Spread of injectate associated with radial or median nerve-type motor response during infraclavicular brachial-plexus block: an ultrasound evaluation

BACKGROUND AND OBJECTIVES

We have compared ultrasound characteristics of spread during infraclavicular brachial-plexus blocks by use of electrically evoked radial-nerve- or median-nerve-type distal motor responses to guide the injection of 30 mL of 1.5% mepivacaine.

METHODS

Consecutive patients who required surgery distal to the upper arm were prospectively included in this study. With radial- or median-evoked distal motor response at a stimulating current intensity of less than 0.5 mA, patients were distributed into 2 equal groups. An independent investigator blinded to the evoked response described ultrasound characteristics of the spread of local anesthetic and assessed block quality 30 minutes after placement. A quality diffusion score proportional to the extent and intensity of spread around the axillary artery was used, and dynamic movements during injection were noted.

RESULTS

Thirty-two patients were included. With radial-nerve-type motor response, the success rate of infraclavicular plexus block was 100%, but 3 supplemental axillary blocks were requested with median-nerve-type motor response. Quality diffusion scores were significantly higher with radial-nerve-type as compared with median-nerve-type motor response (P = .03). Injection after radial-nerve-type motor response resulted in a typical and reproducible ultrasound feature of posterior local-anesthetic spread associated with medial and upper movement of the axillary artery. With median-nerve-type motor response, failed blocks were associated with a specific posterior displacement of the axillary artery that resulted from superficial spread.

CONCLUSION

We have demonstrated that as compared with median-nerve-type motor response, injection performed after a radial-nerve-type motor response promoted reproducible and remarkable ultrasound spread characteristics associated with complete sensory block of the 3 cords at 30 minutes.

Time-dependent changes in median nerve sensory amplitude after local anesthetic administration and tourniquet application

Indirect visualization, as used in several newer mini-open and endoscopic carpal tunnel release (CTR) procedures, may increase the possibility of nerve injury in some cases. Intraoperative neural monitoring may be used to evaluate nerve location and integrity. In the study reported here, we assessed the feasibility of intraoperative neural monitoring by systematically exploring the effect of local anesthetic and tourniquet on median sensory amplitude. Results for 30 median nerves (7 symptomatic) showed that sensory amplitude decreased, on average, 54% with lidocaine injection, 15% with tourniquet application, and 47% with the combination. Sensory amplitudes of 9 of 10 nerves were still above 1.0 microV 15 minutes after anesthetic administration and tourniquet application. Study results demonstrate that intraoperative monitoring, using the amplitude of the median sensory nerve response, is viable under CTR conditions.

Effects of General Anesthesia on High-Frequency Oscillations in Somatosensory Evoked Potentials

To determine the characteristics of high-frequency oscillations (HFOs) of cortical somatosensory evoked potentials (SEPs), the effect of general anesthesia on HFOs and low-frequency primary cortical responses was studied. The authors recorded SEPs elicited by median nerve stimulation directly from human brains of seven patients who underwent implantation of subdural electrodes before surgical treatment of intractable epilepsy. Recordings were made before and during general anesthesia. Changes in the number of HFOs and amplitude ratios of HFOs/primary cortical responses were analyzed. Under general anesthesia, the number of HFO peaks and the amplitude ratios were significantly decreased. General anesthesia induced remarkably decreased HFO activities when compared to low-frequency SEPs, suggesting that each of those originated from different generators. Possible relations between gamma-amino-butyric acid (GABA)ergic inhibitory interneurons and HFOs are discussed.

Peripheral median nerve block impairs precision pinch movement

OBJECTIVE

The objective of this study was to investigate the effects of a simulated peripheral median nerve lesion on precision pinch movement by the thumb and index finger.

METHODS

A median neuropathy was created by blocking the median nerve at the wrist using an anesthetic. The subjects (n=5) were asked to perform pulp-to-pulp precision pinch movements before and after the nerve block. Digit motion data was obtained with a marker-based motion analysis system.

