The Relaxometer: a complete and comprehensive computer-controlled neuromuscular transmission measurement system developed for clinical research on muscle relaxants

The Relaxometer is a computer-controlled system developed for reliable clinical experimental measurements on neuromuscular block. This system is based on an adapted personal computer (Atari 1040 ST) with a monochrome monitor (Atari SM 124), and a microcomputer-driven slave unit (stimulator). There are several stimulation patterns available: single twitch at 0.1 and 1 Hz, single train-of-four, continuous train-of-four every 12 seconds, and tetanic stimulation at 50 Hz for 5 seconds followed by posttetanic count. The system is equipped with a temperature module for continuous monitoring of the skin/muscle temperature and a rechargeable battery to allow uninterrupted measurements if the apparatus is disconnected from the line power. All acquired data, computer-calculated parameters (onset time, duration time, recovery index, train-of-four ratio, tetanic fade, and posttetanic count), and the mechanomyogram are presented on screen continuously, are stored on floppy disk, and can be printed in a well-organized format.

Total intravenous anesthesia for improvement of intraoperative monitoring of somatosensory evoked potentials during aneurysm surgery

Two anesthetic regimens for monitoring somatosensory evoked potentials (SEPs) during intracranial aneurysm surgery were compared. Eighty-four sequential cases of intracranial aneurysms were operated on employing SEP monitoring. The first group of 22 cases was anesthetized with "balanced anesthesia" and the second group of 62 cases received total intravenous anesthesia (TIVA) consisting of propofol and alfentanil. In the TIVA group, the amplitude of early cortical SEP responses (N20-P25, or P40-N50) was significantly higher than that of responses in the balanced anesthesia group. In median nerve SEPs, the averaged amplitude of N20-P25 was 3.22 microV with TIVA and 1.69 microV with balanced anesthesia (P = 0.006). Similarly, posterior tibial nerve SEPs showed a P40-N50 response of 1.85 microV and 1.00 microV, respectively (P = 0.017). The superior signal-to-noise ratio obtained with TIVA allowed more frequent and reliable intraoperative SEP recordings than was possible with balanced anesthesia, resulting in rapid and reliable feedback for the surgeon. In 19% of median nerve SEPs recorded with TIVA, the cortical responses were over 5 microV in amplitude, so that reproducible N20-P25 responses were obtainable by averaging only 10 to 50 serial responses, that is, two to three recordings per minute. The higher amplitude of posterior tibial nerve SEPs recorded with TIVA made monitoring during surgery for anterior communicating artery aneurysms possible in all cases. This was not always the case with balanced anesthesia. The late deflection of median nerve SEPs (N30) was more frequently observed with TIVA.(ABSTRACT TRUNCATED AT 250 WORDS)

Deblocking effect of TRH-T in three cases of chronic progressive multifocal neuropathy

Three cases of acquired demyelinating multifocal neuropathy with persistent conduction blocks are reported. In one of them protyreline tartrate (TRH-T) had an evident deblocking effect; similar but milder effects were seen in the other two cases. The course and consistency of this effect is analyzed on the grounds of clinical and electromyographic findings. The nature of the THR-T responsive conduction block is analysed as a mild variant of CIDP with regard to its occurrence in a late and chronic phase without signs of active immune processes.

Cement burn of the sciatic nerve

We present the case of a 63-year-old woman who sustained an acrylic cement burn of the sciatic nerve at hip replacement. She was treated by resection of the damaged segment and grafting. Electron microscopy showed that the nerve was nearly normal 1 cm from the cement margin indicating that this is a safe level for resection.

Chemically-induced chronic nerve compression in rabbits--a new experimental model for the carpal tunnel syndrome

In order to create an experimental model for the carpal tunnel syndrome without the use of the commonly applied foreign bodies (silicone or rubber tubes, tourniquets etc.), the present study tried to induce a chemically provoked compression of the median nerve in rabbits. In 9 female rabbits 1 ml of Aethoxskerol 3% (Hydrox-polyethoxy dodecan) was instilled into the carpal tunnel around the median nerve after visualisation of the nerve. The other foreleg served as the control and was treated with the same amount of saline solution. Electroneurophysiologic parameters were registered preoperatively, 1 month and 6 months post surgery and histomorphologic investigations by light and electron microscopy were performed after 6 months. 6 months after treatment with Aethoxysklerol, a statistically significant lengthening of the distal latency period as well as a significant reduction of the compound potential amplitude could be observed. In accordance with these findings, morphological investigation revealed the presence of extensive granulation tissue around the median nerve together with signs of demyelination. Our results indicate that we were able to produce the development of extensive granulation tissue in the carpal tunnel of rabbits with subsequent compression of the median nerve which was confirmed by histomorphologic investigation as well as by measurement of nerve conductive velocity.

Axillary plexus block using a peripheral nerve stimulator: single or multiple injections

This prospective, randomized, double-blind study was undertaken to evaluate the success rates of axillary brachial plexus block performed with the help of a peripheral nerve stimulator when either one, two or four of the major nerves of the brachial plexus were located. Seventy-five patients undergoing upper limb surgery were randomly allocated to one of the following five groups according to the nerve and number of nerves to be located; G-1: musculo-cutaneous, radial, median and ulnar nerves; G-2: musculo-cutaneous plus one of the other three nerves; G-3: radial nerve; G-4: median nerve; G-5: ulnar nerve. The sensory block was evaluated before surgery and cutaneous anaesthesia was considered to be present when the needles of a Wartenberg Pinwheel were no longer felt in all the dermatomes of the nerves implicated in the surgical site. Otherwise, the block was considered to need completion before surgery. Only one out of the 15 patients in G-1 and G-2 needed completion of their block before surgery whereas seven out of 15 for G-3 and eight out of 15 for G-4 and G-5 needed completion of their block (P less than 0.01). We conclude that when performing an axillary block with the help of a peripheral nerve stimulator, stimulation of the musculo-cutaneous nerve and one other nerve or stimulation of all four major nerves of the brachial plexus gives a higher success rate than stimulation of only one nerve, whether the stimulated nerve is the median, radial or ulnar.

