main uses for MEPs in studies of behaviour: for understanding execution and performance of actions, as markers of physiological change in the motor system, and as read-out of upstream processes influencing the motor system. Common to all three approaches is the assumption that different experimental manipulations act on the balance of excitatory and inhibitory pre-synaptic (inter)neurons at the stimulation site; this in turn contributes to levels of (post-synaptic) excitability of cortico-spinal output projections, which ultimately determines the size of MEPs recorded from peripheral muscles. We discuss the types of inference one can draw from human MEP measures given that the detailed physiological underpinnings of MEPs elicited by TMS are complex and remain incompletely understood. Awareness of the different mechanistic assumptions underlying different uses of MEPs can help inform both study design and interpretation of results obtained from human MEP studies of behaviour.

Pre- and Postoperative Evaluation of Patients With Lumbosacral Disc Herniation by Neurophysiological and Clinical Assessment

The application of complex neurophysiological examination including motor evoked potentials (MEP) for pre- and postoperative evaluation of patients experiencing acute sciatica. The assessment of sensitivity and specificity of needle electromyography, MEP, and H-reflex examinations. The comparative analysis of preoperative and postoperative neurophysiological examination. In spite of the fact that complex neurophysiological diagnostic tools seem to be important for interpretation of incompatible results of neuroimaging and clinical examination, especially in the patients qualified for surgical treatment, their application has never been completely analyzed and documented. Pre- and postoperative electromyography, electroneurography, F-waves, H-reflex, and MEP examination were performed in 23 patients with confirmed disc-root conflict at lumbosacral spine. Clinical evaluation included examination of sensory perception for L5-S1 dermatomes, muscles strength with Lovett's scale, deep tendon reflexes, pain intensity with visual analogue scale, and straight leg raising test. Sensitivity of electromyography at rest and MEP examination for evaluation of L5-S1 roots injury was 22% to 63% and 31% to 56% whereas specificity was 71% to 83% and 57% to 86%, respectively. H-reflex sensitivity and specificity for evaluation of S1 root injury were 56% and 67%, respectively. A significant improvement of root latency parameter in postoperative MEP studies as compared with preoperative was recorded for L5 (P = 0.039) and S1 root's levels (P = 0.05). The analysis of the results from neurophysiological tests together with neuroimaging and clinical examination allow for a precise preoperative indication of the lumbosacral roots injury and accurate postoperative evaluation of patients experiencing sciatica. 3.

Central motor conduction studies in patients with spinal cord disorders: a review.

Topical review of the literature. The evaluation of patients with myelopathies requires radiological investigations; however, for the correct interpretation of the neuroimaging findings, the functional assessment of corticospinal conduction is helpful or even mandatory in many conditions. The objective of this review article was to assess the utility of the motor evoked potentials (MEPs) in diagnosis and management of the most frequent spinal cord disorders. Salzburg (Austria) and Merano (Italy). A MEDLINE search was performed using following terms: 'motor evoked potentials', 'transcranial magnetic stimulation', 'central motor conduction', 'compressive myelopathy', 'spinal cord infarction', 'spinal cord injury', 'syringomyelia', 'myelitis', 'hereditary spastic paraparesis', 'subacute combined degeneration' and 'hepatic myelopathy'. Central motor conduction abnormalities can be detected also in the absence of neuroradiological abnormalities-for example, in patients with subacute combined degeneration or hepatic myelopathy. In the most frequent patients with compressive myelopathies, MEPs were found to be very helpful in determining the functional significance of neuroimaging findings. MEP recording can supplement clinical examination and neuroimaging findings also in the assessment of the spinal cord injury level. In patients with spinal cord infarction, the MEP study can demonstrate spinal involvement even when radiological evidence for spinal cord damage is absent or equivocal, thus allowing an important early diagnosis. MEPs represent a highly sensitive and accurate diagnostic tool in many different spinal cord disorders. MEPs can also be useful in follow-up evaluation of motor function during treatment and rehabilitation.

Letter to the editor concerning “hepatic myelopathy with spastic paraparesis: report of two cases and review of the literature” by S. Ben Amor et al. (Eur Spine J. 2013, Jun 1)

