THE PLASTICITY OF NERVE FIBRES: THE PROLONGED EFFECTS OF POLARIZATION OF AFFERENT FIBRES

2021 ◽  
Author(s):  
Elzbieta Jankowska ◽  
Ingela Hammar
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injuries ◽  
Dorsal Column ◽  
Membrane Receptors ◽  
Field Potentials ◽  
Spinal Motoneurons ◽  
Nerve Fibres ◽  
Dorsal Columns ◽  
Axonal Excitability ◽  
Sustained Increase

The review surveys various aspects of the plasticity of nerve fibres, in particular the prolonged increase in their excitability evoked by polarization, focusing on a long-lasting increase in the excitability of myelinated afferent fibres traversing the dorsal columns of the spinal cord. We review the evidence that increased axonal excitability (i) follows epidurally applied direct current as well as relatively short (5 or 10 ms) current pulses and synaptically evoked intrinsic field potentials; (ii) critically depends on the polarization of branching regions of afferent fibres at the sites where they bifurcate and give off axon collaterals entering the spinal grey matter in conjunction with actions of extrasynaptic GABAA membrane receptors; and (iii) shares the feature of being activity-independent with the short-lasting effects of polarization of peripheral nerve fibres. A comparison between the polarization evoked sustained increase in the excitability of dorsal column fibres and spinal motoneurons (plateau potentials) indicates the possibility that they are mediated by partly similar membrane channels (including non-inactivating type L Cav++ 1.3 but not Na+ channels) and partly different mechanisms. We finally consider under which conditions trans-spinally applied DC (tsDCS) might reproduce the effects of epidural polarization on dorsal column fibres and the possible advantages of increased excitability of afferent fibres for the rehabilitation of motor and sensory functions after spinal cord injuries.

Intraoperative evoked potentials recorded in man directly from dorsal roots and spinal cord

1985 ◽  
Vol 62 (5) ◽  
pp. 680-693 ◽  
Author(s):  
Blaine S. Nashold ◽  
Janice Ovelmen-Levitt ◽  
Robbin Sharpe ◽  
Alfred C. Higgins
Keyword(s):  
Spinal Cord ◽  
Dorsal Root ◽  
Mean Amplitude ◽  
Dorsal Column ◽  
Intractable Pain ◽  
Neurosurgical Procedures ◽  
Negative Wave ◽  
Content Type ◽  
Root Entry Zone ◽  
Dorsal Columns

✓ Direct spinal cord surface recordings of evoked spinal cord potentials have been made in 26 patients during neurosurgical procedures for intractable pain. Monopolar recordings at the dorsal root entry zone after peripheral nerve stimulation have been made at multiple levels for segmental localization and to monitor the state of the afferent path and dorsal horn. Dorsal root and dorsal column conduction has been tested on diseased and intact sides. Normal afferent conduction velocity was found to have an overall mean of 61.33 m/sec for cervicothoracic and lumbosacral peripheral nerves, and 50 m/sec for the dorsal columns. The normal mean amplitude for the slow negative wave (N1) recorded at the root entry was 52.54 µV, while that for the dorsal column conducted response recorded within 4 cm of the stimulus point on the dorsal columns was 347.5 µV. Several different placements of stimulating and recording electrodes are described, as well as their application. An interpretation of the resulting data is proposed.

Spinal evoked potentials from the motor tracts

1983 ◽  
Vol 58 (1) ◽  
pp. 38-44 ◽  
Author(s):  
Walter J. Levy
Keyword(s):  
Spinal Cord ◽  
Evoked Potentials ◽  
Motor System ◽  
Evoked Potential ◽  
Motor Evoked Potential ◽  
Dorsal Column ◽  
Content Type ◽  
Dorsal Columns ◽  
Evoked Potential Monitoring ◽  
Potential Monitoring

✓ There is a need to monitor the motor system, but it has a different blood supply and a different location in the spinal cord from those measured by traditional somatosensory evoked potential monitoring. This paper reports a motor evoked potential monitoring system that uses direct spinal cord stimulation overlying the areas of the motor tract in the cord. In nine cats, evoked potentials were recorded from the dura, which gave a much faster main signal component than the traditional dorsal column evoked potentials, which were also recorded. This 100-m/sec signal was not affected by sectioning of the dorsal columns, which was verified histologically. This mode of monitoring the motor system can be used during surgery. It may also provide a better evaluation of patients after spinal cord trauma.

