Mapping of tibial nerve evoked magnetic fields over the lower spine

Using a low-noise 49-channel dc-SQUID system spinal somatosensory evoked fields (SEF) were recorded which were generated by compound action currents evoked upon posterior tibial nerve stimulation. The SEF mapping showed the action current propagation along the sciatic nerve, lumbosacral plexus and cauda equina in parallel to simultaneously recorded electrical potentials (SEP). For a reliable intraindividual side-to-side comparison of spinal SEFs the right and left tibial nerves were stimulated in alternating order; this procedure minimizes artifactual inter-nerve SEF map differences due to eventual patient-to-sensor displacements which might occur in serial measurements. These large-area lumbar SEF mappings open up several clinical perspectives for magnetoneurography, in particular with respect to the 3D-localization of proximal conduction blocks.     

七叶莲对蟾蜍坐骨神经动作电位的影响

目的：观察七叶莲水煎液对蟾蜍离体坐骨神经复合动作电位的幅度及传导速度的影响,研究其对坐骨神经电生理特性的作用。方法：将制备的蟾蜍坐骨神经干分为4组,分别在任氏液和浓度为10％,20％,40％的七叶莲水煎液中浸泡,用MedLab生物信号采集处理系统引导神经干复合双相动作电位,并分别测定各组不同浸泡时间的坐骨神经干动作电位的幅度和传导速度两项电生理指标。记录不同浓度的七叶莲水煎液对蟾蜍离体坐骨神经复合动作电位的幅度和传导速度的影响。结果：10％,20％,40％3种浓度的七叶莲水煎液均使坐骨神经复合动作电位的幅度变小（P〈0．01）,传导速度变慢（P〈0．01）并最终使坐骨神经动作电位消失,且经过一段时间后动作电位的幅度和传导速度均能恢复。结论：七叶莲能可逆地阻滞神经动作电位的传导。     

Acute Tarsal Tunnel Syndrome After Total Ankle Arthroplasty With Varus Deformity

BackgroundA 54-year-old woman presented with varus ankle arthritis, which was corrected with total ankle arthroplasty (TAA). Immediately postoperatively, she was insensate throughout the plantar foot. After seven weeks, she underwent tarsal tunnel release, and the tibial nerve was found to be intact. Plantar sensation improved by one week after exploration with neurolysis and was completely intact at one year.ConclusionLoss of plantar sensation can occur following TAA for varus arthritic deformity. One potential cause is tibial nerve compression from tightening the laciniate ligament, resulting in acute tarsal tunnel syndrome. The condition can be remedied with early recognition and tarsal tunnel release. Level of Evidence: V     

神经传导测定技术对腕管综合征病情评估的价值

目的:近年来腕管综合征发病率逐年升高,然而其慢性、隐匿性不易引起人们的重视,发现时往往已造成较大的危害。本文探讨腕管综合征的神经传导测定对病情评估的临床价值,旨在为患者腕管综合征早期发现和后续治疗提供进一步的临床参考依据。方法:选取我院124例确诊的腕管综合征患者。其中无大鱼际肌萎缩者有64例,并选取平均年龄相近的64例正常人作为对照(组A);有大鱼际肌畏缩者60例,并选取平均年龄相近的60例正常人作为对照(组B)。A、B组均经行神经电图检查,握力测定和两点辨别觉测定,分析神经传导速度改变与感觉、运动功能减退程度的关系。结果:A、B两组患者均有不同程度的神经传导改变:在A组患者神经传导改变中,运动和感觉传导速度(MCV和SCV)轻度下降,运动和感觉电位波幅(CMAP和SNAP)轻度下降,潜伏期(ML)轻度延长;在B组患者神经传导中,运动和感觉传导速度(MCV和SCV)明显下降,运动和感觉电位波幅(CMAP和SNAP)明显下降,潜伏期明显延长。结论:腕管综合征患者不同的临床表现有不同程度的神经电图表现,因此神经电图对神经传导的测定结果对腕管综合征患者的病情有良好的评估价值,值得临床推广。     

The latency difference of the tibial and sural nerve sep: Peripheral versus central factors

The latency of the cortical SEP (CSEP) following stimulation of the posterior tibial nerve is nearly always shorter than the latency of the CSEP evoked by stimulation of the sural nerve. Till now this fact was believed to be due mainly to different conduction velocities within the peripheral nerves owing to the muscle afferents of the posterior tibial nerve. The surprising discovery that the lumbar and cervical SEPs exhibit much shorter time lags than the CSEPs led to the experiments described in this paper: during the registration of the peripheral sciatic nerve action potentials only slight differences in the conduction velocities were observed. Thereupon a topographical analysis was performed during which the minimum latency of the sural nerve CSEP was not measured at the usual C′_z electrode position but was found to be shifted to a more occipital and ipsilateral point.From these results it was concluded that, for the main part, the latency difference of the CSEPs results from ‘central factors’, which had already been postulated for the median nerve CSEP by Burke and coworkers.     

