• Annals of Clinical Neurophysiology
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• v.19 no.1
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• pp.3-12
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• 2017

Using threshold tracking, differences have been established between large myelinated sensory and ${\alpha}$ motor axons in humans. Major differences are that sensory axons are relatively depolarised at rest such that they have a greater persistent $Na^+$ current, and have greater activity of hyperpolarisation-activated cyclic nucleotide-gated (HCN) channels. Sensory axons may thereby be protected from hyperpolarising stresses, and are less likely to develop conduction block. However, the corollary is that sensory axons are more excitable and more likely to become ectopically active.

• Annals of Clinical Neurophysiology
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• v.19 no.1
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• pp.34-39
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• 2017

Background: Automated nerve excitability testing is used to assess various peripheral neuropathies and motor neuron diseases. Comparing these excitability parameters with normal data provides information regarding the axonal excitability properties and ion biophysics in diseased axons. This study measured and compared normal values of axonal excitability parameters in both the distal motor and sensory axons of normal Koreans. Methods: The axonal excitability properties of 50 distal median motor axons and 30 distal median sensory axons were measured. An automated nerve excitability test was performed using the QTRACW threshold-tracking software (Institute of Neurology, University College London, London, UK) with the TRONDF multiple excitability recording protocol. Each parameter of stimulus-response curves, threshold electrotonus, current-voltage relationship, and recovery cycle was measured and calculated. Results: Our Korean normal data on axonal excitability showed ranges of values and characteristics similar to previous reports from other countries. We also reaffirmed that there exist characteristic differences in excitability properties between motor and sensory axons: compared to motor axons, sensory axons showed an increased strength-duration time constant, more prominent changes in threshold to hyperpolarizing threshold electrotonus (TE) and less prominent changes in threshold to depolarizing TE, and more prominent refractoriness and less prominent subexcitability and superexcitability. Conclusions: We report normal data on axonal excitability in Koreans. These data can be used to compare various pathological conditions in peripheral nerve axons such as peripheral neuropathies and motor neuron disease.

• Anatomy and Cell Biology
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• v.56 no.2
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• pp.271-275
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• 2023

The abducens nerve (AN; cranial nerve VI) exits the brainstem at the inferior pontine sulcus, pierces the dura of the posterior cranial fossa, passes through the cavernous sinus in close contact to the internal carotid artery (ICA) and traverses the superior orbital fissure to reach the orbit to innervate the lateral rectus muscle. At its exit from the brainstem, the AN includes only axons from lower motor neurons in the abducens nucleus. However, as the AN crosses the ICA it receives a number of branches from the internal carotid sympathetic plexus. The arrangement, neurochemical profile and function of these sympathetic axons running along the AN remain unresolved. Herein, we use gross dissection and microscopic study of hematoxylin and eosin-stained sections and sections with tyrosine hydroxylase immunolabeling. Our results suggest the AN receives multiple bundles of unmyelinated axons that use norepinephrine as a neurotransmitter consistent with postganglionic sympathetic axons.

• Annals of Clinical Neurophysiology
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• v.2 no.1
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• pp.1-7
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• 2000

From among the group of patients diagnosed clinically to have Guillain-Barre syndrome(GBS), subgroups with pure motor involvement have been identified. Some of such patients appear to have an axonal neuropathy by eletrophysiology. Such cases have been termed acute motor axonal neuropathy(AMAN). Many of these patients are found clinically to have normal sensation and to have electrodiagnostic patterns consistent with selective degeneration of motor axons. A serological survey showed some of individuals with AMAN had evidence of antecedent Campylobacter jejuni(CJ) infection. And AMAN has an association with the presence of anti-ganglioside antibodies. This article reviewed briefly the AMAN and their relationship to CJ infection and anti-ganglioside antibodies.