Systemic lidocaine and human somatosensory-evoked potentials during sufentanil-isoflurane anaesthesia

The effect of systemically administered lidocaine on somatosensory evoked potentials (SSEPs) during general anaesthesia has not been widely reported. Knowledge of the influence of anaesthetic agents on evoked potentials assists in interpreting evoked potential waveforms. Accordingly, we studied the behaviour of cortical and subcortical (recorded at the second cervical vertebra) SSEPs after administration of intravenous lidocaine (3 mg.kg-1 bolus followed by infusion at 4 mg.kg-1.hr-1) during a sufentanil-based anaesthetic regimen in 16 patients undergoing abdominal or orthopaedic surgery. When compared to awake baseline recordings, the sufentanil-nitrous oxide, low-dose isoflurane anaesthetic depressed N1 amplitude by approximately 40% and prolonged latency by 10%. Fifteen minutes after establishment of this anaesthetic, the amplitude and latency of N1 were 1.13 +/- 0.56 microV and 19.81 +/- 1.63 msec, respectively. Within five minutes of adding lidocaine, amplitude decreased further to 0.84 +/- 0.39 microV (P = 0.001), while latency was extended to 20.44 +/- 1.48 msec (P = 0.01). Lidocaine did not affect cervical amplitude and prolonged latency only minimally. Despite the observed effects on amplitude and latency, SSEP waveforms were preserved and interpretable. Plasma lidocaine levels obtained at 5, 20, and 40 minutes after lidocaine were 5.17 +/- 1.33, 3.76 +/- 1.14, and 3.66 +/- 0.9 micrograms.dl-1, respectively. Our results indicate that systemically administered lidocaine at therapeutic plasma levels acts synergistically with a sufentanil-based anaesthetic to depress the amplitude and prolong the latency of SSEPs.

Electrophysiological and pharmacological studies of somatosensory reflex myoclonus

Reflex myoclonus displays symptomatological heterogeneity involving the cortical and brain stem types that seem to originate above the spinal cord. Three cases of generalized myoclonus proved to be spontaneous and stimulus-sensitive, and increased with action. Segmental spinal myoclonus was spontaneous, stimulus-sensitive and rhythmical and decreased with action. Two cases of post-anoxic myoclonus seemed to be of the reticular reflex in which myoclonus was manifested in all muscles, particularly the proximal ones, and for which the EEG showed no spikes preceding myoclonus. The evoked electromyogram showed a long-loop reflex (LLR) of high amplitude, with no giant somatosensory evoked potential (SEP). Pharmacological examinations showed that the thyrotropin-releasing hormone (TRH) enhanced the onset of myoclonus, shortened the latency of the LLR and increased its amplitude, but caused no remarkable changes in SEP. These results indicate that TRH stimulates the medullary reticular neuron, thereby enhancing reticular reflex myoclonus. The myoclonus of a 3rd case was believed to be cortical reflex myoclonus on the basis of the emergence of giant SEP, increased LLR and the onset of spikes in the EEGs preceding myoclonic jerks, as ascertained by jerk-locked averaging analysis with muscular discharge. Pharmacologically, LLR, SEP and myoclonus showed no definite changes in response to TRH. Segmental myoclonus which seemed to have a spinal origin, showed no giant SEP, enhanced LLR or cortical spikes in the electrophysiological studies. No definite clinical or electrophysiological changes in response to TRH were observed. We believe the TRH administration test may be useful in the differential diagnosis of stimulus-sensitive myoclonus. In addition, the origins and nature of these types of reflex myoclonus are discussed.

Auditory event-related potential (P300) in relation to peripheral nerve conduction in workers exposed to lead, zinc, and copper: effects of lead on cognitive function and central nervous system

By measuring auditory event-related potential (P300 and N100) and peripheral nerve conduction velocities, the subclinical effects of lead, zinc, and copper on the central and peripheral nervous system were examined in 22 male gun metal foundry workers exposed to these metals. Their blood lead (BPb) concentrations ranged from 12 to 59 micrograms/dl (median 30). Control subjects were 14 healthy workers, employed at the same factory, who had never been occupationally exposed to these metals. In the gun metal foundry workers, the latencies of P300 and N100 were significantly prolonged; the latency of P300 was significantly correlated with BPb concentrations and other indicators of lead absorption. Similarly, the maximal motor and sensory conduction velocities in the radial and median nerves were significantly slowed, and were significantly correlated with indicators of lead absorption. The data suggest that lead exposure at low levels affects cognitive and central auditory nervous system function together with peripheral nerve conduction.

Effects of alcohol on myoclonus and somatosensory evoked potentials in dyssynergia cerebellaris myoclonica

Three brothers with dyssynergia cerebellaris myoclonica received alcohol to study the correlation between improvement of myoclonus and alteration in somatosensory evoked potentials (SEPs). Alcohol considerably improved myoclonus for about six hours in two patients (cases 1 and 2) but had only a mild effect in one (case 3). All three patients had giant cortical SEPs. The amplitudes of median N20-P25 and P25-N35 components and tibial N30-P40 and P40-N50 components were considerably decreased after alcohol ingestion in two patients (cases 1 and 2) but unchanged or slightly decreased in one (case 3). The peak latencies of those components were not affected by alcohol. There was thus a good correlation between the suppression of myoclonus and the decrease in giant SEP amplitude.

[Neural conduction in workers after long-term exposure to mercury vapors]

36 workers exposed to mercury vapour intoxication were examined to estimate the abnormalities in peripheral nervous system. 18 workers showed on physical examination features of polyneuropathy and in this group 15 workers had on emg examination sensory polyneuropathy. Statistical analysis was performed to show correlations between polyneuropathy on emg and age, time of exposure to mercury vapour and urinary mercury level. No such correlations were demonstrated.