RESULTS

The radial offset of the thumb tip, as defined by the minimum distance of the thumb tip to the flexion-extension plane of the index finger, showed an increase of 11.2mm after the nerve block. For the thumb, the nerve block caused a decrease in the range of motion at the metacarpophalangeal (MCP) joint, and a compensatory increase in the range of motion at the interphalangeal (IP) joint. The range of motion ratio (MCP:IP) changed from 1:4.8 (pre-block) to 1:1.0 (post-block). The maximum flexion angle at the MCP joint increased from 18.8 degrees (pre-block) to 33.7 degrees (post-block), and maximum flexion angle at the IP joint decreased from 42.6 degrees (pre-block) to 18.8 degrees (post-block). For the index finger, the nerve block caused a decrease in the range of motion at the MCP joint, and compensatory increases in the ranges of motion at the proximal and distal interphalangeal (PIP and DIP) joints. The range of motion ratio (MCP:PIP:DIP) changed from 1:1.1:0.7 (pre-block) to 1:2.4:1.8 (post-block). The maximum flexion angle at the MCP joint decreased from 56.8 degrees (pre-block) to 34.6 degrees (post-block), and the maximum flexion angle at the PIP joint increased from 51.2 degrees (pre-block) to 76.0 degrees (post-block), but the change at the DIP joint was insignificant.

CONCLUSIONS

The median nerve block caused remarkable degradation of the pinch performance as quantified by an inaccurate pulp-to-pulp contact of the thumb to the index finger and an alteration of joint motion of the digits.

SIGNIFICANCE

Many fine manual tasks require accurate pulp-to-pulp positioning of the thumb to the index finger. Within the hand, the median nerve is critical to the fine sensorimotor function due to the motor supply and the sensory endings to the thumb and index finger. People with median neuropathies (for example, carpal tunnel syndrome) experience clumsiness while performing simple manual tasks. The current approach to the examination of precision pinch movement may be utilized to quantify the apparent hand clumsiness observed in individuals with peripheral neuropathy such as carpal tunnel syndrome.

The use of ciliary neurotrophic factor to promote recovery after peripheral nerve injury by delivering it at the site of the cell body

Despite a body of evidence showing that various neurotrophic factors support the survival of nerve cells and stimulate axonal outgrowth, doubt remains about their optimal site of application as well as the more compelling question of what clinical benefit, if any, they would confer. Ciliary neurotrophic factor (CNTF) supports the survival of motorneurons in vitro and in vivo. Direct delivery of CNTF to the cell bodies may help reduce the side effects and overcome the problem of rapid systemic clearance. The aim of this study was to establish whether nerve regeneration may be improved upon by the controlled addition of a specific humoral neurotrophic substance (CNTF) at the level of the cell body. Three groups of five adult sheep were used. The first group acted as normal controls. In the second and third groups, the median nerve was divided and repaired using an epineurial suture technique. In the second group, CNTF was supplied into the CSF at the level of C6 by an implanted osmotic pump. In the third group physiological saline was placed in the osmotic pump. The animals underwent comprehensive electrophysiological and isometric tension experiments at six months. All of the animals had reduced electrophysiological, morphometric and isometric tension indices after surgery compared to normal. The CNTF group had better results than the saline group in the following; (1) area and amplitude of the muscle action potential (2) the percentage of tetanus and muscle mass preserved after repair. These differences were only statistically significant for amplitude of the muscle action potential. No statistical difference was found in the morphological indices (fibre diameter, axon diameter, myelin thickness and internodal length) between the CNTF and saline groups. CNTF does not confer a functional benefit when applied at the level of the cell body.

Somatosensory evoked potentials as an objective assessment of the sensory median nerve blockade after infraclavicular block

PURPOSE

Median nerve somatosensory evoked responses (MnSSER) alterations were compared to clinical tests (cold and pinprick) variations, in 20 ASA I adult patients following infraclavicular block obtained with 40 mL ropivacaine 0.5% to assess first, the difference of time course of the respective electrophysiological and clinical signs, and second, the objectivity and the reproducibility of MnSSER changes.

CLINICAL FEATURES

Four MnSSER derivations (Erb's point; cutaneous projection of peripheral end of brachial plexus; posterior neck at C6 level, frontal and controlateral parietal scalp) were monitored and recorded for retrospective analysis. Continuous data acquisition were started before ropivacaine injection (baseline) and maintained for 30 min thereafter. Every three minutes after ropivacaine injection, cold and pinprick tests were performed in the hand median nerve cutaneous supply zone and were assessed using a sensory visual score (varying from 0-10). Data were compared using analysis of variance. Although MnSSER values were stable during baseline period, after ropivacaine administration, severe progressive amplitude depressions of selected MnSSER were detected in every patient. While clinical cold and pinprick tests became positive (score > 8) only 15.8 +/- 1.2 min and 20.1 +/- 1.8 min respectively after ropivacaine administration, the mean time to observe the earliest MnSSER 20% amplitude decrease at Erb's point derivation was reduced to 5.6 +/- 1.1 min (P < 0.01).

