Temporal correspondence of intracranial, cochlear and scalp-recorded human auditory nerve action potentials.

Conventional, vertex-ipsilateral ear records ('A'), as well as 3-channel Lissajous' trajectories (3-CLTs) of auditory brain-stem evoked potentials (ABEPs) were recorded from the scalp simultaneously with tympanic membrane electrocochleograms ('TME') and auditory nerve compound action potentials ('8-AP') recorded intracranially using a wick electrode on the auditory nerve between the internal auditory meatus and the brain-stem. The recordings were made during surgical procedures exposing the auditory nerve. The peak latency recorded from 'TME' corresponded to trajectory amplitude peak 'a' of 3-CLT and to peak 'I' of the 'A' channel ABEP. Peak latency of '8-AP' was slightly longer than the latency of peak 'II' of 'A' when '8-AP' was recorded from the root entry zone and the same or shorter when recorded from the nerve trunk. '8-AP' peak latency was shorter than trajectory amplitude peak 'b' of 3-CLT regardless of where the wick electrode was along the nerve. Peak latencies from all recording sites clustered into two distinct groups--those that included N1 from 'TME,' peak 'I' of the 'A' record and trajectory amplitude peak 'a' of 3-CLT, and those that included the negative peak of '8-AP' and trajectory amplitude peak 'b' of 3-CLT, as well as peak 'II' of the 'A' record, when present. In one case, the latency of peak 'II' and trajectory amplitude peak 'b' was manipulated by changing the conductive properties of the medium surrounding the auditory nerve.(ABSTRACT TRUNCATED AT 250 WORDS)     

Median/ulnar premotor potential identification and localization

A small negative waveform is known to precede the median and ulnar compound muscle action potentials when recorded with surface or concentric needle electrodes. This investigation documents that there are two distinct waveforms preceding the median compound muscle action potential (CMAP) depending upon the type of recording electrodes used (concentric needle versus surface) and their respective locations. The negative waveform originally described with a concentric needle electrode positioned within the substance of the distal thenar eminence and having a restricted zone of detection is referred to as the intramuscular nerve action potential (INAP). This potential is shown to be distinct from the premotor potential (the small negative waveform preceding surface recorded ulnar and median CMAPs). Detection of the median and ulnar premotor potentials at multiple locations about the hand with the same respective onset/peak latencies and amplitudes substantiates that this potential is a far-field potential. The median and ulnar premotor potentials most likely originate from a dipolar moment imbalance generated by digital sensory nerve action potentials as they cross the first and fifth metacarpophalangeal junctions, respectively. Applying far-field principles permits the documentation of additional far-field potentials as they are generated at the second through fourth metacarpophalangeal junctions following median nerve stimulation. Also, because the premotor potential is a far-field potential, caution must be exercised with respect to its diagnostic utility as joint position and other unknown factors may affect amplitude and onset/peak latency. The INAP following median nerve excitation, however, is documented to be a near-field potential distinct from the premotor potential arising from the recurrent branch of the median nerve. Therefore, although the median intramuscular nerve action potential and premotor potentials both precede the compound muscle action potential, they are different potentials with unique generator sites. © 1995 John Wiley & Sons, Inc.     

Auditory evoked potentials recorded intracranially from the brain stem in man

Auditory evoked potentials were recorded in patients undergoing neurosurgical operations to manage cranial nerve dysfunctions. Recordings were made intra-operatively from the distal portion of the eighth nerve, from the entrance of the eighth nerve into the brain stem, and from a site overlying the superior olivary complex (rostral and medial to the entrance of the eighth nerve). The potentials at the three different loci showed characteristic differences: the responses recorded at the entrance of the eighth nerve into the brain stem showed three peaks about 1 ms apart. The earliest peaks had longer latencies than did those recorded at a distal locus on the eighth nerve, which is consistent with what we know about propagation of nerve impulses in the auditory nerve. The responses recorded on the brain stem, rostral-medial to the eighth nerve, also showed three peaks but the amplitude of the third peak was greater than those of the other two. It is assumed that the first peak originates in the auditory nerve, the second peak in the cochlear nucleus, and the third peak in the lateral superior olive. The latencies of these peaks match the latencies of peaks II, III, and IV of scalp-recorded brain stem evoked potentials.     

