Investigating the effects of dopamine on short- and long-latency afferent inhibition

Short- and long-latency afferent inhibition (SAI and LAI respectively) are phenomenon whereby the motor evoked potential induced by transcranial magnetic stimulation (TMS) is inhibited by a sensory afferent volley consequent to nerve stimulation. It remains unclear whether dopamine participates in the genesis or modulation of SAI and LAI. The present study aimed to determine if SAI and LAI are modulated by levodopa (l-DOPA). In this placebo-controlled, double-anonymized study Apo-Levocarb (100 mg l-DOPA in combination with 25 mg carbidopa) and a placebo were administered to 32 adult males (mean age 24 ± 3 years) in two separate sessions. SAI and LAI were evoked by stimulating the median nerve and delivering single-pulse TMS over the motor hotspot corresponding to the first dorsal interosseous muscle of the right hand. SAI and LAI were quantified before and 1 h following ingestion of drug or placebo corresponding to the peak plasma concentration of Apo-Levocarb. The results indicate that Apo-Levocarb increases SAI and does not significantly alter LAI. These findings support literature demonstrating increased SAI following exogenous dopamine administration in neurodegenerative disorders. KEY POINTS: Short- and long-latency afferent inhibition (SAI and LAI respectively) are measures of corticospinal excitability evoked using transcranial magnetic stimulation. SAI and LAI are reduced in conditions such as Parkinson's disease which suggests dopamine may be involved in the mechanism of afferent inhibition. 125 mg of Apo-Levocarb (100 mg dopamine) increases SAI but not LAI. This study increases our understanding of the pharmacological mechanism of SAI and LAI.

Cortical somatosensory processing after botulinum toxin therapy in post-stroke spasticity

In dystonic and spastic movement disorders, abnormalities of motor control and somatosensory processing as well as cortical modulations associated with clinical improvement after botulinum toxin A (BoNT-A) treatment have been reported, but electrophysiological evidence remains controversial. In the present observational study, we aimed to uncover central correlates of post-stroke spasticity (PSS) and BoNT-A-related changes in the sensorimotor cortex by investigating the cortical components of somatosensory evoked potentials (SEPs). Thirty-one chronic stroke patients with PSS of the upper limb were treated with BoNT-A application into the affected muscles and physiotherapy. Clinical and electrophysiological evaluations were performed just before BoNT-A application (W0), then 4 weeks (W4) and 11 weeks (W11) later. PSS was evaluated with the modified Ashworth scale (MAS). Median nerve SEPs were examined in both upper limbs with subsequent statistical analysis of the peak-to-peak amplitudes of precentral P22/N30 and postcentral N20/P23 components. At baseline (W0), postcentral SEPs were significantly lower over the affected cortex. At follow up, cortical SEPs did not show any significant changes attributable to BoNT-A and/or physiotherapy, despite clear clinical improvement. Our results imply that conventional SEPs are of limited value in evaluating cortical changes after BoNT-A treatment and further studies are needed to elucidate its central actions.

Motor excitability measurements in early stage familial amyloid polyneuropathy: The influence of tafamidis treatment

OBJECTIVE

To test motor fiber excitability in early affected patients with transthyretin (TTR)-type familial amyloid polyneuropathy (TTR-FAP) before and during tafamidis treatment.

METHODS

We examined the left median nerve of 21 healthy-matched controls and 10 early affected TTR-FAP patients using the automated threshold-tracking program, QTRAC. TTR-FAP patients were tested one day before the initiation of tafamidis treatment, 3 and 6 months later.

RESULTS

The drug was well-tolerated in all patients; there was no drop-out. No statistical difference was found between healthy controls and TTR-FAP patients at study entry. On treatment, both stimulus intensity for 50% of the maximal motor response and rheobase increased significantly from entry to the last evaluation at 6 months (P<0.05). Strength duration time constant decreased significantly from the 3rd to the 6th month of evaluation (P<0.05). There was also a "fanning-out" effect on the late depolarization phase (TEd 90-100ms) as well as a shortened relative refractory period from study entry to the 6th month of evaluation.

