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PubMedDate not supplied

Intraoperative measurements of auditory-evoked potentials in three patients with acoustic neuroma.

Auditory brainstem responses (ABRs), electrocochleograms and the evoked potentials from the internal auditory canal were recorded simultaneously in 3 acoustic neuroma (AN) patients. The neural conduction in the internal auditory canal was examined by recording the compound action potentials of the cochlear nerve. In an AN patient with wave I only in the ABR, the neural conduction of the excitement in the cochlear nerve was blocked within the internal auditory canal. In 2 AN patients with elongated interpeak latency differences between waves I and V in ABRs, the neural conduction velocity of the cochlear nerve was lower than that of normal subjects. These results provide neurophysiological evidence that low neural conduction velocity in the cochlear nerve results in the abnormal ABR.

Adult↗
PubMed2005

Effect of fluidotherapy on superficial radial nerve conduction and skin temperature.

STUDY DESIGN: Cross-sectional study. OBJECTIVES: The purpose of this study was to examine the effects of the superficial heating modality, Fluidotherapy, on skin temperature and on sensory nerve action potential (SNAP) conduction latency and amplitude of the superficial radial nerve in healthy individuals. BACKGROUND: Fluidotherapy is a dry, superficial heating modality, which also provides tactile stimulation through the bombardment of air-fluidized cellulose particles. Previous literature has documented a direct relationship between skin temperature and neural conduction velocity; however, there is an absence of published research examining the effects of Fluidotherapy, and of tactile stimulation specifically, on neural conduction. METHODS AND MEASURES: Twenty-one subjects between the ages of 22 and 31 years (mean+/-SD, 25.5+/-0.7 years) and without prior history of diabetes, alcoholism, renal or metabolic dysfunction, current pregnancy, or heat sensitivity were invited to participate. Subjects completed an upper quarter screening exam and medical history form prior to participation. One group underwent heat (46.7 degrees C-48.9 degrees C) and tactile stimulation, a second group underwent tactile stimulation alone, while a third served as controls. Dependent variables were assessed at 3 intervals: before the intervention, immediately after the intervention, and 20 minutes after the intervention. All interventions were 20 minutes in length. RESULTS: A mixed 2-way analysis of variance indicated a significant interaction between time of neural conduction velocity assessment and treatment group for the dependent variables of sensory nerve action potential latency (P< .001) and skin temperature (P< .001). Appropriate post hoc tests were performed for simple effect comparisons. An inverse linear relationship existed between skin temperature and latency (r2 = .65; Pearson product coefficient, -.81). CONCLUSIONS: Fluidotherapy treatment, which combines the effects of heat and tactile stimulation, significantly elevated superficial skin temperature, while tactile stimulation alone and no treatment (control group) did not bring about a temperature change. As the superficial skin temperature increased, there was a concomitant decrease in the distal sensory latency of the superficial radial sensory nerve action potential. These results should be an important consideration for the clinician using superficial heating modalities.

Action Potentials↗
PubMed2003

Neurophysiological anomalies in brainstem responses of mercury-exposed children of Andean gold miners.

The health hazards of occupational exposure to Mercury (Hg) in adult gold miners are well known, but little attention has been given to the effects of Hg exposure in the children of gold miners. Children who assist their parents in gold mining operations or live in mining enclaves may be exposed to elemental Hg vapors or methylmercury-contaminated food, both of which may induce neurodevelopmental disabilities. Brainstem auditory-evoked responses (BAER) were measured as biomarkers of subtle mercury-induced neurological impairment in Andean children of gold miners living in the Ecuadorian gold mining settlement of Nambija, where Hg exposure is prevalent. Thirty-one children (19 boys and 12 girls, aged 4-14 years, mean age: 10 years) in the study group were found to have a mean blood mercury (HgB) level of 23.0 micrograms/L (SD: 19, range: 2.0-89.0 micrograms/L; median: 20 micrograms/L), which was significantly higher than the mean HgB level of a reference group of 21 Ecuadorian children (4.5 micrograms/L, SD: 2.3; t = 4.39, P = 0.0001), and in excess of the health-based biological limits for the U.S. (10 micrograms/L). The BAER measures indicated statistically significant differences in interpeak III-V (P = 0.03) and I-V (P = 0.008) neural conduction times for children with HgB levels above the median. BAERs at the conventional click stimulus rate of 10/second showed statistically significant positive correlations between HgB level and the absolute latency of wave V (P = 0.03), and the neural conduction times of the eighth nerve to midbrain I-V interval (P = 0.02). BAER at 50/second revealed statistically significant relationships between HgB and the latency of wave VI (P = 0.03), and the I-VI interpeak interval (P = 0.02). Brainstem neural conduction times suggested that some of the Hg-intoxicated children in the study group have subtle neurophysiological anomalies that may be more manifest at higher BAER stimulus rates, and that the Hg-exposed children of gold miners are at risk for neurodevelopmental disabilities.