Short latency somatosensory evoked potentials: studies in patients with focal neurological disease

In non-cephalic reference recordings, the scalp recorded short latency evoked potentials to median nerve stimulation in normal subjects consist of 3 positive potentials followed by a negative potential. The sources of these potentials have not been precisely defined. Therefore, these potentials were recorded in 31 patients with focal lesions of the nervous system. Recordings were evaluated for (a) the presence or absence of these potentials and (b) peak latency differences between components. The results were compared with similar data obtained on 25 normal control subjects. Only the first positive potential was recorded with stimulation ipsilateral to the lesion in one patient with unilateral C5-T1 root avulsion. This indicates that this potential arises in stimulated peripheral nerve fibers. The second potential, although not consistently recorded in normal subjects, had an abnormally prolonged interpeak latency in 2 patients with cervical cord and medullary lesions. Therefore, it seems that it arises in the central nervous system, either in spinal cord or lower brain stem. The third potential was absent in 2 patients with medullary lesions and its interpeak latency was prolonged in 2 patients with brain stem lesions. It was recorded in 3 patients with thalamic lesions in whom subsequent potentials were absent. This suggests that this potential arises primarily in brain stem pathways. The negative potential was absent in 2 patients with cerebral lesions which did not appear to involve the thalamus which suggests that it arises in the thalamocortical radiations or cerebral cortex. Short latency evoked potential abnormalities correlated more with impairment of proprioception than with disturbances in appreciation of pain and temperature.     

Evaluation of the interrelations among auditory potential parameters by means of the technic of correlation-regression analysis

The characteristics (amplitude, latency) of two types of evoked potentials, action potential of the 8th nerve recorded at the cochlea round window and sonomotor evoked potential recorded from the postauricular region and the back of the guinea pigs were studied in response to sound stimulation. The degree and type of interrelation between the parameters of the auditory evoked potentials were established employing the method of correlation-regression analysis. A close linear dependence was established for amplitude values ( r = 0.93) of the action potential and the sonomotor potential irrespective of the recording site of the latter. The similar dependence (r = 0.91) was established when analysing the latency of the action potential and the evoked sonomotor potential, if the latter was in the postauricular region. The performed mathematical simulation permitted justifying the correction of disturbed functions of the auditory system.     

Origin of components P 11 and P 13 in short latency somato-sensory evoked potentials (SSEP): correlative study of SSEP and intraoperative evoked potentials

In 15 patients with cervical or posterior fossa lesion, SSEPs were recorded between the skull and the non-cephalic reference electrodes during the surgical operation and compared with the evoked potentials directly recorded at the same time from the surface of the cervical spinal cord and the brain stem. The directly recorded evoked potential consisted of three main components appeared within about 25 ms., they were a small negative spike wave, a large positive spike wave and a subsequent slow potential. The positive spike wave of the evoked potentials recorded from the surface of the dorsal column was not only coincided in latency with component P 11 of SSEP, but also showed the greatest amplitude at the lower cervical level. Moreover, the positive spike wave gradually delayed in latency and reduced in amplitude from lower to upper cervical segments. The amplitude of the positive spike wave was greater at the surface of the dorsal column ipsilateral to the stimulated median nerve than that of contra-lateral recording. No polarity change was observed between the anterior and posterior surface of the spinal cord. Similarly, the positive spike wave of the evoked potentials, recorded from the surface of the brain stem, showed fairly same latency with P 13 and a maximal amplitude at the surface of the cuneate tuberculum ipsilateral to the median nerve stimulated, and those positive spike wave traveled to contra-lateral ventral surface of the pons, presumably from ipsilateral cuneate nucleus to the contra-lateral medial lemniscus.(ABSTRACT TRUNCATED AT 250 WORDS)     

Electrophysiological studies in spinocerebellar ataxia type 6: a statistical approach

In spinocerebellar ataxia type 6 (SCA6), the cerebellum is predominantly affected, but several electrophysiological studies have revealed subclinical disorders other than cerebellar lesions. We conducted statistical analyses by comparing SCA6 patients and age-matched normal controls to asses whether electrophysiological abnormalities are directly associated with SCA6 because late onset of SCA6 may involve senile changes. We performed brain stem auditory evoked potentials (BAEP), visual evoked potentials, somatosensory evoked potentials and nerve conduction studies in 10 SCA6 patients. The BAEP latencies of wave I was prolonged and compound muscle action potentials of peroneal nerve and sensory nerve action potentials of sural nerve reduced in SCA6 patients. Our results suggest an existence of peripheral impairment in the auditory pathway and axonal neuropathy in SCA6.     

