Sensory Nerve Action Potential Amplitude Research Articles

Somatosensory function in asymptomatic Parkin‐mutation carriers

It is a matter of debate whether somatosensory abnormalities in Parkinson's disease (PD) precede or follow PD motor signs and whether they are of central or peripheral origin. The sensory sural nerve action potential amplitude (SNAP) was previously reported to be reduced in symptomatic Parkin-associated PD. The aim of our study was to investigate asymptomatic Parkin-mutation carriers to elucidate whether putative somatosensory abnormalities precede motor symptoms therewith helping to determine the origin of somatosensory signs. Nine subjects with Parkin-mutations and nine healthy controls were examined clinically, with quantitative sensory testing (QST) and neurography. There was a higher frequency of cold pain threshold abnormalities and hypofunction of Abeta-fibres/central afferent pathways in Parkin-mutation carriers compared to controls. Neurography of Parkin-mutation carriers did not indicate peripheral neuropathy. Sensory abnormalities of asymptomatic Parkin-mutation carriers as obtained by QST suggest impairment of either small and large peripheral pathways or central somatosensory processing. In contrast to Parkin-associated PD, asymptomatic Parkin-mutation carriers do not show a reduced SNAP.

Measuring sensory nerve action potential electrical power

Sensory nerve action potential (SNAP) amplitudes are frequently examined for evidence of axonal loss. Because digital nerves have parallel fibers, and parallel voltages do not add, SNAP amplitude may not accurately reflect axonal loss. In contrast, electrical power can be measured for digital nerves, and is additive. In this study we explore the ability of SNAP electrical power (SELP) to discriminate the increased number of axons in fingers with two median digital nerves versus fingers with only one median digital nerve. Antidromic SNAP amplitudes and SELPs were obtained for 15 fingers. Seventeen external resistors, R(ext), were sequentially connected from electrode to ground for SELP determination. The resulting bell-shaped power vs. R(ext) plot was regressed to the power transfer equation, which has a peak that defines SELP. SELPs of two-digital-nerve (median) fingers were 360-670 femtowatts (mean 525 fW). For one-digital-nerve fingers, SELP was 90-230 fW (mean 190 fW). Evaluation of one- vs. two-median-digital-nerve statistics showed the SNAP amplitude difference-of-means to be insignificant, whereas the SELP difference-of-means was 3.3 SD (P < 0.01). Using a criterion of 2 SDs, SNAP amplitude did not discriminate any one-median-digital-nerve fingers, whereas SELP discriminated all with no false positives. Because parallel voltages do not add, SNAP amplitudes may not reflect axonal loss. In contrast, electrical power is additive. We describe the SELP technique and demonstrate its ability to discriminate different numbers of axons as reflected by one digital nerve vs. two digital nerves.

Effect of L-carnitine on diabetic neuropathy and ventricular dispersion in patients with diabetes mellitus

Diabetes is a common cause of polyneuropathy. Cardiac arrhythmias and markedly increased mortality rate have been demonstrated in patients with diabetic neuropathy and also demonstrated that abnormally prolonged QT dispersion interval (QTd) is associated with a higher risk of ventricular arrhythmias and sudden death. We investigated the efficacy and tolerability of L-carnitine (LC) in the treatment of diabetic neuropathy and ventricular dispersion, mainly by evaluating the effects of treatment on electrophysiological parameters. Materials and methods: We recruited 30 patients with type I or type II diabetes (mean age: 60 ± 9 years, range: 36-75; 18 males, 12 females) meeting clinical and neurophysiological criteria for diabetic neuropathy. All of the patients were given LC 2 g/day for 10 months. Blood glucose regulation was maintained by diet, oral antidiabetic, or insulin. To determine the nerve functions electrophysiologically, superficial electrode distal latency, amplitude, nerve conduction velocity in median and ulnar nerves in the upper extremities and peroneal, tibial and sural nerves in the lower extremities and F response in motor nerves were studied. Resting 12-lead electrocardiograms were recorded for measurements of QTd, corrected QTd (QTcd), JT dispersion (JTd), and corrected JT dispersion (JTcd). Results: After 10 months of treatment, median, ulnar, and tibial nerves' motor nerve conduction velocities (P < 0.05) and M-wave amplitudes (P < 0.05) increased; distal latencies and the F-wave latencies (P < 0.05) decreased; ulnar, sural, and median sensory nerve action potential amplitude (P < 0.01) and nerve conduction velocities (P < 0.05) increased; distal latencies (P < 0.05) decreased; and , QTd, QTcd, JTd, and JTcd (P < 0.05) decreased significantly when compared to basal values. The greatest changes in sensory nerve action potential amplitude and ventricular dispersion parameters were observed in the sensory sural nerve and QTcd, respectively. LC was well tolerated over the study period. Conclusion: LC, well tolerated by diabetic patients, may improve peripheral neuropathy and ventricular dispersion and may be useful in preventing the increased incidence of arrhythmias and sudden death observed in such patients. Larger clinical trials are needed to confirm these data before changes to clinical practice can be advocated.