[Experiences with continuous nerve block of the wrist]

Continuous nerve blocks are effective analgesics for physiotherapy following operative procedures on gliding tissues. In the upper extremity, continuous axillary blocks are regularly used, leading to weak muscular action and even paralysis, although active muscle action is wanted. With continuous wrist blocks, extrinsic motor function of the hand remains undisturbed. Placement of a polyethylene catheter near the nerves with instillation of a local anesthetic (carbostesine 0.5, 3-4 ml per nerve) provides complete anesthesia of the hand without loss of extrinsic motor function. After 124 nerve blocks in 60 patients, no complications (infections, nerve irritations or lesions) have been observed. Continuous wrist blocks are indicated for postoperative treatment after tenolysis, joint mobilisation or arthrolysis, open reduction and internal fixation and in certain cases of chronic pain care.

Effect of aldose reductase inhibition on resistance to ischemic conduction block in diabetic subjects

OBJECTIVE

To study the effect of aldose reductase inhibition with ponalrestat on resistance to ischemic conduction block (RICB) in diabetic subjects.

RESEARCH DESIGN AND METHODS

Twenty-one healthy diabetic subjects without neuropathy were studied. Subjects were randomized to take either a double-blind trial of 600 mg ponalrestat or placebo once daily for 6 wk. The median nerve action potential (MNAP) and conduction velocity (NCV), before and after 20 min of forearm ischemia, were measured at the start and finish of the study.

RESULTS

RICB (MNAP remaining after ischemia) decreased from 39.5 to 29.4% in the ponalrestat-treated group (P less than 0.05) and increased from 48.1 +/- 10.2 to 49.5 +/- 6.5% in the placebo-treated group. MNAP and NCV were unchanged in both groups.

CONCLUSIONS

Aldose reductase inhibition with ponalrestat partly reverses RICB in diabetes, perhaps by improving nerve hypoxia or reducing nerve energy substrates.

[Effects of intravenous lidocaine administration on median nerve somatosensory evoked potentials]

The effect of lidocaine on the median nerve somatosensory evoked potential (SSEP) was investigated in 14 neurologically normal patients. Lidocaine 1.5 mg.kg-1.min-1 was injected intravenously over a 5 min period immediately followed by a continuous infusion of lidocaine 60 micrograms.kg-1.min-1. The peak latencies (N1, P2, N2) and amplitudes (N1-P2, P2-N2) of the SSEP response over the sensory cortex were recorded before and after lidocaine infusion. The peak latencies in the control group and in the experimental group after lidocaine infusion of N1, P1, N2 were 19.4 +/- 1.0 msec, 19.7 +/- 1.0 msec (N1), 24.6 +/- 1.4 msec, 25.0 +/- 1.5 msec (P2), 32.5 +/- 2.5 msec, and 33.3 +/- 2.8 msec (N2), respectively. The amplitudes in the control group and in the experimental group after lidocaine infusion of N1-P2, P2-N2 were 9.0 +/- 4.3 microV, 10.3 +/- 4.7 microV (N1-P2), 7.2 +/- 3.6 microV, 8.6 +/- 3.9 microV (P2-N2), respectively. Peak latencies of all components (N1, P2, N2) increased after lidocaine infusion compared with control values. Amplitude of N1-P2 and P2-N2 increased significantly following lidocaine infusion compared with control values. The data obtained in this study suggested that the changes in peak latencies and amplitude after epidural anesthesia with lidocaine were due to the systemic effect of lidocaine absorbed intravenously from the epidural space.

Changes of nerve excitability and urinary deltamethrin in sprayers

The nerve excitability of median nerve as well as the urinary deltamethrin and its metabolite dibromovinyl-dimethyl-cyclopropane carboxylic acid (Br2A) were detected in 24 deltamethrin sprayers in an assessment of the exposure and effect of deltamethrin. Twenty-nine male, unexposed referents of the same age range were also selected. The urinary deltamethrin and its metabolite Br2A were detectable by GC and HPLC in the sprayers after exposure. The nerve excitability detected with an electromyograph and pairs of stimuli at variable intervals showed that there was a prolongation of supernormal period in median nerve of the exposed group after a 3-d spraying compared with that before spraying which became more significant 2 d after cessation of exposure. In the mean time, no change of supernormal period in the median nerve of reference group was found at the 3-d interval. Nearly half of the sprayers had a supernormal period prolonged by more than 4 ms after spraying, whereas nearly none of the reference group showed similar changes after repeated examinations. Although there was neither correlation between the nerve excitability changes and the urinary deltamethrin or Br2A excretion, nor was a case of acute deltamethrin poisoning diagnosed, the non invasive technique used for nerve excitability detection in this study seems to be valuable in studying deltamethrin toxicity on human.

[Effects of lumbar or thoracic epidural anesthesia on median nerve somatosensory evoked potentials]

Somatosensory evoked potentials (SSEP) are used increasingly to monitor the integrity of neural pathways in anesthetized patients. To evaluate the influence of epidural anesthesia on the central nervous system, we studied the effects of lumbar or thoracic epidural anesthesia with lidocaine on the median nerve SSEP in 9 patients. The peak latencies (N1, P2, N2) and amplitudes (N1-P2, P2-N2) of the SSEP response over the sensory cortex were recorded before and 15 min after epidural anesthesia. The peak latencies of control and post epidural anesthesia of N1, P1, N2 were 19.2 +/- 1.7 msec, 19.6 +/- 1.6 msec (N1), 24.7 +/- 2.3 msec, 25.7 +/- 2.0 msec (P2), 32.8 +/- 2.8 msec and 34.6 +/- 2.5 msec (N2), respectively. The amplitude of control and post epidural anesthesia of N1-P2, P2-N2 were 4.5 +/- 2.9 microV, 5.9 +/- 6.6 microV (N1-P2), 4.4 +/- 3.2 microV and 5.6 +/- 5.2 microV (P2-N2), respectively. Peak latencies of all components (L1, P2, N2) increased after epidural anesthesia compared with control values. Amplitude of N1-P2 increased significantly following epidural anesthesia compared with control values. The data obtained in this study were contrary to the previous concept that anesthetic agents generally increase the latency of SSEP and decrease their amplitude.