CONCLUSIONS

Threshold-tracking of median nerve motor fibers is not a helpful technique for the early diagnosis of TTR-FAP patients. Tafamidis was well-tolerated. We observed possible membrane hyperpolarization during treatment. Threshold tracking can contribute to documenting the action of new drugs to treat neuropathies. Tafamidis may change nerve electrical properties by reducing the burden of amyloid fibrils.

Polydeoxyribonucleotide injection in the treatment of patients with carpal tunnel syndrome: Retrospective preliminary study

BACKGROUND

Corticosteroid injection is beneficial in treating carpal tunnel syndrome (CTS) due to its anti-inflammatory effects. However, its side effects limit widespread usage. Recently, several studies have found that polydeoxyribonucleotide offers anti-inflammatory capabilities with fewer side effects, making it an ideal alternative. Nevertheless, there has been no study on its effectiveness in patients with CTS. Therefore, we evaluate the effectiveness of polydeoxyribonucleotide in patients with CTS. Based on the criteria, 30 patients with CTS who received two-consecutive polydeoxyribonucleotide injections (with a week interval) were initially included.

METHOD

Patients with CTS were investigated retrospectively. To evaluate the effectiveness of polydeoxyribonucleotide in patients with CTS, numeric rating scale (NRS), cross-sectional area (CSA) of the median nerve, and severity and functional status scores of CTS based on the Boston Carpal Tunnel Syndrome Questionnaire (BCTQ) were assessed.

RESULTS

There was a significant improvement in the NRS, CSA, and functional and severity scores of BCTQ after two-consecutive polydeoxyribonucleotide injections (P < .05).

CONCLUSION

In conclusion, although more research is needed to evaluate the effectiveness of polydeoxyribonucleotide in patients with CTS, the findings here suggest that polydeoxyribonucleotide may be a viable alternative to corticosteroids in patients with CTS.

The Use of a Hypoallergenic Dermal Matrix for Wrapping in Peripheral Nerve Lesions Regeneration: Functional and Quantitative Morphological Analysis in an Experimental Animal Model

INTRODUCTION

The aim of this research was to test, in an animal model, the nerve regeneration technique with a hypoallergenic acellular dermal matrix used to wrap the microsurgical neural suture.

MATERIALS AND METHODS

Two groups of rats received the cut of limb right median nerves. The regeneration technique considers for both groups an end-to-end nerve suture. In the experimental group (A) was used also a wrapping protocol by a conduit of collagen matrix currently used in oral surgery. The animals underwent functional grasping tests (at 1, 3, 5, and 7 months) and a histological and quantitative analysis of distal nerve was performed at the end of experimental time.

RESULT

After seven months, the grasping test reveals functional recovery in each tested animal; this improvement is more evident in Group A. The fibers appear well organized with restored myelin sheaths in both groups. Group A showed a great quantity of connective tissue surrounding the nerve. The quantitative morphology analysis in both groups shows a similar fibers density, fiber diameter, and myelin thickness. The differences between the groups in axon mean diameter are significant. In Group A M/d, D/d, and g-ratio is significantly higher compared to control group.

CONCLUSIONS

Histological and functional assessments show a functional recovery of the injured nerve in the test groups, stressed by the results of the grasping tests and the meaningful increasing in fiber diameter and higher g-ratio. Moreover, a connective tissue cuff distinguishes the distal portion of the injured nerve. Considering the easy availability and handling of the material used in this study we can conclude that this experimental technique can be considered as a valid alternative to protect nerves in nerve wrap surgery.

Ultrasound-Guided Hydroneurolysis of the Median Nerve for Recurrent Carpal Tunnel Syndrome

BACKGROUND

Recurrent carpal tunnel syndrome is often associated with perineural scarring around the median nerve. Surgical options include relatively invasive procedures, such as fat pad grafting, ligament reconstruction, muscle transfer, and nerve wraps. All have limited success because of the possibility of repeated recurrent scarring postoperatively.

