Actions of capsaicin on mouse dorsal root ganglion cells in vitro

The effects of capsaicin were investigated on different populations of dorsal root ganglion cells in the in vitro mouse spinal cord-dorsal root ganglion preparation using intracellular electrodes. Dorsal root ganglion cells were characterised by the conduction velocity of their propagated action potential evoked by electrical stimulation of the dorsal root, and by the shape of their action potential. All cells with C-fiber characteristics (conduction velocity < 0.6 m/s; broad action potential with shoulder on the descending slope) were depolarised and generated action potentials when capsaicin (100-700 nM) was added to the bathing solution for 30 s. At these concentrations the membrane potential of DRG cells with myelinated fibers (conduction velocity > 2.0 m/s) was unaffected. Concentrations of capsaicin of 1.0-5.0 microM depolarised 50% of cells with conduction velocity > 10 m/s. During the depolarization of the membrane no action potentials were generated. In 50% of the capsaicin-sensitive neurons with conduction velocity faster than 10 m/s there was an initial hyperpolarization. Electrical stimulation of the dorsal root failed to evoke action potentials during the depolarization in 38% of the DRG cells with myelinated fibers and in all C-fibers tested within 10 min of the onset of the capsaicin effect. Passive depolarization of the membrane by intrasomal current injection mimicked the conduction block in neurons with large myelinated fibers. These observations confirm that capsaicin applied directly to the dorsal root ganglion affects, in a dose-dependent manner, both myelinated and unmyelinated primary afferents with a higher potency for C-neurons. Capsaicin evoked action potentials in C-neurons but not in neurons with myelinated fibers.(ABSTRACT TRUNCATED AT 250 WORDS)     

Recovery of nerve conduction following microvascular decompression for trigeminal neuralgia

OBJECTIVE: To assess the function of trigeminal nerve before and after microvascular decompression for trigeminal neuralgia. BACKGROUND: To date there is no direct evidence that microvascular decompression of the trigeminal root restores normal conduction in the nerve. METHODS: The authors examined 10 patients with trigeminal neuralgia in whom preoperative MRI and MR angiography demonstrated neurovascular contact. During microvascular decompression, the trigeminal nerve was monitored by recording early scalp trigeminal evoked potentials immediately before, during, and after decompression. Direct recordings from the root entry zone were also performed. RESULTS: In all patients preoperative scalp evoked potentials showed impaired conduction of the trigeminal root. Microvascular decompression was associated with immediate recovery of conduction in seven patients, demonstrated by both scalp evoked potentials and direct root recordings. All 10 patients were pain free postoperatively. CONCLUSIONS: Improvement in trigeminal neuralgia following microvascular decompression is often associated with normalization of neurophysiologic data, suggesting recovery of nerve function. Rapid electrophysiologic recovery and pain relief following microvascular decompression argue that neither phenomenon is linked to remyelination. It is possible that the trigeminal evoked potentials might predict an effective microvascular decompression.     

A clinical, MRI and neurophysiological study of acute transverse myelitis

There is paucity of studies correlating the MRI and evoked potential changes in acute transverse myelitis (ATM). We studied ten patients with ATM (age range 14-57 years; 8 men, 2 women) who were subjected to clinical, MRI and neurophysiological evaluation. The latter included median and tibial somatosensory evoked potentials (SEP), motor evoked potentials (MEP) to upper and lower limbs and concentric needle EMG. The outcome was defined on the basis of three month Barthel Index score. All the patients had pronounced lower limb and three had upper limb weakness. Magnetic resonance imaging scans revealed diffuse to hypointense lesions in T1, which became hyperintense in T2 in all except one patient, who had patchy hyperintense lesions in both T1 and T2 sequences suggesting haemorrhage. The signal changes extended at least three segments above the sensory level. Tibial SEP and central motor conduction time to tibialis anterior (CMCT-TA) were abnormal in nine patients each. Median SEP was normal in all, but CMCT to abductor digiti minimi (CMCT-ADM) was abnormal in four patients. The extent of MRI signal alterations and CMCT-TA correlated with the outcome. Seven patients had a poor outcome, in them MRI changes extended 10 spinal segments or more. In these patients, MEP on lumbar stimulation was either unrecordable or of low amplitude and extensive fibrillations were present in the lower limb muscles. From this study, we conclude that in ATM, extensive MRI changes, unrecordable MEP to lower limbs especially on lumbar stimulation and evidence of denervation in leg muscles seem to predict a poor outcome.     

