Spinal Cord Potentials Research Articles

Movement-related potentials in the human spinal cord preceding toe movement

Objectives: A method by which potentials related to voluntary movement can be recorded noninvasively from the human spinal cord is presented. Methods: A novel signal processing technique performed on signals recorded by surface electrodes placed over the spinal column was used to filter time-locked back muscle noise, so that the only remaining signals were the spinal movement-related potentials from the brain to the limbs and vice versa. Results: The signals obtained from 7 subjects using this technique are shown and temporally compared with movement-related cortical potentials (MRCP) and muscle electromyogram. It is demonstrated that the spinal signal starts approximately 600 ms before the actual movement, and that some features of this signal correspond to changes in cortical potentials. Conclusions: These findings imply that the spinal cord is not a simple command-carrying medium from the brain to the limbs, and implies that some computational activities take place at the spinal cord level.

Posttraumatic erectile potential of spinal cord injured men: How physiologic recordings supplement subjective reports

Objective: To investigate by means of a neurophysiologic model the remaining erectile function in spinal cord injured men. Design: A nonrandomized control trial. Setting: A Referred Care Center. Subjects: Forty-seven spinal cord injured men and 7 noninjured controls. Intervention: The subject penile responses were recorded by a penile strain gauge during two sessions—one to obtain baseline responses, and one with reflexogenic stimulation (masturbation) and psychogenic stimulation (film). Measures: Average tumescence, maximal tumescence, percentage rigidity, and duration of tumescence and rigidity. Results: Significant results were found for subjects with lower lesions using psychogenic stimulation as their optimal mode compared with reflexogenic stimulation as an alternate mode, and for subjects with higher lesions using reflexogenic stimulation as their optimal mode, compared with psychogenic stimulation as an alternate mode. The responses with optimal stimulation modes were comparable to those achieved by controls. Conclusion: The findings validate the neurophysiologic model of posttraumatic erectile potential as a function of the lesion type and stimulation source. The results were comparable to those of noninjured subjects; the potential for normal function is present and may be amenable to sexual rehabilitation or use in conjunction with new oral drug treatments for impotence.

Influence of fentanyl, alfentanil, and sufentanil on motor evoked potentials.

The effects of the opioids fentanyl, alfentanil, and sufentanil on motor pathways were studied in a total of 30 rabbits. Compound muscle action potentials (CMAP) were recorded from the extensor muscles of the upper extremity as well as evoked spinal cord potentials (ESCP) from the thoracic epidural space in response to electrical stimulation of the motor cortex. After establishing stable baseline values, an equipotent intravenous bolus of one of the three opioids was applied that abolished reflex motor response to noxious stimulation. Motor evoked potentials (MEP) were recorded from the time of bolus administration until recovery of MEP amplitudes and latencies. Afterwards, the opioids were administered continuously with cumulative dosage up to total absence of motor evoked response. Our results show a dose-dependent suppression of the CMAP: When reflex movement to noxious stimulation was extinguished, we found a significant (P < .001) reduction of the amplitudes to 34+/-18% (mean +/- SD) in the fentanyl group, to 43+/-24% in the alfentanil group, and to 53+/-20% of baseline values in the sufentanil group. Increasing opioid plasma levels were associated with complete extinction of the CMAP. We hypothesize that the descending volleys within motor pathways are mainly inhibited at a spinal level, because ESCP, particularly the number of spinal I-waves, are not severely affected even when CMAP are completely suppressed. In conclusion, intraoperative monitoring of descending pathways by means of MEP during anesthesia with opioids is feasible at anesthetic plasma concentrations maintaining a surgical level of analgesia. Even with high opioid plasma levels, a valid MEP monitoring could be performed evaluating neural activity of spinal MEP.

Peculiarities of extraspinally recorded field spinal potentials

It is demonstrated that field potentials generated in the lumbosacral spinal cord and usually recorded as a dorsal surface potential spread to the tissues of the back body surface. The component composition of these extraspinally recorded responses somewhat differs from that of the potential recorded from the spinal cord surface. The reasons for such a difference and possible approaches providing higher informative value of non-invasive studies of spinal cord potentials are discussed.