Adolescent↗
PubMed2003

The effects of intrathecal tramadol on spinal somatosensory-evoked potentials and motor-evoked responses in rats.

UNLABELLED: Tramadol has been proven to exert a local anesthetic-type effect on peripheral nerves in both clinical and laboratory studies. In this study, we evaluated the effects of tramadol on sensory and motor neural conduction when administered intrathecally in the rat. Tramadol (0, 1, or 2 mg) was administered through an intrathecal catheter. Spinal somatosensory-evoked potentials (SSEPs) were recorded at the thoracolumbar junction after stimulation of the sciatic nerve. An evoked compound muscle action potential (CMAP) was recorded in the intrinsic muscles of the foot in response to electric stimulation of the lower thoracic (T1213) interspinous space. Both SSEP and CMAP were obtained before drug application as the pretreatment baseline and at 5, 15, and 30 min after treatment, and at 30- or 60-min intervals thereafter for another 4.5 h. SSEP was averaged from 20 responses, whereas CMAP was obtained from a single stimulation. Reproducible SSEPs and CMAP were consistently recorded in all rats. Intrathecal tramadol dose-dependently reduced the amplitude and delayed the latency in both SSEPs and CMAP. Generally, the suppressive effects occurred immediately after injection and recovered over 2 h. Combined administration with 20 micro g of intrathecal naloxone did not attenuate the inhibition of spinal SSEPs. We conclude that intrathecal tramadol causes a dose-related suppressive effect on both sensory and motor neural conduction in the spinal cord. IMPLICATIONS: Spinal somatosensory-evoked potentials and evoked compound muscle action potential were used to evaluate the effects of intrathecal tramadol on sensory and motor neural conduction. Intrathecal tramadol dose-dependently reduced the amplitude and delayed the latency of both spinal somatosensory-evoked potentials and compound muscle action potential. These results indicate that tramadol exerts a dose-related central neural blockade.

Analgesics, Opioid↗
PubMed2003

Activity-dependent developmental plasticity of the auditory brain stem in children who use cochlear implants.