Electrophysiological characteristics of asymptomatic relatives of patients with type 2 spinocerebellar ataxia

INTRODUCTION: Electrophysiological studies have been shown to be useful in hereditary ataxia, but only a small number of patients have been studied, and the duration of the illness, serial studies and molecular definition have not been taken into account. OBJECTIVE: We proposed, by means of electrophysiological techniques, to characterize the functional evolutionary state of the afferent and efferent systems in asymptomatic relations of patients with type 2 spinocerebellar ataxia (SCA2). Patients and methods. A 10 year longitudinal, prospective study was made of 59 children of patients with SCA2. The sequence included four studies: 1986, 1991, 1994 and 1996, all with informed consent for the investigation. The control group consisted of 108 volunteers. The electrophysiological studies recorded were: conduction studies in peripheral nerves and multimodal evoked potentials. For statistical analysis multivariate methods were used with a confidence interval of 95% (alpha = 0.05). RESULTS: Electrophysiological alterations were observed even in the absence of clinical signs, such as reduced amplitude of sensory potentials, morphological changes and prolonged latency of the central components of somatosensory evoked potentials, and of brain stem auditory evoked potentials, whilst the visual evoked potentials remained normal. Of 79 relations studied during the 10 year investigation, 17 had clinical signs and were considered to be patients with SCA2. CONCLUSIONS: Four stages of the illness were defined: 'healthy', presymptomatic, and patients with and without nerve conduction block. These characterized the degenerative mechanisms of the afferent and efferent systems of the relations of patients with SCA2 who became ill themselves.     

Neurophysiological methods in occupational and environmental health: methodology and recent findings

Neurophysiological measurement, a promising technique for assessment of the subclinical effects of occupational and environmental factors, is rapidly progressing following development of computer technology. The methods include measurement of evoked and event-related potentials, nerve conduction velocity, distribution of nerve conduction velocities, electrocardiographic R-R interval variability, and computerized static posturography. This paper provides an overview of these methods, except for evoked and event-related potentials, which have been reviewed previously by the authors, to evaluate the effects of occupational and environmental factors on the peripheral, autonomic, and cerebellar nervous systems. The available data indicate that these methods are sensitive, reliable, and easily applied in a field study. When conducting these measurements, controlling for confounding factors such as age, sex, height, skin temperature, alcohol ingestion, and neurologic diseases is necessary.     

Comparison of etidocaine and bupivacaine + lidocaine in retrobulbar anaesthesia

Etidocaine (15 mg/ml) was compared with bupivacaine (5 mg/ml) combined with lidocaine (10 mg/ml) in retrobulbar anaesthesia. One hundred and twelve patients were randomised into two groups. Supplemental anaesthesia was needed in 41% of cases of the etidocaine group and 32% of the bupivacaine-lidocaine group. Akinesia was evaluated by the surgeon both pre- and postoperatively and was found to be good or complete in more than 95% of both groups. Recovery from the motor and sensory block was investigated three times during the first 24 postoperative hours. The motor block of the orbicular muscle disappeared earlier than that of the globe. Akinesia lasted significantly longer in the etidocaine group than in the bupivacaine-lidocaine group: after 14 h 69% vs 100%, respectively, of the eyes showed normal movements. Sensation in the cornea was also regained more rapidly in patients treated with the mixture.     