Attenuation of the early anterior negativity of median nerve somatosensory evoked potential in the MPTP-treated monkey

Median nerve somatosensory evoked potentials (SEP) were recorded in 7 Cynomolgus monkeys, before and after the administration of N-Methyl 1,4 Phenyl 1,2,3,6 tetrahydropiridine (MPTP), a neurotoxin which induces a parkinsonian syndrome in primates. Following MPTP administration, the amplitude of the negative component recorded at 15 ms over the frontal derivations (N15) decreased by 70% or more. This amplitude reduction was not modified by administration of dopamine precursors. These findings shed light on recent findings in human parkinsonian patients.

An automated technique for measuring the recovery cycle of human nerves

Action potentials conducted along a nerve fiber leave in their wake consistent alterations in excitability, including the absolute and relative refractory periods, a supernormal period (SNP) and a late phase of subnormality. We describe an automated technique for reliably determining the recovery cycle of human sensory nerve fibers by delivering series of paired stimuli and precisely measuring the latencies (to within 0.5 microseconds) of the compound action potentials. The recovery cycle can be compiled from the differences in latency between the two responses of a pair. Consistent changes in conduction velocity are demonstrated during each phase of altered excitability. Possible physiological mechanisms underlying the recovery cycle are discussed, and the effects of cold, ischemia, prior tetanization and subcutaneous lidocaine are presented. This technique may prove to be a useful and more sensitive tool for the study of certain disorders of peripheral nerves.

Pancuronium improves the neuromuscular transmission defect of human organophosphate intoxication

Two patients with acute severe organophosphate intoxication showed (1) single evoked compound muscle action potentials (CMAP) with repetitive discharges and (2) prominent decremental responses of CMAP with 20 and 50 Hz supramaximal nerve stimulation. Following the intravenous injection of single small doses of pancuronium, marked improvement in these abnormalities occurred and persisted for several hours. We postulate that the physiologic improvement following low-dose pancuronium results from blockade of acetylcholine receptors, especially those located on the terminal axon responsible for antidromic backfiring.

Anesthetic induction with thiopental: its effect on scalp topography of median nerve somatosensory evoked potentials

The effects on median nerve somatosensory evoked potentials (SEPs) of analgesic doses of fentanyl, meperidine or morphine and of sodium thiopental (STP) anesthesia (4 mg/kg) were tested in 36 surgical patients. We also explored changes in SEP components as a function of their scalp location. Before and after medication, responses were recorded from the scalp overlying the parietal cortex (ipsi- and contralateral to the stimulated arm) and the precentral (contralateral) cortex. None of the three opiates affected SEP latencies or amplitudes. The barbiturate increased the amplitudes of subcortical and early cortical components (N18, N20, P22, P25), whose latencies, however, were not significantly modified. The effect of STP on later SEP cortical components depended on their scalp topography: parietal N33 and P45 underwent significant changes in both latency and amplitude, whereas precentral N30 showed a significant amplitude increase only. Thiopental anesthesia produces clearer short-latency SEP recordings, from both parietal (components N20-P25) and precentral (P22, N30) areas.

Pregnancy increases median nerve susceptibility to lidocaine

To determine whether pregnancy renders women more sensitive to local anesthetics, nine nonpregnant and nine pregnant (third trimester) women underwent median nerve block at the wrist using 1% lidocaine HCl. Inhibition of median nerve A alpha sensory and motor fibers was assessed using measurements of sensory nerve action potential (SNAP) amplitude and compound motor action potential (CMAP) amplitude, respectively. Inhibition of median nerve C fibers was assessed by the increase in skin temperature and by the decrease in median (relative to ulnar) galvanic skin potential (GSP) amplitude. Lidocaine inhibited SNAP to a greater extent in pregnant than nonpregnant women at all time points (P = 0.019). CMAP declined differently in the pregnant and nonpregnant groups (P = 0.01): the pregnant subjects achieved steady state inhibition before the nonpregnant subjects. The two groups developed comparable steady state inhibition. Skin temperature was higher in pregnant women at all time points (P less than 0.0001); moreover, the increased skin temperature of pregnant women differed from that of the nonpregnant women (P = 0.037), reflecting a more rapid temperature increase in the pregnant women. GSP amplitude declined to 50% of control more rapidly in pregnant (mean = 4 min) than nonpregnant women (mean = 11.5 min), but these differences did not achieve statistical significance. It is concluded that pregnancy increases median nerve susceptibility to lidocaine.

Effects of midazolam on median nerve somatosensory evoked potentials

We have studied the effect of i.v. midazolam on median nerve somatosensory evoked potentials (SSEP) in 10 unpremedicated adults. Anaesthesia was induced with midazolam by bolus administration (0.2 mg kg-1) followed by infusion (5 mg h-1). The latency and amplitudes of the SSEP responses over the second cervical vertebrae (SC2) and sensory cortex (P17, N20, P25) were recorded before and for 10 min after induction. Data were analysed over that period for time-related alterations. Small but statistically significant increases in latency of the cortical N20 (P less than 0.005) and P25 (P less than 0.001) waves and interwave conduction times of SC2 to P25 (P less than 0.005) and N20 to P25 (P less than 0.021) were observed. Cortical amplitude (N20-P25) decreased significantly (P less than 0.012), to approximately 60% of baseline. These results demonstrated that midazolam produced a depression of cortical SSEP amplitude without clinically significant alterations in latency.

Cooling potentiates lidocaine inhibition of median nerve sensory fibers

To determine the effect of cooling on lidocaine potency, nine consenting volunteers underwent bilateral median nerve blocks using 1% lidocaine HCl solution. Room-temperature and ice-cold lidocaine were injected into either dominant or nondominant wrists. Subjects were blinded to the temperature of the anesthetic. Inhibition of A alpha sensory and motor fibers was assessed as the decline in sensory nerve action potentials and compound motor action potentials, respectively. Inhibition of C fibers was measured as an increase in skin temperature and a decline in galvanic skin potentials. All indices of nerve function demonstrated profound (P less than 0.001) time-related changes after injection of local anesthetic. When ice-cold lidocaine was injected, inhibition of sensory nerve action potentials was significantly greater at all time points (P = 0.001) than when room-temperature lidocaine was injected. Inhibition of C fibers as assessed by galvanic skin potentials was marginally faster (P = 0.07) when ice-cold lidocaine was used compared with room-temperature lidocaine. No differences between room-temperature and ice-cold lidocaine were observed in inhibition of compound motor action potentials, or in the increase in skin temperature. We conclude that inhibition of median sensory fibers may be increased by cooling 1% lidocaine HCl in an ice bath before injection.