Stage-dependent restoration of sensory dorsal columns following spinal cord transection in anuran tadpoles

1986 ◽  
Vol 227 (1246) ◽  
pp. 67-82 ◽  
Keyword(s):  
Spinal Cord ◽  
Rana Temporaria ◽  
Axon Growth ◽  
Dorsal Column ◽  
Anterograde Transport ◽  
Thoracic Spinal Cord ◽  
Complete Transection ◽  
Thoracic Spinal ◽  
Dorsal Columns ◽  
Stage Viii

In frogs sensory axons from the lumbar dorsal roots ascend in the dorsal column of the spinal cord to terminate in the medulla and cerebellum. The response of these axons to complete transection of the thoracic spinal cord has been analysed in Rana temporaria tadpoles at different stages of development. The presence and position of dorsal column axons were assessed by using the anterograde transport of horseradish peroxidase or by electrophysiological methods. Before developmental stage VIII, dorsal column axons can grow across the transection and reach their normal areas of termination in the brainstem. Axons that do cross the transection follow their normal pathways. From stage VIII onwards this capacity for growth is largely lost. These results are discussed in terms of the relation between neurogenesis, axon growth and axonal regeneration.

Revisiting intradural spinal cord stimulation: an introduction to a novel intradural spinal cord stimulation device

2014 ◽  
Vol 2 (1-4) ◽  
Author(s):  
Brian D. Dalm ◽  
Sephanus V. Viljoen ◽  
Nader S. Dahdaleh ◽  
Chandan G. Reddy ◽  
Timothy J. Brennan ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Stimulation ◽  
Spinal Cord Injuries ◽  
Electrical Current ◽  
Auditory Brainstem ◽  
Dorsal Column ◽  
Neurological Deficits ◽  
Vessel Injury ◽  
Present Design ◽  
Sensory Evoked

AbstractSpinal cord stimulation has been in use for decades and is growing as a therapeutic treatment option. A significant problem arising from the epidural location of the lead is electrical shunting through the cerebrospinal fluid, providing sub-optimal delivery of the electrical current specifically to the Aβ fibers of the dorsal column.Our goal is to design a safe and effective intradural spinal cord stimulator (SCS) that places the stimulating electrodes directly against the pia similar to what is currently employed with the auditory brainstem implant.We have reviewed the literature on the early original intradural SCSs and designed, built, and tested an improved device that seeks to overcome the limitations the existing epidural stimulators.In particular, we have shown that the present design of our device allows for motion of the spinal cord without the device being displaced itself, exerts a surface pressure on the spinal cord surface that is below what would cause ischemia or vessel injury, activates somato-sensory evoked potentials at a lower threshold than epidural stimulation, and (iv) does not cause deleterious neurological deficits in a chronic ovine model of intradural stimulator implantation.While further studies to prove long-term safety and durability of the device are underway, we believe that revisiting an intradural approach to spinal cord stimulation may continue to improve our ability to treat certain chronic pain states and possibly the spasticity associated with spinal cord injuries.

scholarly journals Manganese-enhanced MRI Offers Correlation with Severity of Spinal Cord Injury in Experimental Models

2016 ◽  
Vol 10 (1) ◽  
pp. 139-147 ◽  
Author(s):  
Nikolay L. Martirosyan ◽  
Gregory H. Turner ◽  
Jason Kaufman ◽  
Arpan A. Patel ◽  
Evgenii Belykh ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injuries ◽  
Diffusion Tensor ◽  
Neuronal Damage ◽  
Experimental Models ◽  
Dorsal Column ◽  
Neural Regeneration ◽  
Post Surgery ◽  
Percentage Difference ◽  
Cord Injury