Carpal Tunnel Syndrome in Manual Wheelchair Users with Spinal Cord Injury

To investigate relationships between carpal tunnel syndrome, functional status, subject demographics, physical examination findings, and median nerve conduction study findings in manual wheelchair users with paraplegia. Multicenter cross-sectional study. One hundred twenty-six manual wheelchair-using individuals with chronic paraplegia answered self-administered questionnaires on demographics, symptoms, and functional status. They underwent physical examination specific for carpal tunnel syndrome and upper-limb nerve conduction studies. Fifty-seven percent of subjects had symptoms (72.2% bilateral); hand numbness was most common. Sixty percent of subjects had carpal tunnel syndrome physical examination findings (59.2% bilateral). Those with physical examination findings were more likely to have longer duration of injury (P = 0.003). Seventy-eight percent of subjects had electrophysiologic evidence of median mononeuropathy. Symptomatic subjects had significantly greater median-ulnar motor latency difference in the dominant hand (P = 0.02) and smaller compound muscle action potential amplitudes bilaterally (dominant hand, P = 0.01; nondominant hand, P = 0.04). Persons with carpal tunnel syndrome symptoms and physical examination findings had significantly worse functional status (symptoms, P < 0.001; physical examination, P = 0.02) and symptom severity scores (symptoms, P < 0.001; physical examination, P = 0.01), but a similar difference between subjects with and without median mononeuropathy was not seen. Logistic regression analysis revealed that the presence of symptoms was predicted by median-ulnar motor latency difference in the dominant hand (odds ratio, 4.38; 95% confidence interval 1.72-11.14) and sensory nerve action potential amplitude in the nondominant hand (odds ratio, 0.97; 95% confidence interval, 0.94-0.99). The interaction among symptoms, physical examination, and nerve conduction study findings is complex. Carpal tunnel syndrome and median mononeuropathy are highly prevalent and functionally significant. This study highlights the need for primary prevention and patient education for preserving upper-limb function.

Effect of Hand Warming on Electrodiagnostic Testing Results and Diagnosis in Patients With Suspected Carpal Tunnel Syndrome

Burnham RS, Burnham TR. Effect of hand warming on electrodiagnostic testing results and diagnosis in patients with suspected carpal tunnel syndrome. Objectives To evaluate the effects of hand warming on electrodiagnostic (EDX) parameters of carpal tunnel syndrome (CTS). Specifically, to evaluate the type and magnitude of change in EDX values; to determine whether warming can change the EDX diagnosis of CTS and, if so, to determine whether specific EDX tests are more vulnerable to the effects of warming. Design Interventional before-after trial. Setting Community EDX laboratory. Participants Consecutive patients (N=33) referred for EDX evaluation of suspected CTS. Intervention Each upper limb was tested at room temperature (average hand temperature, 31.9°C) and retested after 20 minutes of heating pad warming (average hand temperature, 33.5°C). Main Outcome Measures Median and ulnar nerve motor and sensory latency, conduction velocity, and amplitude. Results Warming resulted in significantly faster transcarpal tunnel sensory and motor conduction (6%–10%), reduced median: ulnar sensory latency to digit 4 difference (23%), and reduced sensory nerve and compound motor action potential amplitude (10% and 13%, respectively). The changes resulted in 15% fewer limbs meeting the EDX conduction velocity criteria of CTS and 9% fewer by median: ulnar sensory latency to digit 4 difference. Waveform amplitudes became abnormally low after warming in 12% of limbs. Conclusions Hand warming using a heating pad for 20 minutes increases median nerve transcarpal tunnel conduction velocity and reduces amplitude. These phenomena introduce potential sources of diagnostic error, particularly in borderline cases. Generally, within hand, between nerve, and within nerve comparison techniques are less susceptible to the conduction velocity effects of warming.

