Simulation study of spinal cord stimulation evoked compound action potential / 生物医学工程学杂志

Spinal cord stimulation (SCS) for pain is usually implanted as an open loop system using unchanged parameters. To avoid the under and over stimulation caused by lead migration, evoked compound action potentials (ECAP) is used as feedback signal to change the stimulating parameters. This study established a simulation model of ECAP recording to investigate the relationship between ECAP component and dorsal column (DC) fiber recruitment. Finite element model of SCS and multi-compartment model of sensory fiber were coupled to calculate the single fiber action potential (SFAP) caused by single fiber in different spinal cord regions. The synthetized ECAP, superimposition of SFAP, could be considered as an index of DC fiber excitation degree, because the position of crests and amplitude of ECAP corresponds to different fiber diameters. When 10% or less DC fibers were excited, the crests corresponded to fibers with large diameters. When 20% or more DC fibers were excited, ECAP showed a slow conduction crest, which corresponded to fibers with small diameters. The amplitude of this slow conduction crest increased as the stimulating intensity increased while the amplitude of the fast conduction crest almost remained unchanged. Therefore, the simulated ECAP signal in this paper could be used to evaluate the degree of excitation of DC fibers. This SCS-ECAP model may provide theoretical basis for future clinical application of close loop SCS base on ECAP.

Effects of Lippia sidoides essential oil, thymol, p-cymene, myrcene and caryophyllene on rat sciatic nerve excitability

Lippia sidoides Cham is a typical herb species of Northeast Brazil with widespread use in folk medicine. The major constituents of the essential oil of L. sidoides (EOLs) are thymol, p-cymene, myrcene, and caryophyllene. Several studies have shown that the EOLs and its constituents have pharmacological effects, including antibacterial, anti-inflammatory, antioxidant and neuroprotective activity. Therefore, this work aimed to investigate the effects of the EOLs and their main constituents on rat sciatic nerve excitability. The sciatic nerves of adult Wistar rats were dissected and mounted in a moist chamber. Nerves were stimulated by square wave pulses, with an amplitude of 40 V, duration of 100 μs to 0.2 Hz. Both EOLs and thymol inhibited compound action potential (CAP) in a concentration-dependent manner. Half maximal inhibitory concentration for CAP peak-to-peak amplitude blockade were 67.85 and 40 µg/mL for EOLs and thymol, respectively. CAP peak-to-peak amplitude was significantly reduced by concentrations ≥60 µg/mL for EOLs and ≥30 µg/mL for thymol. EOLs and thymol in the concentration of 60 µg/mL significantly increased chronaxie and rheobase. The conduction velocities of 1st and 2nd CAP components were also concentration-dependently reduced by EOLs and thymol in the range of 30-100 µg/mL. Differently from EOLs and thymol, p-cymene, myrcene and caryophyllene did not reduce CAP in the higher concentrations of 10 mM. These data demonstrated that EOLs and thymol inhibited neuronal excitability and were promising agents for the development of new drugs for therapeutic use.

Analysis of Auditory Rehabilitation Outcomes of the Cochlear Neural Canal Stenosis Patients after Cochlea Implantation / 听力学及言语疾病杂志

Objective To study the analysis of auditory rehabilitation outcomes of patients with cochlear nerve canal stenosis after cochlear implantation(CI).Methods A cohort of 30 patients with bilateral profound senso-rineural hearing loss who were diagnosed with cochlear neural canal stenosis by high-resolution CT were tested with evoked compound action potential (ECAP)and evoked auditory brainstem response (EABR)during and 3 ,6 , 9 months after CI.Audiometry in sound field was also assessed before and 3 ,6 ,9 months after CI.Among the co-hort,1 7 patients over 3 years old underwent postoperative speech recognition rate test.All the auditory rehabilita-tion outcomes were analyzed.Results ① For all 30 patients,there were no obvious differences of ECAP and EABR waveforms tested in 3,6 and 9 months after CI.②The thresholds in sound field in 3,6,9 months after CI were 65 ±8 dB HL,62 ±4 dB HL and 61 ±7 dB HL,respectively.The thresholds in sound field were significantly im-proved after than before CI (100 ±5 dB HL).③ The single vowel recognition rates of 17 patients in 3 ,6 and 9 months after CI were 55%±7%,56%±8% and 80%±4%,respectively.The single vowel recognition rate was significantly improved in 9 months after than before CI(52%±8%).The single consonant recognition rates of 17 pa-tients in 3 ,6 and 9 months after CI were 9%±3%,8%±4% and 9%±2%,respectively.The single consonant recognition rates were not significantly improved after than before CI (8%±2%).Conclusion ① For patients with bi-lateral cochlear neural canal stenosis,neither ECAP nor EABR waves were produced during or after CI.The language com-munication of patients is limited as a result of their poor subjective thresholds in sound field and speech recognition rates.