• Journal of Korean Neurosurgical Society
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• v.53 no.2
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• pp.65-71
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• 2013

Objective : In order to develop a novel nerve guidance channel using porcine small intestinal submucosa (SIS) for nerve regeneration, we investigated the possibility of SIS, a tissue consisting of acellular collagen material without cellular immunogenicity, and containing many kinds of growth factors, as a natural material with a new bioactive functionality. Methods : Left sciatic nerves were cut 5 mm in length, in 14 Sprague-Dawley rats. Grafts between the cut nerve ends were performed with a silicone tube (Silicon group, n=7) and rolled porcine SIS (SIS group, n=7). All rats underwent a motor function test and an electromyography (EMG) study on 4 and 10 weeks after grafting. After last EMG studies, the grafts, including proximal and distal nerve segments, were retrieved for histological analysis. Results : Foot ulcers, due to hypesthesia, were fewer in SIS group than in Silicon group. The run time tests for motor function study were 2.67 seconds in Silicon group and 5.92 seconds in SIS group. Rats in SIS group showed a better EMG response for distal motor latency and amplitude than in Silicon group. Histologically, all grafts contained some axons and myelination. However, the number of axons and the degree of myelination were significantly higher in SIS group than Silicon group. Conclusion : These results show that the porcine SIS was an excellent option as a natural biomaterial for peripheral nerve regeneration since this material contains many kinds of nerve growth factors. Furthermore, it could be used as a biocompatible barrier covering neural tissue.

• Journal of Physiology & Pathology in Korean Medicine
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• v.22 no.4
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• pp.896-902
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• 2008

Yukmijihwang-tang(YM) is used in Oriental medicine for treatments of diverse systemic symptoms including neurological dosorders. The present study was performed to examine potential effects of YM on growth-promoting activity of injured sciatic nerve axons. YM treatment in the injured sciatic nerve induced enhanced distal elongation of injured axons when measured 3 and 7 days after injury. Retrograde tracing of sciatic nerve axons showed YM-mediated increases in the number of DiI-labeled dorsal root ganglion (DRG) sensory neurons and spinal cord motor neurons at 3 days after injury. Hoechst nuclear staining showed that non-neuronal cell population was largely elevated by YM treatment in distal nerve area undergoing axonal regeneration. Furthermore, phospho-Erk1/2 protein levels were upregulated by YM treatment in the injured nerve area. These data suggest that YM may play a role in facilitated axonal regeneration in injured peripheral nerves. Further investigations of individual herbal components would be useful to explore effective molecular components and develop therapeutic strategies.

• Applied Microscopy
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• v.26 no.3
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• pp.329-348
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• 1996

The prenatal development of lateral motor columns in the lumbar spinal cord was studied by electron microscopy in human embryos and fetuses ranging from 9 mm to 260 mm crown-rump length ($5{\sim}30$ weeks of gestational age). At 9 mm embryo, the lateral motor column were developed from ventro-lateral projection into the marginal layer and composed of primitive neuroblasts. At 20 mm embryo the primitive motor neurons were packed closely together and could readly be distinguished from primitive glioblasts by a presence of large nuclei. The primitive multipolar neurons were observed in lateral motor column at 40 mm fetus. At 80 mm fetus multipolar neurons were characterized by their many dendrites and axons in the vicinity of motor neuron perikarya. At 260 mm fetus, the motor neurons were large and contained all intracytoplasmic structures in the cytoplasm which were also found in mature motor neuron in lateral motor column. The first axo-dendritic synapses found at 40 mm fetus and increased in number throughout fetal development. Axo-somatic synapses with spherical vesicles were first observed at 80 mm fetus. A few axo-somatic synapses were found at next prenatal stages. Axo-dendritic and axo-somatic synapses contained mixed populations of spherical and flattened vesicles by 120 mm fetus. These findings indicate that axo-dendritic synapses develop prior to axo-somatic synapses in the spinal cord during neurogenesis.

• Journal of Korean Neurosurgical Society
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• v.46 no.1
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• pp.1-4
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• 2009

Objective: To report an unsuspected adaptive plasticity of single upper motor neurons and of primary motor cortex found after microsurgical connection of the spinal cord with peripheral nerve via grafts in paraplegics and focussed discussion of the reviewed literature. Methods: The research aimed at making paraplegics walk again, after 20 years of experimental surgery in animals. Amongst other things, animal experiments demonstrated the alteration of the motor endplates receptors from cholinergic to glutamatergic induced by connection with upper motor neurons. The same paradigm was successfully performed in paraplegic humans. The nerve grafts were put into the ventral-lateral spinal tract randomly, with out possibility of choosing the axons coming from different areas of the motor cortex. Results: The patient became able to selectively activate the re-innervated muscles she wanted without concurrent activities of other muscles connected with the same cortical areas. Conclusion: Authors believe that unlike in nerve or tendon transfers, where the whole cortical area corresponding to the transfer changes its function a phenomenon that we call "brain plasticity by areas". in our paradigm due to the direct connection of upper motor neurons with different peripheral nerves and muscles via nerve grafts motor learning occurs based on adaptive neuronal plasticity so that simultaneous contractions of other muscles are prevented. We propose to call it adaptive functional "plasticity by single neurons". We speculate that this phenomenon is due to the simultaneous activation of neurons spread in different cortical areas for a given specific movement, whilst the other neurons of the same areas connected with peripheral nerves of different muscles are not activated at the same time. Why different neurons of the same area fire at different times according to different voluntary demands remains to be discovered. We are committed to solve this enigma hereafter.

