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[A study of peripheral neural conduction, motor and sensory, in diabetic patients treated with hyperbaric oxygenation].

INTRODUCTION: There are some occlusive disorders in the vasa nervorum and metabolic changes disminishing oxygen liberation by erytrocites at the capillary blood vessels, and these disturbances lead to endoneural microhypoxia. Hyperbaric oxygen reverts hypoxia in the diabetic neuropathy. OBJECTIVE: We studied motor and sensitive peripheric neuroconduction in nine diabetic patients, with distal symmetrical polyneuropathy, during normoglycemia. Four of them were insulin dependent and five were non insulin dependent. PATIENTS AND METHODS: The electrophysiological studies were done before treatment with hyperbaric oxygen, in a week, three and six months later. The abnormal electrophysiological parameters detected in diabetics were terminal latencies (enlarged), velocities of conduction (slowed) and distal amplitudes of compound action potentials (reduced). RESULTS: Neither distal latencies nor distal amplitudes and conduction velocities in peroneal nerve showed significative changes in the statistical analysis. We observed slower conduction velocities in the motor fibers of the median nerve in the examination performed six months after treatment. There was an increase of distal latency and retardation of the velocity of conduction six months later after treatment in the sensitive fibers of median nerve, whereas the amplitudes of sensitive action potentials decreased progressively. These changes suggest large diameter peripheral fibers didn't receive benefit with hyperbaric oxygen treatment. CONCLUSIONS: In all patients disappeared all symptoms of dysesthesias, paresthesias, distal pains and cramps in the legs and arms, suggesting functional changes in small unmyelinated fibers which we can't test with conventional techniques to prove it.

Adult↗
PubMed1999

Manic-depression neural conduction speeds and action potential event dyscorrelation.

In manic-depressive disorder, the monotonic, humor/receptor, excess/deficit, i.e. gain, theories have prevailed for many years, even though there is increasing evidence of a timing abnormality that may or may not be related to gain. In addition, the manic-depressive course is clearly multimodal and unpredictable except in revealing but rare cases, yet the system is real, and thus presumably deterministic, clearly suggesting a dynamic instability. A wide range of disciplines was reviewed by the author. Those data that were significantly different by standard tests were considered. However, averaged values were always questioned. During this review, higher water compartmentalization differentials were found in manic-depressive patients. Also indicated, event-related potential components differed in latency correlations, suggesting action potential firing event dyscorrelation. In conclusion, the manic-depressive action potential firing events may be dyscorrelated in a space-time reference frame.

Action Potentials↗
PubMed1982

Paradoxical preservation of neural conduction by lidocaine.

The interaction of glucose lack and local anesthetic on impulse conduction was investigated in rabbit vagus nerve. Glucose lack depressed the compound action potential 50 per cent in 47 +/- 7 min (+/- SD, n = 5) and extinguished it in 69 +/- 7 min. Lidocaine hydrochloride, 0.1 mmol/1 (0.0027 g/dl), delayed the onset of inexcitability caused by glucose lack: 50 per cent depression required 85 +/- 9 min, extinction required 131 +/- 20 min (P less than 0.001). The delay decreased with lower and higher lidocaine concentrations. Lidocaine also significantly decreased the potassium loss and sodium gain occasioned by 2.5 h of glucose deprivation. Thus, delayed extinction of excitability by local anesthetic in very low concentration may be due to decrease in permeability of the axonal plasma membrane not only to sodium but also to potassium ions.

Action Potentials↗
PubMed1983

[Circadian, infradian and seasonal changes in neural conduction velocity with reference to the effects of temperature. II: Infradian and seasonal changes].