Relationship of CD4 counts to neurophysiological function in HIV-1--infected homosexual men

OBJECTIVE: To explore the relationship of immune dysfunction to neurophysiological measures of brain-stem conduction time. DESIGN: Three-year longitudinal prospective cohort study; results of time 1 analyses reported. SETTING: San Francisco (California) General Hospital, Departments of Psychiatry and Epidemiology. PATIENTS: Volunteer sample of 55 human immunodeficiency virus (HIV)-positive and 37 HIV-negative homosexual men recruited from a larger cohort of homosexual men followed up since 1983 at San Francisco General Hospital as part of an ongoing study of the natural history and course of HIV type 1 infection. INTERVENTION: None. MAIN OUTCOME MEASURES: Auditory brain-stem responses and somatosensory evoked potentials for subjects stratified separately on HIV serostatus, Centers for Disease Control and Prevention symptom groupings, and absolute CD4 counts. RESULTS: The HIV-positive subjects had an increased wave III-V interpeak latency of the right ear auditory brain-stem response compared with the HIV-negative subjects (t test, P < .05). There were no significant differences among the three Centers for Disease Control and Prevention groupings on any evoked potential measure. When HIV-positive subjects were stratified on a measure of immune functioning, ie, CD4 counts, individuals with greater immune suppression were more impaired on speed of auditory brain-stem conduction time (Mann-Whitney U test, P < .05). Furthermore, 85% of subjects impaired on this evoked potential measure had CD4 counts of less than 0.40 x 10(9)/L (400/microL), whereas only 15% of those impaired on this measure had CD4 counts of greater than 0.40 x 10(9)/L. CONCLUSIONS: Asymptomatic HIV-positive subjects who do not have evidence of immune suppression do not appear to be at greater risk for neurophysiological impairment than HIV-negative subjects. The HIV-positive individuals who are immune suppressed (even while asymptomatic) appear to have an increased likelihood of central conduction time slowing as measured by evoked potential procedures.     

Response of peripheral nerve to cyclic compression in a laboratory rat model

Repetitive cyclic loading of a nerve has been proposed as a pathogenic factor in the development of occupational compression neuropathies. Little is known about the basic response of peripheral nerve to cyclic compression. We investigated the hypothesis that cyclic compression is more detrimental to nerve function than constant compression. We measured the amplitudes and velocities of distally evoked action potentials in the presence of constant or cyclic compression of the tibial nerve in rats. Seven groups were subjected to constant or cyclic compression for 6 h by a computer controlled, hydraulically activated compression chamber. Nerves were compressed with 0 (control group), 30, 60, or 90 mm Hg of constant pressure or 0-30, 20-50, or 30-60 mm Hg of cyclic compression for approximately 20,000 compression cycles. Action potentials were recorded every 15 min. The effects of cyclic compression on nerve conduction were equivalent to the effects of constant compression at the average applied pressure. Cyclic loading itself does not appear to be an important pathogenic factor in the development of nerve conduction block.     

Cancer incidence of sulfite pulp workers in Denmark

A follow-up clinical study, peripheral motor and sensory nerve conduction velocities and central motor conduction by magnetic stimulation of the cortex were performed in 13 patients with classical Friedreich's ataxia (FA) phenotype, for a period of 9-12 years. Clinical worsening was unrelated to peripheral nerve abnormalities. The amplitude of the nerve action potentials and delayed conduction velocity remained unchanged for several years. Central motor conduction times were abnormal in all patients. Clinical conditions worsened significantly between successive examinations with significant increments in threshold and significant decrement of the amplitude of motor evoked potentials. The results are consistent with progressive pyramidal and cerebellar pathways involvement as the cause of clinical worsening in FA.     

Treatment of sudden deafness apropos of 447 cases

Tibial nerve and S1 dermatome somatosensory evoked potentials (SSEPs) were recorded before and after iohexol lumbar myelography in order to evaluate possible neurotoxic effects of this contrast medium. No significant change in SSEP latencies nor amplitudes was noted after iohexol myelography, supporting the low neurotoxic profile of this contrast agent. Results were compared to those of a control group of patients before and after lumbar puncture (LP), without injection of contrast agent. In this group also no significant change in SSEP components was found, indicating that a preceding LP does not affect this electrophysiological examination.     