Prospective study of nerve conduction parameters and serum magnesium following cisplatin therapy

This study evaluated the effects of cisplatin on 18 nerve conduction parameters of median, ulnar, peroneal, and sural nerves in relation to age, magnesium nadir, average magnesium, and magnesium replacement in gynecologic oncology patients. The 37 patients in this study received cisplatin (70 mg/m2) at 4-week intervals either as a single agent (17 patients) or in combination with doxorubicin and cyclophosphamide (20 patients) following inpatient hydration. The patients were placed randomly on either magnesium supplementation (intravenous plus oral) or placebo. For all patients, nerve conduction studies were performed before and after cisplatin therapy in the same EMG laboratory. Statistical analysis revealed that postcisplatin nerve conduction parameters were significantly predictable based upon pretherapy nerve conduction parameters, magnesium supplementation, total cisplatin, age, magnesium nadir, and average magnesium. Total cisplatin, age, and serum magnesium level were significant predictors in 8, 2, and 2 of the 18 nerve conduction parameters, respectively. Following cisplatin therapy, there was a significant decrease in sensory nerve action potential amplitude of median, ulnar, and sural nerves, whereas sensory latency of median and ulnar nerves was significantly increased. Cisplatin therapy had no effect on motor nerve conduction parameters of median, ulnar, and peroneal nerves. Factors responsible for the decrease in sural sensory action potential amplitude were not identified. Sensory nerve action potential amplitude and sensory latency of ulnar nerve are the two best objective parameters that can be utilized to monitor patients for adverse nerve conduction side effects of cisplatin.

Peripheral nerve functions in chronic alcoholic patients on disulfiram: a six month follow up

The peripheral nerve functions of chronic alcoholic patients were studied clinically and electrophysiologically before they were placed on disulfiram (Antabuse). The evaluations were repeated while they were treated with 250 mg (n = 33) and 125 mg (n = 9) of disulfiram for one, three and six months. The data were compared with that of 24 untreated chronic alcoholic patients. None of the patients developed overt symptoms of peripheral neuropathy during the period of study. The patients on 250 mg disulfiram showed a significant decline in several components of the peripheral nerve functions, but no significant electrophysiological abnormalities were noted in patients taking 125 mg of disulfiram. Interestingly, the control group showed a significant electrophysiological improvement during the same period of observation.

Carbaryl poisoning and edrophonium: electrophysiologic changes

A case of poisoning with the insecticide carbaryl, a cholinesterase inhibitor, was studied using repetitive stimulation and edrophonium administration. Without edrophonium, repetitive stimulation studies were normal. After 5mg of edrophonium was administered intravenously, a 40% decrement was recorded using 3Hz stimulation and an 80% decrement was seen with 30Hz stimulation. It is concluded that edrophonium is useful in testing for poisoning with cholinesterase inhibitors when other electrophysiologic studies are normal. These changes are most likely due to a recently described fast desensitization of the acetylcholine (ACh) receptor induced by high ACh concentrations.

Nerve conduction velocity in patients under long term treatment with antiepileptic drugs

Motor and sensory nerve conduction velocity (NCV) of median nerve and motor NCV of peroneal nerve were measured in 548 epileptic patients, aged 20 to 40 years, under long term treatment with antiepileptic drugs. Compared with a control collective of 70 healthy persons in the same age the epileptics showed a reduction of all NCVs. 19 percent of the epileptic collective had at least 1 diminished NCV. Negative correlations with total amount and average daily dose of antiepileptic drugs were found in both sexes for sensory NCV of median nerve and motor NCV of peroneal nerve, only in males also for motor NCV of median nerve. Only in females, duration of therapy correlated negative with sensory NCV of median and motor NCV of peroneal nerve. In patients under monotherapy the group with carbamazepine treatment showed the lowest NCV values, the difference being significant for motor NCV of median nerve in comparison to phenytoin and valproate sodium. It is concluded, that NCV generally is lowered under long term treatment with antiepileptic drugs and that phenytoin has no specific influence compared with the other drugs.

Intraneural steroid injection as a complication in the management of carpal tunnel syndrome. A report of three cases

Steroid injection can provide symptomatic relief in patients with carpal tunnel syndrome (CTS). Its role should be limited to a diagnostic aid in cases in which symptoms are atypical, a temporizing agent in patients with severe symptoms either who are awaiting surgery or in whom spontaneous remission might be expected, and as a definitive treatment in patients who do not desire surgery. Injection should be performed using proper technique by physicians skilled in carpal tunnel surgery. A soluble preparation of dexamethasone is recommended. Immediate paresthesia in the median nerve distribution or exacerbation of symptoms beyond 48 hours following injection is suspect for inadvertent nerve injury; therefore, early surgical decompression is indicated.

The effect of ketamine on human somatosensory evoked potentials and its modification by nitrous oxide