Using the longitudinal study it was shown that a number of sensory neurographic parameters changed systematically throughout the 4-day investigation. In particular the sensory NCV of the n. medianus of the hand increased significantly. Possible causes i.e. the activation of the metabolism are discussed. Should this assumption prove to be true repetitive stimulation of a nerve could have a therapeutic effect. The seasonal influences are displayed using the results of a cross-sectional study. Six out of 21 neurographic parameters showed significant seasonal variations. In the NCVs of the n. medianus and the n. ulnaris maxima were present in summer and autumn while the NCVs of the lower extremities had minima. In winter and spring differences between the NCVs of the lower and upper arm and leg were lowest. These differences may be caused by seasonal changes of the metabolism which modifies the coefficient of the temperature of the neurographic parameters.

Circadian Rhythm↗
PubMed1986

Disturbances of neural conduction in isolated frog nerves following exposure to strong electric fields.

Frog sciatic nerves were isolated and the middle portion of each exposed to condenser discharges (field strength up to 1000 V/cm; time constants 0.2-8.0 ms) through the bathing fluid. The ability of the nerve to propagate action potentials (AP) was examined by stimulating the proximal end and recording the AP from the distal end of the exposed section. The fraction of the nerve fibers remaining propagative was estimated from the amplitude (or the area) of the compound AP. Strong discharges brought about a total block of propagation lasting for up to 30 minutes, followed by slow, but almost complete, restitution. The restitution was exponential against time and depended on the field strength and duration of the discharge. Discharges equal in energy but different in their voltage--condenser combinations had markedly different actions, with stronger effects being found at higher voltages and vice versa. Hence, the described effects are unlikely to be caused by dissipation of thermal energy only. Other mechanisms (ionic imbalance, dielectric breakdown, punch through) are discussed.

Action Potentials↗
PubMed1999

Multifocal neural conduction impairment in forestry workers exposed and not exposed to vibration.

OBJECTIVE: The aim of the study was to assess peripheral neural involvement induced by exposure to hand-arm vibration. METHODS: Twenty lumberjacks, working regularly with chain-saws and exposed to hand-arm vibration (group E) and 20 forestry workers performing heavy manual work and not exposed to vibration (group NE) were matched with a control group of 20 healthy non-manual workers (group C). The subjects of groups E and NE, all symptomatic, and of group C underwent extensive bilateral neurophysiological examination consisting of: sensory conduction (velocity and amplitude) of radial, median and ulnar nerves in digit-wrist segments; sensory conduction (velocity) of median nerve in wrist-elbow segment; mixed conduction (velocity and amplitude) of median and ulnar nerves in palm-wrist segments; motor conduction velocity, including distal motor latencies, and amplitude of median (elbow-wrist) and ulnar (elbow-wrist and across the elbow) nerves. RESULTS: Electrophysiological abnormalities were found in 85% of group E's limbs, versus 62.5% of group NE's limbs. The most frequent pathological pattern in group E was a 'multifocal' impairment (multiple sites of several nerve segments), with a prevalent involvement of sensory rather than motor fibres in the hand, seldom extending to the forearm. Multivariate analysis showed that the neurographic parameters which better characterized workers exposed to hand-arm vibration had a pattern different from that usually found in idiopathic carpal tunnel syndrome (CTS). CONCLUSION: These results suggest that vibration-induced neural involvement can be considered neither pure digital neuropathy, nor definite CTS, as previously described.

Action Potentials↗
PubMed1994

Sensory neural conduction of median nerve from digits and palm stimulation in carpal tunnel syndrome.