METHODS

We discuss a technique involving injection with external hydroneurolysis of the median nerve under ultrasound guidance for recurrent carpal tunnel. Injection enables a gentler dissection of the surrounding tissues compared with open external neurolysis, with less chance of recurrent scarring. This technique is a unique alternative to repeat operative intervention in recurrent carpal tunnel, as well as a prelude to repeat open decompression and salvage procedures.

RESULTS

Ultrasound-guided injection with external hydroneurolysis of the median nerve is a safer, more limited procedure compared with repeat open surgery, usually performed in an office setting. This procedure limits risk, anesthesia, and operating/recovery room expenses, offering relief in 70% to 80% of cases. Furthermore, in the 20% to 30% of patients with inadequate relief, surgery remains a viable option. US provides important information on the anatomy of the median nerve and carpal canal and can rule out covert pathology.

CONCLUSIONS

We offer an alternative treatment for recurrent carpal tunnel syndrome, a difficult problem for which many surgeons recommend nonoperative treatment. US provides objective data concerning residual nerve compression and allows for dynamic assessment. Theoretically, this also offers a viable solution for surgeons and their patients with recurrent carpal tunnel syndrome before being pressed to consider repeat open surgery.

Is pharmacologic treatment better than neural mobilization for cervicobrachial pain? A randomized clinical trial

Purpose: This study aim was to compare the effectiveness of the median nerve neural mobilization (MNNM) and cervical lateral glide (CLG) intervention versus oral ibuprofen (OI) in subjects who suffer cervicobrachial pain (CP). Methods: This investigation was a, multicenter, blinded, randomized controlled clinical trial (NCT02595294; NCT02593721). A number of 105 individuals diagnosed with CP were enrolled in the study and treated in 2 different medical facilities from July to November 2015. Participants were recruited and randomly assigned into 3 groups of 35 subjects. Intervention groups received MNNM or CLG neurodynamic treatments, and the (active treatment) control group received an OI treatment for 6 weeks. Primary outcome was pain intensity reported through the Numeric Rating Scale for Pain (NRSP). Secondary outcomes were physical function involving the affected upper limb using the Quick DASH scale, and ipsilateral cervical rotation (ICR) using a cervical range of motion (CROM) device. Assessments were performed before and 1 hour after treatment for NRSP (baseline, 3 and 6 weeks) and CROM (baseline and 6 weeks), as well as only 1 assessment for Quick DASH (baseline and 6 weeks). Results: Repeated-measures ANOVA intergroup statistically significant differences were shown for CP intensity (F(2,72) = 22.343; P < .001; Eta2 = 0.383) and Quick DASH (F(2,72) = 15.338; P < .001; Eta2 = 0.299), although not for CROM (F(2,72) = 1.434; P = .245; Eta2 = 0.038). Indeed, Bonferroni´s correction showed statistically significant differences for CP intensity (P < .01; 95% CI = 0.22 - 3.26) and Quick DASH reduction (P < .01; 95% CI = 8.48 - 24.67) in favor of the OI treatment at all measurement moments after baseline. Conclusions: OI pharmacologic treatment may reduce pain intensity and disability with respect to neural mobilization (MNNM and CLG) in patients with CP during six weeks. Nevertheless, the non-existence of between-groups ROM differences and possible OI adverse effects should be considered.

Cross-sectional area of the median nerve is increased in primary autoimmune hypothyroidism and decreases upon treatment with thyroxine

BACKGROUND

The purpose of this study was to assess changes in the cross-sectional area (CSA) of nervus medianus by ultrasound in newly diagnosed primary hypothyroid patients after thyroxine replacement treatment.

PATIENTS AND METHODS

The cohort comprised 30 patients with newly diagnosed primary autoimmune hypothyroidism. These were subsequently compared with 30 controls, matched for sex, BMI and age. Ultrasound evaluation, including measurement of CSA at the level of the pisiform bone or tunnel inlet was performed at baseline and after 3months. A CSA threshold of more than 10mm(2) was considered pathological.