Neuropathic pain is associated with increased nodal persistent Na+ currents in human diabetic neuropathy

Peripheral nerve injury alters function and expression of voltage gated Na(+) channels on the axolemma, leading to ectopic firing and neuropathic pain/paresthesia. Hyperglycemia also affects nodal Na(+) currents, presumably due to activation of polyol pathway and impaired Na(+)-K(+) pump. We investigated changes in nodal Na(+) currents in peripheral sensory axons and their relation with pain in human diabetic neuropathy. Latent addition using computerized threshold tracking was used to estimate nodal persistent Na(+) currents in radial sensory axons of 81 diabetic patients. Of these, 36 (44%) had chronic neuropathic pain and severe paresthesia. Compared to patients without pain, those with pain had greater nodal Na(+) currents (p = 0.001), smaller amplitudes of sensory nerve action potentials (SNAP) (p = 0.0003), and lower hemoglobin A1c levels (p = 0.006). Higher axonal Na(+) conductance was associated with smaller SNAP amplitudes (p = 0.03) and lower hemoglobin A1c levels (p = 0.008). These results suggest that development of neuropathic pain depends on axonal hyperexcitability due to increased nodal Na(+) currents associated with structural changes, but the currents could also be affected by the state of glycemic control. Our findings support the view that altered Na(+) channels could be responsible for neuropathic pain/paresthesia in diabetic neuropathy.

Prospective study of peripheral neuropathy in Machado–Joseph disease

Peripheral neuropathy (PN) has long been recognized in Machado-Joseph disease (MJD), but its natural history is an unsettled issue. Therefore, we prospectively assessed 40 with MJD for 13 months with nerve conduction (NC) studies and the revised total neuropathy score (TNSr) to study the progression of PN. There was no significant change in the TNSr score over the follow-up period. In contrast, the average sural sensory nerve action potential (SNAP) amplitude decreased significantly over the same interval from a mean of 13.2 muV to 9.8 muV (P < 0.001). There was an inverse correlation between the change in the sural SNAP amplitude and the length of the CAG triplet repeat expansion (r = 0.574, P < 0.001). The reduction in the mean sural SNAP amplitude also correlated with progression of ataxia. This indicates that PN progresses faster in individuals with larger (CAG)(n) expansions, and nerve conduction studies may be useful to study disease progression in MJD.

The consequences of stimulus intensity on sensory nerve action potentials

Although clinical references recommend evoking sensory nerve action potentials (SNAPs) using supramaximal stimulation, many patients and research subjects report that the maximal and supramaximal stimulation is uncomfortable. The purpose of this study was to determine whether using stimulation intensities at maximal and submaximal levels results in differences in SNAP latency or amplitude outcomes relative to SNAPs recorded using supramaximal stimulation. Twenty healthy male and female subjects participated. Antidromic SNAPs were evoked at two separate sites along the course of the median nerve: (1) just proximal to the wrist and (2) just proximal to the antecubital fossa in each subject. All evoked potentials were recorded from the second digit. The stimulation current that resulted in a maximal amplitude SNAP was determined and 10 SNAPs were ensemble averaged using this stimulation level. Ten SNAPs were then evoked at each of four other stimulation intensities (20% and 10% both above and below that which generated a maximal amplitude SNAP) and were ensemble averaged. For each stimulation intensity and stimulation site, SNAP amplitude and latency determined for each ensemble average. SNAP amplitudes and latencies were compared among stimulus levels and between sexes using a repeated measures analyses of variance. The results of this study suggest that stimulus intensities used to generate SNAPs at the median nerve do not need to be supramaximal in order to generate valid and reliable SNAP data, with stimulation intensities as low as 20% below maximal proving to be sufficient, particularly for the measurement of SNAP latency.