The effect of ketamine alone and in combination with N2O (70% inspired) on median nerve somatosensory evoked potentials (SSEPs) was investigated in 16 neurologically normal patients undergoing elective abdominopelvic procedures. The anesthetic regimen consisted of ketamine (2 mg/kg iv bolus followed by continuous infusion at a rate of 30 micrograms.kg-1.min-1) [corrected], neuromuscular blockade (atracurium), and mechanical ventilation with 100% oxygen. SSEP recordings were obtained immediately preinduction and at 2, 5, 10, 15, 20, and 30 min postinduction. Thereafter, N2O was added with surgical incision and maintained for 15 min. At 5-min intervals, SSEP recordings were again taken during and after N2O. With minor exceptions, mean cortical and noncortical latencies as well as noncortical-evoked potential amplitude were unaffected by either ketamine or N2O. Ketamine induction increased cortical amplitude significantly with maximal increases occurring within 2-10 min. For example, at 5-min postinduction, mean N1-P1 amplitude increased from 2.58 +/- 1.05 (baseline) to 2.98 +/- 1.20 microV and P1-N2 amplitude increased from 2.12 +/- 1.50 (baseline) to 3.99 +/- 1.76 microV. Throughout the 30-min period after ketamine induction, mean P1-N2 amplitude increased generally by more (57-88%) than did mean N1-P1 amplitude (6-16%). N2O added to the background ketamine anesthetic produced a rapid and consistent reduction in both N1-P1 and P1-N2 amplitude. Thus, at 1 min after N2O, mean N1-P1 amplitude decreased from 2.74 +/- 1.11 to 1.64 +/- 0.63 microV, while P1-N2 amplitude decreased from 3.32 +/- 1.52 to 1.84 +/- 0.87 microV.(ABSTRACT TRUNCATED AT 250 WORDS)

Isoflurane for thymectomy in myasthenia gravis

The clinical and electromyographic effects of isoflurane were studied in eight myasthenic patients undergoing trans-sternal thymectomy. After inhalational induction of anaesthesia, intubating and operating conditions were good. Recovery from anaesthesia was rapid with minimal postoperative residual muscle weakness or respiratory depression. All patients were extubated within the first postoperative hour. Integrated electromyographic monitoring of the train-of-four response of adductor pollicis demonstrated that myasthenics are more sensitive than nonmyasthenics to the neuromuscular depressant effects of isoflurane. Recovery of the integrated electromyographic response was incomplete despite a satisfactory clinical recovery.

Neuromuscular recovery using calcium protease inhibition after median nerve repair in primates

Inhibition of calcium-activated neutral protease, in muscle and nerve, by the tripeptide leupeptin after median nerve transection and epineural repair in monkeys (Cebus apella) was studied. Results indicate that inhibition of the protease after nerve repair facilitates morphologic recovery in denervated thenar muscles and in distal thenar nerve branches. In addition, functional recovery was facilitated in leupeptin-treated animals after nerve repair as measured by sensory and motor conduction velocities. Toxicologic testing showed that leupeptin, administered at 18 mg/kg, intramuscularly, twice daily, for 6 months did not adversely affect hematology, clotting, or plasma complement component C3 profiles. These data indicate that leupeptin is an effective and safe adjunct to peripheral nerve repair.

End-plate dysfunction in acute organophosphate intoxication

Acute organophosphate intoxication resulting from suicide attempts in 14 patients produced a series of electrophysiologic abnormalities that correlated with the clinical course. Spontaneous repetitive firing of single evoked compound muscle action potentials (CMAP) was the earliest and most sensitive indicator of the acetylcholinesterase inhibition. A decrement of evoked CMAP following repetitive nerve stimulation was the most severe abnormality. At the height of the intoxication no CMAP was evoked after the first few stimuli. The decrement-increment phenomenon occurred only at milder stages of intoxication and its features are characteristic of acetylcholinesterase inhibition. These electrophysiologic features proved to be the most useful for determining initial severity and clinical course of the acute organophosphate intoxication and differentiated this syndrome from those of myasthenia gravis, Eaton-Lambert syndrome, and botulism.

[Neurotoxicity in long-term lithium therapy: an electroneurographic study]

In a series of 16 patients on long-term lithium therapy pathological changes were found in peripheral nerve conduction. Such changes correlated with the duration of lithium therapy (mean: 8.3 years, range: 3-15 years; p less than 0.05). No patient showed clinical signs of polyneuropathy or any other disease known to be frequently associated with peripheral nerve lesions. Compared with an age-matched normal control group (n = 27) the nerve conduction velocity of the sural nerve was reduced (p less than 0.05), for which a chronic neurotoxic effect is considered to be the most probable mechanism.

Effects of thiopentone and etomidate on median nerve somatosensory evoked responses

Somatosensory evoked potentials (SEP) after median nerve stimulation were recorded in 40 patients during infusion of either 15 mg/kg bw thiopentone or 1 mg/kg bw etomidate (n = 10) within 15 min and after 0.3 mg/kg bw etomidate (n = 20). Marked alterations of SEP waveforms and changes in latencies were observed in all patients. Central conduction time (CCT) was significantly correlated to plasma thiopentone concentration. Infusion of high doses of thiopentone and etomidate was followed by a complete loss of middle and long latency components. Amplitude of the primary cortical SEP N20 was found to be unchanged after thiopentone and to be increased after etomidate, indicating the synchronizing properties of this drug. A pronounced increase in SEP latencies and CCT and waveform alterations have to be considered during hypnotic drug administration in intensive care medicine and intraoperatively.

[The decrement-increment phenomenon in disorders of neuromuscular transmission by inhibition of acetylcholinesterase]

Repetitive stimulation of the median nerve elicited a so far unknown course of the muscle action potentials in four patients with organophosphate intoxications. The amplitude of the initial muscle action potential decreased with the second stimulus and gradually increased to normal values by subsequent stimuli. With the second stimulus a loss of the repetitive muscle action potentials occurred. The Decrement-increment phenomenon was seen in early and/or late stages of severe intoxications when fasciculations were prominent. We suppose that the repetitive muscle action potential following the first stimulus results from backfiring. The second orthodromic nerve action potential collides with this antidromic activity leading to a partial extinction. Loss of backfiring with the second stimulus abolishes the phenomenon of collision and enables a recovery of the muscle action potential amplitudes.

Effect of ingestion of smokeless tobacco on motor distal latency of the median nerve

Subjects were 17 men between the ages of 18 and 32 yr. and regular users of smokeless tobacco. Each subject received three treatments consisting of one pouch of Skoal Bandits, one pinch of their regular brand, and a nonnicotine piece of chewing gum. The nervous transmission at the neuromuscular junction in the right thumb was compared before treatment and once every minute for 15 min. after treatment. Repeated-measures analysis of variance indicated a significant increase in the distal latencies for both the brand-name grouping and in the regularly used brand. No such difference was found in a control group when compared to the pretest results. It was concluded that smokeless tobacco ingestion resulted in a delay in the nervous transmission across the neuromuscular junction. This delay was hypothesized to be caused by the enduring binding action of nicotine to the acetylcholine receptor sites, thereby blocking the impulse in some of the faster conducting nerve fibers.