CONCLUSION

Selected MnSSER amplitude reduction indicates objectively the onset of median nerve anesthesia following infraclavicular brachial plexus block before the appearance of clinical signs.

A randomized controlled trial of surgery vs steroid injection for carpal tunnel syndrome

BACKGROUND

Decompressive surgery and steroid injection are widely used forms of treatment for carpal tunnel syndrome (CTS) but there is no consensus on their effectiveness in comparison to each other. The authors evaluated the efficacy of surgery vs steroid injection in relieving symptoms in patients with CTS.

METHODS

The authors conducted a randomized, single blind, controlled trial. Fifty patients with electrophysiologically confirmed idiopathic CTS were randomized and assigned to open carpal tunnel release (25 patients) or to a single injection of steroid (25 patients). Patients were followed up at 6 and 20 weeks. The primary outcome was symptom relief in terms of the Global Symptom Score (GSS), which rates symptoms on a scale of 0 (no symptoms) to 50 (most severe). Nerve conduction studies and grip strength measurements were used as secondary outcome assessments.

RESULTS

At 20 weeks after randomization, patients who underwent surgery had greater symptomatic improvement than those who were injected. The mean improvement in GSS after 20 weeks was 24.2 (SD 11.0) in the surgery group vs 8.7 (SD 13.0) in the injection group (p < 0.001); surgical decompression also resulted in greater improvement in median nerve distal motor latencies and sensory nerve conduction velocity. Mean grip strength in the surgical group was reduced by 1.7 kg (SD 5.1) compared with a gain of 2.4 kg (SD 5.5) in the injection group.

CONCLUSION

Compared with steroid injection, open carpal tunnel release resulted in better symptomatic and neurophysiologic outcome but not grip strength in patients with idiopathic carpal tunnel syndrome over a 20-week period.

Determination of sensitive electrophysiologic parameters at follow-up of different steroid treatments of carpal tunnel syndrome

Nonsurgical treatment for carpal tunnel syndrome (CTS) is frequently offered to those with mild to moderate symptoms. However, the most sensitive electrophysiological parameters at follow-up, and most effective type of different methods of steroid treatment for CTS, remain unknown. The aim of this study was to compare the efficacy of local corticosteroid injection, phonophoresis, and iontophoresis for the treatment of CTS, and to evaluate the most sensitive electrophysiologic parameters at the follow-up visit. Different conservative treatments were applied in this prospective study. Fifty-six hands of 31 patients were randomly treated with local steroid injection, iontophoresis, or phonophoresis with 2- and 4-month follow-up visits. Conventional and new neurophysiologic sensorimotor nerve conduction parameters for CTS diagnosis were performed on the initial visit and at 2 and 4 months after treatment. The local steroid injection group showed a significant improvement in the mean nerve conduction parameters after the second and fourth months when compared with basal values, whereas no significant changes except the difference between the median and ulnar distal latency to the fourth digit (D4M-D4U), difference between sensory median distal latency to second digit and ulnar distal latency to the fifth digit (D2M-D5U), and median motor distal latency were observed in the iontophoresis and phonophoresis groups. At the end of follow-up period, the most sensitive parameters were D4M-D4U and D2M-D5U; the D4M-D4U was improved 60% in the injection group, 33% in iontophoresis group, and 39% in phonophoresis group, and the improvement of the D2M-D5U was 70%, 28%, and 28%, respectively, in the injection, iontophoresis, and phonophoresis groups. These findings show that steroid injection is superior to iontophoresis and phonophoresis in the treatment of CTS, and that the most sensitive neurophysiologic parameters in follow-up are D4M-D4U and D2M-D5U, being the objective measures of the outcome of CTS treatment.