RESULTS

CSA was increased in patients compared with controls (9.8±0.7mm(2) vs 7.2±1.1mm(2); P<0.001). Thyroxin substitution increased fT4 levels (baseline, 11.0±0.6pmol/L vs 15.5±0.4pmol/L; P<0.001) and decreased TSH (baseline, 23.9±6.0mIU/L vs 2.7±0.2mIU/L; P<0.001). Thyroxine treatment decreased CSA to 8.4mm(2)±0.3mm(2) (P=0.033). Before treatment, four patients experienced distal paresthesia in the median nerve distribution area. Increased CSA pathognomonic for carpal tunnel syndrome found in two symptomatic patients normalized after 3months. No clinical symptoms were observed after 3months. A positive correlation was found between TSH and CSA (R=0.155, P=0.05) before treatment.

CONCLUSION

Our study demonstrates that increase in median nerve CSA caused by primary autoimmune hypothyroidism can be fully reversible after achieving target levels of TSH and fT4.

Sonoelastographic Findings of Carpal Tunnel Injection

PURPOSE

The objectives of this study were to compare sonoelastographic color findings of the perineural area between carpal tunnel syndrome patients and healthy volunteers, and to analyze elastographic findings in that area before and immediately after intracarpal tunnel injection in carpal tunnel syndrome patients.

MATERIALS AND METHODS

We studied both hands of 15 healthy volunteers (7 men, 8 women; mean age: 60.1 years, range: 41 - 88 years) and 72 hands from 70 patients with symptomatic carpal tunnel syndrome (24 men, 46 women; mean age: 54.2 years, range: 24 - 83 years). Sonoelastographic color distribution was assessed in the perineural area between the median nerve and adjacent flexor tendons. The color elastograms were graded using the following system: Grade 1 as red (softest), grade 2 as yellow (soft), grade 3 as green (hard), grade 4 as blue (hardest). The patients were treated with corticosteroid injection and were reassessed with sonoelastography immediately after the injection.

RESULTS

The median color grading in the perineural area of carpal tunnel syndrome patients was grade 3 (3.1 ± 0.3, mean ± 95 % Cl), which was stiffer than that of healthy volunteers (grade 1, 1.9 ± 0.4) (p < 0.0001). Immediately after injection, the diffusion of the injected fluid was observed as having a softer appearance (grade 1, 1.4 ± 0.2) (p < 0.0001).

CONCLUSION

The perineural area surrounding the median nerve in carpal tunnel syndrome patients was stiffer than that in healthy volunteers. Diffusion of the injected fluid in the carpal tunnel was seen as a softer finding after injection in real time using sonoelastography.

Long term recovery of median nerve repair using laser-activated chitosan adhesive films

Sutures remain the standard peripheral nerve repair technique, whether applied directly or indirectly to nerve tissue. Unfortunately, significant postoperative complications can result, such as inflammation, neuroma formation and foreign body reactions. Photochemical-tissue-bonding (PTB) using rose Bengal (RB) integrated into a chitosan bioadhesive is an alternative nerve repair device that removes the need for sutures. Rats were arranged into three groups: RB-chitosan adhesives-repair, end-to-end epineural suture-repair (surgical standard) and sham laser-irradiated control. Groups were compared through histological assessment, electrophysiological recordings and grip motor strength. RB-chitosan adhesive repaired nerves displayed comparable results when compared to the standard suture-repair based on histological and electrophysiological findings. Functionally, RB-chitosan adhesive was associated with a quicker and more pronounced recovery of grip force when compared to the suture-repair.

Meta-analysis of methylcobalamin alone and in combination with prostaglandin E1 in the treatment of diabetic peripheral neuropathy