The median sensory nerve conduction between ring finger and wrist is a suitable parameter for early detection of carpal tunnel syndrome (CTS), although shorter segments of median nerve have also been proposed for the same goal. In order to assess the relative diagnostic value of the sensory nerve conduction velocity (SNCV) of the third palmar branch versus the SNCV of the second palmar branch, generally performed until now, we studied 62 patients with typical signs and symptoms of CTS. The following parameters were evaluated by surface recording: orthodromic SNCVs in digit-wrist segments for median (index = M2, third = M3 and ring = M4 fingers), ulnar (fourth = U4 finger) and radial (thumb = R1) nerves; SNCVs in palm-wrist segments by surface bipolar stimulation at each metacarpo-phalangeal interspace (second = P2 and third = P3 for the median nerve and fourth = P4 for the ulnar nerve); and distal motor latencies of the median and ulnar nerves. No responses at the wrist were recorded in 22.6% of patients after digital stimulation of M4, whereas the SNCV of P3, the palmar nerve branch arising from digital nerves of the medial side of M3 and the lateral side of M4, was measurable in 93.5% of patients. As significantly expressed (P < 0.001) by the increased ratio of the mean values of P2 and P3 in CTS patients, the SNCV of P3 decreased more frequently and to a greater extent than the SNCV of P2.

Action Potentials↗
PubMed1983

[Circadian, infradian and seasonal changes in neural conduction velocity with reference to effects of temperature; I.: Circadian rhythm].

Using results of two collectives (one cross-section study covering 212 individuals and a longitudinal study of 10 individuals over a period of 4 days with 4 examinations/individual/day) circadian, infradian and seasonal influences on the changes observed are considered. The skin temperatures displayed significant circadian variations subsequent to electrical stimulation in 4 of 5 topographic regions from which the measurements were performed. Before stimulation in only one of five regions significant circadian changes were observed. Thus stimulation caused an increase in amplitude but no changes in phase. Pre- and post-stimulation rhythms were in phase. There was found a two-peaked circadian rhythm with maxima at late noon and at midnight. Probably there were systematic differences in skin temperature in the upper extremities compared to the lower ones. The latter showed a minimum in the early morning hours. The circadian effects are presented almost completely free of temperature influences for the sensory NCV of the n. medianus on the hand. As opposed to the simultaneously acquired 2-peaked circadian rhythm of the skin temperature an almost continuous decrease in the NCV can be observed from the early morning until midnight. After midnight there was an abrupt increase of the NCV by about 5%. The significant influences of the time-of-day on the NCV of the upper- and lower-arm could not be attained independent of temperature influences. It was nonetheless apparent that the motor and sensory NCV of the lower arm increased throughout the day in contrast to the NCV of the hand. Possibly, local' influences interfered thereby with the autonomic rhythm of the nerve.

Adolescent↗
PubMed2003

Conduction of neural impulses in diabetic neuropathy.

OBJECTIVE: To measure the conduction velocity, absolute refractory period and duration of the action potential for individual afferents of the median nerve in diabetic patients and to examine correlations between measures and with temperature and compare this to data from normal subjects. METHODS: The technique of percutaneous microneurography was used to record from individual afferents and intradermal electrical stimuli were applied to generate action potentials in distal axons. RESULTS: Like normal afferents, afferents in diabetic subjects demonstrated temperature sensitivity. Durations of the action potential and refractory periods correlated with temperature (r=-0.59 and r=-0.51). Conduction velocities and durations of the action potential did not differ between diabetic (means of 34 m/s and 0.42 ms) and normal (means of 34 m/s and 0.45 ms) subjects. However, refractory periods were significantly shorter in diabetic (mean 1.3 ms) than in normal (mean 1.8 ms) nerves and the normal correlation between conduction velocity and refractory period was disrupted. CONCLUSIONS: The results reveal disturbances of the axonal recovery process in diabetic patients, possibly due to membrane potential fluctuations after the generation of an action potential. Uncovering specific excitability changes in diabetic nerve facilitates the design of pharmacological interventions for restoring nerve function.

Action Potentials↗
PubMed1988

Conduction of neural impulses in human mechanoreceptive cutaneous afferents.