Functional and structural nerve fiber findings in heterozygote patients with Fabry disease

Fabry disease is an X-linked inherited lysosomal disorder with dysfunction of the lysosomal enzyme α-galactosidase A causing accumulation of glycolipids in multiple organs including the nervous system. Pain and somatosensory disturbances are prominent manifestations of this disease. Until recently disease manifestations in female carriers of Fabry disease have been questioned. To explore the frequency of symptoms and the functional and structural involvement of the nervous system in female patients we examined the presence of pain, manifestations of peripheral neuropathy and nerve density in skin biopsies in 19 female patients with Fabry disease and 19 sex- and age-matched controls. Diaries, quantitative sensory testing, neurophysiologic tests and skin biopsies were performed. Daily pain was present in 63% of patients, with a median VAS score of 4.0. Tactile detection threshold and pressure pain threshold were lower and cold detection thresholds increased in patients. Sensory nerve action potential amplitude and maximal sensory conduction velocity were not different, whereas there was a highly significant reduction in intraepidermal nerve fiber density. We found no correlation between pain VAS score, quantitative sensory testing and intraepidermal nerve fiber density. Our study demonstrates that careful evaluation of symptoms in female Fabry patients is important as small fiber disease manifestations are present, which in some cases is only detected by skin biopsy.

An animal study of peripheral neurophysiologic mechanism in osseoperception phenomena of dental implant

To investigate the existence of functional neuroreceptors in peri-implant bone tissue and to test the peri-implant neural feedback pathway reconstruction and its influential factors. Three beagle dogs were involved in this study. After the extraction of 3 premolars and 1 molar of the bilateral mandible, 27 implants were placed immediately or delayed. The implants were loaded for 3 - 6 months, then sensory nerve action potential (SNAP) tests were performed. The stimulating electrode was connected to the implant or natural tooth. The recording electrode was fixed near the inferior alveolar nerve (IAN) to record the latency period and amplitude of SNAP. The specimens with peri-implant bone tissues were taken and examined by immunohistochemistry. SNAP of IAN could be recorded following stimulations to natural teeth and implants. The differences in SNAP amplitudes between natural teeth [(44.04 +/- 6.23) microV] and all implant groups were statistically significant (P < 0.01). Free nerve endings and nerve tract were found in the peri-implant bone tissue, but much less than those in periodontal membrane. Some nerve fibers were directly connected with implant surface. Functional neuroreceptors, though much less than that of natural tooth, exist in peri-implant bone tissue. Surgical methods and loading time do not have obvious influences on peri-implant neural feedback pathway reconstruction.

Do patients having a decrease in SNAP amplitude during the course of MMN present with a different condition?

A decrease in sensory nerve action potentials (SNAP) amplitude has been recently reported in some patients during the course of multifocal motor neuropathy with conduction blocks (MMNCB). It is not known if those patients have different clinical expression and disability when compared with typical MMNCB. Clinical, biological and electrophysiological assessments were performed in 15 patients fitting the diagnosis criteria of MMNCB, including normal SNAP amplitude at initial examination. Patients presenting with nerve entrapment or associated disease causative of sensory neuropathy were excluded. Median time of follow-up was 3 years (1-17 years). At the last examination, four patients had at least one SNAP amplitude below 50% of normal value. None had clinically objective sensory loss. Clinical and electrophysiological data obtained at the last examination were compared between patients with normal SNAP amplitude and patients with decreased SNAP amplitude. No difference between both population in term of age, sex, disease duration, anti-GM1 antibody titers, CSF data and number of conduction blocks was noted. In contrast, patients with decreased SNAP amplitude had worse overall neuropathy limitation scale (ONLS) scores (7 vs. 2; p = 0.02), a higher number of affected nerves (12.5 vs. 4; p = 0.018), a higher number of affected limb regions (6 vs. 2; p = 0.019) and lower median CMAP amplitude (2 mV vs. 6.5 mV; p = 0.04). They were all dependent on higher doses of IVIg (1.4 g/(kg 4 weeks vs. 0.6; p = 0.018). A reduction in SNAP amplitude during the course of MMNCB is associated with a more severe disease and a more prominent axonal loss. This result needs to be confirmed in a larger cohort.

