Polyethylene glycol fusion repair of severed rat sciatic nerves reestablishes axonal continuity and reorganizes sensory terminal fields in the spinal cord

Peripheral nerve injuries result in the rapid degeneration of distal nerve segments and immediate loss of motor and sensory functions;behavioral recovery is typically poor.We used a plasmalemmal fusogen,polyethylene glycol(PEG),to immediately fuse closely apposed open ends of severed proximal and distal axons in rat sciatic nerves.We have previously reported that sciatic nerve axons repaired by PEG-fusion do not undergo Wallerian degeneration,and PEG-fused animals exhibit rapid(within 2–6 weeks)and extensive locomotor recovery.Furthermore,our previous report showed that PEG-fusion of severed sciatic motor axons was non-specific,i.e.,spinal motoneurons in PEG-fused animals were found to project to appropriate as well as inappropriate target muscles.In this study,we examined the consequences of PEG-fusion for sensory axons of the sciatic nerve.Young adult male and female rats(Sprague–Dawley)received either a unilateral single cut or ablation injury to the sciatic nerve and subsequent repair with or without(Negative Control)the application of PEG.Compound action potentials recorded immediately after PEG-fusion repair confirmed conduction across the injury site.The success of PEG-fusion was confirmed through Sciatic Functional Index testing with PEG-fused animals showing improvement in locomotor function beginning at 35 days postoperatively.At 2–42 days postoperatively,we anterogradely labeled sensory afferents from the dorsal aspect of the hindpaw following bilateral intradermal injection of wheat germ agglutinin conjugated horseradish peroxidase.PEG-fusion repair reestablished axonal continuity.Compared to unoperated animals,labeled sensory afferents ipsilateral to the injury in PEG-fused animals were found in the appropriate area of the dorsal horn,as well as inappropriate mediolateral and rostrocaudal areas.Unexpectedly,despite having intact peripheral nerves,similar reorganizations of labeled sensory afferents were also observed contralateral to the injury and repair.This central reorganization may contribute to the improved behavioral recovery seen after PEG-fusion repair,supporting the use of this novel repair methodology over currently available treatments.

Polyethylene glycol fusion repair of severed sciatic nerves accelerates recovery of nociceptive sensory perceptions in male and female rats of different strains

Successful polyethylene glycol fusion(PEG-fusion)of severed axons following peripheral nerve injuries for PEG-fused axons has been reported to:(1)rapidly restore electrophysiological continuity;(2)prevent distal Wallerian Degeneration and maintain their myelin sheaths;(3)promote primarily motor,voluntary behavioral recoveries as assessed by the Sciatic Functional Index;and,(4)rapidly produce correct and incorrect connections in many possible combinations that produce rapid and extensive recovery of functional peripheral nervous system/central nervous system connections and reflex(e.g.,toe twitch)or voluntary behaviors.The preceding companion paper describes sensory terminal field reo rganization following PEG-fusion repair of sciatic nerve transections or ablations;howeve r,sensory behavioral recovery has not been explicitly explored following PEG-fusion repair.In the current study,we confirmed the success of PEG-fusion surgeries according to criteria(1-3)above and more extensively investigated whether PEG-fusion enhanced mechanical nociceptive recovery following sciatic transection in male and female outbred Sprague-Dawley and inbred Lewis rats.Mechanical nociceptive responses were assessed by measuring withdrawal thresholds using von Frey filaments on the dorsal and midplantar regions of the hindpaws.Dorsal von Frey filament tests were a more reliable method than plantar von Frey filament tests to assess mechanical nociceptive sensitivity following sciatic nerve transections.Baseline withdrawal thresholds of the sciatic-mediated lateral dorsal region differed significantly across strain but not sex.Withdrawal thresholds did not change significantly from baseline in chronic Unoperated and Sham-operated rats.Following sciatic transection,all rats exhibited severe hyposensitivity to stimuli at the lateral dorsal region of the hindpaw ipsilateral to the injury.However,PEG-fused rats exhibited significantly earlier return to baseline withdrawal thresholds than Negative Control rats.Furthermore,PEG-fused rats with significantly improved Sciatic Functional Index scores at or after 4 weeks postoperatively exhibited yet-earlier von Frey filament recove ry compared with those without Sciatic Functional Index recovery,suggesting a correlation between successful PEG-fusion and both motor-dominant and sensory-dominant behavioral recoveries.This correlation was independent of the sex or strain of the rat.Furthermore,our data showed that the acceleration of von Frey filament sensory recovery to baseline was solely due to the PEG-fused sciatic nerve and not saphenous nerve collateral outgrowths.No chronic hypersensitivity developed in any rat up to 12 weeks.All these data suggest that PEG-fusion repair of transection peripheral nerve injuries co uld have important clinical benefits.