Amelioration by mecobalamin of subclinical carpal tunnel syndrome involving unaffected limbs in stroke patients

Our previous study showed that overuse of the nonparetic hand and wrist of the nonparetic side following stroke result in significantly more abnormal on the nonparetic side than on the hemiparetic side in terms of electrophysiologic indices of median nerve function. The purpose of this study was to evaluate the effects of the orally administered mecobalamin, an analogue of vitamin B12, for carpal tunnel syndrome (CTS) in the nonparetic side in patients following stroke. In a randomized open label and prospective study of stroke patients, 67 received of 1500 mug mecobalamin daily for 2 years, and the remaining 68 (untreated group) did not. At baseline, sensory nerve conduction velocity, motor nerve conduction velocity, sensory nerve action potentials (SNAP) at the wrist, palm-to-wrist distal sensory latency, palm-to-wrist SNAP, motor nerve conduction velocity compound motor action potentials, and distal motor latency of median nerve were significantly more abnormal on the nonparetic side than on the hemiparetic side or in controls. Before the treatment 21 patients (31%) of untreated and 20 patients (30%) of treated group met electrophysiologic criteria for CTS. Sensory impairment of the nonparetic side had lessened in the treated group. After 2 years, all electrophysiologic indices of nonparetic side were significantly improved in the treated group compared with those in the untreated group. The improvement from baseline of electrophysiologic parameters in sensory nerve in the treated group was greater than the improvement measured in motor nerve. There were no side effects. Oral mecobalamin treatment is a safe and potentially beneficial therapy for CTS in stroke patients.

[Distribution of conduction velocity in the ulnar nerve among lead exposed workers]

BACKGROUND

Neuropathy can be one of the symptoms of the toxic effect of lead on the nervous system. The aim of this work was to perform clinical and neurophysiological assessment of the peripheral nervous system in workers exposed to lead.

MATERIALS AND METHODS

The study included 34 exposed workers and 20 healthy controls. Motor (ulnar, peroneal) and sensory (ulnar, sural) conduction velocity as well as conduction velocity distribution in ulnar n. and EMG from the I. interosseus muscle were assayed. The whole blood value of Pb 400 microg/l was adopted as a borderline between workers with low and increased blood lead concentrations. The FEP value of 70 microg/100 ml erythrocytes was the borderline between those without or with biochemical signs of Pb loading. The workers' age and duration of occupational exposure did not differ significantly between the study and control groups.

RESULTS

None of the workers showed clinical signs of neuropathy or abnormalities in routine neurographic examination. As compared with controls, a significantly lowered conduction in slow-conducting motor fibers and neurogenic changes in EMG were observed in workers with the whole blood Pb concentration over 400 microg/l and in workers with FEP level over 70 tig/100 ml erythrocytes.

CONCLUSION

Neurotoxic effect of Pb on peripheral nerves is manifested by the damage of slow-conducting motor nerves fibers when overt neuropathy is not yet visible.

The Hemodynamic Effects of Ephedrine on the Onset Time of Rocuronium in Pigs

Several studies have found a correlation between the onset time of muscle relaxants, cardiac index, and muscle blood flow. Ephedrine increases these hemodynamic variables and shortens onset time of rocuronium in humans. Our aim in this animal study was to determine the effect of ephedrine on the onset time of rocuronium, cardiac index, and muscle blood flow after administration of thiopental. At predefined measuring points, mean arterial blood pressure and cardiac index were measured invasively and onset time was determined mechanomyographically. Twenty-four pigs were randomly assigned to three groups. Group I received etomidate and subsequently rocuronium (2 x 95% effective dose). Instead of etomidate, Group II received thiopental. In Group III, ephedrine 100 mug/kg was given before thiopental; additionally, muscle blood flow was measured (fluorescent microspheres). Although there were differences in hemodynamics between Groups I and II, this was not reflected in different onset times of rocuronium. In Group III, ephedrine compensated the thiopental-induced decrease of mean arterial blood pressure, cardiac index, and muscle blood flow, but no significant shortening of onset time (Group I: 74 +/- 21 s; Group II: 71 +/- 24; Group III: 69 +/- 22 s) was found. Our results demonstrated that ephedrine-related increases in cardiac index and blood flow did not shorten onset time of rocuronium in healthy pigs.