Effect of treatment with 21-aminosteroid U-74389G and glucocorticoid steroid methylprednisolone on somatosensory evoked potentials in rat spinal cord during mild compression.

The purpose of this investigation was to compare the effects of treatment with glucocorticoid steroid methylprednisolone (MP) and the 21-aminosteroid U-74389G on the conduction of somatosensory evoked potentials (SEPs) during experimental spinal cord compression. Forty-five adult male Wistar rats were anesthetized and a laminectomy performed at the Th9-Th10 level. Animals with the same SEP patterns prior to and after laminectomy were randomly allocated to one of three groups (15 rats in each). A 14.8-g weight was applied to the dural surface of the spinal cord for 60 min. The SEPs were continually recorded during compression. The rats received a single intravenous bolus dose of three different agents two minutes after the start of compression. Animals in the first group received 0.5 ml of 0.9% NaCl, the second group received 30 mg/kg methylprednisolone and the third group received 3 mg/kg U-74389G. Following drug infusion the time period required for the SEPs to be completely suppressed was assessed. If the SEPs were not fully suppressed, the amplitude of the most stable and significant component of the SEPs was measured. The time taken to complete the SEPs suppression was significantly shorter in the control group (p < 0.001, Wilcoxon) than in the groups with either MP or U-74389G. However, the time taken to achieve full suppression was not significantly different between the MP and U-74389G groups. The proportional reduction of amplitude N1P1 was significantly different between the control and MP groups as well as between the control and U-74389G groups. The proportional reduction of amplitude N1P1 was not significant between the MP and the U-74389G groups. The present data indicate that both the glucocorticoid steroid MP and the 21-aminosteroid U-74389G protect spinal cord function to a similar extent during mild compression.

高齢者ＣＳＭ症例における高位診断について 臨床所見および電気生理学における検討

Recently asymptomatical cervical cord compression has been proposed in elderly patients especially by magnetic resonance images (MRI). We determined symptomatic levels in compressive cervical myelopathy by evoked spinal cord potentials (ESCPs) recorded epidurally and compared the results with radiologic findings.7 patients over sixty-five years old with compressive cervical myelopathy were studied. ESCPs following median nerve (MN-ESCPs) and transcranial magnetic stimulation (TCM-ESCPs) were recorded pre-operatively from the epidural space. Symptomatic compression was limited to one (n=4) or two (n=3) disc levels and anterior interbody fusion showed good results.The specificity between the symptomatic levels determined by electrophysiological assesment and high intensity change in the spinal crod on T2-weighted MRI was 92% and that of abnormal findings on myelography was 95%. We considered that high intensity change in the spinal cord on T2-weighted MRI and abnormal findings on myelography were very useful for level diagnosis.

Effects of coil orientation and magnetic field shield on transcranial magnetic stimulation in cats

To obtain suitable stimulus conditions for transcranial magnetic stimulation, the evoked compound muscle action potential (ECMAP), evoked spinal cord potential (ESCP), and magnetic and electric fields were analyzed in cats with and without the use of a magnetic field shield. Cats were stimulated using a figure 8 magnetic coil placed on the cranium above the motor cortex. The maximum ECMAP amplitude was recorded when the electric current in the coil was in the mediolateral direction, regardless of whether a magnetic shield with a 5 × 5 cm window was used. ECMAP and ESCP thresholds were reduced when magnetic shielding was in place. Due to the edge effect, the strengths of the magnetic and electric fields were highest in the brainstem area, which is an inhomogeneous volume conductor of the cat's cranium. A large induced electric field directed caudally elicited ECMAP and ESCP responses effectively when a magnetic shield with a 5 × 5 cm window was in place. © 1998 John Wiley & Sons, Inc. Muscle Nerve 21: 1172–1180, 1998.

Effects of coil orientation and magnetic field shield on transcranial magnetic stimulation in cats.