1. It was the aim of the present study to isolate and identify the components underlying the human sensory compound action potential and to study their axonal conduction velocities and refractory periods. For this purpose the technique of percutaneous microneurography was combined with intradermal electrical stimulation of nerve fibre terminals. Sixty-four median and ulnar nerve afferents innervating the glabrous skin of the digits were isolated and type identified. 2. The range of axonal conduction velocities was wide (20-60 m/s), but similar for each afferent category (20-60 m/s). Most afferents conducted slower than expected from the intrafascicularly recorded compound potential (50-60 m/s) and their conduction velocities generally decreased from the base to the tip of the digits. 3. The duration of the absolute axonal refractory periods of all types of afferents ranged from 0.7 to 3.5 ms. The duration of the total refractory periods ranged from 3 to 9 ms. Both absolute and total axonal refractory periods were inversely correlated (r = -0.70 and r = -0.67) with their axonal conduction velocities. 4. The size of individual action potentials was significantly correlated with axonal conduction velocities, although the correlation coefficient was relatively low (r = 0.43), even after correction for variability due to electrode resistance (partial correlation r = 0.44). 5. The results showed that different types of cutaneous afferents cannot be separated on the basis of their axonal conduction properties. The data demonstrate features of neural impulse conduction along the entire axonal tree and which are inaccessible to routine electrodiagnostic procedures. The present approach provides a sensitive means for assessing, in health and disease, nerve conduction in terminal axons.

Action Potentials↗
PubMed2005

Movement analysis in neonates with spina bifida aperta.

INTRODUCTION: In neonates with spina bifida aperta (SBA), leg movements by myotomes caudal to the meningomyelocele (MMC) are transiently observed. It is unclear whether these leg movements relate to functional neural conduction through the MMC. For optimal therapeutical intervention, pathophysiological insight in these transient leg movements seems relevant. If leg movements by myotomes caudal to the MMC concur with the execution of general movements (GMs), functional neural conduction through the MMC is implicated. OBJECTIVE: In neonates with SBA, we aimed to determine whether the transiently present leg movements caudal to the MMC indicate functional neural conduction through the MMC. METHODS: During the perinatal period, fetuses and neonates with SBA (n = 7 and n = 13, respectively) were longitudinally analysed for concurrency between leg movements caudal to the MMC and GMs. To address the integrity of the reflex arc in spinal segments (at, or) caudal to the MMC, tendon leg reflexes were assessed during the first postnatal week. RESULTS: At postnatal day 1, leg movements caudal to the MMC concurred with GMs in 12 of 13 infants. Isolated leg movements were observed in only 3 of these 12 infants (isolated vs. concurrent; p < 0.005). Leg movements concurring with GMs lasted longer than isolated leg movements (median duration = 11 s vs. 2 s; p < 0.05). Between days 1 and 7, tendon leg reflexes (at, or) caudal to the MMC had disappeared in all but 1 neonate. However, leg movements caudal to the MMC remained concurrently present with GMs in all five neonates available for follow-up after day 7. Comparing these leg movements between days 1 and 7 indicated a decreased duration (-44%, p < 0.05). CONCLUSIONS: In neonates with SBA, leg movements caudal to the MMC concur with GMs, indicative of functional neural conduction through the MMC. The disappearance of these leg movements is caused by lower motor neuron dysfunction at the reflex arc, whereas neural conduction through the MMC is still functional.

Fetus↗
PubMed1984

A "convertible pore" model of neural membrane conductance.

Instead of the single-channel pore proposed earlier [Wooldridge, D. E. (1984) Proc. Natl. Acad. Sci. USA 81, 5609-5612] for the transit of conductance ions through the neural membrane, a pore with a second channel for "influence ions" of calcium or magnesium is considered in this paper. By entering trapping centers at the closed inner ends of the new channels, the influence ions are postulated to alter the rates of chemical reactions that change the configurational state of the gates guarding the inner ends of the nearby conductance channels. This makes the permeability of the conductance channels strongly dependent on voltage. Using a four-state reaction scheme for both the sodium and potassium pore systems, a computer model of the membrane conductance is constructed. When suitable values are assigned to its parameters, the model closely reproduces the results of the Hodgkin-Huxley voltage-clamp and action potential experiments.

Action Potentials↗