This study aimed to compare the efficacy and safety of prostaglandin E1 plus methylcobalamin (PGE1-MC) with that of methylcobalamin alone (MC) on diabetic peripheral neuropathy (DPN). We searched published randomized controlled trials (RCTs) of PGE1 combined with MC for DPN up to June 1, 2013. Data were extracted to evaluate methodological quality and describe characteristics of studies in duplicate. A random or a fixed effect model was used to analyze outcomes which were expressed as relative risk (RR) or mean difference with a 95 % confidence interval (CI). All data were analyzed using Review Manager 5.2 software. Twenty-six RCTs involving 2,107 individuals were included. Meta-analysis showed that PGE1-MC combination therapy was significantly better than MC monotherapy (RR = 1.40; 95 % CI 1.33-1.48) on efficacy. The weighted mean differences in nerve conduction velocities (NCVs) were 6.72 (95 % CI: 5.42-8.02) for median motor nerve conduction velocity (MNCV), 5.13 (CI 4.13-6.13) for median sensory nerve conduction velocity (SNCV), 5.74 (CI 4.87-6.61) for peroneal MNCV and 4.62 (CI 3.89-5.34) for peroneal SNCV in favor of the PGE1 + MC combination group. Moreover, there were no serious adverse events in both groups during the treatment period. The results of the meta-analysis show that treatment with PGE1-MC is safe and can gain better outcomes in neuropathic symptoms and NCVs compared with MC alone. However, the conclusion may not be strong because most of the studies included in this meta-analysis have poor methodological quality.

Ischemic block of the forearm abolishes finger movements but not their associated anticipatory postural adjustments

Voluntary movement is known to induce postural perturbations that are counteracted by unconscious anticipatory postural adjustments (APAs). Thus, for every movement, two motor commands are dispatched: a voluntary command recruiting the prime mover and a postural command driving the APAs. These commands are classically thought to be separated; this study investigates whether they could be instead considered as two elements within the same motor program. We analyzed the APAs in biceps brachii, triceps brachii and anterior deltoid that stabilize the arm when briskly flexing the index finger (prime mover flexor digitorum superficialis). APAs and prime mover activation were recorded before, under and after ischemic block of the forearm. Ischemia paralyzed the prime mover, thus suppressing the finger movement and the ensuing postural perturbation. If the two commands had been separated, it would have been expected that after a few failed attempts to flex the index finger, the APAs were suppressed too, being purposeless without postural perturbation. APAs were still present under ischemia even after 60 movement trials. No significant changes were found in APA amplitude in biceps and triceps among different conditions, or in the average APA latency. Inhibitory APA in anterior deltoid was reduced but still present under ischemia. In addition, the pharmacologic block of the sole median nerve produced similar effects. APAs were instead almost abolished when applying a fixation point to the wrist. The observation that APAs remained tailored to the expected perturbation even when that perturbation did not occur supports the idea of a functionally unique motor command driving both the prime mover and the muscles of the APA chain.

Laser-activated adhesive films for sutureless median nerve anastomosis

A novel chitosan adhesive film that incorporates the dye 'Rose Bengal' (RB) was used in conjunction with a green laser to repair transected rat median nerves in vivo. Histology and electrophysiological recording assessed the impact of the laser-adhesive technique on nerves. One week post-operatively, the sham-control group (laser-adhesive technique applied on un-transected nerves) conserved the average number and size of myelinated fibres in comparison to its contralateral side and electrophysiological recordings demonstrated no significant difference with un-operated nerves. Twelve weeks after the laser-adhesive anastomoses, nerves were in continuity with regenerated axons that crossed the anastomotic site.

Differences in dopaminergic modulation to motor cortical plasticity between Parkinson's disease and multiple system atrophy

Dopamine modulates the synaptic plasticity in the primary motor cortex (M1). To evaluate whether the functioning of the cortico-striatal circuit is necessary for this modulation, we applied a paired associative stimulation (PAS) protocol that comprised an electric stimulus to the right median nerve at the wrist and subsequent transcranial magnetic stimulation of the left M1, to 10 patients with Parkinson's disease (PD) and 10 with multiple system atrophy of the parkinsonian type (MSA-P) with and without dopamine replacement therapy (-on/off). To investigate the M1 function, motor-evoked potentials (MEPs) were measured before and after the PAS. In both patient groups without medication, the PAS protocol failed to increase the averaged amplitude of MEPs. The dopamine replacement therapy in PD, but not in MSA-P effectively restored the PAS-induced MEP increase. This suggests that not the existence of dopamine itself but the activation of cortico-striatal circuit might play an important role for cortical plasticity in the human M1.

