Simulation Analysis of Conduction Block in Myelinated Axons Using Three Models

2008 ◽  
Author(s):  
Lei Yu ◽  
Xu Zhang ◽  
Anyu Chen ◽  
Z. H. Ren
Keyword(s):  
Simulation Analysis ◽  
Conduction Block ◽  
Myelinated Axons

scholarly journals Conduction block in myelinated axons induced by high-frequency (kHz) non-symmetric biphasic stimulation

2015 ◽  
Vol 9 ◽  
Author(s):  
Shouguo Zhao ◽  
Guangning Yang ◽  
Jicheng Wang ◽  
James R. Roppolo ◽  
William C. de Groat ◽  
...  
Keyword(s):  
High Frequency ◽  
Conduction Block ◽  
Myelinated Axons

scholarly journals Preferential conduction block of myelinated axons by nitric oxide

2016 ◽  
Vol 95 (7) ◽  
pp. 1402-1414
Author(s):  
Peter Shrager ◽  
Margaret Youngman
Keyword(s):  
Nitric Oxide ◽  
Conduction Block ◽  
Myelinated Axons

Differential Nerve Block

1996 ◽  
Vol 84 (6) ◽  
pp. 1455-1464 ◽  
Author(s):  
Richard A. Jaffe ◽  
Michael A. Rowe
Keyword(s):  
Steady State ◽  
Conduction Velocity ◽  
Nerve Block ◽  
Dorsal Root ◽  
Conduction Block ◽  
Differential Sensitivity ◽  
Vagus Nerves ◽  
Myelinated Axons ◽  
Adult Rats ◽  
Unmyelinated Axons

Background Clinically, differential block is manifested by the loss of small fiber mediated sensation (e.g., temperature) two or more dermatomes beyond the sensory limit for large fiber mediated sensations. These observations support the belief that sensitivity to local anesthetics is inversely proportional to axon diameter. This study reports the first measurements of differential sensitivity to lidocaine in individual myelinated and unmyelinated mammalian dorsal root axons. Methods Lumbar dorsal roots and vagus nerves were isolated from anesthetized adult rats and maintained in vitro in a perfusion/recording chamber at 37 +/- 0.3 degrees C. Using single fiber techniques, evoked action potentials in individual myelinated and unmyelinated axons were digitized and recorded for subsequent analysis. Axons were exposed to lidocaine at 150, 260, or 520 microM. Sensitivity to local anesthetic was assessed by measuring the incidence of conduction block and the magnitude of conduction velocity slowing under steady-state conditions. Results Data were obtained from 77 dorsal root axons and 41 vagal axons. The estimated steady-state EC50 lidocaine concentration for myelinated dorsal root axons (232 microM) was comparable to that for unmyelinated axons (228 microM). Similarly, the incidence of conduction block was not significantly different among dorsal root axon groups. However, unmyelinated dorsal root axons were significantly less sensitive to the conduction velocity slowing effect of lidocaine than their myelinated counterparts (P < 0.01). The incidence of conduction block in short (mean length 13.5 mm) dorsal root axons was not significantly different from that in long (mean length 22.4 mm) axons. Compared with dorsal root axons, the estimated EC50s for vagal myelinated and unmyelinated axons (345 and 285 microM, respectively), while lower were not significantly different. However, the incidence of conduction block at 260 microM lidocaine was significantly lower (16.7% vs. 56.7%; P < 0.05) in vagal myelinated axons. Conclusions Although no difference in sensitivity to the conduction blocking effects of lidocaine could be demonstrated among dorsal root axons, myelinated axons were more sensitive to the conduction velocity slowing effects of lidocaine. This differential effect cannot explain clinical observations of differential nerve block. Differential sensory block with lidocaine may depend on factors (e.g., physiologic function) related only indirectly to individual axon conduction velocity (diameter).

Entrapment Neuropathies: Electrodiagnostic Criteria

2019 ◽  
Vol 24 (6) ◽  
pp. 12-15
Author(s):  
Jay Blaisdell ◽  
James B. Talmage
Keyword(s):  
Nerve Conduction ◽  
Task Force ◽  
Conduction Block ◽  
Cubital Tunnel Syndrome ◽  
Conduction Delay ◽  
Test Results ◽  
Sixth Edition ◽  
Entrapment Neuropathies ◽  
Axon Loss ◽  
Tunnel Syndrome

Abstract Like the diagnosis-based impairment (DBI) method and the range-of-motion (ROM) method for rating permanent impairment, the approach for rating compression or entrapment neuropathy in the upper extremity (eg, carpal tunnel syndrome [CTS]) is a separate and distinct methodology in the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), Sixth Edition. Rating entrapment neuropathies is similar to the DBI method because the evaluator uses three grade modifiers (ie, test findings, functional history, and physical evaluation findings), but the way these modifiers are applied is different from that in the DBI method. Notably, the evaluator must have valid nerve conduction test results and cannot diagnose or rate nerve entrapment or compression without them; postoperative nerve conduction studies are not necessary for impairment rating purposes. The AMA Guides, Sixth Edition, uses criteria that match those established by the Normative Data Task Force and endorsed by the American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM); evaluators should be aware of updated definitions of normal from AANEM. It is possible that some patients may be diagnosed with carpal or cubital tunnel syndrome for treatment but will not qualify for that diagnosis for impairment rating; evaluating physicians must be familiar with electrodiagnostic test results to interpret them and determine if they confirm to the criteria for conduction delay, conduction block, or axon loss; if this is not the case, the evaluator may use the DBI method with the diagnosis of nonspecific pain.

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