To obtain suitable stimulus conditions for transcranial magnetic stimulation, the evoked compound muscle action potential (ECMAP), evoked spinal cord potential (ESCP), and magnetic and electric fields were analyzed in cats with and without the use of a magnetic field shield. Cats were stimulated using a figure 8 magnetic coil placed on the cranium above the motor cortex. The maximum ECMAP amplitude was recorded when the electric current in the coil was in the mediolateral direction, regardless of whether a magnetic shield with a 5 x 5 cm window was used. ECMAP and ESCP thresholds were reduced when magnetic shielding was in place. Due to the edge effect, the strengths of the magnetic and electric fields were highest in the brainstem area, which is an inhomogeneous volume conductor of the cat's cranium. A large induced electric field directed caudally elicited ECMAP and ESCP responses effectively when a magnetic shield with a 5 x 5 cm window was in place.

Cortical motor neuron excitability during cutaneous silent period

Objective: To investigate cortical motor neuron excitability during cutaneous silent period (CSP), motor evoked potentials (MEPs) from abductor pollicis brevis following transcranial magnetic stimulation (TCM) were recorded with and without a conditioning of ipsilateral painful digital nerve electric stimulation. Methods: MEPs following TCM were recorded with and without a conditioning stimulation at an interstimulus interval (ISI) from 0 ms to 100ms in 6 controls and four patients who had reduced pain sensation in unilateral upper limbs associated with cervical syringomyelia. In addition MEPs and evoked spinal cord potentials (ESCPs) from cervical epidural space following TCM with and without a conditioning stimulation were recorded in four patients with thoracic myelopathy. Results: MEP amplitude was clearly attenuated by a conditioning stimulation at an ISI from 40 ms to 80 ms in controls (statistically significant at 60 ms). In patients with cervical syringomyelia, MEP amplitude was attenuated by a conditioning stimulation in asymptomatic hands similarly in controls but that was unchanged by a conditioning stimulation in the symptomatic hand with reduced pain sensation. In patients with thoracic myelopathy MEP amplitude was attenuated by conditioning stimulation similarly in controls, but ESCP amplitude was unchanged. Conclusions: We demonstrated that noxious cutaneous nerve stimulation suppressed spinal motor neurons but cortical motor neuron excitability was unchanged during CSP. In clinical practice, measurement of MEP suppression after noxious cutaneous nerve stimulation may provide useful information in patients with damaged pain related nerve fibers.

Preliminary report on prediction of spinal cord ischemia in endovascular stent graft repair of thoracic aortic aneurysm by retrievable stent graft

Objective: To predict spinal cord ischemia after endovascular stent graft repair of descending thoracic aortic aneurysms, temporary interruption of the intercostal arteries (including the aneurysm) was performed by placement of a novel retrievable stent graft (Retriever) in the aorta under evoked spinal cord potential monitoring. Methods: From February 1995 to October 1997, endovascular stent graft repair of descending thoracic aortic aneurysms was performed in 49 patients after informed consent was obtained. In 16 patients with aneurysms located in the middle and distal segment of the descending aorta, the Retriever was placed temporarily before stent graft deployment. The Retriever consisted of two units of self-expanding zigzag stents connected in tandem with stainless steel struts. Each strut was collected in a bundle fixed to a pushing rod, and the stent framework was lined with an expanded polytetrafluoroethylene sheet. The Retriever was delivered beyond the aneurysm through a sheath and was retracted into the sheath 20 minutes later. A stent graft for permanent use was deployed in patients whose predeployment test results with the Retriever were favorable. Evoked spinal cord potential was monitored throughout placement of the Retriever and stent grafting until the next day. Results: The Retriever was placed in 17 aneurysms in 16 patients. There were no changes in amplitude or latency of evoked spinal cord potential records obtained before or during Retriever placement. After withdrawal of the Retriever, all aneurysms were excluded from circulation immediately after permanent stent grafting. There were no changes in evoked spinal cord potential, nor were neurologic deficits seen after stent graft deployment in any patient. Conclusions: These results suggest that predeployment testing with the Retriever under evoked spinal cord potential monitoring is promising as a predictor of spinal cord ischemia in candidates for stent graft repair of thoracic aortic aneurysms. (J Thorac Cardiovasc Surg 1998;115:811-8)

Spinal cord blood flow and pathophysiological changes after transient spinal cord ischemia in cats.

