Differences in potentials and excitability properties in simulated cases of demyelinating neuropathies. Part I

Differences in Membrane Properties in Simulated Cases of Demyelinating Neuropathies: Internodal Focal Demyelinations with Conduction Block

“…The 70% myelin reduction value involved in the previous papers [14][15][16] is close to the final degree of systematic demyelination for achieving conduction block. These values allow different demyelination types (systematic and focal) to be compared.…”

“…The findings may not necessarily be identical to those in human demyelinating neuropathies, which can be associated with additional factors such as activation of cytokines, complements or other inflammatory substances, resulting in dysfunction of ion channels, and macrophage invasion or nerve edema/fibrosis leading to structural changes. However, the simulated results [13][14][15][16][17] indicate that this model is a rather promising tool in studying the prominent features in neuropathies and neuronopathies which up till now have not been sufficiently well understood.…”

“…The strength-duration time constants and rheobasic currents are calculated by the method, which is described earlier [13][14][15][16][17] and, in brief, the threshold stimulus duration is increased in 0.025 ms steps from 0.025 ms to 1 ms, to obtain the strength-duration curves. A polynomial function of degree 2 (transfer standard parabola), which relates threshold charge (Q) to stimulus duration (t), provides an accurate fit of the data:…”

“…Recently, the method of mathematical modelling has also been applied as a promising tool for studying excitability properties in nerve disorders [13][14][15][16][17]. Our previous study [16], investigating membrane properties in simulated cases of CMT1A, shows that greater negative electrotonic responses, longer strength-duration time constants, and greater refractoriness and supernormality in the recovery cycles can be used as specific indicators of internodal systematic demyelinations (ISD). The uniformly reduced amplitudes, prolonged duration and slowed conduction velocities of the intracellular potentials are also characteristic of these abnormal cases.…”

“…These indices, which depend on the biophysical properties of the axonal membrane and myelin sheath, can now be measured in healthy subjects and patients with demyelinating neuropathies [8][9][10][11][12]. Recently, the method of mathematical modelling has also been applied as a promising tool for studying excitability properties in nerve disorders [13][14][15][16][17]. Our previous study [16], investigating membrane properties in simulated cases of CMT1A, shows that greater negative electrotonic responses, longer strength-duration time constants, and greater refractoriness and supernormality in the recovery cycles can be used as specific indicators of internodal systematic demyelinations (ISD).…”