Cyclosporin A in treatment of refractory patients with chronic inflammatory demyelinating polyradiculoneuropathy

To investigate the therapeutic efficacy of cyclosporin A (CyA) in the treatment of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), a microemulsion form of this drug (Neoral) was orally given to seven patients with the disease who were unresponsive or resistant to conventional therapies. The daily dose of CyA was carefully controlled in order to keep the plasma trough concentration between 100 and 150 ng/ml. Within 1 month of initiation of CyA, all patients subjectively showed improvement of clinical symptoms, while both modified Rankin and INCAT disability scores were significantly decreased (p < 0.05) and grip strength was significantly increased (p < 0.05) 3 months after initiation compared with before. Total protein in the cerebrospinal fluid was significantly decreased 3 and 6 months after starting CyA (p < 0.05). Although the maximal motor nerve conduction velocity showed a significant improvement in the median nerve 1 to 1.5 years after commencement of CyA (p < 0.05), there were no significant changes in any other neurophysiological parameters. One patient with anti-sulphoglucuronyl paragloboside IgM antibodies gradually became resistant to CyA, but the rest have since been in good neurological condition without complications ascribable to this drug. These results suggest that oral CyA may be effective even for refractory cases with CIDP. CyA should be actively considered as a therapeutic option when patients with CIDP are resistant to conventional treatment.

Clonidine added to bupivacaine enhances and prolongs analgesia after brachial plexus block via a local mechanism in healthy volunteers

BACKGROUND AND OBJECTIVE

The addition of clonidine to local anaesthetics enhances pain relief after peripheral nerve block, but the site of action is unproven.

METHODS

Seven healthy volunteers underwent three brachial block procedures using bupivacaine 0.25% 1 mg kg(-1) + epinephrine 1:200,000 (=local analgesic) in a randomized, double-blind cross-over fashion: (a) control treatment: local analgesic with 0.9% sodium chloride solution for the block and an intramuscular injection of saline; (b) intramuscular treatment: local analgesic with 0.9% NaCl for block and an intramuscular injection of clonidine 2 microg kg(-1) and (c) block treatment: local analgesic with clonidine 2 microg kg(-1) for block and an intramuscular injection of saline.

RESULTS

The onset and duration of complete blockade (sensory/motor/temperature) was evaluated in the four nerve regions of the hand and forearm. Additionally, sedation score, blood pressure, heart rate and plasma clonidine concentrations were determined. The median duration of complete sensory blockade was 270 min (range 0-600) for block treatment compared to 0 min (range 0-480) for intramuscular treatment (P < 0.05) and 0 min (range 0-180) for control treatment (P < 0.05). Motor and temperature blockade exhibited similar results. Administration of clonidine was associated with sedation and a decrease in heart rate and blood pressure independent of the route of administration. Plasma clonidine concentrations were lower for block compared to the intramuscular treatment.

CONCLUSIONS

The admixture of clonidine to bupivacaine plus epinephrine prolongs and enhances brachial plexus blockade. Lower clonidine plasma concentrations for block treatment strongly suggest a local effect.

Intracarpal steroid injection is safe and effective for short-term management of carpal tunnel syndrome

A double-blinded placebo-controlled trial was performed to evaluate the use of steroid injections beneath the transverse carpal ligament in the treatment of carpal tunnel syndrome (CTS) refractory to nonsurgical therapy. Forty-three patients received 6 mg betamethasone and lidocaine and 38 patients received 1 ml saline placebo and lidocaine. The primary outcome measure was satisfaction with symptom relief. Thirty patients (70%) in the steroid-treated group were satisfied or highly satisfied compared with 13 (34%) of placebo-treated patients (P < 0.001). Patients receiving steroids also showed significant improvement in median nerve conduction parameters and scores on validated symptom/function questionnaires. Forty-six patients were treated with serial injections for recurrent CTS symptoms. After 18 months, 17 patients reported adequate symptom relief with steroid injection, and 18 patients with unsatisfactory symptom relief were referred for carpal tunnel release surgery. We conclude that although steroid injections are safe and effective for temporary relief of CTS, most patients will eventually require surgery for long-term control of their symptoms.

Dopaminergic effects on electrophysiological and functional MRI measures of human cortical stimulus–response power laws

Power laws have been widely used to formulate relationships between objective intensity of stimulation and subjective intensity of sensation. We investigated the effects of dopaminergic drug treatment (sulpiride) on the relationship between somatosensory stimulus intensity and cortical response measured electrophysiologically by somatosensory-evoked potentials (SEP) and functional magnetic resonance imaging (fMRI). The intensity of stimulation was related by a simple power law to both electrophysiological and fMRI measures of cortical response, with overlapping confidence intervals for both power law exponents. Sulpiride did not modulate the power law exponent, but significantly attenuated the "gain" of both stimulus-response functions. Using path analysis we decomposed dopaminergic effects on fMRI data into an indirect component (16%), predictable by drug effects on SEP, and a direct component (84%), not explained electrophysiologically. Results indicate that sulpiride has comparable effects on power law parameters estimated from SEP and fMRI, but fMRI has superior sensitivity to detect drug effects on somatosensory cortical recruitment by graded stimulation.