The goal was to study the hemodynamics and regional pathophysiological changes in the spinal cord after transient vascular occlusion in cats. We measured spinal cord blood flow (SCBF) continuously in the lumbar region with a laser-doppler flowmeter, before, during, and after spinal cord ischemia induced by balloon occlusion of the thoracic aorta, in 24 cats (divided into three groups) and simultaneously recorded the evoked spinal cord potentials (ESPs). In each group (n = 8), 10-, 20-, and 30-minute ischemic loading was performed. All animals were evaluated neurologically 36 hours later, and then their spinal cords were examined histologically. The amplitude of ESPs decreased 10 minutes and disappeared 20 minutes after occlusion. SCBF increased to as much as 2 times the control values after reperfusion and decreased gradually in all groups. Then, in all animals in the 10-minute group and six animals in the 20-minute group, SCBF returned to the control values, which were subsequently maintained throughout the experiment, and ESPs returned to normal patterns within 1 hour. For all animals in the 30-minute group and two in the 20-minute group, hypoperfusion after recirculation, irreversible amplitude changes in ESPs, postischemic paraparesis, and pathological ischemic changes in the lower thoracic and lumbar spinal segments were recognized. Our results showed that > 20-minute occlusion of the thoracic aorta in cats resulted in irreversible spinal perfusion disorders and that the monitoring of SCBF and ESPs could be useful for predicting potential neurological deficits. Furthermore, postischemic hypoperfusion may have an important role in the development of secondary spinal cord ischemia, resulting in severe neurological dysfunction. This observation suggested the possibility of therapeutic modification of the secondary processes inducing hypoperfusion after spinal ischemia.

Characteristics of human fetal spinal cord grafts in the adult rat spinal cord: influences of lesion and grafting conditions.

The present study evaluated the growth potential and differentiation of human fetal spinal cord (FSC) tissue in the injured adult rat spinal cord under different lesion and grafting conditions. Donor tissue at 6-9 weeks of gestational age was obtained through elective abortions and transplanted either immediately into acute resection (solid grafts) or into chronic contusion (suspension and solid grafts) lesions (i.e., 14-40 days after injury) in the thoracic spinal cord. The xenografts were then examined either histologically in plastic sections or immunocytochemically 1-3 months postgrafting. Intraspinal grafts in acute lesions demonstrated an 83% survival rate and developed as well-circumscribed nodules that were predominantly composed of immature astrocytes. Solid-piece grafts in chronic contusion lesions exhibited a 92% survival rate and also developed as nodular masses. These grafts, however, contained many immature neurons 2 months postgrafting. Suspension grafts in chronic contusion lesions had an 85% survival rate and expanded in a nonrestrictive, diffuse pattern. These transplants demonstrated large neuronally rich areas of neural parenchyma. Extensive neuritic outgrowth could also be seen extending from these grafts into the surrounding host spinal cord. These findings show that human FSC tissue reliably survives and differentiates in both acute and chronic lesions. However, both the lesion environment and the grafting techniques can greatly influence the pattern of differentiation and degree of host-graft integration achieved.

Spatial distribution of corticospinal potentials following transcranial electric and magnetic stimulation in human spinal cord

To investigate the spatial distribution of the human corticospinal tract in the spinal cord, evoked spinal cord potentials (ESCPs) following transcranial electrical and magnetic stimulation were recorded simultaneously from both the anterior and posterior epidural space in five anesthetized patients. One ESCP component following transcranial electrical stimulation (D-wave) and at least two ESCP components (initially D-wave and later I-wave) following transcranial magnetic stimulation were recorded in all subjects. The negative peak latency of all the potentials recorded from the posterior epidural space was the same as that recorded anteriorly. The amplitude ratio of the ESCP following electrical stimulation (posterior/anterior) was 1.10±0.12, while that of ESCPs following magnetic stimulation was 1.08±0.12 (N1) and 1.15±0.16 (N2). These results suggest that lateral corticospinal tract descending dorsolateral fasciculus in the spinal cord is main corticospinal pathway and spatial distribution of D and I-waves are similar in the human cervical cord.