Blockade of Rho-associated kinase prevents inhibition of axon regeneration of peripheral nerves induced by anti-ganglioside antibodies

Anti-ganglioside antibodies are associated with delayed/poor clinical recovery in Guillain-Barrèsyndrome,mostly related to halted axon regeneration.Cross-linking of cell surface gangliosides by anti-ganglioside antibodies triggers inhibition of nerve repair in in vitro and in vivo paradigms of axon regeneration.These effects involve the activation of the small GTPase Rho A/ROCK signaling pathways,which negatively modulate growth cone cytoskeleton,similarly to well stablished inhibitors of axon regeneration described so far.The aim of this work was to perform a proof of concept study to demonstrate the effectiveness of Y-27632,a selective pharmacological inhibitor of ROCK,in a mouse model of axon regeneration of peripheral nerves,where the passive immunization with a monoclonal antibody targeting gangliosides GD1a and GT1b was previously reported to exert a potent inhibitory effect on regeneration of both myelinated and unmyelinated fibers.Our results demonstrate a differential sensitivity of myelinated and unmyelinated axons to the pro-regenerative effect of Y-27632.Treatment with a total dosage of 9 mg/kg of Y-27632 resulted in a complete prevention of anti-GD1a/GT1b monoclonal antibody-mediated inhibition of axon regeneration of unmyelinated fibers to skin and the functional recovery of mechanical cutaneous sensitivity.In contrast,the same dose showed toxic effects on the regeneration of myelinated fibers.Interestingly,scale down of the dosage of Y-27632 to 5 mg/kg resulted in a significant although not complete recovery of regenerated myelinated axons exposed to anti-GD1a/GT1b monoclonal antibody in the absence of toxicity in animals exposed to only Y-27632.Overall,these findings confirm the in vivo participation of Rho A/ROCK signaling pathways in the molecular mechanisms associated with the inhibition of axon regeneration induced by anti-GD1a/GT1b monoclonal antibody.Our findings open the possibility of therapeutic pharmacological intervention targeting Rho A/Rock pathway in immune neuropathies associated with the presence of anti-ganglioside antibodies and delayed or incomplete clinical recovery after injury in the peripheral nervous system.

Nerve conduction models in myelinated and unmyelinated nerves based on three-dimensional electrostatic interaction

Until now, nerve conduction has been described on the basis of equivalent circuit model and cable theory, both of which supposed closed electric circuits spreading inside and outside the axoplasm. With these conventional models, we can simulate the propagating pattern of action potential along the axonal membrane based on Ohm＇s law and Kirchhoff＇s law. However, we could not fully explain the different conductive patterns in unmyelinated and myelinated nerves with these theories. Also, whether we can really suppose closed electrical circuits in the actual site of the nerves or not has not been fully discussed yet. In this report, a recently introduced new theoretical model of nerve conduction based on electrostatic molecular interactions within the axoplasm will be reviewed. With this new approach, we can explain the different conductive patterns in unmyelinated and myelinated nerves. This new mathematical conductive model based on electrostatic compressional wave in the intracellular fluid may also be able to explain the signal integration in the neuronal cell body and the back-propagation mechanism from the axons to the dendrites. With this new mathematical nerve conduction model based on electrostatic molecular interactions within the intracellular fluid, we may be able to achieve an integrated explanation for the physiological phenomena taking place in the nervous system.

Automated Segmentation of the Brainstem,Cranial Nerves and Vessels for Trigeminal Neuralgia and Hemifacial Spasm

Accurate localization of cranial nerves and responsible blood vessels is important for diagnosing trigeminal neuralgia(TN)and hemifacial spasm(HFS).Manual delineation of the nerves and vessels on medical images is time-consuming and labor-intensive.Due to the development of convolutional neural networks(CNNs),the performance of medical image segmentation has been improved.In this work,we investigate the plans for automated segmentation of cranial nerves and responsible vessels for TN and HFS,which has not been comprehensively studied before.Different inputs are given to the CNN to find the best training configuration of segmenting trigeminal nerves,facial nerves,responsible vessels and brainstem,including the image modality and the number of segmentation targets.According to multiple experiments with seven training plans,we suggest training with the combination of three-dimensional fast imaging employing steady-state acquisition(3D-FIESTA)and three-dimensional time-of-flight magnetic resonance angiography(3DTOF-MRA),and separate segmentation of cranial nerves and vessels.