The effects of age, gender, and body mass index on amplitude of sensory nerve action potentials: Multivariate analyses

Previous studies have shown that age, gender, and body mass index (BMI) affect amplitude of sensory nerve action potentials (SNAP), but the total effects of multiple factors or the most prominently affected nerves have not been elucidated. This study systematically investigated effects of these factors. Amplitude of SNAP of the median, ulnar, superficial radial, superficial peroneal, and sural nerves was measured in 105 healthy subjects. The effects of age, gender, and BMI on each nerve were estimated by multivariate linear regression analysis. SNAP amplitude decreased with age in all five nerves. Women had greater SNAP amplitude than men in the upper limb nerves (median, ulnar, and radial), but not in the lower limb nerves (peroneal and sural). Similarly, greater BMI was associated with smaller amplitudes in the upper limb nerves, but not in the lower limb nerves. Multivariate analyses showed the three factors explained 50% of the variation in the median nerve, 46% in the ulnar nerve, and 22-32% in the remaining nerves. The effects of age, gender, and BMI on SNAP amplitudes are not identical in different sensory nerves. Age was strongly correlated with SNAP amplitude in the nerves tested, whereas gender and BMI affect amplitudes only in the upper limb nerves. Age, gender, and BMI should be taken into account in clinical practice, but the extent of influence depends on the sensory nerves examined.

Glial fibrillary acidic protein as a marker of axonal damage in chronic neuropathies

We evaluated serum glial fibrillary acidic protein (GFAP) levels by enzyme-linked immunosorbent assay (ELISA) in controls (n = 30) and in patients with chronic sensory-motor axonal neuropathy (CSMAN) (n = 30), chronic inflammatory demyelinating polyneuropathy (CIDP) (n = 30), multifocal motor neuropathy (MMN) (n = 30), and primary muscular spinal atrophy (PMSA) (n = 15). GFAP levels, expressed as optical density, were increased in CSMAN (median = 1.05) compared to controls (median = 0.41; P < 0.05) and CIDP (median = 0.53, P < 0.05). They were also increased in PMSA (median = 0.99) compared to controls (P < 0.05) and MMN (median = 0.66; P < 0.05). To differentiate CSMAN from CIDP and PMSA from MMN, we applied a cutoff of GFAP levels at 0.66, and we obtained good sensitivity and specificity. In neuropathies, serum GFAP correlated with summated sensory nerve action potential amplitudes (r = -0.57; P = 0.0006) and disease severity (r = 0.37; P = 0.0011). Thus, we propose serum GFAP as a marker of axonal damage and severity in chronic neuropathies.

Perineural meperidine blocks nerve conduction in a dose‐related manner: a randomized double‐blind study

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. 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. 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. Meperidine blocks sensory and motor nerve conduction in a dose-related manner.

Experimental study on combined effect of low temperature and vibration on peripheral circulation function and peripheral nerve function

To study the combined effect of low temperature and vibration on function of peripheral circulation and nerve. 64 rabbits were divided into control group, low temperature group, vibration group and combined effect group randomly, 16 each group. The changes of concentration of ET, Ang II, NO in plasma and SCV, amplitude of sensory nerve action potential, latency of sensory nerve action potential, MCV, distal amplitude of motor nerve, and distal latency of motor nerve were measured before and after experiment. After experiment, the concentration of ET, Ang II, NO and SCV, amplitude of sensory nerve action potential, latency of sensory nerve action potential, MCV, distal amplitude of motor nerve, and distal latency of motor nerve were (68.84+/-14.81) pg/ml, (544.01+/-70.20) pg/ml, (123.73+/-9.58) nmol/ml, (25.36+/-6.96) m/s, (1.84+/-0.65) microV, (4.05+/-1.04) m/s, (27.40+/-6.05) m/s, (1.60+/-0.52) microV, (3.51+/-1.30) m/s respectively in low temperature group; (70.22+/-15.02) pg/ml, (540.77+/-68.25) pg/ml, (129.46+/-11.99) nmol/ml, (27.69+/-6.16) m/s, (2.19+/-0.53) microV, (3.86+/-0.89) m/s, (30.03+/-5.21) m/s, (1.65+/-0.49) microV, (3.36+/-l.11) m/s respectively in vibration group; (88.47+/-13.20) pg/ml, (687.38+/-101.44) pg/ml, (70.66+/-4.99) nmol/ml, (20.82+/-3.65) m/s, (1.21+/-0.64) microV, (5.05+/-0.94) m/s, (19.97+/-4.37) m/s, (1.09+/-0.49) microV, (4.49+/-1.26) m/s respectively in combined effect group; compared with pre-experiment, the concentration of ET and Ang II in low temperature group, vibration group and combined effect group were increased after experiment, and the NO was decreased (P<0.05); the nerve conduct velocity and amplitude was decreased and the latency was delayed (P<0.05). After experiment, the concentrations of ET and Ang II in combined effect group were higher than low temperature group and vibration group, and the concentration of NO in combined effect group was lower than low temperature group and vibration group (P<0.05). After experiment, the SCV and MCV in combined effect group were slower than low temperature group and vibration group; the amplitude of sensory nerve action potential and distal amplitude of motor nerve were less than low temperature group and vibration group; the latency of sensory nerve action potential and distal latency of motor nerve in combined effect group was longer than low temperature group and vibration group. The factorial analysis results indicated the synergistic effect between low temperature and vibration (P<0.05). Vibration-induced peripheral vascular impairment and nerve impairment would be intensified by low temperature.

