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Nerve Action Potential (nerve + action_potential)
Kinds of Nerve Action Potential Selected AbstractsElectrophysiological sensory demyelination in typical chronic inflammatory demyelinating polyneuropathyEUROPEAN JOURNAL OF NEUROLOGY, Issue 7 2010Y. A. Rajabally Background:, The presence of electrophysiological demyelination of sensory nerves is not routinely assessed in the evaluation of suspected chronic inflammatory demyelinating polyneuropathy (CIDP). Whether this can be useful is unknown. Methods:, We compared, using surface recording techniques, in 19 patients with typical CIDP and 26 controls with distal large fibre sensory axonal neuropathy, the forearm median sensory conductions, sensory nerve action potential (SNAP) amplitudes and durations and sensory nerve conduction velocities (SNCVs) of median, radial and sural nerves. Results:, Median nerve sensory conduction block (SCB) across the forearm was greater in CIDP patients than in controls (P = 0.005). SNAP durations were longer in CIDP patients for median (P = 0.001) and sural nerves (P = 0.004). Receiver operating characteristic (ROC) curves provided sensitive (>40%) and specific (>95%) cut-offs for median nerve SCB as well as median and sural SNAP durations. SNCVs were significantly slower for median and sural nerves in CIDP patients, but ROC curves did not demonstrate cut-offs with useful sensitivities/specificities. Median SCB or prolonged median SNAP duration or prolonged sural SNAP duration offered a sensitivity of 73.7% for CIDP and specificity of 96.2%. Used as additional parameters, they improved diagnostic sensitivity of the American Academy of Neurology (AAN) criteria for CIDP of 1991, from 42.1% to 78.9% in this population, with preserved specificity of 100%. Discussion:, Sensory electrophysiological demyelination is present and may be diagnostically useful in typical CIDP. SCB detection and SNAP duration prolongation appear to represent more useful markers of demyelination than SNCV reduction. [source] Perineural meperidine blocks nerve conduction in a dose-related manner: a randomized double-blind studyACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 6 2009E. ÖZTÜRK Background: Meperidine has been shown to exhibit a sensory block in peripheral nerves. However, its motor blockade ability is controversial. The aim of this study was to investigate, electroneurographically, the ability of meperidine to inhibit conduction in both sensory and motor fibres in the ulnar nerve. Materials and methods: The study was conducted in a double-blind, placebo-controlled fashion. Eighteen healthy volunteers were randomized into three groups (Saline, meperidine 1% and meperidine 2%). Three millilitre of the study solution was administered to the ulnar nerve perineurally at the level of the wrist by the guidance of a nerve stimulator. Sensory nerve action potential (SNAP) and compound motor action potential (CMAP) amplitudes were recorded. At least a 20% decrease in the initial response amplitude was accepted as a block. Results: The number of individuals with sensory and motor block with saline, meperidine 1% and meperidine 2% were 0/6, 6/6, 6/6 and 0/6, 5/6, 6/6, respectively (P<0.05). The maximum decrease in the median SNAP and CMAP amplitude values were 4.7% and 8.3% with saline; 38.5% and 46.4% with meperidine 1%; and 100% and 97.8% with meperidine 2%, respectively (P<0.05). Median values for the duration of sensory and motor block with meperidine 1% and meperidine 2% were 45, 52.5 and 30, 32.5 min, respectively. Conclusion: Meperidine blocks sensory and motor nerve conduction in a dose-related manner. [source] Electrophysiological findings of peripheral neuropathy in newly diagnosed type II diabetes mellitusJOURNAL OF THE PERIPHERAL NERVOUS SYSTEM, Issue 4 2005Eugenia Rota Abstract This study was aimed at assessing the electrophysiological signs of peripheral neuropathy in diabetes mellitus (DM) type II patients at diagnosis. Nerve conduction studies (NCS) of median, ulnar, peroneal, tibial and sural nerves were performed in 39 newly diagnosed DM subjects and compared to those of 40 healthy controls. Metabolic indices were also investigated. Electrophysiological alterations were found in 32 (82%) of the DM patients, and more than half of them (62.2%) showed multiple (two to five) abnormal parameters. Because most of the subjects (84.4%) had from two to five nerves involved, these alterations were widespread in the seven nerves evaluated. Forty-two percent of the patients had NCS alterations suggestive of distal median mononeuropathy, implying that metabolic factors in DM make the median