Low-Power CMOS IC for Function Electrical Stimulation of Nerves

A low-power IC for function electrical stimulation （FES） of nerves is designed for an implantable system and fabricated in CSMC＇s 0.6μm CMOS technology. The IC can be used for stimulating animals＇ spinal nerve bundles and other nerves connected with a cuff type electrode. It consists of a pre-amplifier,a main amplifier,and an output stage. According to the neural signal spectrum,the bandwidth of the FES signal generator circuit is defined from 1Hz to 400kHz. The gain of the circuit is about 66dB with an output impedance of 900. The 1C can function under a single supply voltage of 3-5V. A rail-to-rail output stage helps to use the coupled power efficiently. The measured time domain performance shows that the bandwidth and the gain of the IC agree with the design. The power consumption is lower than 6mW.

Cystic lesions of peripheral nerves:Are we missing the diagnosis of the intraneural ganglion cyst?

AIM To highlight the salient magnetic resonance imaging(MRI) features of the intraneural ganglion cyst(INGC) of various peripheral nerves for their precise diagnosis and to differentiate them from other intra and extraneural cystic lesions.METHODS A retrospective analysis of the magnetic resonance(MR) images of a cohort of 245 patients presenting with nerve palsy involving different peripheral nerves was done.MR images were analyzed for the presence of a nerve lesion,and if found,it was further characterized as solid or cystic.The serial axial,coronal and sagittal MR images of the lesions diagnosed as INGC were studied for their pattern and the anatomical extent along the course of the affected nerve and its branches.Its relation to identifiable anatomical landmarks,intraarticular communication and presence of denervation changes in the muscles supplied by involved nerve was also studied.RESULTS A total of 45 cystic lesions in the intra or extraneurallocations of the nerves were identified from the 245 MR scans done for patients presenting with nerve palsy.Out of these 45 cystic lesions,13 were diagnosed to have INGC of a peripheral nerve on MRI.The other cystic lesions included extraneural ganglion cyst,paralabral cyst impinging upon the suprascapular nerve,cystic schwannoma and nerve abscesses related to Hansen's disease involving various peripheral nerves.Thirteen lesions of INGC were identified in 12 patients.Seven of these affected the common peroneal nerve with one patient having a bilateral involvement.Two lesions each were noted in the tibial and suprascapular nerves,and one each in the obturator and proximal sciatic nerve.An intra-articular connection along the articular branch was demonstrated in 12 out of 13 lesions.Varying stages of denervation atrophy of the supplied muscles of the affected nerves were seen in 7 cases.Out of these 13 lesions in 12 patients,6 underwent surgery.CONCLUSION INGC is an important cause of reversible mono-neuropathy if diagnosed early and surgically treated.Its classic MRI pattern differentiates it from other lesions of the peripheral nerve and aid in its therapeutic planning.In each case,the joint connection has to be identified preoperatively,and the same should be excised during surgery to prevent further cyst recurrence.

Neural regeneration after peripheral nerve injury repair is a system remodelling process of interaction between nerves and terminal effector

In China, there are approximately 20 million people suffering from peripheral nerve injury and this number is increasing at a rate of 2 million per year. These patients cannot live or work independently and are a heavy responsibility on both family and society because of extreme disability and dysfunction caused by peripheral nerve injury （PNI）. Thus, repair of PNI has become a major public health issue in China.

Recent neuroanatomical studies on the neurovascular bundle of the prostate and cavernosal nerves:clinical reflections on radical prostatectomy

The neurovascular bundle of the prostate and cavernosal nerves have been used to describe the same structure ever since the publication of the first studies on the neuroanatomy of the lower urogenital tract of men, studies that were prompted by postoperative complications arising from radical prostatectomy. In urological surgery every effort is made to preserve or restore the neurovascular bundle of the prostate to avoid erectile dysfunction （ED）. However, the postoperative potency rates are yet to be satisfactory despite all advancements in radical prostatectomy technique. As the technology associated with urological surgery develops and topographical studies on neuroanatomy are cultivated, new observations seriously challenge the classical teachings on the topography of the neurovascular bundle of the prostate and the cavernosal nerves. The present review revisits the classical and most recent data on the topographical anatomy of the neurovascular bundle of the prostate prostatectomy techniques.