Melatonin reduces median nerve injury-induced mechanical hypersensitivity via inhibition of microglial p38 mitogen-activated protein kinase activation in rat cuneate nucleus

In this study, we examined the relationships between p38 mitogen-activated protein kinase (MAPK) activation in the cuneate nucleus (CN) and behavioral hypersensitivity after chronic constriction injury (CCI) of the median nerve. We further investigated effects of melatonin administration and pinealectomy on p38 MAPK activation and development of hypersensitivity. Using immunohistochemistry and immunoblotting, low levels of phosphorylated p38 (p-p38) MAPK were detected in CN of normal rats. As early as 1 day after CCI, p-p38 MAPK levels in the ipsilateral CN were significantly increased (1.4 ± 0.2-fold, P < 0.05), which reached a maximum at 7 days (5.1 ± 0.4-fold, P < 0.001). Double immunofluorescence labeling with cell-specific markers showed that p-p38 MAPK immunoreactive cells co-expressed OX-42, a microglia activation maker, suggesting the expression of p-p38 MAPK in microglia. Microinjection of SB203580, a p38 MAPK inhibitor, into the CN 1 day after CCI attenuated injury-induced behavioral hypersensitivity in a dose-dependent manner. Furthermore, animals received melatonin treatment at daily doses of 37.5, 75, 150, or 300 mg/kg from 30 min before until 3 days after CCI. Melatonin treatment dose-dependently attenuated p-p38 MAPK levels, release of pro-inflammatory cytokines, and behavioral hypersensitivity following CCI; conversely, pinealectomy that resulted in a reduction in endogenous melatonin levels exacerbated these effects. In conclusion, median nerve injury-induced microglial p38 MAPK activation in the CN modulated development of behavioral hypersensitivity. Melatonin supplementation eased neuropathic pain via inhibition of p38 MAPK signaling pathway; contrarily, reducing endogenous blood melatonin levels by pinealectomy promoted phosphorylation of p38 MAPK and made rats more vulnerable to nerve injury-induced neuropathic pain.

The effect of local corticosteroid injection on F-wave conduction velocity and sympathetic skin response in carpal tunnel syndrome

The aim of this study was to evaluate the efficacy of steroid injection for the treatment of the carpal tunnel syndrome (CTS), with F-wave parameters and sympathetic skin response (SSR). Seventeen hands of 10 women patients were treated with local steroid injection with 2-month follow-up. All patients underwent single injection into the carpal tunnel. Response to injection was measured nerve conduction studies (NCSs), median nerve F waves, and SSR before and after treatment. To determine the normal values, 42 hands of 21 healthy women were also studied. There was a significant improvement of sensory and motor nerve conduction values when compared to baseline values (P < 0.01). At the end of follow-up period, the median sensory distal latency and the sensory latency differences between the median and the ulnar nerve were improved 35 and 65%, respectively. The maximum, mean F-wave amplitudes and chronodispersion showed a slight improvement with respect to baseline values and controls, but statistical significance was not achieved after treatment. Although no statistically significant improvements were observed in SSR parameters, slightly decreased amplitudes and increased habituation of SSR were noted at the end of the treatment. The present study shows that the local steroid injection results in improvement in NCSs values, but the F-wave parameters were not effectual in short-term outcome of CTS treatment. These findings suggest that the sensory latency differences between the median and the ulnar wrist-to-digit 4 are better parameters in the median nerve recovery after treatment than the median sensory distal latency. Furthermore, the SSR does not seem to be a sensitive method in follow-up of CTS treatment.

Occupational exposure to pesticides and nerve conduction studies among Korean farmers

This study aimed to determine whether occupational exposure to pesticides was associated with decreased nerve conduction studies among farmers. On 2 separate occasions, the authors performed a cross-sectional study of a group of 31 male farmers who periodically applied pesticides. The study included questionnaire interviews and nerve conduction studies on the median, ulnar, posterior tibial, peroneal, and sural nerves. Although all mean values remained within laboratory normal limits, significant differences between the first and second tests were found in sensory conduction velocities on the median and sural nerves, and motor conduction velocities on the posterior tibial nerve. Lifetime days of pesticide application was negatively associated with nerve conduction velocities at most nerves after adjusting for potential confounders. These findings may reflect a link between occupational pesticide exposure and peripheral neurophysiologic abnormality that deserves further evaluation.