Ultrasound in Dual Nerve Impairment after Proximal Radial Nerve Lesion

IntroductionSonography in classical nerve entrapment syndromes is an established and validated method. In contrast, few publications highlight lesions of the radial nerve, particularly of the posterior interosseus nerve (PIN).MethodFive patients with a radial nerve lesion were investigated by electromyography, nerve conduction velocity and ultrasound. Further normative values of 26 healthy subjects were evaluated.ResultsFour patients presented a clinical and electrophysiological proximal axonal radial nerve lesion and one patient showed a typical posterior interosseous nerve syndrome (PINS). The patient with PINS presented an enlargement of the PIN anterior to the supinator muscle. However four patients with proximal lesions showed an unexpected significant enlargement of the PIN within the supinator muscle.ConclusionHigh-resolution sonography is a feasible method to demonstrate the radial nerve including its distal branches. At least in axonal radial nerve lesions, sonography might reveal abnormalities far distant from a primary proximal lesion site clearly distinct from the appearance in classical PINS.     

Prostaglandin E1 modifies nerve conduction and interferes with local anaesthetic action.

Prostaglandin E1 (PGE1) altered both the amplitude and conduction velocity of the compound action potential in frog sciatic nerve. Concentrations up to 1 ng/ml increased both amplitude and conduction velocity but at higher concentrations both effects were reversed. Procaine, chloroquine, indomethacin and SC19220 all reduced action potential amplitude and conduction velocity. These local anaesthetic type actions could be partially or completely prevented by PGE1.     

Prostaglandin E1 modifies nerve conduction and interferes with local anaesthetic action

Prostaglandin E1 (PGE1) altered both the amplitude and conduction velocity of the compound action potential in frog sciatic nerve. Concentrations up to 1 ng/ml increased both amplitude and conduction velocity but at higher concentrations both effects were reversed. Procaine, chloroquine, indomethacin and SC19220 all reduced action potential amplitude and conduction velocity. These local anaesthetic type actions could be partially or completely prevented by PGE1.     

Effects of millimeter band electromagnetic radiation of low intensity on sciatic nerve regeneration in rats

The effect of millimeter-band electromagnetic radiation of low intensity on the regeneration of the sciatic nerve was studied in experiments conducted on rats. The restoration of the functional properties of the nerve following its section and microsurgical suturing was investigated. It was established that irradiation of the site of operation stimulates the growth of nerve fibers and increases the conduction velocity of action potentials along the regenerating nerve.Translated from Neirofiziologiya, Vol. 25, No. 1, pp. 27–31, January–February, 1993.     

不同浓度酒精任氏液对蛙坐骨神经干双相复合动作电位的影响*

目的:定量探究1%～80%酒精任氏液对蛙坐骨神经干双相复合动作电位(AP)的作用及其恢复情况。方法:制备长为6～8 cm的蛙坐骨神经干标本,分别将含有0%、1%、2%、4%、8%、16%、32%、48%、64%、80%酒精的标准任氏液通过新加装在神经屏蔽盒中的加药液槽浸泡位于刺激电极和接地电极之间的神经干各5 min,用BL-420F系统分别记录由刺激所诱发的双相AP;之后用标准任氏液冲洗5遍,浸泡5 min, 分别记录冲洗后AP。结果:与标准任氏液相比, ≤4%酒精任氏液对AP峰值和传导速度无影响,≥8%酒精任氏液作用后可使AP峰值和传导速度均下降;16%、32%和≥48%酒精任氏液作用后分别使神经干失去产生AP能力的比例为30%、90%和100%。≤32%酒精任氏液作用后冲洗,AP峰值可完全恢复;48%、64%和80%酒精任氏液作用后冲洗,能恢复产生动作电位能力的比例分别为90%、40%和0%,平均峰值分别下降至正常的60%、36%和0%;冲洗后: ≤8%酒精任氏液作用后的AP速度与正常无异,≥16%酒精任氏液作用后的AP速度无法完全恢复。结论:不同浓度酒精对AP峰值和传导速度影响不同,这对酒精的合理使用及过度使用后的损伤恢复有参考意义。     

Org.2766 improves functional and electrophysiological aspects of regenerating sciatic nerve in the rat

The beneficial effect of short-term (8 days) melanocortin therapy on regenerating peripheral nerves is demonstrated using functional and electrophysiological tests. Following a crush lesion of the rat sciatic nerve, recovery of sensory function is monitored by assessing the responsiveness of the rat to a small electric current applied to the footsole. Recovery of motor function is assessed by means of an analysis of walking patterns. Normalization of the walking pattern reflects reinnervation of different muscle groups. The motor and H-reflex related sensory nerve conduction velocity of the regenerated nerves are longitudinally investigated in the same rats in which the recovery of motor and sensory function had been assessed previously. Functional tests show an enhanced recovery under melanocortin therapy, but in the end both saline- and melanocortin-treated rats show 100% recovery. However, when compared to the contralateral sciatic nerve, in the peptide-treated animals motor nerve conduction in the regenerated nerves has fully recovered after about 90 days following the crush lesion and the sensory conduction after about 120 days, whereas in the saline-treated rats a deficit of 20-40% in both motor and sensory conduction remains. This difference is observed even 214 days following crush.     