Essential oil of Lippia alba and its main constituent citral block the excitability of rat sciatic nerves

Lippia alba is empirically used for infusions, teas, macerates, and hydroalcoholic extracts because of its antispasmodic, analgesic, sedative, and anxiolytic effects. Citral is a mixture of trans-geranial and cis-neral and is the main constituent of L. alba essential oil and possesses analgesic, anxiolytic, anticonvulsant, and sedative effects. The present study evaluated the effects of the essential oil of L. alba (EOLa) and citral on compound action potentials (CAPs) in Wistar rat sciatic nerves. Both drugs inhibited CAP in a concentration-dependent manner. The calculated half-maximal inhibitory concentrations (IC50) of peak-to-peak amplitude were 53.2 µg/mL and 35.00 µg/mL (or 230 µM) for EOLa and citral, respectively. Peak-to-peak amplitude of the CAP was significantly reduced by 30 µg/mL EOLa and 10 µg/mL citral. EOLa and citral (at 60 and 30 µg/mL, values close to their respective IC50 for CAP blockade) significantly increased chronaxy and rheobase. The conduction velocity of the first and second CAP components was statistically reduced to ∼86% of control with 10 µg/mL EOLa and ∼90% of control with 3 µg/mL citral. This study showed that EOLa inhibited nerve excitability and this effect can be explained by the presence of citral in its composition. Both EOLa and citral showed inhibitory actions at lower concentrations compared with other essential oils and constituents with local anesthetic activity. In conclusion, these data demonstrate that EOLa and citral are promising agents in the development of new drugs with local anesthetic activity.

Ruido eléctrico de la ventana redonda / Round window electrical noise

Desde hace décadas se sabe que al colocar un electrodo cerca de la ventana redonda de la cóclea es posible registrar potenciales cocleares en respuesta a estímulos sonoros, tales como el potencial microfónico coclear o el potencial de acción compuesto del nervio auditivo. Sin embargo, hace algunos años, se ha descrito que al posicionar un electrodo en el nicho de la ventana redonda en animales de experimentación y en ausencia de estimulación acústica, se obtiene actividad eléctrica aparentemente aleatoria y no desencadenada por estímulo. Esta actividad eléctrica se ha denominado ruido eléctrico de ventana redonda (RWN, por su sigla en inglés Round Window Noise) y representaría la descarga espontánea de fibras del nervio auditivo. La técnica para su registro es similar a la utilizada en la electrococleografía para obtener potenciales cocleares en humanos. Esta señal se distingue del ruido eléctrico no biológico por tener un peak en su poder espectral centrado en torno a los 900 Hz. La amplitud de esta banda de frecuencia se correlaciona con la sensibilidad auditiva en la región basal de la cóclea, entre los 12 a 30 kHz en cobayos y gatos. El RWN se ha estudiado a través de estimulación acústica y bloqueo farmacológico, logrando caracterizar sus propiedades electrofisiológicas para desarrollar modelos de estudio con aplicación clínica.

For decades, it has been known that placing an electrode near the round window niche allows the recording of cochlear potentials in response to auditory stimuli, such as the cochlear microphonic potential and the compound action potential of the auditory nerve. However, some years ago, it was discovered, that by positioning an electrode in the round window niche of experimental animals, and in the absence of acoustic stimulation, apparently random electrical activity is obtained. This electrical activity is called round window electrical noise (RWN) and represents the spontaneous discharge of auditory nerve fibers. The recording technique is similar to that used in electrocochleography in humans. This bioelectrical signal is distinguished from that of non-biological electrical noise, as it has a power spectral peak centered around 900 Hz. The magnitude of this frequency peak is correlated with hearing sensitivity in the basal region of the cochlea, between 12 to 30 kHz in guinea pigs and cats. The RWN has been characterized using sound stimulation or pharmacologic suppression, and its electrophysiological properties could be used to develop models of auditory nerve function with possible clinical application.