Ultrasound-guided needle positioning in sensory nerve conduction study of the sural nerve

To evaluate the usefulness of ultrasound imaging to improve the positioning of the recording needle for nerve conduction studies (NCS) of the sural nerve. Orthodromic NCS of the sural nerve was performed in 44 consecutive patients evaluated for polyneuropathy. Ultrasound-guided needle positioning (USNP) was compared to conventional "blind" needle positioning (BNP), electrically guided needle positioning (EGNP), and to recordings with surface electrodes (SFN). The mean distance between the needle tip and the nerve was 1.1 mm with USNP compared to 5.1 mm with BNP (p<0.0001). The mean amplitude of the sensory nerve action potential (SNAP) was 21 microV with USNP and 11 microV with BNP (p<0.0001). Compared to BNP, nerve-needle distances and SNAP amplitudes did not improve with EGNP. SNAP amplitudes recorded with SFN were significantly smaller than with BNP, EGNP and USNP. Ultrasound increases the precision of needle positioning markedly, compared to conventional methods. The amplitude of the recorded SNAP is usually clearly greater using USNP. In addition, USNP is faster, less painful and less dependent on the patient. USNP is superior to BNP, EGNP, and SFN in accurate measurement of SNAP amplitude. It has a potential use in the routine near-nerve needle sensory NCS of pure sensory nerves.

Carpal tunnel syndrome: long-term nerve conduction studies in 261 hands

To compare a long-term carpal tunnel syndrome (CTS) on nerve conduction studies (NCS) in hands treated non-surgically. We retrospectively selected 261 symptomatic CTS hands (166 patients), all of them confirmed by NCS. In all cases, at least 2 NCS were performed in an interval greater than 12 months. Cases with associated polyneuropathy were excluded. NCS parameters for CTS electrodiagnosis included a sensory conduction velocity (SCV) < or =46.6 m/s (wrist to index finger, 14 cm) and distal motor latency (DML) > or =4.25 ms (wrist to APB, 8 cm). 92.8% were women; mean age was 49 years (20-76); the mean interval between NCS was 47 months (12-150). In the first exam, the median sensory nerve action potential (SNAP) and the compound action muscular potential were absent in 9.8% and 1.9%, respectively. In the second/last exam, SCV worsened in 54.2%, remained unchanged in 11.6% and improved in 34.2%. SNAP amplitude worsened in 57.7%, remained unchanged in 13.1% and improved in 29.2%. DML worsened in 52.9%, remained unchanged in 7.6% and improved in 39.5%. Overall, NCS parameters worsened in 54.9%, improved in 34.3% and remained unchanged in 10.8%. Long-term changing in NCS of CTS hands apparently were not related to clinical symptomatology and could lead to some difficulty in clinical correlation and prognosis. Aging, male gender and absent SNAP were more related to NCS worsening, regardless the mean interval time between the NCS.

5. Sural and radial sensory responses in patients with sensory polyneuropathy

Introduction: The sural/radial nerve amplitude ratio (SRAR) is the quotient of the Sensory Nerve Action Potential (SNAP) amplitudes (Amp) of the sural and the superficial radial nerve. It has been hypothesized that this ratio can be used for the detection of early axonal loss; because the sural SNAP amplitude will decrease first, thereby also decreasing the SRAR value. Objectives: To determine the sensitivity and specificity of SRAR, age-adjusted sural and radial SNAP Amp in the diagnosis of axonal sensory polyneuropathy in cancer patients. Design: Retrospective review. Setting: Comprehensive cancer center.