nerve more susceptible to focal entrapment. A reduced sensory nerve action potential (SNAP) amplitude was observed in the median nerve in 70% of the patients, in the ulnar in 69% and in the sural nerve only in 22%. In the presence of a decrease in the SNAP amplitude of the ulnar or median nerve, the SNAP amplitude of the sural nerve was normal in 82 or 80% of the subjects, respectively. This finding may be in keeping with a distal involvement of the sensory fibres, as explored by routine median or ulnar NCS. No correlation was found between metabolic indices and NCS parameters. In conclusion, a high percentage of newly diagnosed DM patients show signs of neuropathy, and upper limb nerve sensory NCS seem to be more sensitive in detecting it than lower limb NCS. [source] Effect of size and pressure of surface recording electrodes on amplitude of sensory nerve action potentialsMUSCLE AND NERVE, Issue 2 2004Antoon A. Ven MSc Abstract The influence of electrode size on sensory nerve action potential (SNAP) amplitude of the lateral antebrachial cutaneous nerve (LACN) and sural nerve (SN) was studied in 63 healthy volunteers. The SNAP amplitudes were measured using surface recording electrodes of three different sizes, positioned across the nerve. Mean amplitudes using a 5-mm electrode were 9.0% (SN) and 15.3% (LACN) higher than with a 20-mm electrode and 19.4% (SN) and 25.8% (LACN) higher than using a 40-mm electrode. To study the influence of pressure on surface recording electrodes, studies were performed on the LACN in 31 healthy volunteers. Light pressure of the recording electrodes on the skin gave lower amplitudes (15.3%) than did greater pressure or pressure applied between active and reference electrodes. These studies demonstrate that standardized surface recording electrode size and pressure are imperative for obtaining valid and reliable results in experimental studies or in clinical follow-up of patients undergoing nerve conduction studies. Muscle Nerve 30: 234,238, 2004 [source] Clinical utility of dorsal sural nerve conduction studiesMUSCLE AND NERVE, Issue 6 2001James M. Killian MD Abstract A technique of testing sensory nerve conduction of the dorsal sural nerve in the foot was used in 38 normal subjects and 70 patients with peripheral neuropathies. The normal dorsal sural sensory nerve action potential (SNAP) had a mean amplitude of 8.9 ,V (range 5,15 ,V), mean latency to negative peak of 4.0 ms (range 3.2,4.7 ms), and mean conduction velocity of 34.8 m/s (range 30,44 m/s). Optimal placement of the recording electrodes to obtain a maximal nerve action potential was proximal to digits 4 and 5. Cooling to below 25°C prolonged the latency but did not decrease the SNAP amplitude. Among the patients with peripheral neuropathy, dorsal sural SNAP was absent in 68 (97%), whereas only 54 (77%) showed abnormalities of sural sensory conduction. The diagnostic sensitivity of sensory nerve conduction studies in peripheral neuropathies may be significantly improved by the use of this technique for evaluating the action potential of the dorsal sural nerve. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 817,820, 2001 [source] Diabetes mellitus exacerbates motor and sensory impairment in CMT1AJOURNAL OF THE PERIPHERAL NERVOUS SYSTEM, Issue 4 2008Soham Sheth Abstract Charcot-Marie-Tooth disease type 1A (CMT1A) is caused by a duplication of PMP22 on chromosome 17 and is the most commonly inherited demyelinating neuropathy. Diabetes frequently causes predominantly sensory neuropathy. Whether diabetes exacerbates CMT1A is unknown. We identified 10 patients with CMT1A and diabetes and compared their impairment with 48 age-matched control patients with CMT1A alone. Comparisons were made with the Charcot-Marie-Tooth disease (CMT) neuropathy score (CMTNS) and by electrophysiology. The CMTNS was significantly higher in patients with diabetes (20.25 ± 2.35) compared with controls (15.19 ± 0.69; p = 0.01). Values were particularly higher for motor signs and symptoms. Seven of the 10 diabetic patients had CMTNS >20 (severe CMT), while only 7 of the 48 age-matched controls had scores >20. There was a trend for CMT1A patients with diabetes to have low compound muscle action potentials and sensory nerve action potentials, although nerve conduction velocities were not slower in diabetic patients compared with controls. Diabetes was associated with more severe motor and sensory impairment in patients with CMT1A. [source] Effect of size and pressure of surface recording electrodes on amplitude of sensory nerve action potentialsMUSCLE AND NERVE, Issue 2 2004Antoon A. Ven MSc Abstract The influence of electrode size on