Limb immobilization alters functional electrophysiological parameters of sciatic nerve

Immobilization, used in clinical practice to treat traumatologic problems, causes changes in muscle, but it is not known whether changes also occur in nerves. We investigated the effects of immobilization on excitability and compound action potential (CAP) and the ultrastructure of the rat sciatic nerve. Fourteen days after immobilization of the right leg of adult male Wistar rats (n=34), animals were killed and the right sciatic nerve was dissected and mounted in a moist chamber. Nerves were stimulated at a baseline frequency of 0.2 Hz and tested for 2 min at 20, 50, and 100 Hz. Immobilization altered nerve excitability. Rheobase and chronaxy changed from 3.13±0.05 V and 52.31±1.95 µs (control group, n=13) to 2.84±0.06 V and 59.71±2.79 µs (immobilized group, n=15), respectively. Immobilization altered the amplitude of CAP waves and decreased the conduction velocity of the first CAP wave (from 93.63±7.49 to 79.14±5.59 m/s) but not of the second wave. Transmission electron microscopy showed fragmentation of the myelin sheath of the sciatic nerve of immobilized limbs and degeneration of the axon. In conclusion, we demonstrated that long-lasting leg immobilization can induce alterations in nerve function.

The Relationship between Thresholds of Electrically Evoked Compound Action Potential and Speech Perception in Children with Cochlear Implants / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Neuropathology around the cochlea could create variation from site to site in physiological thresholds of cochlear implant users. This variability would be detrimental to speech recognition with a cochlear implant for a variety of reasons, including distortion of the place code and variation in the number of neurons. The purpose of this study is to examine the relationship between thresholds of electrically evoked compound action potential (ECAP) and speech perception in children implanted with the Nucleus Freedom devices. SUBJECTS AND METHOD: Fifty-seven children implanted with the Nucleus Freedom device participated in this study. ECAP thresholds were recorded using the automated neural response telemetry test protocol. We then calculated mean threshold and three metrics to assess across-site variation within subjects: 1) the variance of T levels for all tested sites, 2) the range of T levels (highest minus lowest) across all tested sites and 3) site-to-site variation. For each subject, these measures were compared with performance on tests of word recognition. RESULTS: There was considerable across-site (within-subject) and across-subject variability in thresholds. However, we found no significant correlation between speech recognition and across-site variation of thresholds as well as mean threshold levels. CONCLUSION: These data suggest that the ECAP measures of thresholds may not be an accurate predictor of speech perception ability.

The Relationship between Electrically Evoked Compound Action Potential and Speech Perception in CI24RE Implant Users / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Since performance with a cochlear implant is negatively correlated with an individual's duration of deafness prior to implantation, neural survival may be an important factor in determining outcome. To date, studies relating physiological measures such as the threshold and growth of the electrically evoked potentials have not shown clear relationships to human speech perception abilities, although there are positive results correlating these measures to nerve survival in animals. The primary goal of this study was to determine the extent to which the growth functions of electrically evoked compound action potential (ECAP) are related with speech perception performance in recent CI24RE implant users and to investigate the relationship between ECAP growth function and performance according to more limited electrodes. SUBJECTS AND METHOD: We measured ECAP growth functions to biphasic pulses using reverse neural telemetry system in 21 CI24RE implant users. For each subject, the slope of the growth function was compared with speech perception tests. In addition, this measure was also evaluated for a more limited set of electrodes. RESULTS: Significant correlations have been found between the slope of ECAP growth functions and speech performance in CI24RE implant recipients. In addition, a relatively strong correlation has been found between the slope of ECAP growth function and performance on word recognition test in the group of basal electrodes. CONCLUSION: Effectiveness of the cochlear implant can be quite variable. These results show that ECAP measure may be useful in developing a test for predicting the outcomes of using the implant.

Effects of Histamine on Nerve Block with Lidocaine / 대한마취과학회지

BACKGROUND: The failure to achieve satisfactory anesthesia following the administration of local anesthetic agents in acute inflammatory tissues is a recognized clinical phenomenon. Many inflammatory mediators can reduce the threshold of nociception during inflammation, and histamine, one of the most important inflammatory mediator, may attenuated local anesthetic effect during inflammation. The purpose of this study was to investigate if histamine can antagonize a lidocaine induced nerve block in vitro. METHODS: Recordings of the compound action potentials (CAP) of A-fiber components were obtained from the isolated sciatic nerves of male Sprague-Dawley rats. The nerve sheath of the sciatic nerve was removed and desheathed nerve was mounted in a recording chamber. Single pulse stimuli (0.5 msec, supramaximal stimuli) were repeatedly applied (2 Hz) to one end of the nerve and CAP recordings were made at the other. The effect of histamine on the suppression of CAP by lidocaine and the effect of histamine on the recovery time to the nerve block by lidocaine were measured. RESULTS: Compared with the baseline amplitude, the amplitudes of CAP were 11.7+/-4.1% for the lidocaine group, 18.3+/-4.6% for the lidocaine histamine 0.05% group, and 26.1+/-5.6% for the lidocaine histamine 0.5% group. Nerve block recovery times were: 38.6+/-3.5 min for the modified Krebs group, 29.8+/-4.2 min for histamine 0.05% in the modified Krebs group, and 19.2+/-1.1 min for histamine 0.5% in the modified Krebs group. CONCLUSIONS: Histamine shortened the recovery time induced by lidocaine. We suggest that histamine may significantly attenuate the effects of local anesthetics in inflammed tissue.