Effects of intravenous anesthetics on spinal cord potentials and electromyogram evoked by transcranial magnetic stimulation in man

Effects of intravenous anesthetics on spinal cord potentials and electromyogram evoked by transcranial magnetic stimulation in man

Techniques and basics of recording human spinal cord potentials from the epidural space

Techniques and basics of recording human spinal cord potentials from the epidural space

Effect of coil position and stimulus intensity in transcranial magnetic stimulation on human brain

Evoked spinal cord potentials (ESCPs) from the cervical and high thoracic epidural space following transcranial magnetic stimulation were recorded from eight subjects in awake and anesthetized condition. Motor evoked potentials (MEPs) from the right abductor digiti minimi (ADM) and rectus femoris (RF) muscles were simultaneously recorded during voluntary contraction. The stimulus intensity was at 30% above the MEPs threshold of the ADM when the coil center was fixed on 10–20 international Cz position. In awake condition, multiple ESCP components (greater than 3) were recorded from the cervical epidural space but no or minimal components were recorded from the upper thoracic epidural space. When the coil was moved anteriorly so that the posterior edge of the coil was positioned on Cz, the amplitude of the first ESCP component was significantly increased ( P < 0.02) and shortened (not significant) at cervical levels. In addition, several ESCP components were more evident at high thoracic levels. Although the amplitude of the ADM was not enhanced, that of the RF was enhanced. During general anesthesia with volatile anesthetics (sevoflurane), only the first component of the ESCPs (D-wave) was elicited. Its amplitude was enhanced ( P < 0.02) when the coil edge was fixed on Cz, similar to results in awake condition. This enhancement of the first ESCP component was accompanied by enhancement of those recorded from the high thoracic epidural space. However the amplitude of D-wave was the same in the two different coil positions when the stimulus intensity was set at 100% of the output. These results suggest that at low stimulus intensity, positioning the coil edge on Cz is optimal in inducing D-wave effectively but at high stimulus intensity, D-wave generation can be achieved in either if the two different coil position.

Dopaminergic modulation of spinal neurons and synaptic potentials in the lamprey spinal cord.

It has been shown previously that dopamine-immunoreactive cells and processes are present in the lamprey spinal cord and that dopamine modulates the cycle period of fictive swimming. The present study was undertaken to further characterize the effects of dopamine on the cellular properties of lamprey spinal neurons and on inhibitory and excitatory postsynaptic potentials to determine how dopaminergic modulation may affect the central pattern generator for locomotion. Dopamine reduced the late afterhyperpolarization (late AHP) following the action potential of motoneurons, and in three types of sensory neurons: dorsal cells, edge cells, and giant interneurons. The late AHP was not reduced in lateral interneurons or CC interneurons, both of which are part of the central motor pattern generating neural network. The reduction of the late AHP in motoneurons, edge cells, and giant interneurons resulted in an increase in firing frequency in response to depolarizing current injection. In the six cell classes examined, no changes were observed in the resting membrane potential, input resistance, rheobase, spike amplitude, or spike duration after application of dopamine. The durations of action potentials broadened by application of tetraethylammonium in motoneurons and of calcium action potentials in dorsal cells and giant interneurons were decreased after bath application of 10 microM dopamine. The durations of tetrodotoxin-resistant, N-methyl-D-aspartate-induced membrane potential oscillations in lamprey spinal motoneurons were increased after bath application of 1-100 microM dopamine, due perhaps to reduced calcium entry and thus reduced Ca(2+)-dependent K+ current responsible for the repolarization of the membrane potential during each oscillation. Polysynaptic inhibitory postsynaptic potentials (IPSPs) elicited in lamprey spinal motoneurons by stimulation of the contralateral half of the spinal cord were reduced by bath application of 10 microM dopamine. Polysynaptic excitatory postsynaptic potentials were not reduced by dopamine. Monosynaptic IPSPs in motoneurons elicited by stimulation of single contralateral inhibitory CC interneurons and single ipsilateral axons were reduced by bath application of dopamine (10 microM). Monosynaptic IPSPs in CC interneurons elicited by stimulation of ipsilateral lateral interneurons, however, showed no change after application of dopamine. The lack of dopaminergic effect on the late AHP of the locomotor network neurons, lateral interneurons and CC interneurons, and the selective reduction of IPSPs from CC interneurons suggest that synaptic modulation may play an important role in dopaminergic modulation of cycle period during fictive swimming in the lamprey.