To the Editor, We read with great interest the article by Ben Amor et al. [1] published in the European Spine Journal entitled “Hepatic myelopathy with spastic paraparesis: report of two cases and review of the literature”. The authors state in their paper that there is no special diagnostic tool for hepatic myelopathy (HM), and that the diagnosis has to be established on clinical grounds after exclusion of other possible entities. However, in our opinion, there is a noticeable omission in this important article. Our previous study [2] revealed that motor evoked potentials (MEP) elicited by transcranial magnetic stimulation (TMS) may be very helpful in the diagnosis of this rare complication of chronic liver diseases that is usually associated with a portosystemic shunt and likely to be overlooked. The authors demonstrated that central motor conduction studies by means of TMS are sensitive, accurate and easily applicable methods for detecting even a subclinical damage of the corticospinal tract. The threshold for corticospinal electrophysiological abnormalities was below that for clinical and/or radiological changes. Spinal cord involvement was evident even at the preclinical stage and became more overt as the disease progressed. Most of the examined patients did not have clinical symptoms and presented only physiological subclinical abnormalities. MEP studies may thus disclose an impairment of the corticospinal pathways even before HM is clinically manifest and enable an early diagnosis of HM. Since, liver transplantation (the first therapeutic option) should be performed before spinal cord damage becomes irreversible [3–5], the diagnosis of HM must be established as early as possible to enhance the chance of a complete recovery of the spinal cord. Therefore, we believe that such an important examination, which is at present widely and easily performed in the most neurophysiology laboratories, cannot be neglected. We found important to highlight that, especially in a review article on HM, this important diagnostic tool should be included and discussed.

Effect of neck flexion on somatosensory and motor evoked potentials in Hirayama disease

Hirayama disease (HD) is a rare motor disorder mainly affecting young men, characterized by atrophy and weakness of forearm and hand muscles corresponding to a C7–T1 myotome distribution. The weakness is usually unilateral or asymmetric and progression usually stops within several years. The etiology of HD is not well understood. One hypothesis, mainly based on MRI findings, is that the weakness is a consequence of cervical flexion myelopathy. The aim of this study was to explore the function of corticospinal and ascending somatosensory pathways during neck flexion using evoked responses. Materials and methods15 men with HD and 7 age-matched control male subjects underwent somatosensory evoked potentials (SSEP) and motor evoked potentials (MEP) studies with the neck in neutral position and fully flexed. SSEP studies included electrical stimulation of median and ulnar nerves at the wrist, and tibial nerve at the ankle with recording over the ipsilateral Erb's point, cervical spine, and contralateral sensory cortex. MEP recordings were obtained by magnetic stimulation of the motor cortex and the cervical lower spinal roots; the evoked responses were recorded from the contralateral thenar and abductor hallucis muscles. ResultsMEP recordings demonstrated significant lower amplitudes, and slightly prolonged latencies in HD patients on cervical stimulation, compared to control subjects. During neck flexion, MEP studies also demonstrated a statistically significant drop in mean upper limb amplitude on cervical stimulation in HD patients, as well as in control subjects, although to a lesser degree. In contrast, no significant differences were found in SSEP studies in HD patients compared to control subjects, or between neutral and flexed position in these groups. ConclusionThe study shows a negative effect of cervical flexion on MEP amplitudes in HD patients as well as in control subjects, requiring more studies to investigate its significance. Neck flexion did not have an influence on any SSEP parameters in patients or controls.

The role of motor-evoked potentials in the management of cervical spondylotic myelopathy

Background contextCervical spondylotic myelopathy (CSM) is a common disorder, but its management and the role of surgery are still a matter of controversy. The assessment of surgical outcome is complicated by the lack of reliable and objective methods to assess the severity of the myelopathy and its evolution. Motor-evoked potentials (MEPs) are a useful and reliable tool to measure noninvasively the involvement of the corticospinal tract in patients with CSM. Recent evidence suggests that MEPs could also have a role in monitoring the effect of surgical therapy. PurposeThe aim of the present study is to use MEPs for the functional assessment of spinal cord before and after surgery and to correlate changes in MEPs with clinical findings. Study design/settingThis is a retrospective cohort study. Patient sampleThirty-eight patients affected by CSM who underwent surgical intervention. Outcome measuresWe used the 18-point modified Japanese Orthopedic Association (mJOA) score for clinical evaluation and the central motor conduction time (CMCT) for the study of MEPs. MethodsAll patients were evaluated both clinically and neurophysiologically before (7–15 days) and after (6–12 months) surgery. MEPs were recorded from the biceps, abductor digiti minimi, and tibialis anterior muscles bilaterally. ResultsAfter surgery, the 18-point mJOA score increased significantly from 10.1 to 15.1, and the value of CMCT for tibialis anterior muscles showed a slight but significant reduction, more evident in patients with mild to moderate symptoms. ConclusionsEarly surgical intervention for CSM could produce a beneficial effect on spinal cord functionality that can be detected by MEPs.