Contributions from the auditory nerve to the brain-stem auditory evoked potentials (BAEPs): results of intracranial recording in man

Intraoperative recordings obtained from electrodes placed on the scalp (vertex and earlobe or ear canal) in response to click stimulation were compared with recordings made directly from the auditory nerve in patients undergoing microvascular decompression (MVD) operations to relieve hemifacial spasm (HFS) and disabling positional vertigo (DPV). The results support earlier findings that show that the auditory nerve is the generator of both peak I and peak II in man, and that it is the intracranial portion of the auditory nerve that generates peak II. The results indicate that the second negative peak in the potentials recorded from the earlobe is generated by the auditory nerve where it passes through the porus acusticus into the skull cavity, and that the proximal portion of the intracranial portion of the auditory nerve generates a positive peak in the potentials that are recorded from the vertex. This peak appears with a latency that is slightly longer than that of the second negative peak in the potentials recorded from the earlobe (or ear canal). The second negative peak in the recording from the ear canal and the positive peak in the vertex recording contribute to peak II in the differentially recorded BAEP. Since our results indicate that the difference in the latency of the second negative peak in the recording from the earlobe and that of the positive peak in the vertex recording represents the neural travel time in the intracranial portion of the auditory nerve, this measure may be valuable in the differential diagnosis of eighth nerve disorders such as vascular compression syndrome.     

Cochlear potentials and auditory evoked potentials in the caiman (Caiman crocodilus (L.)).

Brain-stem auditory evoked potentials (BAEPs) and round window compound action potentials (CAPs) in response to rarefaction and condensation clicks were recorded from anaesthetized and artificially respired caiman. The recorded wave forms were substantially different from the brain-stem and round window potentials recorded in mammals, including man. In particular, wave latencies were much longer than in mammals. Wave amplitudes increased and latencies decreased significantly and reversibly with increases in stimulus intensity and body temperature. The latencies of the first positive wave (P1) in the BAEP and the first negative wave (N1) in the CAP are correlated and co-vary with stimulus level and body temperature. BAEP P1 thus represents the response of the auditory nerve. The cochlear microphonic (CM) latency in caiman is unaffected by stimulus intensity and by cooling of the animal.     

瞬目反射及脑干听觉诱发电位对脑干梗死疗效的评价

目的探讨瞬目反射和脑干听觉诱发电位对脑干梗死患者疗效的评价作用。方法40例经临床症状、体征定位于脑干髓内并经头部MRI检查明确诊断的脑干梗死患者(脑桥梗死31例、中脑梗死4例和延髓梗死5例),分别计算治疗前后瞬目反射各成分的平均潜伏期;观察脑干听觉诱发电位波形及各波潜伏期、峰间期的变化。结果经治疗后40例患者临床症状及体征均有不同程度改善,治疗前后瞬目反射各成分平均潜伏期之间差异无统计学意义(P>0.05);3例脑桥梗死患者R1波恢复正常,临床基本痊愈。治疗前后脑干听觉诱发电位各波潜伏期及峰间期比较,差异亦无统计学意义(P>0.05);治疗后中脑梗死及脑桥梗死患者各有2例恢复正常,临床症状明显好转。结论瞬目反射与脑干听觉诱发电位均能敏感地反映脑干功能的变化,与临床表现具有一致性,但在发病15d内大部分病例的电生理活动不能恢复正常。     

Multimodal evoked potentials in the early period after cranio-cerebral trauma]