頚髄症のＭＲＩ所見と術中脊髄誘発電位 頭尾側の病変の広がりについて

To investigate the location and extent of intraspinal cord lesions, evoked spinal cord potentials (ESCPs) following transcranial electrical stimulation (TE-ESCPs) and median nerve stimulation (MN-ESCPs) were recorded in 9 patients with cervical myelopathy. Comparison of the abnormal lesion in ESCPs and high signal intensity area of the spinal cord on T2-weighted MRI was also investigated.High signal intensity areas on T2W MRI were observed in 6 of 9 patients. In 4 of 6 patients, this area corresponded to the area showing abnormal findings in both TE-ESCPs and MN-ESCPs. In 2 of 6 patients, the lesion confirmed by ESCPs is more extensive than the area revealed by MRI. In these 2 cases, the lesion confirmed by ESCPs was from C4/5 to C5/6 disc level but the high signal intensity area was observed at only C5/6.We concluded that high signal intensity on T2-weighted MRI exactly matched the abnormal disc level confirmed by MN-ESCPs, although this lesion can also include spinal tract lesions (corticospinal tract) observed in TE-ESCPs.

The effect of current direction induced by transcranial magnetic stimulation on the corticospinal excitability in human brain.

Evoked spinal cord potentials (ESCPs) from the cervical epidural space and motor evoked potentials (MEPs) from the hand muscles were recorded simultaneously in 6 subjects following transcranial magnetic stimulation in two different coil orientations on motor cortex. The onset latency of the MEPs was approximately 1 ms shorter when the induced current flowed in a latero-medial direction (L-M stimulation) on the motor cortex as compared to a postero-anterior direction (P-A stimulation). Hence, L-M stimulation elicited an earlier component of the ESCPs than that induced by P-A stimulation. During general anesthesia with Sevoflurane, only the first component of the ESCPs could be elicited routinely following L-M stimulation. In contrast, all components of the ESCPs were dramatically attenuated following P-A stimulation. Moreover, first component latency of the ESCPs induced by L-M stimulation was almost the same as that induced by transcranial anodal electrical stimulation. These results suggest that if the induced current following transcranial magnetic stimulation flows in a latero-medial direction on motor cortex, it preferentially stimulates the corticospinal tract non-synaptically (producing a D-wave). However, if the induced current flows in a postero-anterior direction, it preferentially stimulates the corticospinal tract trans-synaptically (producing I-waves). Therefore, the direction of magnetically induced current is crucial in determining corticospinal excitability in the human brain.

The effect of current direction induced by transcranial magnetic stimulation on the corticospinal excitability in human brain

Evoked spinal cord potentials (ESCPs) from the cervical epidural space and motor evoked potentials (MEPs) from the hand muscles were recorded simultaneously in 6 subjects following transcranial magnetic stimulation in two different coil orientations on motor cortex. The onset latency of the MEPs was approximately 1 ms shorter when the induced current flowed in a latero-medial direction (L-M stimulation) on the motor cortex as compared to a postero-anterior direction (P-A stimulation). Hence, L-M stimulation elicited an earlier component of the ESCPs than that induced by P-A stimulation. During general anesthesia with Sevoflurane, only the first component of the ESCPs could be elicited routinely following L-M stimulation. In contrast, all components of the ESCPs were dramatically attenuated following P-A stimulation. Moreover, first component latency of the ESCPs induced by L-M stimulation was almost the same as that induced by transcranial anodal electrical stimulation. These results suggest that if the induced current following transcranial magnetic stimulation flows in a latero-medial direction on motor cortex, it preferentially stimulates the corticospinal tract non-synaptically (producing a D-wave). However, if the induced current flows in a postero-anterior direction, it preferentially stimulates the corticospinal tract trans-synaptically (producing I-waves). Therefore, the direction of magnetically induced current is crucial in determining corticospinal excitability in the human brain.