sensory nerve action potential (SNAP) amplitude of the lateral antebrachial cutaneous nerve (LACN) and sural nerve (SN) was studied in 63 healthy volunteers. The SNAP amplitudes were measured using surface recording electrodes of three different sizes, positioned across the nerve. Mean amplitudes using a 5-mm electrode were 9.0% (SN) and 15.3% (LACN) higher than with a 20-mm electrode and 19.4% (SN) and 25.8% (LACN) higher than using a 40-mm electrode. To study the influence of pressure on surface recording electrodes, studies were performed on the LACN in 31 healthy volunteers. Light pressure of the recording electrodes on the skin gave lower amplitudes (15.3%) than did greater pressure or pressure applied between active and reference electrodes. These studies demonstrate that standardized surface recording electrode size and pressure are imperative for obtaining valid and reliable results in experimental studies or in clinical follow-up of patients undergoing nerve conduction studies. Muscle Nerve 30: 234,238, 2004 [source] Increased Nerve Fiber Expression of Sensory Sodium Channels Nav1.7, Nav1.8, and Nav1.9 in Rhinitis,,THE LARYNGOSCOPE, Issue 4 2008Siew M. Keh MRCS Abstract Introduction: Voltage-gated sodium channels Nav1.7, Nav1.8, and Nav1.9 are involved in nerve action potentials and have been proposed to underlie neuronal hypersensitivity. We have therefore studied their levels in allergic and nonallergic rhinitis. Materials and Methods: Inferior turbinate biopsies from 50 patients (n = 18 controls, n = 20 allergic, and n = 12 nonallergic rhinitis) were studied by immunohistology using antibodies to Nav1.7, Nav1.8, and Nav1.9, the structural nerve marker (protein gene product [PGP]9.5), nerve growth factor (NGF), mast cells (c-kit), macrophages (CD68), and T cells (CD3). Sodium channel-positive nerve fibers were counted per millimeter length of subepithelium, and immunoreactivity for inflammatory cell markers PGP9.5 and NGF were image analyzed. Results: All three sodium channel-immunoreactive nerve fiber numbers were significantly increased in allergic (Nav1.7, P = .0004; Nav1.8, P = .028; Nav1.9, P = .02) and nonallergic (Nav1.7, P = .006; Nav1.8, P = .019; Nav1.9, P = .0037) rhinitis. There was a significant increase of subepithelial innervation (PGP9.5, P = .01) and epithelial NGF immunoreactivity (P = .03) in nonallergic rhinitis, comparable with our previous report in allergic rhinitis. Inflammatory cell markers were significantly increased in allergic (mast cells, P = .06; macrophages, P = .044; T cells, P = .007) but not nonallergic rhinitis. Conclusion: The increased levels of sensory sodium channels in allergic and nonallergic rhinitis may contribute to the hypersensitive state, irrespective of the degree of active inflammation. Selective blockers of these sodium channels, administered topically, may have therapeutic potential in rhinitis. [source] Mild carbon monoxide exposure and auditory function in the developing ratJOURNAL OF NEUROSCIENCE RESEARCH, Issue 5 2003Janet E. Stockard-Sullivan Abstract We have examined the influence of chronic mild exposure to carbon monoxide (CO) on cognitive (learning) and auditory function in the developing rat. We have demonstrated that the auditory pathway is compromised at exposures less than 50 ppm, whereas learning was not influenced at 100 ppm. Artificially reared rat pups were exposed to CO during the brain growth spurt and onset of myelination. Spatial learning was assessed using the Morris Water Maze and three tests of auditory function: (1) auditory brainstem conduction times; (2) the amplitude of the eighth nerve's action potential; and (3) otoacoustic emissions carried out on rat pups (age 22, 24 days). The pups were gastrostomy-reared on a rat milk substitute and chronically exposed to CO at discrete concentrations in the range of 12,100 ppm from 6 days of age to post-weaning at 21,23 days of age. We found no difference in auditory brainstem conduction times at all CO concentrations in comparison to non-exposed controls. There was a difference in otoacoustic emissions for test and controls at CO concentrations of 50 ppm but not at lower concentrations. There was a consistent attenuation of the amplitude of the eighth nerve's action potential, even at the lowest CO exposure examined. The attenuation of the amplitude of the action potential of the eighth nerve at 50 ppm carbon monoxide exposure did not completely recover by 73 days of age. We conclude that prolonged mild exposure to carbon monoxide during development causes measurable functional changes at the level of the eighth cranial nerve. © 2003 Wiley-Liss, Inc. [source] | ||||||||||