OBJECTIVES: 1) To determine if a period of early auditory deprivation influences neural activity patterns as revealed by human auditory brain stem potentials evoked by electrical stimulation from a cochlear implant. 2) To examine the potential for plasticity in the human auditory brain stem. Specifically, we asked if electrically evoked auditory potentials from the auditory nerve and brain stem in children show evidence of development as a result of implant use. 3) To assess whether a sensitive or critical period exists in auditory brain stem development. Specifically, is there an age of implantation after which there are no longer developmental changes in auditory brain stem activity as revealed by electrically evoked potentials? DESIGN: The electrically evoked compound potential of the auditory nerve (ECAP) and the electrically evoked auditory brain stem response (EABR) were recorded repeatedly during the first year of implant use in each of 50 children. The children all had pre- or peri-lingual onset of severe to profound sensorineural hearing loss and received their implants at ages ranging from 12 mo to 17 yr. All children received Nucleus cochlear implant devices. All children were in therapy and in school programs that emphasized listening and required the children to wear their implants consistently. RESULTS: Initial stimulation from the cochlear implant evoked clear responses from the auditory nerve and auditory brain stem in most children. There was no correlation between minimum latency, maximum amplitude, or slope of amplitude growth of initial responses with age at implantation for ECAP eN1, EABR eIII and eV components (p > 0.05). During the first year of implant use, minimum latency of these waves significantly decreased (p < 0.01, p < 0.0001, p < 0.0001, respectively). Neural conduction time, measured using the interwave latency of ECAP eN1-EABR eIII for lower brain stem and EABR eIII-eV for upper brain stem, decreased during the period of 6 to 12 mo of cochlear implant use (p < 0.01 (lower), p < 0.0001(upper)). The ECAP wave eN1 and the EABR wave eV showed significant increases in amplitude during time of implant use (p < 0.05 and p < 0.01, respectively). There were no correlations between the rate of interwave latency decrease and the rate of amplitude increases and the age at which children underwent implantation (p < 0.05). CONCLUSIONS: Activity in the auditory pathways to the level of the midbrain can be evoked by acute stimulation from a cochlear implant. EABR measures are not influenced by any period of auditory deprivation. Auditory development proceeds once the implant is activated and involves improvements in neural conduction velocity and neural synchrony. Underlying mechanisms likely include improvements in synaptic efficacy and possibly increased myelination. The developmental plasticity that we have shown in the human auditory brain stem does not appear from EABR data to be limited by a critical period during childhood.

Adolescent↗
PubMed2002

Transcranial magnetic stimulation: neurophysiological applications and safety.

TMS is a non-invasive tool for measuring neural conduction and processing time, activation thresholds, facilitation and inhibition in brain cortex, and neural connections in humans. It is used to study motor, visual, somatosensory, and cognitive functions. TMS does not appear to cause long-term adverse neurological, cardiovascular, hormonal, motor, sensory, or cognitive effects in healthy subjects. Single-pulse (<1Hz) TMS is safe in normal subjects. High frequency, high-intensity repetitive TMS (rTMS) can elicit seizures even in normal subjects. Safety guidelines for using rTMS have been published.

Cognition↗
PubMed2000

Vibration-induced multifocal neuropathy in forestry workers: electrophysiological findings in relation to vibration exposure and finger circulation.

OBJECTIVES: To investigate neural conduction in the upper limbs of symptomatic forestry workers with and without exposure to hand-transmitted vibration. A further aim was to assess the possible relationships between vibration exposure, nerve conduction and finger circulation in the forestry workers who used chain saws. METHODS: A detailed neurophysiological investigation was performed on the upper extremities of 20 chain saw workers, 20 forestry operators with heavy manual work but without vibration exposure, and 20 healthy male controls. All subjects were screened to exclude polyneuropathy. Measurements of sensory and motor nerve conduction (velocity and amplitude) were obtained bilaterally from the median, ulnar and radial nerves. To assess peripheral vascular function, the forestry workers underwent a cold test with plethysmographic measurement of finger systolic blood pressure (FSBP). In the chain saw operators, vibration exposure was evaluated according to the International Standard ISO 5349. Indices of daily vibration exposure and lifetime cumulative vibration dose were estimated for each chain saw operator. RESULTS: Sensory nerve conduction in several segments of the median and radial nerves was significantly reduced in the chain saw operators compared with that in the workers doing heavy manual work and the controls. The neurophysiological pattern more frequently observed in the chain saw operators was a multifocal nerve conduction impairment to several neural segments with predominant involvement of sensory rather than motor fibres. Sensory nerve conduction velocities in the hands of the chain saw operators were inversely related to both daily and lifetime cumulative vibration exposures. In the vibration-exposed forestry workers, neither were sensori-motor complaints associated with vascular symptoms (finger whiteness) nor were electrophysiological data related to cold-induced changes in FSBP. CONCLUSIONS: Exposure to hand-transmitted vibration, in addition to ergonomic stress factors, can contribute to peripheral nerve disorders occurring in forestry workers who operate chain saws. The findings of this study suggest the existence of an exposure-effect relationship for vibration-induced neuropathy. Different underlying mechanisms are likely to be involved in the pathogenesis of the neurological and vascular components of the hand-arm vibration syndrome.