Single stimulation of the posterior cord is superior to dual nerve stimulation in a coracoid block

BACKGROUND

Both multiple injection and single posterior cord injection techniques are associated with extensive anesthesia of the upper limb after an infraclavicular coracoid block (ICB). The main objective of this study was to directly compare the efficacy of both techniques in terms of the rates of completely anesthetizing cutaneous nerves below the elbow.

METHODS

Seventy patients undergoing surgery at or below the elbow were randomly assigned to receive an ICB after the elicitation of either a single radial nerve-type response (Radial group) or of two different main nerve-type responses of the upper limb, except for the radial nerve (Dual group). Forty milliliters of 1.5% mepivacaine was given in a single or a dual dose, according to group assignment. The sensory block was assessed in each of the cutaneous nerves at 10, 20 and 30 min. Block performance times and the rates of complete anesthesia below the elbow were also noted.

RESULTS

Higher rates of sensory block of the radial nerve were found in the Radial group at 10, 20 and 30 min (P<0.05). The rates of sensory block of the ulnar nerve at 30 min were 97% and 75% in the Radial and in the Dual groups, respectively (P<0.05). The rate of complete anesthesia below the elbow was also higher in the Radial group at 30 min (P<0.05).

CONCLUSIONS

Injection of a local anesthetic after a single stimulation of the radial nerve fibers produced more extensive anesthesia than using a dual stimulation technique under the conditions of our study.

Effects of the antiepileptic drugs on peripheral nerve function

OBJECTIVE

We aimed to compare the effects of antiepileptic drugs and provide findings of peripheral nerve impairment using standard electrophysiological techniques.

MATERIALS AND METHODS

Young adult outpatients with epilepsy on monotherapy for no less than 6 months with carbamazepine (CBZ), valproic acid (VPA), oxcarbazepine (OXC) and topiramate (TPM) were examined. Patients who had any other disease that could effect nerve conduction studies and who had neuropathic symptoms were excluded.

RESULTS

Each group contained 15 patients and 20 healthy subjects were examined as the control group. Prolonged latency of median sensory nerve (P = 0.004), ulnar sensory nerve (P = 0.01) and sural nerve (P = 0.003) with a diminished nerve conduction velocity was observed in the CBZ group (P = 0.014, P = 0.002, P = 0.025, respectively). No correlation was found between VPA, OXC and TPM and the nerve conduction studies (P > 0.05).

CONCLUSIONS

Valproic acid, oxcarbazepine and topiramate don't have effects on nerve conduction studies. Mild electrophysiological changes contribute to carbamazepine therapy.

Sensory integration in writer's cramp: comparison with controls and evaluation of botulinum toxin effect

OBJECTIVE

Abnormal temporal and spatial sensory integration have been described in mixed groups of dystonic patients. We tested somatosensory integration and the effect of botulinum toxin (BoNT) in patients with writer's cramp (WC).

METHODS

Median and ulnar SEPs were recorded in 29 WC patients and in 10 controls. We performed: individual and simultaneous stimulation of median and ulnar nerves (MU) and paired stimulation of median nerve at interstimulus-interval (ISI) of 40 and 100 ms. All the trials were repeated after blinded randomized treatment with placebo or BoNT-A.

RESULTS

We found no differences between patients and controls in standard SEPs. Spatial (except for N9) and temporal suppression after ISI 40 were present in both groups for all the waves; after ISI 100, suppression was present only for N70. There were no differences between patients and controls. After BoNT-A treatment, no changes were observed.

CONCLUSIONS

In contrast with previous findings in heterogeneous dystonic groups, and although some studies suggest impairment of spatial and temporal sensory discrimination in patients with focal dystonia, in our large cohort of patients with WC we found no evidence of abnormal somatosensory integration investigated by means of SEPs and no changes in somatosensory variables after BoNT-A treatment.

SIGNIFICANCE

Our findings may suggest pathophysiological differences between focal and generalized dystonia, and may also point to an inferior sensitivity of SEPs in detecting abnormalities in sensory discrimination as compared to methods based on subjective discrimination.