补阳还五汤口服和药浴对损伤的大鼠坐骨神经传导速度的影响

目的探讨补阳还五汤口服加药浴对坐骨神经传导速度的影响。方法60只SD大鼠暴露左侧坐骨神经。对照组只钳夹;实验组钳夹并加用补阳还五汤口服及药浴治疗。观察钳夹前和钳夹切除后大鼠坐骨神经传导速度（SNCV）。结果于2、4、6周分别测对照组、实验组的坐骨神经传导速度（SNCV）。各时间段实验组坐骨神经传导速度恢复快于对照组,P〈0．01。结论补阳还五汤口服加药浴对坐骨神经传导速度有明显的促进作用。     

High-Frequency Electrical Stimulation Can Be a Complementary Therapy to Promote Nerve Regeneration in Diabetic Rats

The purpose of this study was to evaluate whether 1 mA of percutaneous electrical stimulation (ES) at 0, 2, 20, or 200 Hz augments regeneration between the proximal and distal nerve stumps in streptozotocin diabetic rats. A10-mm gap was made in the diabetic rat sciatic nerve by suturing the stumps into silicone rubber tubes. Normal animals were used as the controls. Starting 1 week after transection, ES was applied between the cathode placed at the distal stump and the anode at the proximal stump every other day for 3 weeks. At 4 weeks after surgery, the normal controls and the groups receiving ES at 20, and 200 Hz had a higher success percentage of regeneration compared to the ES groups at 0 and 2 Hz. In addition, quantitative histology of the successfully regenerated nerves revealed that the groups receiving ES at a higher frequency, especially at 200 Hz, had a more mature structure with more myelinated fibers compared to those in the lower-frequency ES groups. Similarly, electrophysiology in the ES group at 200 Hz showed significantly shorter latency, larger amplitude, larger area of evoked muscle action potentials and faster conduction velocity compared to other groups. Immunohistochemical staining showed that ES at a higher frequency could significantly promote calcitonin gene-related peptide expression in lamina I-II regions in the dorsal horn and recruit a higher number of macrophages in the diabetic distal sciatic nerve. The macrophages were found that they could stimulate the secretion of nerve growth factor, platelet-derived growth factor, and transforming growth factor-β in dissected sciatic nerve segments. The ES at a higher frequency could also increase cutaneous blood flow in the ipsilateral hindpaw to the injury. These results indicated that a high-frequency ES could be necessary to heal severed diabetic peripheral nerve with a long gap to be repaired.     

In Vivo Electrophysiological Measurements on Mouse Sciatic Nerves

Electrophysiological studies allow a rational classification of various neuromuscular diseases and are of help, together with neuropathological techniques, in the understanding of the underlying pathophysiology¹. Here we describe a method to perform electrophysiological studies on mouse sciatic nerves in vivo.The animals are anesthetized with isoflurane in order to ensure analgesia for the tested mice and undisturbed working environment during the measurements that take about 30 min/animal. A constant body temperature of 37 °C is maintained by a heating plate and continuously measured by a rectal thermo probe². Additionally, an electrocardiogram (ECG) is routinely recorded during the measurements in order to continuously monitor the physiological state of the investigated animals.Electrophysiological recordings are performed on the sciatic nerve, the largest nerve of the peripheral nervous system (PNS), supplying the mouse hind limb with both motoric and sensory fiber tracts. In our protocol, sciatic nerves remain in situ and therefore do not have to be extracted or exposed, allowing measurements without any adverse nerve irritations along with actual recordings. Using appropriate needle electrodes³ we perform both proximal and distal nerve stimulations, registering the transmitted potentials with sensing electrodes at gastrocnemius muscles. After data processing, reliable and highly consistent values for the nerve conduction velocity (NCV) and the compound motor action potential (CMAP), the key parameters for quantification of gross peripheral nerve functioning, can be achieved.     