The effect of benfothiamine in the therapy of diabetic polyneuropathy

Diabetic polyneuropathy (DPN) is one of the most common diabetic complications, which can result in a significant functional impairment and reduction of the quality of life in affected individuals. It occurs due to alterations in different biochemical mechanisms which require the presence of thiamine, which is why this vitamin is used in the therapy of DPN. Due to the low bioavailability of the hydrosolubile forms of thiamine, its liposolubile preparations (benfotiamine) are preferentially used. The aim of this study was to determine the efficacy of benfotiamine in combination with vitamin B6 in the therapy of DPN. The study group comprised of 22 patients with DPN who were treated with the combination of benfotiamine and vitamin B6 during 45 days. The effect of the therapy was evaluated by the analysis of different clinical, laboratory and electrophysiological parameters before and after conducted treatment. After the treatment period, a statistically highly significant reduction of pain (p < 0.01) was noted with the reduction of pain score on visual analogue scale in 86.4% of patients. A significant reduction of subjective complaints was also noted, with decreased modified total symptom score in 95.5% of patients (p < 0.01). The presence of alodynia was reported at the beginning of the study in 77.3%, and after the benfotiamine therapy only in 22.7% of patients, while hyperpathy was initially present in 90.9%, and after treatment in 31.8% of patients (p < 0.01). Neurophysiological parameters of polyneuropathy also significantly improved, with the improvement of the compound muscle action potential amplitude in 68.2% ( p < 0.01) and motor conduction velocity of the peroneal nerve in 45.5% of patients (p < 0.01). The improvement of the sensory nerve action potential amplitude (p < 0.01) and sensory conduction velocity (p = 0.05) of the sural nerve was found in 45.5% of patients. After the treatment period, there was a highly statistically significant lowering of the glycosylated haemoglobin (p < 0.01), with improved findings in 63.6% of patients. After completed study treatment protocol 86.4% of patients rated their overall condition as improved. Our results showed that the conducted treatment resulted in significant subjective and objective improvement of the disease signs symptoms, which confirmed that benfotiamine was good starting choice for the treatment of diabetic polyneuropathy.

Repeatability of nerve conduction measurements derived entirely by computer methods

BackgroundNerve conduction studies are an objective, quantitative, and reproducible measure of peripheral nerve function and are widely used in the diagnosis of neuropathies. The purpose of this study is to determine the reliability of nerve conduction parameters derived entirely from computer based data acquisition and waveform cursor assignments and to quantify the relative contributions of test variability sources.MethodsThirty volunteers, some with symptoms suggestive of neuropathies; of these, 29 completed the study. The median, ulnar, deep peroneal, posterior tibial, and sural nerves were evaluated bilaterally at two test sessions 3-7 days apart. Within each session, nerves were tested twice within 10 minutes. The analyzed nerve conduction parameters include motor latencies, motor conduction velocity (CV), compound muscle action potential (CMAP) amplitude, F-wave latencies (minimum, mean and maximum), sensory peak latency (DSL), sensory CV, and sensory nerve action potential (SNAP) amplitude. The primary outcome measure is variance component analysis and the corresponding coefficient of variation (CoV). The between-session-test variance is the sum of within-session variance and between-session variance, quantifying the total variation between test sessions. Additional statistical measures include the intraclass correlation coefficient (ICC) and relative interval variation (RIV).ResultsMotor and sensory latencies, CV and F-wave latency parameters have low between-session-test CoVs, ranging from 4.2% to 9.8%. Amplitude parameters have a higher between-session-test CoVs in the range of 15.6--19.8%. Between-test CoVs are about 30--80% lower than between-session CoVs with the exception of F-wave latency parameters. Between-test ICC values are 0.96 or above for all parameters. Between-session ICC ranges from 0.98 for F-wave latency to 0.77 for sural sensory CV. All latency-related between-session ICCs have a value 0.83 or above. The RIVs are the tightest for F-wave latency parameters and widest for CMAP amplitude parameters. Repeatability in a sub-group of subjects with more severe symptom grades follows the same trend as the overall study population without substantial quantitative differences.ConclusionThe study demonstrates the high repeatability of nerve conduction parameters acquired by modern electrodiagnostic instruments using computer based waveform cursor assignment. The reliability is comparable to benchmark studies in which the nerve conduction measurements were performed manually in controlled multi-center clinical trials. Furthermore, the ranking of reliability, whereby F-wave latencies have the best reproducibility and amplitudes the worst, is also consistent with the benchmark studies.