Acute isovolemic anemia does not impair peripheral or central nerve conduction

BACKGROUND

Previous studies have found subtle slowing of responses in tests of addition and digit-symbol substitution during acute severe isovolemic anemia to a hemoglobin concentration of 5 g/dl in healthy unmedicated humans. In this study, the authors tested the hypothesis that such changes relate to the slowing of afferent neural traffic.

METHODS

The median nerve was stimulated at the wrist in seven healthy unmedicated volunteers before and after induction of acute isovolemic anemia to a nadir hemoglobin concentration of 5.1 +/- 0.3 g/dl (mean +/- SD). Times for neural impulses to travel from the stimulus site to the brachial plexus, cervical spinal cord, and cerebral cortex were measured using somatosensory evoked potentials. Tests were repeated during acute anemia with the subject breathing oxygen. As a control for time and intrasubject variation, the testing was repeated on a separate day when anemia was not produced at times equivalent to those on the experimental day.

RESULTS

Induced acute severe isovolemic anemia decreased nerve conduction latencies from the wrist to the contralateral cerebral cortex (i.e., to the N20 peak) by 2.3 +/- 1.6% compared with values at a mean hemoglobin concentration of 12.7 g/dl (P < 0.01). These decreased latencies were due solely to an increased peripheral conduction velocity, from the wrist to the brachial plexus (P < 0.05), and were not altered when subjects breathed oxygen (P > 0.05). Conduction velocity from the brachial plexus or cervical spinal cord to the cerebral cortex did not change with acute anemia (P > 0.05). Latencies did not differ on the control day among the times of testing (all P > 0.05), nor did they differ at baseline between the control and experimental days (all P > 0.05).

CONCLUSION

Somatosensory evoked potential latencies were not increased by acute severe isovolemic anemia, making it unlikely that the afferent portion of the neural system is responsible for slowing of cognitive responses previously observed during acute anemia. Because severe isovolemic anemia did not increase somatosensory evoked potential latencies, etiologies other than anemia should be sought if latencies are increased during intraoperative monitoring.

Influence of cholinergic circuitries in generation of high-frequency somatosensory evoked potentials

OBJECTIVE

High-frequency oscillations (HFOs) evoked by upper limb stimulation reflect highly synchronised spikes generated in the somatosensory human system. Since acetylcholine produces differential modulation in subgroups of neurons, we would determine whether cholinergic drive influences HFOs.

METHODS

We recorded somatosensory evoked potentials (SEPs) from 31 scalp electrodes in 7 healthy volunteers, before and after single administration of rivastigmine, an inhibitor of central acetylcholinesterase. Right median nerve SEPs have been analysed after digital narrow bandpass filtering (500-700 Hz). Raw data were further submitted to Brain Electrical Source analysis (BESA) to evaluate the respective contribution of lemniscal, thalamic and cortical sources. Lastly, we analysed by Fast Fourier transform spectral changes after drug administration in the 10-30 ms latency range.

RESULTS

Rivastigmine administration caused a significant increase of HFOs in the 18-28 ms latency range. Wavelets occurring before the onset latency of the conventional N20 SEP did not show any significant change. A similar increase concerned the strength of cortical dipolar sources in our BESA model. Lastly, we found a significant power increase of the frequency peak at about 600 Hz in P3-F3 traces after drug intake.

CONCLUSIONS

Our findings demonstrate that the cortical component of HFOs is significantly enhanced by cholinergic activation. Pyramidal chattering cells, which are capable to discharge high-frequency bursts, are mainly modulated by cholinergic inputs; by contrast, acetylcholine does not modify the firing rate of fast-spiking GABAergic interneurons. We thus discuss the hypothesis that cortical HFOs are mainly generated by specialised pyramidal cells.