[Effect of isoflurane and enflurane on somatosensory evoked potentials following stimulation of the median nerve]

The effects of enflurane and isoflurane on somatosensory evoked potentials (SEP) after median nerve stimulation were studied in 25 healthy adult patients. Cervical and cortical SEP were recorded simultaneously. pCO2 and tympanic membrane temperature were kept constant. Following induction of anaesthesia with thiopentone, fentanyl and succinylcholine SEP were recorded during normoventilation with 100% oxygen and after inhalation of 66.6% nitrous oxide. Isoflurane at inspired concentrations of 0.8, 1.65, 2.5, 3.3% was given to 10 patients at 15 minutes intervals and was reduced after nitrous oxide had been replaced by oxygen. 15 patients received equipotent doses of enflurane (1.1, 2.2, 3.25, 4.3%.) SEP were recorded at the end of each interval. Isoflurane and enflurane caused dose dependent increases in latency of the cortical SEP. This effect was more pronounced with enflurane. Isoflurane reduced amplitude of the primary cortical response more than enflurane, when ventilation was performed with 66.6% nitrous oxide in oxygen. High doses of enflurane in oxygen augmented cortical SEP amplitudes associated with a marked increase in latency. Isoflurance and enflurance anaesthesia slightly altered cervical SEP. Middle latency components of the cortical SEP were progressively diminished with increasing isoflurane or enflurane concentrations. The effect of both agents in terms of delayed latencies and reduced amplitudes should be considered when recordings are performed intraoperatively.

Effect of the acute administration of high dose pentobarbital on human brain stem auditory and median nerve somatosensory evoked responses

Brain stem auditory (BAERs) and median nerve somatosensory evoked responses (MnSSERs) were recorded from normal neural pathways during the induction of pentobarbital coma in six patients undergoing elective excision of complex arteriovenous malformations. Each patient received a 33-minute infusion of pentobarbital at a rate of 0.6 mg/kg (total dose, 19.8 mg/kg). This regimen resulted in burst suppression or isoelectricity of the electroencephalogram in all patients. Although statistically significant changes in latency and amplitude occurred, both BAERs and MnSSERs were readily recordable in all patients throughout the infusion. For the BAER, there were significant increases in the latencies of Waves III and V. However, these increases are sufficiently small that misinterpretation of these changes as an evolving neurological injury is unlikely, e.g., Wave V latency increased from 6.25 +/- 0.25 (SD) to 6.58 +/- 0.16 ms (P less than 0.006). For the MnSSER, changes of greater potential clinical relevance were observed. There were substantial increases in the latencies of the early components of the primary cortical response and in the central conduction time (e.g., CCT of 6.1 +/- 0.6 ms preinduction vs. 7.7 +/- 1.1 ms at t = 33 min, P less than 0.003), and the amplitude of the early cortical response (N20-P25) decreased by a mean of 45% (P less than 0.02). By contrast, subcortical components of the MnSSER (brachial plexus, upper cervical spine) were only minimally affected. We conclude that, in patients who are initially neurologically intact, BAERs and MnSSERs can be monitored effectively during pentobarbital coma and that the loss of these responses should not be ascribed to the effects of this drug alone. However, the interpretation of evoked response changes, particularly MnSSER changes, that occur during pentobarbital administration should take into account the dose-related changes in latency and amplitude that we have observed.

Enhancement of Neuromuscular Recovery after Nerve Repair in Primates

This investigation describes the use of the calcium-activated protease inhibitor, leupeptin, as an adjunctive therapy to the microsurgical repair of median nerves in a primate model. Our results indicate that leupeptin facilitates morphological recovery in denervated thenar muscles and in distal sensory and mixed motor-sensory nerve trunks and functional recovery measured by motor nerve conduction velocity. Toxicological testing of leupeptin showed that, when administered at a dose of 12mg/kg, intramuscularly, once daily, haematological and clotting profiles were not adversely affected.

Differential effects of isoflurane on human median nerve somatosensory evoked potentials

The effect of isoflurane on median nerve somatosensory evoked potentials (MN-SSEPs) was studied in 15 patients. Anesthesia was induced with thiamylal and maintained with oxygen and isoflurane. MN-SSEPs were recorded in awake patients and after achieving 0.5, 1.0, 1.5, and 2.0% stable end-tidal concentrations of isoflurane. Peak latencies and amplitudes of EP, N13, and N20 and conduction times EP-N13, N13-N20, and EP-N20 were measured. Peak latencies of all components increased after all concentrations of isoflurane compared with control values. N20 peak latencies after 1% and 1.5% isoflurane differed significantly, whereas EP and N13 latencies showed no significant difference. No significant change in conduction time EP-N13 resulted from 1% and 1.5% concentrations of isoflurane compared with control values. Isoflurane increased conduction time N13-N20 significantly when compared with control values, and this increase was dose related. Amplitude of EP and N13 did not show significant change with 1% and 1.5% isoflurane when compared with control values. Amplitude of N20 decreased significantly following isoflurane anesthesia compared with control values, and the difference between 1% and 1.5% isoflurane recordings was also statistically significant. N20 was not discernible in one out of 14 patients after 1.5% and in three out of ten patients after 2% isoflurane. These results indicate that subcortical potentials are less affected by isoflurane anesthesia than cortical potentials. Amplitude reduction of cortical potentials was more noticeable than either prolongation of peak latency or conduction time.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of high-dose fentanyl on human median nerve somatosensory-evoked responses