Adult↗
PubMed1986

Compression of rat spinal cord in vitro: effects of ethanol on recovery of axonal conduction.

The effect of ethanol on recovery of neural conduction after spinal cord compression was evaluated in an isolated rat spinal cord preparation. Controlled compression of 50 to 75 percent of the cord cross-section was delivered using a piezoelectric translator. Postcompression compound action potential (CAP) amplitude, latency, and refractory periods were measured relative to pre-compression values. Recovery of CAP's was compared for spinal cords exposed to ethanol in vitro (100 mg/dl bath concentration, started one hour prior to compression) versus those maintained in normal artificial CSF. The in vitro effects of ethanol were evaluated on spinal cords from rats maintained on a normal diet and from those repeatedly intoxicated with ethanol for 15 days prior to the acute experiment. Compression of the cord resulted in an immediate 68% decrease in CAP peak amplitude and an increase in latency (171%) and refractory period (256%). In normal bathing medium, CAP amplitude recovered to 83% of pre-compression values 180 minutes after compression. The addition of ethanol to the artificial CSF did not directly affect CAP parameters, but combined with compression, CAP amplitude recovered to only 42% of pre-compression values 180 minutes after impact (p less than .01). Recovery was less affected by acute ethanol exposure in cords from ethanol pretreated animals. CAP amplitude recovered to 83% of pre-compression levels and was not different from compression-only recovery (p less than 0.10). The data suggest that direct effects of ethanol on axonal membranes may affect the sensitivity of axons to mechanical trauma or their capacity to recover normal function. Since spinal cords from repeatedly exposed animals are less sensitive to the acute effects of ethanol, ethanol may be acting to "fluidize" the axonal membrane.

Alcoholic Intoxication↗
PubMed1989

Brainstem auditory evoked responses in chronic renal failure and the effect of hemodialysis.

Brainstem auditory evoked responses (BAER) were recorded in patients with chronic renal failure before commencement of chronic dialysis treatment, and in patients with end-stage renal failure on chronic hemodialysis for several years. Both groups of patients had delayed latencies of the third and fifth waves. The patients on hemodialysis revealed delayed latency of interpeak I-V as well. There was no correlation between wave latency, serum urea, creatinine, PTH or duration of chronic hemodialysis treatment. A hemodialysis session led to a slight shortening of the third wave. This study suggests that neural conduction along the brainstem in patients with chronic renal failure is delayed even before hemodialysis is started. Although 1 dialysis session may have some beneficial effect, long-term hemodialysis treatment does not seem to shorten the delay in neural conduction observed in patients with chronic renal failure.

Adolescent↗
PubMed2002

Aquaporin 4 expression in the mammalian inner ear and its role in hearing.

Aquaporin 4 (Aqp4), a member of a family of water transport proteins, is a candidate for playing a critical role in inner ear fluid homeostasis. In this study, we assess cross-species Aqp4 expression in the inner ear, sequence conservation in the 5'-UTR, and hearing in Aqp4 knockout mice. A single Aqp4 isoform was expressed in a highly conserved pattern within the supporting epithelia surrounding the sensory cells of the auditory and vestibular sensory organs and the glial cells surrounding the auditory nerve of the mouse and rat. In the 5'-UTR of mouse and rat Aqp4 gene, sequence conservation was highest in the region spanning the transcription start site. Aqp4 knockout mice demonstrated impaired hearing, but normal neural conduction time. Similar Aqp4 expression pattern and regulatory sequence conservation across species suggest a highly conserved role for Aqp4 in the inner ear. In the Aqp4 deficient mouse, cochlear dysfunction is suggested as the primary cause of hearing impairment in the absence of neural conduction abnormality.

5' Untranslated Regions↗
PubMed1996

Auditory evoked potentials in multiple sclerosis: correlation with magnetic resonance imaging.