Visual evoked potentials in multiple sclerosis

A study was carried out of 32 patients suffering from multiple sclerosis the diagnois of which was quite definite according to Mac Alpine's criteria and which had developed over more than two years. Comparison was made with patient suffering from optic neuritis of a different aetiology and with normal subjects. The method of investigation was dynamic electroretinoencephalography : the visual evoked potentials were investigated after stimulation by white and coloured light before and after adapatation to darkness. The specificity of the results was tested by, firstly, electro-retinogram recording for control of the visual system, and secondly, by the recording of auditory evoked potentials for control cerebral function. Abnormalities in visual evoked potentials were found in 77 percent of the cases. In particular, there was delayed latency, that is, a slowing of retino-cortical conduction. The significance of these abnormalities is discussed, by analyzing the electroclinical correlationships according to whether there was obvious or subclinical optic neuritis, and the dissemination, activity or duration of the disease. The incidence of visual evoked potential abnormalities was considerably greater than that in optic neuritis (35 percent). The links between abnormalities in nervous conduction and demyelinisation are emphasized. The role and specificity of electrophysiological investigation in diagnosis of multiple sclerosis are discussed.     

Usefulness and diagnostic value of evoked potentials in patients with neurologic diseases in postoperative intensive care

PURPOSE: To analyse the diagnostic value of evoked potentials, 176 examinations in 71 sedated, ventilated ICU-patients who could only be examined neurologically on a very limited scale, were registered. We focussed on the evoked potentials, the results having prognostic relevance and being useful in the anatomical localisation of the pathological process. The Glasgow coma scale, neuroradiological findings and the data of the outcome status after hospital or rehabilitation discharge were therefore obtained. RESULTS: We could show in distinct cases how evoked potentials could make a contribution to localise a pathogenic process. Failures in peripheral nerves, brachial plexus, myelin, brainstem and cerebrum were detected, respectively excluded. In the vast majority of cases, suspected, symptoms were very precisely predicted. This was especially evident in patients suffering from head injury, hypoxia and spinal cord injury. We found that a good outcome can be expected even with high intracranial pressures if the repeatedly registered central conduction time stays normal. CONCLUSION: We conclude that non-invasive evoked potentials do enrich the bedside diagnostic pattern in sedated intensive-care unit patients. While neuroradiological methods only allow statements on morphological changing, evoked potentials demonstrate the functional status of the peripheral and central nervous system. This method is easy to learn and the cost involved is justified both financially and from the viewpoint of personnel expenditure.     

Respiratory effects of extradural analgesia after lower abdominal surgery

Blood-gas tensions, FRC and volume of trapped gas (VTG) in the lung were measured in patients on the day before lower abdominal gynaecological surgery, and twice on the day following surgery, before and after establishing lumbar extradural block (EDB) using 0.5% bupivacaine to provide analgesia after operation. FRC and VTG were measured with the closed-circuit helium-dilution technique. Mean VTG was 175 ml before operation and 275 ml after operation. PaO2 decreased significantly after operation, and the changes in FRC and VTG that occurred were related qualitatively. EDB did not significantly alter FRC, VTG or PaO2. Individual changes in FRC could not be related to changes in VTG or PaO2. Although EDB provided effective analgesia, the variables measured did not indicate that EDB conferred an immediate respiratory advantage.     

Clinical application for gene therapy in prostate cancer

We report a patient with peripheral neuropathy caused by cisplatin for the treatment of testicular tumor. Routine studies of nerve conduction and somatosensory evoked potentials demonstrated large myelinated fiber neuropathy suggesting ganglioneuronopathy. We also performed a CO2 laser evoked potential study, and found that small myelinated fibers, which are related to pain sensation, were well preserved in this patient.     