Median nerve somatosensory evoked responses (MnSSERs) were recorded in nine neurologically normal adult cardiac patients before and during the administration of high-dose fentanyl. MnSSERs were recorded prior to induction and at t = 20 min and t = 45 min postinduction. Fentanyl was administered as a slow bolus (53.2 +/- 9.1 micrograms X kg-1), followed by a continuous infusion at 10-20 micrograms X kg-1 X hr-1 (total dose 63.6 +/- 10.1 micrograms X kg-1). All MnSSER waveform components remained recordable and easily identifiable during anaesthesia. The effect of fentanyl was more pronounced on cortical waveform components, leaving subcortical components largely unaffected. There was a significant increase in the latency of the cortical MnSSER at t = 20 min, e.g., for the initial negative cortical wave, N1, the latency was 21.18 +/- 1.55 ms preinduction versus 22.18 +/- 1.42 ms at t = 20 min. There was also a significant decrease in the amplitude of the cortical response at t = 20 min, i.e., 2.04 +/- 1.30 microV preinduction versus 1.31 +/- 0.74 microV at t = 20 min. However, the degree of change was quite variable (range = 0-65 per cent). No further changes occurred at t = 45 min. The authors conclude that MnSSERs can be consistently and reliably monitored during high-dose fentanyl anaesthesia. However, fentanyl produces modest but significant changes in the MnSSER which should be taken into account lest they be misinterpreted as neurologic injury in evolution.

Adverse effect of verapamil in a patient with the Lambert-Eaton syndrome

A patient with the Lambert-Eaton syndrome (LES) and small cell lung cancer developed respiratory failure several hours after verapamil was given. Improvement in respiratory function did not occur when guanidine was given, but was delayed until verapamil was discontinued 3 days later. Although other factors may have contributed to the clinical deterioration of our patient, the temporal relationship to verapamil and the theoretical danger of calcium channel blockade lead us to believe that the drug should be used cautiously in LES.

Exposure to triarylphosphate and polyneuropathy: a case report

This report describes a case of polyneuropathy in a 48-year-old mechanic who was heavily exposed to hydraulic fluids containing isopropylated triphenylphosphate (ITP). A cross-sectional examination of eight other men exposed to hydraulic fluids and eight controls showed differences in EMGs but not in nerve conduction velocities or other values measured in a clinical examination. The study indicates a possible association between heavy occupational exposure to hydraulic fluids and ITP and polyneuropathy.

[Somatosensory evoked potentials (SEP) by isoflurane and enflurane in cardiosurgical interventions]

In the order to gain further insight into the sensory nervous pathways during enflurane- and isoflurane anaesthesia, two different concentrations (1 and 2 vol.%) of the anaesthetics were given to patients during extracorporeal circulation in normothermia and normocarbia, while somatosensory-evoked potentials (SEP) were recorded. As SEP-changes either reflect a change in functional integrity of the sensory nervous pathways (amplitude suppression) and a change in the speed of conduction (latency changes), the central effects of the volatile anaesthetics could be more fully evaluated. Isoflurane as well as enflurane induced a concentration-related change in latency especially of the late N100-component. However, in contrast to isoflurane administration the isomer enflurane in the high concentration range (2 vol.%) induced an increase of amplitudes of the early N20 and late N100-peak. Such an increase in amplitudes is interpreted as a disinhibition of medullary inhibitory centres, a possible premonitory sign of epileptogenic cortical activity, which already had been observed by various investigators.

The effect of high dose sodium thiopental on brain stem auditory and median nerve somatosensory evoked responses in humans

Median nerve somatosensory evoked potentials (MnSSEPs), brain stem auditory evoked responses (BAERs), and the cortical electro-encephalogram (EEG) were recorded in six patients during a 62-min infusion of sodium thiopental (STP) at a rate of 1.25 mg X kg-1 X min-1 (total dose, 77.5 mg/kg). The EEG became isoelectric after 22 +/- 8 (SD) min of STP infusion. Dose-related changes in the latencies and amplitudes of various evoked response wave forms were observed. However, in no instance was any component of either the MnSSEP or the BAER rendered unobtainable by STP administration. For the MnSSEP, progressive increases in the central conduction time (5.33 +/- 0.41 ms preinduction vs. 7.46 +/- 1.2 ms at t = 60 min) and in the latency of the cortical primary specific complex were observed simultaneously with significant reductions in the amplitude of the latter (2.10 +/- 0.85 muV preinduction vs. 0.85 +/- 0.55 muV at t = 60 min). Changes in the latency and amplitude of the response recorded over the upper cervical spine (C2) were not statistically significant in this small population. For the BAER, progressive and significant increases in the latencies of Waves I, III, V (e.g., Wave V latency: 6.16 +/- 0.24 vs. 6.87 +/- 0.31 ms) and in the I-III, III-V, and the I-V interwave latencies were observed. The amplitudes of the BAER components were not significantly altered. The authors conclude that the administration of a dose of STP in excess of twice that required to produce EEG isoelectricity can be compatible with effective monitoring of MnSSEPs and BAERs. However, STP produces dose-related changes in both evoked response wave forms, which must be considered in the interpretation of responses elicited during STP anesthesia.

The steroid treatment of hereditary motor and sensory neuropathy

A placebo or methylprednisolone (45-60 mg/M2) was administered in a crossover study as a single morning dose on alternate days to fourteen patients who had a familial progressive polyneuropathy that either began or was maximum in the distribution of the peroneal nerves. Neither the patients nor the examining physician were told whether the patient was taking a placebo or steroid but the steroid side-effects made a double-blind trial impossible. Patients were evaluated at the initiation of the study, the time of crossover, and at the conclusion of the study. Five patients with proven HMSN-I completed the study; eight patients with HMSN-I were placed on a placebo or on steroids for a six-month-period. In neither group was there any evidence of a significant increase in nerve conduction times, a decrease in terminal latencies, an increase in strength or a decrease in sensory loss when evaluated by quantitative methods. These patients were subject to a high incidence of complications from steroids possibly because of root hypertrophy, relative inactivity, and high CSF proteins. These included excessive weight gain, a compression fracture of T-12; cord compression from enlarged nerve roots; myopathy; pseudotumor; and psychiatric disturbances. Considering the lack of benefit of steroids and the high incidence of complications due to the medication further trials of adrenal-corticosteroids in patients who definitely have familial HMSN-I do not seem to be justified.