Reversal of iron deficiency anemia-induced peripheral neuropathy by iron treatment in children with iron deficiency anemia

The effects of iron deficiency anemia (IDA) on nerve conduction and efficiency of iron therapy were investigated by peripheral nerve-electrophysiological measurements. Eighteen children (10 boys, eight girls; mean age 31 +/- 1.3 months) with IDA and 12 healthy children (six boys, six girls; mean age 29 +/- 1.3 months) were enrolled into the study. Nerve conduction velocity was measured in the median and posterior tibial nerve. After nerve conduction values were determined in the patients and controls, 6 mg/kg/24 h ferrous sulphate was given orally to the patients for 3 months and nerve conduction velocity tests were performed again. Median/motor and sensory nerve conduction velocity and tibial/motor nerve distal-amplitute values of children with IDA were lower than for the control group (p < 0.05, p < 0.01 and p < 0.001 respectively). With iron supplementation these values increased to the normal levels and even higher than control levels for some parameters. In correlation studies between whole blood parameters and nerve conduction velocity results, there was a correlation between median/sensory nerve conduction velocity values and serum iron levels. Additionally there was a correlation between some nerve conduction velocity values and age. In conclusion, the evidence from this preliminary study suggests that peripheral neuropathy may develop in children with IDA. Peripheral neuropathy symptoms in these patients may be improved by iron therapy.

Partial conduction blocks in N-hexane neuropathy

Nerve conduction blocks, defined by a significant reduction in amplitude or area of the compound muscle action potential at proximal compared with distal sites of stimulation, have been described in glue-sniffers and in workers with industrial exposure at an early stage of n-hexane neuropathy. The frequency with which this focal conduction anomaly appears is described and discussed in the case of a very homogeneous group of 10 young workers diagnosed with n-hexane polyneuropathy. Partial conduction blocks occurred in only two workers and may have been related to the intensity and duration of toxic exposure.

Does fibromyalgia affect the outcomes of local steroid treatment in patients with carpal tunnel syndrome?

Carpal tunnel syndrome (CTS) and fibromyalgia (FM) are common diseases in adult women. The aim of this study was to investigate the effect of FM on the outcome of local steroid treatment in patients with CTS. Forty-eight female patients with CTS and 26 female patients with CTS who also met the 1990 American College of Rheumatology (ACR) criteria for FM were enrolled the study. All patients underwent single steroid injections into the carpal tunnel. Response to injection was measured using Boston Questionnaire (BQ) and electrophysiological tests. The BQ scores and electrophysiological findings showed significant improvement 3 months after the treatment in both groups ( P<0.001). However, less improvement in BQ symptom severity scores was observed in the FM group than the other group ( P<0.05). Bilateral CTS was also more common in the FM group ( P<0.05). The present data suggest that FM must be kept in mind in patients with CTS giving poor response to local steroid treatment.

Propofol reduces spinal motor neuron excitability in humans

IMPLICATIONS

We investigated in humans whether changes in spinal motor neuron excitability correlate with the predicted propofol concentration (Cpt) achieved by a target-controlled infusion system. Propofol suppressed F-wave persistence in a Cpt-dependent manner, indicating that propofol depresses spinal motor neuron excitability at clinically relevant concentrations.

Comparison of open carpal tunnel release and local steroid treatment outcomes in idiopathic carpal tunnel syndrome

To compare the efficacy of local steroid injection and open carpal tunnel release, a symptom and functional status questionnaire (Boston Questionnaire) and sensory and motor nerve conduction studies were performed in 90 patients with electrophysiologically proven idiopathic carpal tunnel syndrome, of whom 44 were treated surgically and 46 by two-dose steroid injection. Electrophysiologic studies and the Boston Questionnaire were applied before and at the 3rd and 6th months after treatment. Both groups showed significant improvement at first follow-up. The surgically treated group showed a significant and further improvement of symptoms and conduction values between the 3rd- and 6th-month evaluations, whereas no significant change was observed in the patient group treated by steroid injection. By the end of follow-up, 5% of the hands in the open carpal tunnel release (OCTR) group and 13% of the hands in the local steroid injection (LSIG) group showed electrophysiological worsening, and 5% of the hands in the OCTR group and 22% of the hands in the LSIG group showed symptomatic worsening. Our results show that steroid injection provides an improvement comparable with that from surgical release of the median nerve at a 3-month interval. However, this improvement is not long-lasting.