Microsurgical decompression of the median nerves for treating diabetic peripheral neuropathy in the upper limbs: A 21-month follow-up

BACKGROUND： Peripheral nerve injured by abnormal glucose metabolism is compressed, which is an important etiological factor of diabetic peripheral neuropathy （DPN）. Microsurgical decompression of peripheral nerve maybe effectively releases the symptoms of DPN. OBJECTIVE： To investigate the curative effects of microsurgical decompression of median nerves for treatment of DPN in upper limbs. DESIGN： Case-follow up observation. SETTING： Department of Orthopaedics, Department of Neurosurgery, China-Japan Friendship Hospital, Ministry of Health. PARTICIPANTS： Twelve patients with DPN in upper limbs （19 hands） who received treatment in the Department of Orthopaedics, Department of Neurosurgery, China-Japan Friendship Hospital, Ministry of Public Health between March 2004 and July 2006 were involved in this experiment. The involved patients, 5 male and 7 female, were aged 44 to 77 years, with DPN course of 6 months to 16 years. They all met 1999 WHO diabetic diagnosis criteria. Both two hands had symptom in 7 patients, and only one hand had symptom in 5 patients. Informed consents of detected items were obtained from all the patients, who also received 21 months of follow-up treatment. METHODS： （1）Operation was carried out under the anesthetic status of brachial plexus. Under an operating microscope, transverse carpal ligament was exposed. Subsequently, transverse carpal ligament, forearm superficial fascia and palmar aponeurosis were fully liberated, and then part of them was cut off. Connective tissue around median nerve, superficial flexor muscle of fingers, radial flexor, palmaris longus and other flexor tendons were completely loosened. Finally, epineurium was opened with microinstrument for neurolysis. After tourniquet was loosened, and bipolar coagulator was used to stop bleeding, and the incision was closed. （2） In postoperative 21 months, the subjective symptom, two-point discrimination （The smallest distance of two normal points was 3 to 6 mm）, nerve conduction velocity and action potential amplitude （short abductor muscle of thumb end Lat 〈 4.5 ms; Motor nerve conduction velocity of forearm 〉 50 m/s）, etc. of all the patients were followed up. MAIN OUTCOME MEASURES＂ The objective evaluation and long-term follow up of curative effect of microsurgical decompression of median nerves for treatment of DPN in upper limbs. RESULTS： Twelve patients with DPN in upper limbs participated in the final analysis. （1） After operation, numbness and pain symptom releasing 100% were found in 19 hands of 12 patients with DPN. During follow up, numbness and recrudescent pain symptom were found in one hand （5%, 1/19）. （2）Postoperatively, index finger two point discrimination in 15 （94%, 15/16） hands recovered to normal. （3） nerve conduction velocity and action potential amplitude improved completely. （4） Two hands （2/19, 10% ）had poor healing at incision, and they late healed at postoperative 1 and 1.5 months, respectively. CONCLUSION： Long-term follow-up results show that microsurgical decompression is an effective method to treat DPN in upper limbs.

Brain injury in combination with tacrolimus promotes the regeneration of injured peripheral nerves

Both brain injury and tacrolimus have been reported to promote the regeneration of injured peripheral nerves. In this study, before transection of rat sciatic nerve, moderate brain contusion was（or was not） induced. After sciatic nerve injury, tacrolimus, an immunosuppressant, was（or was not） intraperitoneally administered. At 4, 8 and 12 weeks after surgery, Masson＇s trichrome, hematoxylin-eosin, and toluidine blue staining results revealed that brain injury or tacrolimus alone or their combination alleviated gastrocnemius muscle atrophy and sciatic nerve fiber impairment on the experimental side, simultaneously improved sciatic nerve function, and increased gastrocnemius muscle wet weight on the experimental side. At 8 and 12 weeks after surgery, brain injury induction and/or tacrolimus treatment increased action potential amplitude in the sciatic nerve trunk. Horseradish peroxidase retrograde tracing revealed that the number of horseradish peroxidase-positive neurons in the anterior horn of the spinal cord was greatly increased. Brain injury in combination with tacrolimus exhibited better effects on repair of injured peripheral nerves than brain injury or tacrolimus alone. This result suggests that brain injury in combination with tacrolimus promotes repair of peripheral nerve injury.