• Archives of Reconstructive Microsurgery
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• v.6 no.1
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• pp.29-38
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• 1997

A peripheral nerve when approximation of the ends imparts tension at the anastomosis and with a relatively long segment defect after excision of neuroma and neurofibroma cannnot be repaired by early primary suture. The one of the optimistic reconstruction method of severed peripheral nerves is to restore tension-free continuity at the repair site putting an autogenous nerve graft into the neural gap despite of ancipating motor or sensory deficit of the donor nerve area. To overcome the deficit of the autogenous nerve graft, several other conduits supplying a metabolically active environment which is able to support axon regeneration and progression, providing protection against scar invasion, and guiding the regrowing axons to the distal stump of the nerve have been studied. An author have used ipsilateral femoral vein, ipsilateral femoral vein filled with fresh thigh muscle, and autogenous sciatic nerve for the sciatic nerve defect of around 10 mm in length to observe the regeneration pattern in rat by light and electron microscopy. The results were as follows. 1. Light microscopically regeneration pattern of nerve fibers in the autogenous graft group was more abundant than vein graft and vein filled with muscle group. 2. On ultrastructural findings, the proxial end of the graft in various groups showed similar regenerating features of the axons, myelin sheaths, and Schwann cells. The fascicular arrangement of the myelinated and unmyelinated fibers was same regardless of the type of conduits. There were more or less increasing tendency in the number and the diameter of myelinated fibers correlated with the regeneration time. 3. In the middle of the graft, myelinated nerve fibers of vein filled with muscle group were more in number and myelin sheath was thinner than in the venous graft, but the number of regenerating axons in autogenous nerve graft was superior to that in both groups of the graft. The amount of collagen fibrils and amorphous materials in the endoneurial space was increased to elapsed time. 4. There was no difference in regenerating patterns of the nerve fibers of distal end of the graft. The size and shape of the myelinated nerve fbers were more different than that of proximal and middle portion of the graft. From the above results, the degree of myelination and regenerating activity in autogenous nerve is more effective and active in other types of the graft and there were no morphological differences in either ends of the graft regardless of regeneration time.

• Annals of Clinical Neurophysiology
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• v.14 no.2
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• pp.64-71
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• 2012

Background: It is generally accepted that upper motor neuron (UMN) lesion can alter lower motor neuron (LMN) function by the plasticity of neural circuit. However there have been only few researches regarding the axonal excitability of LMN after UMN injury especially during the acute stage. The aim of this study was to investigate the nerve excitability properties of the LMNs following an acute to subacute supratentorial corticospinal tract lesion. Methods: An automated nerve excitability test (NET) using the threshold tracking technique was utilized to measure multiple excitability indices in median motor axons of 15 stroke patients and 20 controls. Testing of both paretic and non-paretic side was repeated twice, during the acute stage and subacute stage. The protocols calculated the strength-duration time constant from the duration-charge curve, parameters of threshold electrotonus (TE), the current-threshold relationship from sequential sub-threshold current, and the recovery cycle from sequential supra-threshold stimulation. Results: On the paretic side, compared with the control group, significant decline of superexcitablity and increase in the relative refractory period were observed during the subacute stage of stroke. Additionally, despite the absence of statistical significance, a mildly collapsing in ('fanning in') of the TE was found. Conclusions: Our results suggest that supratentorial brain lesions can affect peripheral axonal excitability even during the early stage. The NET pattern probably suggests background membrane depolarization of LMNs. These features could be associated with trans-synaptic regulation of UMNs to LMNs as one of the "neural plasticity" mechanisms in acute brain injury.