The Effect of Adrenaline on the Blockade of Compound Action Potential by Local Anesthetics in Rat Sciatic Nerves / 대한마취과학회지

BACKGROUND: Adrenaline has often been used to prolong the local anesthetic effect during surgical procedures. As a possible explanation for this, a local vasoconstriction caused by adrenaline has been proposed. However, in a recent study, clonidine, an alpha2 adrenergic receptor agonist, was reported to block the conduction of mammalian nerves in vitro. Thus, there is a possibility that adrenaline may block nerve conduction by acting on the adrenergic receptor. The present study is performed to see : (1) If adrenaline directly affects nerve conduction ; (2) If adrenaline affects conduction blockade caused by local anesthetic. METHODS: Recordings of compound action potentials (CAPs) of A- and C-components were obtained from isolated sciatic nerves of adult male Sprague-Dawley rats. Dose-response curves of lidocaine and adrenaline regarding depression of CAPs were determined. Effects of adrenaline on the lidocaine-induced nerve block was assessed by comparing the effect of lidocaine (3.5x 10 5) with a lidocaine-epinephrine mixture (Lido-Epi, 3.5 x10 5 lidocaine with 1:100,000 epinephrine). RESULTS: Adrenaline, near the clinical concentrations, had no effect on the size of either A- or C-component of CAPs. The ED50 of lidocaine was 3.5x 10 5. Lidocaine depressed A-CAP 45.9+/- 7.0 when compared with baseline value, and the Lido-Epi solution depressed A-CAP to 41.7+/- 5.0 (P > 0.05). Lidocaine depressed C-CAP 59.8 +/- 3.4 when compared with the baseline value, and the Lido-Epi solution depressed C-CAP to 60.5 8.1 (P > 0.05). Consequently, adrenaline did not augment lidocaine induced nerve blockade. CONCLUSION: This study confirmed that adrenaline applied to the peripheral nerve has no effect either on nerve conduction itself or on conduction block produced by lidocaine.

Effects of Phase Difference on the Latency of Compound Action Potential (CAP) in the Harmonic Stimulation / 대한이비인후과학회지

BACKGROUND AND OBJECTIVE: Comprehensive auditory evaluation often requires complex sounds in addition to pure tones. The sum of pure tones (harmonic stack) is a useful complex stimulus in examining auditory response interactions. In a harmonic stimulus, the phase relationship between pure tones may affect the results of auditory evaluation. The aim of this study was to investigate the effects of relative phases between harmonic frequencies on the latency of compound action potentials (CAP). MATERIALS AND METHODS: Relative phases between two frequencies of a harmonic were varied systematically and compound action potentials (CAP) were, then, recorded in guinea pigs in response to these stimuli. These latencies were compared with the latency to the harmonic complex with the relative phase of zero. RESULTS: The latency of the CAP was shifted within a restricted range to the stimuli with systematically varied phases. These relative phases between the two frequencies directly affected the temporal waveform of the harmonic stimulus although all of these stimuli exhibited the same frequency spectrum. Some phase spectra appeared to contribute more to the latency difference of the CAP. CONCLUSIONS: Findings indicated that the phase relationship in a tonal complex is important to the latency of the CAP, and the phase should be controlled carefully in the objective auditory evaluation with tonal complex stimuli.

Effects of Hydrogen Peroxide on Function and Morphology of Guinea Pig Cochlea / 听力学及言语疾病杂志

Objective To investigate the effects of hydrogen peroxide on function and morphology of guinea pig cochlea in vivo.Methods Animals were divided into four groups and their cochleas were perfused with artificial perilymph(AP), 50 ?M H 2O 2, 100 ?M H 2O 2 and 200 ?M H 2O 2 resolved in AP separately. The compound action potential(AP) and cochlear microphonic(CM) were recorded after two-hours' perfusion. Then hydrogen peroxide-induced cell damage in the inner ear was investigated with morphologic method.Results In all H 2O 2 groups, CAP threshold shifts and CM amplitude shifts were significantly greater than that of APL group. The effect of H 2O 2 perfusion on cochlear function showed dose-dependence. OHCs were major targets of H 2O 2-induced cell death, while Hensen's cells did not show any signs of damage in the presence of H 2O 2. Conclusion Hydrogen peroxide, as an ubiquitous reactive oxygen species(ROS), can induce cochlea dysfunction and damage of cells in guinea pig inner ear. Hensen's cells maybe more resistant to the damage of ROS than hair cells.