Vecuronium dose requirement and pupillary response in a patient with olivopontocerebellar atrophy (OPCA)

BACKGROUND: Anticholinergic drugs are known to impair the motor function of the oesophagus but their effects on the oesophageal afferent pathways are unknown. AIM: To determine the effects of a peripherally-acting (trospium chloride) and a centrally-acting (biperiden) anticholinergic drug on the motility and the evoked potentials of the oesophagus. METHODS: Nine healthy volunteers were randomized to receive 1.2 mg trospium chloride (TC), 5 mg biperiden (BIP) or saline i.v. Primary peristalsis was elicited by swallowing a 5 mL water bolus and secondary peristalsis by insufflation of 20 mL air, 10 times each. Oesophageal potentials were evoked by electrical stimulation in the distal and proximal oesophagus (30 stimulations at 0.4 Hz, two runs). RESULTS: Both anticholinergic drugs reduced by a similiar amount the contraction amplitudes (TC 17 mmHg, BIP 25 mmHg, saline 67 mmHg; P < 0.01) and the rate of secondary contractions (TC 60%, BIP 70%, saline 95%; P < 0.01). In contrast, only biperiden prolonged the latencies of the evoked potentials (N1 peak, distal oesophagus: BIP 191 ms, TC 102 ms, saline 101 ms; P < 0.01; P1 peak: BIP 322 ms, TC 161 ms, saline 144 ms; P < 0.01). CONCLUSIONS: Both anticholinergic drugs depress oesophageal motility, but only the centrally-acting anticholinergic drug biperiden modifies the oesophageal evoked potentials, suggesting a central cholinergic transmission of the oesophageal afferent pathways.     

One-week test-retest reliability of spinal and cortical somatosensory evoked potentials by tibial nerve stimulation

Spinal (Th12) and cortical somatosensory evoked potentials by right and left posterior tibial nerve stimulation at the ankle were performed in 20 healthy volunteers (10 females and 10 males) aged 23-50 years. The procedure was repeated after one week to assess the reliability of the parameters and to establish upper normal variability limits. Reliability was measured by the intraclass correlation coefficient and was excellent for all absolute latencies and at least good for amplitudes and for the spinal-cortical conduction time. Upper variability limits were calculated using a method based on the within-subject mean square, which can be also applied in the case of more than two repetitions.     

A two-year trial of oleic and erucic acids ("Lorenzo's oil") as treatment for adrenomyeloneuropathy

BACKGROUND: Adrenomyeloneuropathy is an X-linked recessive disorder characterized by myelopathy, peripheral neuropathy, and cerebral demyelination, which develop in association with the accumulation of very-long-chain fatty acids. The administration of oleic and erucic acids inhibits the synthesis of very-long-chain fatty acids. Recently such dietary treatment has been widely publicized as a possible cure for this disease. METHODS: We conducted an open trial in 14 men with adrenomyeloneuropathy, 5 symptomatic heterozygous women, and 5 boys (mean age, 13 years) with preclinical adrenomyeloneuropathy. The patients ate a low-fat diet and received daily doses of glycerol trioleate oil (1.7 g per kilogram of body weight) and glycerol trierucate oil (0.3 g per kilogram). Clinical manifestations, cerebral and spinal cord magnetic resonance imaging (MRI) scans, nerve conduction, and brain-stem auditory and somatosensory evoked potentials were studied prospectively over 18 to 48 months. Plasma levels of very-long-chain fatty acids and the side effects of erucic acid were monitored monthly. RESULTS: By week 10, plasma very-long-chain fatty acid levels declined nearly to normal. Nonetheless, over a mean follow-up of 33 months none of the 14 men with adrenomyeloneuropathy improved. In nine men there was functional deterioration, coincident in four with new cerebral lesions on MRI. In a single patient there was a reduction in cerebellar demyelination, but without clinical improvement. In one of the five asymptomatic boys signs of myelopathy developed. There were no changes in the symptomatic heterozygous women. There was some improvement in peroneal-nerve conduction, but no detectable clinical improvement. Conduction to the parietal cortex (T12-P37 interpeak latency) worsened in both the symptomatic men and the boys with preclinical adrenomyeloneuropathy. There was no change in other somatosensory evoked potentials or in brain-stem auditory evoked potentials. Asymptomatic thrombocytopenia (< 100,000 cells per cubic millimeter) was noted in six patients. CONCLUSIONS: In this open trial we found no evidence of a clinically relevant benefit from dietary treatment with oleic and erucic acids ("Lorenzo's oil") in patients with adrenomyeloneuropathy.     