Response of single alpha motoneurons to high-frequency pulse trains. Firing behavior and conduction block phenomenon

Studies were conducted on 25 cats to document the discharge rates of alpha motoneurons during stimulation of the sciatic nerve at frequencies from 100 to 10,000 pulses per second (pps). In addition, the feasibility of using high-frequency pulse trains to block the conduction of action potentials was investigated. Two cuff electrodes were placed around the proximal portion of the left sciatic nerve, and recordings of antidromic potentials were taken from single fibers of the L7 ventral root. When stimulating through the more proximal electrode, discharge rates were generally equal to or were subharmonics of the stimulation rate up to 1,000 pps. Firing often decreased in rate during 3-min runs. At 2,000-10,000 pps, fibers responded briefly at rates of several hundred per second but stopped firing within seconds after stimulus initiation. After cessation of response to the high-frequency pulse train, action potentials generated at 50 pps at the more distal electrode did not propagate to the recording electrodes. The 'electrical block' so induced was maintained for up to 20 min, and recovery following termination of the pulse train was complete within 1 s.     

Somatosensory cerebral potentials evoke by stimulation of the lumbo-sacral spinal cord in normal subjects and in patients with conus medullaris and cauda equina lesions

Somatosensory cerebral evoked potentials were recorded by intrathecal stimulation of the lumbo-sacral cord and roots in 16 normal subjects and patients having cauda/conus injury (group A, 15 cases), compressive lesions of cauda equina (group B, 13 cases) and lesions of both types covering the lumbar cord (group C, 24 cases). The shape of the intrathecally evoked cerebral potential (IECP) was basically the same as that obtained by posterior tibial nerve stimulation from 12 normal subjects except that the early components were 10–15 msec shorter in latency in the former potential, with an average of 12 msec.IECPs were easily recorded in groups A and B, but a significant delay was found in both groups, especially group A. It was difficult to obtain the IECP in group C, When it could be recorded the latency increase was apparent. These findings were explained on the basis of degeneration of the ascending spinal nerve fibers proximal to the lesion site.     

Some physiological characteristics of myelinated and unmyelinated fibers with very low conduction velocity

The compound action potential arising in response to supramaximal stimulation of Aδ- or C-fibers of a cat cutaneous nerve (the saphenous nerve) was investigated by methods improving the signal/noise ratio in the record of the unit evoked response. By the use of optical and computer (BÉSM-3M) methods of coherent signal accumulation followed by averaging, potentials of nerve fibers ranging in amplitude from 20 to 0.05 µV and in duration from 10 to 0.4 msec were distinguished from the apparatus noise. A continuous distribution of nerve fibers by conduction velocity was found over the range from 80 to 0.15 m/sec. The conditions of appearance of low-amplitude action potentials of nerve fibers with a low conduction velocity are discussed.     

Findings of somatosensory evoked potential to stimulation of the sciatic nerve in two different rat strains.

No comparative study about somatosensory evoked potentials (SEP) on different rat strains has been done yet. It is evident that comparative SEP studies are important since different rat strains have different physiological properties. We aimed to compare early latency SEP values from stimulation of sciatic nerve in Wistar (Wr) and Sprague-Dawley (SDr) rats which are frequently used rat strains in experimental studies. In Wr group, the mean of first far field potential (Ff1) latency was shorter and the mean Ff1 amplitude was lower than that of Sprague-Dawley rat group. Mean cortical potential latency in Wr group was longer than that of SDr group while amplitude was not different. Central conduction time (CCT) in Wistar rat group was found to be longer than that of SDr group. Shorter Ff1 latency in Wr group implies that afferent volley reaches cervical posterior fasciculus from sciatic nerve earlier than SDr group while longer CP latency implies that afferent volley reaches cortex later than SDr group. Similarity between the latencies of lumbar potentials implies that peripheral conduction velocity has no effect on the difference of Ff1 latencies.     

Spinal cord dorsum potentials recorded in vivo after cold injury to the sural nerve in the rabbit

Evoked potentials were recorded in the spinal cord dorsum of rabbits during and after local cooling or freezing of the sural nerve. The potentials were elicited by stimulation through implanted bipolar electrodes distal and proximal to the site of cooling. Recordings were made with a unipolar electrode implanted dorsally into the epidural space.The first two negative deflections of the evoked field potentials (s- and n-potentials) decreased or disappeared during cooling to temperatures between 12 and 2 °C. Immediately following cooling the potentials were depressed by as much as 40% below that of controls. Gradual recovery of the nerve conduction velocity and of both potentials occurred between postoperative Days 20 and 60. Cooling of the nerve to between +2 and ?2 °C caused a 70–80% decrease in amplitude and the precooling values were not obtained within 90 days' follow-up. Local freezing of the sural nerve to ?45 °C resulted in disappearance of the cord dorsum potentials previously obtained by stimulation of the sural nerve with electrode distal to the site frozen. About 40% decrease occurred when stimulated proximal to the site frozen. A fast amplitude increase took place between days 50 and 100 and a slower increase between days 150 and 450 to values more than twice the preoperative amplitudes. A similar amplitude increase was obtained by stimulation of the nerve proximal to the site frozen.