Influence of Changing the Parameters on the Wave of NRT / 听力学及言语疾病杂志

Objective To inevestigate the changes of the responses by changing the parameters in the neural response tetemety(NRT).Methods In this project,twenty patients who were implanted in Nucleus C124M were measured the electrically evoked compound action potential(ECAP)using the NRT system.It was expected to observe the changes of the responses by changing the parameters in the NRT 2.04 software.Results It was found that the parameters that made great influences to the responses were current level,stimulate pulse width,gain,delay and masker advance.Conclusion The parameters that made great influences to the record time were stimulate rate and number of sweeps.

Influence of Total Stapedectomy and Suction Noise on Cochlear Function and Ultrastructures in Guinea Pigs / 听力学及言语疾病杂志

In this study, the influence of the duration of opening vestibular window and the application of suction in auditory bulla on cochlear function and ultrastructures were observed by ECochG and scanning and transmission election microscopy in 44 guinea pigs divided into six groups. The results were as follows: (1) The CAP thresholds progressively enhanced as the prolongation of duration in some of outer hair cells in the basal turn occured 180 minutes after total stapedectomy. (2)Significant CAP threshold shift and irreversible pathological changes in some outer hair cells in the basal turn of cochlea were found with continuous suction for 60 minutes in auditory bulla after total stapedectomy. (3)CAP threshold shift without damage of outer hair cells could be fourd with the application of suction for 60 mimutes in auditory bulla before stapedectomy. The results suggested that opening vestibular window for longer time with suction in auditory bulla might be one of the factors to cause postoperative sensorineural hearing loss in total stapedectomy. But the suction noise might not be enough to cause postoperative sensorineural hearing loss in tympanoplasty due to its relatively low intensity.

The Study of EABR and ECAP in Cochlear Implantation / 听力学及言语疾病杂志

Objective To explore the threshold and latency of patients receiving cochlear implantation using electrically evoked auditory brainstem responses (EABR), and to evaluate the significance of EABR applied to those patients.Methods The EABR and ECAP were recorded in 14 subjects who were operated for Nucleus24 cochlear implant.They were assigned to Group A and Group B according to the results of ECAP. The threshholds of EABR, the wave latency of III and V and inter-wave latency of III-V of EABR were compared and analyzed between Group A and Group B.Results The threshholds of EABR were higher in Group B than in Group A on electrode No 22 when the pulse width was 25,50,75,100,125 ?s,respectively. There were significant differences between Group A and Group B(P0.05).Conclusion The threshholds of EABR were lower in patients whose ECAP findings were positive. The latencies of III and V,and inter-wave latency of III–V of EABR had no significant difference according to the positive findings of ECAP.

The Effect of Tetraethylammonium Chloride on the Impulse Conduction Block by bupivacaine / 대한마취과학회지

Potassium channel blockers slow depolarization, broaden the action potential, and thus pro- mote the open and inactivated Na+ channel states. The ability of local anesthetics to reduce the amplitude of compound action potential(CAP) of rat sciatic nerve was examined in the presence and absence of teteraethylammonium chloride(TEA) that selectively block K+ channels, In the presence of 1.3X10-5 M bupivacaine that inhibit the CAP by 22.5% at tonic stimulation, the addition of TEA(10-1M) increased this inhibition by another 27.5% and increased another 50% by phasic stimulation(20Hz). Also, dose response curve of bupivacaine in the presence of TEA(10-1M) showed marked shift to left of curve. The re- covery kinetics of bupivacaine in the presence of various coneentration of TEA(10-2-10-1M) showed marked delay of recovery(2X10-2 M), reocurrence of inhibition(90min,5X10-2 M), even no recovery(10-1M). TEA alone slightly depolarized the resting membrane which was represented as increment of CAP height from 0.9%(3min) to 12.3%(80min), and broadened mid-peak amplitude width by 2 times in 5X10-1M, 5.3 times in 1M. These experiments directly demonstrated that TEA potentiated the inhibition of CAP by bupivacaine and showed the poesibility of mixture of TEA and local anesthetics to potenti- ate impulse conduction blockade.