The present study addresses issues regarding the location of neural sources (i.e. generators) of human auditory evoked potentials (AEPs), and the pattern of neural conduction in the auditory pathway. AEPs were recorded from fifteen patients with multiple sclerosis (MS) and compared to normals. The recordings included auditory brainstem responses (ABRs), mid-latency responses (MLRs), and long-latency responses (LLRs). AEP latency abnormalities were related to the locus of demyelinating lesions, as determined by magnetic resonance imaging (MRI) scans. The data demonstrated several anatomical patterns relating abnormal ABR wave intervals and abnormal MRI signals. From these patterns specific loci for ABR neural sources in the brainstem might be postulated. In addition, the earlier the ABR waves, the more unilateral the abnormalities appeared, suggesting bilateral sources for later waves. The MLRs were highly correlated with ABR wave V and were associated with greater abnormality in MRI signals in midbrain and forebrain regions. In general, patients with abnormal LLRs also had widespread AEP and MRI abnormalities, supporting a multiple source approach for the N1 wave of the LLRs. The observation that LLRs were only abnormal in the presence of bilateral ABR abnormalities suggests a cross wiring which would serve as a compensatory mechanism for unilateral disturbances. The AEP data showed dissociation between early and late wave abnormalities, thus supporting parallel channels for neural conduction in the central auditory system. Such a model calls for some degree of independence of AEP generators along the auditory pathway.

Adult↗
PubMedDate not supplied

The monkey (Macaca fascicularis) heart neural structures and conducting system: an immunochemical study of selected neural biomarkers and glutamate receptors.

The neural markers, protein gene product 9.5 (PGP 9.5), neurofilaments (NF) and glutamate receptors (GluRs) were visualized by immunohistochemistry in the monkey heart. PGP 9.5 showed the greatest affinity for intramural ganglia cells and nerve fibres. Structural components of the conducting system were also stained, particularly the bundle of His, AV node and Purkinje fibres. Anti-NF 200 and NF 160 showed strong, preferential affinity to nerve fibres and ganglia throughout the heart. Further studies concentrated on the presence and the distribution of glutamate receptors: NMDAR 1, GluR 1, GluR 2/3, GluR 5/6/7, mGluR 2/3, and mGluR 5. Positive immunoreactivity of GluRs was evident in nerve terminals within the atrium, myocardium, intramural ganglia and elements of the conducting system. The intensity of the stain varied for each antibody according to the anatomical distribution within neural structures and conducting system. The specificity of immunolabelling was confirmed by absorption studies with each corresponding peptide. There is preferential affinity to and differential distribution of staining with PGP 9.5, NFs and several subtypes of GluRs in the various components of the cardiac conducting system in adult monkeys. The expression of specific neural markers and glutamate receptors common to nerve fibers and ganglia cells is consistent to our previous report in rodents. These expressions suggests that such structures in the heart share common characteristics with a variety of neural tissues and hence are potential targets for neurotoxins. Furthermore, the strong affinity and specific distribution of several subtypes of GluRs in the monkey heart fosters our view that these receptors may be able to influence the physiology and pathophysiology of cardiac rhythm and excitation. Hence as in the brain, the GluRs may be involved in the mediation of excitatory effects in the heart.

Animals↗
PubMed1983

Nervous impulse propagation along peripheral and central fibres in patients with chronic renal failure.

In thirty-one patients with chronic renal failure we measured the conduction velocities in the proximal regions of median and peroneal nerves and concurrently evaluated the propagation properties of an afferent input along the related central (spinal and supraspinal) sensory pathways. In 26 of these patients the sensorimotor velocities of median, peroneal and sural nerves were also calculated. Lower limb peripheral conduction was more frequently abnormal than that of upper limb, the distal segment being involved to a greater degree. Since central propagation was more impaired during lower (11 out of 27 cases) than during upper limb (1 out of 27 patients) stimulation and the intracranial propagation time was rarely prolonged, a predominantly spinal defective impulse conduction was hypothesized. Neurophysiological data seem to confirm that early stages of defective neural conduction in CRF are in agreement with the model of central-peripheral distal axonopathy. However, an abnormal impulse propagation was also rarely found in proximal districts of peripheral fibres as well as along the intracranial sensory pathways. Correlations were found between some of the impulse propagation properties and the duration of CRF or dialysis. Serum parathyroid hormone, creatinine and BUN levels were correlated with some peripheral and central conduction indexes.