Sensory nerve conduction velocity: technical requirements and normal values for branches of the radial and ulnar nerves of the dog

Conduction velocities of compound action potentials of sensory axons of alteral superficial radial (LSR) and dorsal ulnar nerves (DUN) of the dog were determined by averaging potentials evoked and recorded through subcutaneous needle electrodes. Suitable locations for electrodes were identified and specificities of sites for LSR and DUN were verified by recording before and after cutting the nerves. Stimulus rates of 4/second to 20/second did not markedly affect conduction velocities. Increasing stimulus intensity in steps from threshold to 8 X threshold recruited more axons into the compound action potentials but resulted in interference from movement and muscle potentials at 4 X or 8 X threshold. Mean conduction velocities at 2 X threshold were: LSR = 61.7 +/- 0.76 SEM; DUN = 68.1 +/- 2.71 SEM.     

Computer in child psychotherapy--on the use of computer games in child guidance counseling]

The authors report a comparative study of peripheral nerve conductions and nerve biopsy and somatosensory evoked potentials between 15 patients with Friedreich's ataxia and 15 patients with Friedreich's ataxia phenotype with selective vitamin E deficiency. The patients in the two groups are of similar age, age of onset, and clinical phenotype. Peripheral motor nerve action potential amplitude, and conduction velocities are within normal ranges in the two groups. In the Friedreich's ataxia group there is an early and severe peripheral sensory axonal neuronopathy, characterised by an important reduction of the amplitude of sensory action potential, and important loss of myelinated fibres with complete disappearance of large myelinated fibres without any regenerative process. In the Friedreich's ataxia phenotype with selective vitamin E deficiency group there is slight-to-moderate axonal sensory neuropathy with normal to moderate decrease of large myelinated fibre density and important regeneration in nerve biopsy. Somatosensory evoked potentials are markedly involved in the two groups asserting a severe involvement of somatosensory pathway in lumbar, thoracic and cervical spinal cord. These findings suggest that the pathological mechanism involved in the two diseases are different: central peripheral axonopathy in Friedreich's ataxia and central distal axonopathy in Friedreich's ataxia phenotype with selective vitamin E deficiency.     

An electrophysiological and histological study on the neurotoxicity of lidocaine in excised rabbit cervical vagus nerve

We studied the neurotoxic effect of lidocaine at different concentrations on the desheathed rabbit vagus nerve by measuring the amplitudes of evoked compound action potentials and the histological changes of the nerve by means of the electron microscopy after incubation in lidocaine-Ringer's bicarbonate (RB) solution. The following results were obtained. 1) Minimum concentrations of lidocaine for producing complete conduction block (minimum blocking concentration, MBC) were 0.02% for A beta and A delta fibers, and 0.03% for C fibers. 2) Irreversible conduction blocks of compound action potentials were observed in relation with lidocaine concentrations and the duration of incubation: e.g. 0.5% for 2 hours incubation was equivalent to the block with 1% for 1 hour. 3) Degenerative change of axons was revealed morphologically in the preparations exposed to 2% or a higher concentration of lidocaine. 4) Risk ratio, which means a numerical value calculated as clinical concentration/irreversible concentration with 2 hr exposure, was similar to other local anesthetics except dibucaine HCl, which shows an higher risk ratio. However, it should be noted that lidocaine has an risk of producing irreversible changes in nerve fibers, when applied to the nervous tissue at higher concentrations for longer durations.