Presence of Fleischer ring and prominent corneal nerves in keratoconus relatives and normal controls

AIMTo examine the occurrence of commonly known clinical signs of keratoconus (KC), i.e. Fleischer ring, prominent corneal nerves and thinning, among unaffected family members of KC patients and healthy control individuals.METHODSData of both eyes of 117 relatives of KC patients having no manifest disease based on videokeratography indices (KC relatives), and 142 controls were used for Pearson correlation and t-test statistics. Correlation of Fleischer ring, prominent corneal nerves and central pachymetry data were tested with each other and with videokeratography indices (KSI, KISA, 3 and 6 mm Fourier asymmetry, and I-S).RESULTSA moderate correlation was found between Fleischer ring and all examined topographical indices. Most important correlation was present with 6 mm Fourier asymmetry, and corneal pachymetry (r=0.272, P<0.001; r=-0.234, P=0.027, respectively). Similar correlations were found with prominent corneal nerves (r=0.234, P<0.001 for 6 mm Fourier asymmetry and r=-0.235, P=0.0265 for pachymetry). KC family members who exhibited Fleischer ring or prominent nerves had thinner and more asymmetric corneas than those without Fleischer ring or prominent corneal nerves (P<0.05 for pachymetry and topographic indices with t-test and Mann-Whitney rank sum test). Though rarely, Fleischer ring and prominent corneal nerves occurred among normal controls, indicating the existence of forme fruste cases in the normal population. Control subjects, who had corneal Fleischer ring or prominent nerves had corneas more similar to KC than other controls (t-test: increased KSI and KISA, P=0.048 and 0.012, respectively).CONCLUSIONIn KC family members and healthy individuals, Fleischer ring and prominent corneal nerves are associated with features of KC and may suggest a possibility of forme fruste KC. Searching for the possible presence of Fleischer ring or prominent nerves on the cornea may help in the decision whether or not to diagnose subclinical KC in a borderline case.

THE RELATIONSHIP BETWEEN THE INVASION OF PARAPHARYNGEAL SPACES AND THE INVOLVEMENT OF CERVICAL NODES AND POSTERIOR GROUP CRANIAL NERVES IN NASOPHARYNGEAL CARCINOMA

Two hundred cates of nasopharyngeal carcinoma (NPC) admitted to this department from Feb. 1985 to May. 1988 were analysed according to the CT scanning and clinical findings of the primary lesions prior to radiotherapy. The results showed that involvement of parapharyngeal space was very common in NPC, about 80% (160/200 cases) ; particularly unilateral or bilateral retro-styloid spaces, about 69.5% (139/200 cases). It was proposed that patients with NPC had a high Incidence of ipsilateral cervical node metastasis. Contralateral cervical node metastasis was rare. The development of cervical node metastasto in NPC has two modes: one Is direct Infiltration of the retro-stylold space by the lesion; the other Is along the nasopharyngeal lymphatic rete. The data also showed that patients with NPC who presented symptoms of Ⅸ- Ⅲ cranial nerve paralyses always had ipsilateral or bilateral retro- styloid space Infiltrations.

Cartilage oligomeric matrix protein enhances the vascularization of acellular nerves

Vascularization of acellular nerves has been shown to contribute to nerve bridging.In this study,we used a 10-mm sciatic nerve defect model in rats to determine whether cartilage oligomeric matrix protein enhances the vascularization of injured acellular nerves.The rat nerve defects were treated with acellular nerve grafting（control group） alone or acellular nerve grafting combined with intraperitoneal injection of cartilage oligomeric matrix protein（experimental group）.As shown through two-dimensional imaging,the vessels began to invade into the acellular nerve graft from both anastomotic ends at day 7 post-operation,and gradually covered the entire graft at day 21.The vascular density,vascular area,and the velocity of revascularization in the experimental group were all higher than those in the control group.These results indicate that cartilage oligomeric matrix protein enhances the vascularization of acellular nerves.