Adolescent↗
PubMed1987

Compression induced damage on in-situ severed and intact nerves.

The effect of rapid as well as sustained compressive forces applied to the surface of intact and severed peroneal nerves of rabbits was studied. Considerable effort was taken to ensure a quantitative and consistent experimental paradigm. Stimuli were delivered to the sciatic nerve, and the compound action potential was recorded in the peroneal nerve, with compressive forces applied more proximally on the peroneal nerve. It was found that the conduction of action potentials on the larger nerve fibers was more sensitive to compressive force than that of the smaller nerve fibers, although all nerve fibers stopped conducting when sufficient compression was applied to the nerve. The effect on the conduction of action potentials on the nerve fibers appeared to be determined both by Laplace's law (as previously reported by others) and the viscoelastic properties of the entire nerve. Relatively low compressive forces (20 gm applied over approximately 7 sq mm) were found to decrease the neutral conduction of the larger nerve fibers for at least two hours, whereas stagnation of blood circulation was not found to affect measurably the neural conduction of all the nerve fibers for up to two hours.

Action Potentials↗
PubMed2004

Visualization of incomplete conduction block by neuromagnetic recording.

OBJECTIVE: We previously reported on evoked compound action magnetic fields (CAFs) in isolated sciatic nerves with complete conduction block. In this study, we examined evoked CAFs of the nerve with incomplete conduction block, which is clinically common. METHODS: Rabbits' isolated nerves were electrically stimulated in a chamber containing Ringer's solution. Compound action potentials (CAPs) and CAFs were recorded before and after the incomplete conduction block induced by a vascular clip. The positions of the lesion were estimated by dipole localization. RESULTS: Before the nerve clipping, magnetic contour maps showed CAFs with a characteristic quadrupolar pattern. After the clipping, CAFs attenuated in the amplitude and decelerated through the lesion. Estimated position of the lesion was 0.12+/-3.23 mm (mean+/-SD, n=10) assuming that the real position of the clip was 0 mm. CONCLUSIONS: The time-course of changes of CAFs in the incomplete conduction block was visualized by magnetic contour maps, and the lesions were closely localized focusing on the velocity change of the leading dipole. SIGNIFICANCE: The neural conduction with incomplete conduction block was visualized and the lesion was closely localized by neuromagnetic recordings.

Action Potentials↗
PubMedDate not supplied

[Evaluation of sensitivity in the fasciocutaneous neurovascular medial plantar island flap in reconstruction of soft tissue defects in the calcaneal region].

The soft tissue cover in the calcaneal region represents one of the great problems in the reconstructive surgery. The distant skin, muscle and musculocutaneous flaps are subjected to ulcers even with the orthopedic shoes. The island fasciocutaneus mid sole neurocutaneous flap can be a good substitute for the soft tissue cover due to its anatomic structure. The flap has the required dimensions, sticks well to the bone and the movements and mobility of the patient is unrestricted. This paper analyses the sensitivity of the transposed flap and the sole distal to the secondary defect observed in 30 patients. The evaluation was made after tactile tests, two-point discrimination test, the warm-cold test, the electrostatus of medial plantar nerve (MPN), and the ninhydrin test. All the tests, including the electrostatus MPN, done after 3 weeks and 3 months after the surgery, showed successful recovery of sensitivity in the transposed medial plantar flap. The results monitored after three months showed that the speed of the neural conduction recovery was 70% of normal neural reaction speed of the MPN. The modified operative techniques provide safe dissection of the plantar nerve with minimal neuropraxia. The postoperative recovery of sensitivity was more rapid, and without loss of sensitivity on the sole.

Adult↗