Background: Spinal cord injuries (SCI) are clinically challenging, because neural regeneration after cord damage is unknown. In SCI animal models, regeneration is evaluated histologically, requiring animal sacrifice. Noninvasive techniques are needed to detect longitudinal SCI changes. Objective: To compare manganese-enhanced magnetic resonance imaging (MRI [MEMRI]) in hemisection and transection of SCI rat models with diffusion tensor imaging (DTI) and histology. Methods: Rats underwent T9 spinal cord transection (n=6), hemisection (n=6), or laminectomy without SCI (controls, n=6). One-half of each group received lateral ventricle MnCl2 injections 24 hours later. Conventional DTI or T1-weighted MRI was performed 84 hours post-surgery. MEMRI signal intensity ratio above and below the SCI level was calculated. Fractional anisotropy (FA) measurements were taken 1 cm rostral to the SCI. The percentage of FA change was calculated 10 mm rostral to the SCI epicenter, between FA at the dorsal column lesion normalized to a lateral area without FA change. Myelin load (percentage difference) among groups was analyzed by histology. Results: In transection and hemisection groups, mean MEMRI ratios were 0.62 and 0.87, respectively, versus 0.99 in controls (P<0.001 and P<0.001, respectively); mean FA decreases were 67.5% and 40.1%, respectively, compared with a 6.1% increase in controls (P=0.002 and P=0.019, respectively). Mean myelin load decreased by 38.8% (transection) and 51.8% (hemisection) compared to controls (99.1%) (P<0.001 and P<0.001, respectively). Pearson’s correlation coefficients were -0.94 for MEMRI ratio and FA changes and 0.87 for MEMRI and myelin load. Conclusion: MEMERI results correlated to SCI severity measured by FA and myelin load. MEMRI is a useful noninvasive tool to assess neuronal damage after SCI.

Phase Reversal of Somatosensory Evoked Potentials Triggered by Gracilis Tract Stimulation: Case Report of a New Technique for Neurophysiologic Dorsal Column Mapping

Neurosurgery ◽  
2011 ◽  
Vol 70 (3) ◽  
pp. 783-783 ◽  
Author(s):  
Mirela V. Simon ◽  
Keith H. Chiappa ◽  
Lawrence F. Borges ◽  
Marc R. Nuwer ◽  
Vedran Deletis
Keyword(s):  
Spinal Cord ◽  
Evoked Potentials ◽  
Somatosensory Evoked Potentials ◽  
Spinal Cord Tumor ◽  
Tumor Resection ◽  
Dorsal Column ◽  
Intramedullary Spinal Cord ◽  
Phase Reversal ◽  
Dorsal Columns ◽  
A New Technique

Abstract Background and Importance: Reliable visual identification of the median raphae, essential for the preservation of function of the posterior dorsal columns during intramedullary spinal cord tumor resection, is not possible in many cases, because of distorted local anatomy. In such cases, intraoperative neurophysiologic mapping of the dorsal columns offers invaluable information to the surgeon, and guides the myelotomy. We hereby describe such a new technique. Clinical Presentation: A 41 -year-old man with a C3-C4 intramedullary spinal cord tumor underwent successful myelotomy and tumor resection. Dorsal column mapping was performed by use of an 8-contact minielectrode strip placed on the dorsal spinal cord. Direct electrical stimulation was applied via 2 adjacent contacts of the strip at a time, in an attempt to stimulate in succession the left and right dorsal columns. Somatosensory evoked potentials (SSEPs) were recorded after each stimulation, via scalp electrodes. A sharp change in polarity of the recorded scalp SSEPs (phase reversal) indicated when the stimulation of the opposite dorsal column occurred. Myelotomy was performed in between the minielectrode contacts identified as being situated closest to the raphe. The posterior tibial SSEPs were continuously monitored during and after myelotomy and until the dura closure. No changes from premyelotomy SSEPs were present. Postoperatively, the patient had preservation of the posterior column function. Conclusion: SSEP phase-reversal technique is a promising new method to identify the neurophysiologic midline in intramedullary tumor resection. Fast and easy to perform, its final role in neurophysiologic dorsal column mapping awaits confirmation in future applications.

Spinal evoked potentials in the primate: Neural substrate

1978 ◽  
Vol 49 (4) ◽  
pp. 551-557 ◽  
Author(s):  
Joseph F. Cusick ◽  
Joel Myklebust ◽  
Sanford J. Larson ◽  
Anthony Sances
Keyword(s):  
Spinal Cord ◽  
Peripheral Nerve ◽  
Evoked Potentials ◽  
Dorsal Column ◽  
Wave Form ◽  
Content Type ◽  
Neural Substrate ◽  
Dorsal Columns ◽  
Microsurgical Resection ◽  
Fine Print

✓ Summated responses evoked by peripheral nerve stimulation were recorded from electrodes located in the epidural and subdural spaces anterior and posterior to the monkey spinal cord. Segmental microsurgical resection of the dorsal columns both at the thoracic and cervical levels resulted in total obliteration of the response recorded rostral to these lesions. Isolated segmental dorsal column preservation did not significantly alter response latency or wave form recorded at the rostral electrodes. Bilateral cervical dorsolateral column resection also resulted in no discernible alterations of these responses. These data indicate that spinal evoked potentials recorded from levels rostral to their root entry zones arise almost exclusively from the dorsal columns.