Effect of Neck Flexion on Somatosensory and Motor Evoked Potentials in Hirayama Disease (P03.169)

Objective: Determining the effect of neck flexion on measured SEP and MEP parameters, regarding the hypothesis that Hirayama disease (HD) is a consequence of cervical flexion myelopathy. Background Hirayama disease (HD) develops mainly in young men, characterized by atrophy and weakness of the forearm and hand muscles, in a C7-T1 myotome distribution, usually unilaterally or asymmetrically, followed by spontaneous arrest within several years. The etiology of HD is not well understood. One hypothesis, mainly based on MRI findings, is that HD is a consequence of cervical flexion myelopathy. Concerning this hypothesis, previous neurophysiological and pathological studies produced conflicting findings. Design/Methods: 15 Israeli male patients, mean age 23 ± 6.5 years (range 17-31), with definite HD underwent somatosensory evoked potentials (SEP) and motor evoked potentials (MEP) studies in neutral position and with the neck fully flexed. SEP studies included stimulation of median and ulnar nerves at the wrist, and tibial nerve at the ankle with recording over ipsilateral erb9s point and cervical spine, and contralateral sensory cortex. MEP recordings were obtained by magnetic stimulation of the motor cortex and the cervical spinal cord; the evoked responses were recorded from the contralateral thenar and abductor hallucis muscles. Results: No significant differences were found in SEP studies for the mean values of median and ulnar N9, N13, N20, and tibial P38 latencies and amplitudes in HD patients between neutral and flexed position. MEP studies detected a statistically significant drop in mean upper limb cervical amplitude, and prolongation in lower limb latency during neck flexion compared to the neutral position. Conclusions: In this large cohort of patients neck flexion had no effect on measured SEP parameters, but influenced slightly part of the MEP variables, supporting the view of a negative effect of neck positioning in HD. Disclosure: Dr. Abraham has nothing to disclose. Dr. Gotkine has nothing to disclose. Dr. Drory has nothing to disclose. Dr. Blumen has nothing to disclose.

Surgical treatment of severe cervical dystrophic kyphosis due to neurofibromatosis Type 1: a review of 8 cases

the goal in this study was to retrospectively investigate the clinical efficacy of surgical treatment for cervical dystrophic kyphotic deformity due to neurofibromatosis Type 1. between January 1998 and July 2008, 8 patients with cervical dystrophic kyphotic deformity due to neurofibromatosis Type 1 (mean Cobb angle of 58.5°) were surgically treated in the authors' department. The mean age at surgery was 19 years (range 12-38 years). Among these patients, 1 with a Cobb angle of 52° and good flexibility underwent single anterior correction, whereas the other 7 patients with severe deformity and poor flexibility received combined anterior and posterior cervical osteotomy. Motor-evoked potential studies were used intraoperatively for spinal cord monitoring. Radiographic assessment and Japanese Orthopaedic Association scoring were used to evaluate the clinical outcome. no severe neurological complications were noted. Two patients complained of persistent neck and shoulder pain after combined anterior and posterior correction, which alleviated after conservative treatment half a year later. All patients were followed up for a mean of 21.1 months (range 6-36 months). All patients had a solid bone fusion at the latest follow-up, with Japanese Orthopaedic Association scoring improving from 11.5 preoperatively to 14.1 postoperatively (p < 0.01) at the final follow-up. The kyphotic deformities improved significantly, with average Cobb angles of 2.5° postoperatively and 4.1° at final follow-up. the deformity of neurofibromatosis with cervical kyphosis is severe, and surgery carries a high risk of failure. Although premature fusion may be performed, the deformity may still progress, and this situation may lead to failure of surgery. The successful management of this disease requires early recognition and a more aggressive and reliable intervention to prevent disastrous worsening of the deformity. Meticulous preoperative evaluation, appropriate surgical strategy, and skilled technique were essential for successful surgical treatment and good clinical results.

A bi-directional assessment of the human brain-anorectal axis.

Brain-gut dysfunction has been implicated in gastrointestinal disorders but a comprehensive test of brain-gut axis is lacking. We developed and tested a novel method for assessing both afferent anorectal-brain function using cortical evoked potentials (CEP), and efferent brain-anorectal function using motor evoked potentials (MEP). Cortical evoked potentials was assessed following electrical stimulations of anus and rectum with bipolar electrodes in 26 healthy subjects. Anorectal MEPs were recorded following transcranial magnetic stimulation (TMS) over paramedian motor cortices bilaterally. Anal and rectal latencies/amplitudes for CEP and MEP responses and thresholds for first sensation and pain (mA) were analyzed and compared. Reproducibility and interobserver agreement of responses were examined. Reproducible polyphasic rectal and anal CEPs were recorded in all subjects, without gender differences, and with negative correlation between BMI and CEP amplitude (r -0.66, P=0.001). Transcranial magnetic stimulation evoked triphasic rectal and anal MEPs, without gender differences. Reproducibility for CEP and MEP was excellent (CV <10%). The inter-rater CV for anal and rectal MEPs was excellent (ICC 97-99), although there was inter-subject variation. Combined CEP and MEP studies offer a simple, inexpensive and valid method of examining bidirectional brain-anorectal axes. This comprehensive method could provide mechanistic insights into lower gut disorders.