Clinical Application of Quantitative Nursing for Lower Cranial Nerves Injury after Cerebellopontine Angle Tumors

Objective: To retrospectively analyze the clinical utility of quantitative nursing measures of 10 cases of lower cranial nerves injury after cerebellopontine angle tumors surgery to provide the experience for improving the recovery rate and living quality of these patients. Methods: The clinical data of 10 cases of lower cranial nerves injury after cerebellopontine angle tumors surgery was analyzed. For problems such as dysphagia and dyspnea of these patients, the nursing care focused on strict monitoring, timely oxygen inhalation nursing, posture nursing, ventilator nursing, swallowing function training, etc. Results: After received quantitative care, 10 patients with lower cranial nerves injury after cerebellopontine angle tumors surgery were recovered well, and their symptoms such as dysphagia and dyspnea were gradually improved and safely discharged. Conclusion: Lower cranial nerves injury is one of the serious complications after removal of cerebellopontine angle tumors, which impacts the life and health of patients. Caregivers should accurately understand and analyze the symptoms, and quantitative and targeted nursing measures for posterior cranial nerves injury are helpful in the postoperative rehabilitation of patients and improve their living quality.

Role of Ultrasonography in Evaluation of Peripheral Nerves

Ultrasonography is first line, cost-effective modality in imaging of peripheral nerves. High frequency probes allow high resolution imaging of peripheral nerves located at relatively superficial location. USG can diagnose and localize various pathologies that involve the peripheral nerves such as traumatic, inflammatory, infective, neoplastic, and traumatic neuropathies. USG exceptionally has an important role to play in evaluation of patients with suspected nerve injury, as MRI may not differentiate neural contusion from nerve disruption. Neurapraxic injury is seen as swollen nerve with hypoechoic appearance.

Treatment for Injury of Superior Clunial Nerves by Triple Puncture Needling with Massage

Superior clunial nerve injury occupies a high percentage in lumbocluneal tissue injuries. It is commonly seen in winter and in athletic competition and training. The authors have treated 67 cases of pain of the superior clunial nerves by triple puncture needling combined with massage and obtained satisfactory therapeutic result. A report follows.

Security breach:peripheral nerves provide unrestricted access for toxin delivery into the central nervous system

We explore the hypothesis that a potential explanation for the initiation of motor neuron disease is an unappreciated vulnerability in central nervous system defense,the direct delivery of neurotoxins into motor neurons via peripheral nerve retrograde transport.This further suggests a mechanism for focal initiation of neuro-degenerative diseases in general,with subsequent spread by network degeneration as suggested by the Frost-Diamond hypothesis.We propose this vulnerability may be a byproduct of vertebrate evolution in a benign aquatic environment,where external surfaces were not exposed to concentrated neurotoxins.

Trick or treat?Does cancer fool Schwann cells by mimicking axons to promote metastasis into nerves?

The Schwann cell reaction to nerve injury,termed the repair program,is crucial to successful nerve regeneration.Over the last decade,substantial advances have been made in elucidating the underlying molecular mechanisms in Schwann cells that lead to functional nerve repair.Moreover,the field has identified situations,such as aging and chronic denervation where these mechanisms go awry,paving the way for the development of therapeutic interventions(Arthur-Farraj and Coleman,2021;Cattin and Lloyd,2016;Jessen and Mirsky,2019).A recent article by Deborde et al.(2022)has demonstrated that unfortunately there is a downside to Schwann cells having such an efficient regeneration-promoting program;the promotion of tumor invasion of peripheral nerves.

A NEW MODEL AND IMPROVED CABLE FUNCTION FOR REPRESENTING THE ACTIVATING PERIPHERAL NERVES BY A TRANSVERSE ELECTRIC FIELD DURING MAGNETIC STIMULATION

Objective Previous studies of peripheral nerves activation during magnetic stimulation have focused almost exclusively on the cause of high external parallel electric field along the nerves, whereas the effect of the transverse component has been ignored. In the present paper, the classical cable function is modified to represent the excitation of peripheral nerves stimulated by a transverse electric field during magnetic stimulation. Methods Responses of the Ranvier nodes to a transverse-field are thoroughly investigated by mathematic simulation. Results The simulation demonstrates that the excitation results from the net inward current driven by an external field. Based on a two-stage process, a novel model is introduced to describe peripheral nerves stimulated by a transverse-field. Based on the new model, the classical cable function is modified. Conclusion Using this modified cable equation, the excitation threshold of peripheral nerves in a transverse field during MS is obtained. The modified cable equation can be used to represent the response of peripheral nerves by an arbitrary electric field.