scholarly journals Pathfinding by dorsal column axons in the spinal cord of the frog tadpole

Development ◽  
1987 ◽  
Vol 99 (4) ◽  
pp. 577-587 ◽  
Author(s):  
N. Holder ◽  
J.D. Clarke ◽  
D. Tonge
Keyword(s):  
Spinal Cord ◽  
Dorsal Root ◽  
Rana Temporaria ◽  
Dorsal Column ◽  
Lumbar Region ◽  
Dorsal Funiculus ◽  
Thoracic Spinal Cord ◽  
Thoracic Spinal ◽  
Frog Tadpole ◽  
Dorsal Columns

Sensory fibres from dorsal root ganglia (DRG) enter the spinal cord and run within a clearly defined ipsilateral pathway, the dorsal column, which lies in the dorsal funiculus. We have examined the characteristics of this pathway as a defined substrate for dorsal column axons in Rana temporaria tadpoles by rotating the thoracic spinal cord through 180 degrees from dorsal to ventral. Using HRP as a neuronal tracer we establish that many dorsal column axons from the hindlimb locate the ipsilateral or contralateral dorsal column pathway in the rotated cord. Other axons locate and grow caudally down the contralateral dorsal column returning to the lumbar region. Axons of the dorsal column never take an inappropriate pathway except at the transection sites where they negotiate abnormal routes to reach the contralateral or ipsilateral dorsal columns in normally positioned or rotated cord. The results demonstrate that the dorsal columns act as highly specific pathways for axons from DRG neurones but the axons' interactions with the pathway do not control the craniocaudal or left-right options for growth.

Postsynaptic dorsal column pathway of the rat. I. Anatomical studies

1984 ◽  
Vol 51 (2) ◽  
pp. 260-275 ◽  
Author(s):  
G. J. Giesler ◽  
R. L. Nahin ◽  
A. M. Madsen
Keyword(s):  
Spinal Cord ◽  
Dorsal Horn ◽  
Gray Matter ◽  
Dorsal Column ◽  
Spinal Cord Dorsal Horn ◽  
Substantia Gelatinosa ◽  
Cervical Cord ◽  
Dorsal Column Nuclei ◽  
Dorsal Columns ◽  
Postsynaptic Dorsal Column

As one of a series of studies of the ascending spinal cord pathways that might be involved in nociception in the rat, we have examined the projection to the dorsal column nuclei that originates in the spinal cord dorsal horn using the retrograde transport of horseradish peroxidase (HRP). This projection in other animals has been called the postsynaptic dorsal column (PSDC) pathway. Small iontophoretic injections of HRP into the cuneate nucleus (CN) labeled more than 350 neurons in alternate sections within the ipsilateral gray matter of segments C6-8. Fewer than 25 neurons were labeled in L4-6 by injections into CN. Injections of HRP confined to the gracile nucleus (GN) labeled more than 200 neurons within a narrow band extending across the ipsilateral dorsal horn subjacent to substantia gelatinosa of L4-6. Fewer than 10 cells were labeled in C6-8 by such injections. Labeling in lumbar neurons following injections into GN was prevented by transection of the dorsal columns at T10, T8, or C2. Thus, neurons labeled by such injections ascend entirely within the dorsal columns. Lesions of the dorsal columns in C2 reduced the number of labeled neurons in the cervical cord following CN injections by approximately 90%. Combined lesions of the dorsal columns and ipsilateral dorsal lateral funiculus (DLF) reduced the number of cells labeled in C6-8 by approximately 98%. Thus, the majority of labeled neurons in the cervical enlargement project to CN via the dorsal columns; a small secondary component of the cervical projection to CN appears to ascend within the DLF. To compare the relative sizes of the projections to the dorsal column nuclei from PSDC neurons and dorsal root ganglion cells (DRG), labeled neurons were counted in the gray matter of the cervical and lumbar enlargements and the corresponding DRG. In the four animals so examined, PSDC neurons constituted over 38% of the neurons that projected to CN and approximately 30% of the cells that projected to GN. These findings indicate that the PSDC projection of the rat is capable of providing a large somatotopically organized input to the dorsal column nuclei.

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