In 83 patients aged 17-68 years somatosensory evoked potentials by median nerve stimulation, and visual and auditory evoked potentials were studied 5-28 days after craniocerebral trauma. Brain concussion was diagnoses in 43 cases on the basis of neurological examination, CT and duration of unconsciousness. In the remaining 40 cases brain contusion was diagnosed. In SSEP the latency was calculated of waves N9, N13, P16, N20, P22, N35 and P40: in the visual evoked potentials the latency of the P100 component, and in auditory evoked potential the latency of waves I, III and V, and interpeak latency I-III, III-V and I-V SSEP changes were found in 39% of cases of brain concussion and 52.9% of brain contusion cases. The abnormalities in both groups involved mainly the component of latency and deviation P100 of visual evoked potential P40 and N35. Prolongation of the latency of P100 of the visual evoked potential was recorded in 20% of patients with brain concussion and 16.7% with brain contusion. Auditory evoked potentials were abnormal in 10.3% of brain concussion and 26.5% of brain contusion cases. In 64 cases all three types of evoked potentials were studied and pathological changes in at least one of these types were found in 56.4% of brain concussion and 72% of brain contusion cases. The results show that as least in a part of cases diagnosed as brain concussion according to generally accepted criteria, central nervous system injury is present.     

Evoked potentials in olivopontocerebellar atrophy

Pattern-reveral visual evoked potentials, far-field and cortical somatosensory evoked potentials, and auditory brainstem potentials were recorded in two patients with olivopontocerebellar atrophy. In one patient, visual evoked potentials exhibited prolonged latency and interocular latency differences in the absence of clinical visual dysfunction. Median and tibial nerve evoked cortical potentials were severely attenuated in the absence of somatosensory deficit or peripheral nerve slowing. The far-field somatosensory potentials, however, were well preserved. All components of the auditory brain-stem potentials had latencies within normal limits. In the other, more severely afflicted, patient, all visual, somatosensory, and auditory evoked potentials were abnormal.     

The optimal recording electrode configuration for compound sensory action potentials.

There is no uniformity in the published literature from different laboratories on the optimal electrode configuration for recording nerve action potentials, and a number of standard texts omit any reference to the effects that interelectrode distance and electrode orientation can have on the shape, amplitude and latency of nerve action potentials. The sensory action potential from the digital nerves of the index finger was recorded at wrist and elbow using bipolar electrodes with the "active" electrode over the median nerve and the "reference" placed 4 cm laterally or proximally along the nerve using interelectrode distances of 4, 3 and 2 cm. These potentials were compared with that recorded using a remote reference on the ipsilateral shoulder, the assumption being that this configuration eliminated the contribution of the reference electrode to the compound nerve action potential. With different electrode configurations, there were significant differences in the shape of the potential, the latencies to onset and peak and the rising- and falling-phase amplitudes. The shorter the distance between the electrodes the greater the distortions. Overall, the distortions were least with the 4 cm interelectrode separation, particularly for short conduction distances.     

Auditory brain stem potentials in chronic alcohol intoxication and alcohol withdrawal

Auditory brain stem evoked responses were in unrestrained rats during periods of acute and chronic alcohol intoxication, alcohol withdrawal, and recovery. Acute alcohol administration altered the auditory brain stem potentials by a prolongation of both peak latency and central conduction time, beginning with early peaks. Similar but lesser effects affecting only the latter peaks were observed during chronic alcohol intoxication. By contrast, alcohol withdrawal resulted in a decrease in the peak latencies of auditory brain stem potentials and a facilitation of central conduction time. Recovery of the auditory brain stem potentials to the normal form required at least three to four weeks. The present study provides the first quantitative data, to our knowledge, on manifestations of alcohol tolerance and withdrawal.     

Brain stem auditory evoked potentials and myelin changes in triethyltin-induced edema in young adult rats

The effect of white matter edema induced by triethyltin (TET) intoxication on the brain stem auditory evoked potentials was examined in young adult rats. Results show that animals which received TET had lower body weight, increased brain weight, and increased water content in brain tissue. The amount of myelin (normal flotation density) recovered was reduced in TET-treated rats by approximately 45%, however, the recovery of synaptosomes was normal. The decrease in myelin content in the central nervous system of the TET-treated rats was accompanied by a significant increase in the peak latencies of all brain stem auditory evoked potentials (waves I, II, III, IV) as well as the interpeak (IV – I) difference. The potential latencies and the amount of myelin recovered became normal within 2 weeks after discontinuing TET treatment. These results demonstrate the relationship between the amount of myelin in the central nervous system and the latencies of the brain stem auditory evoked potentials and suggest that they may serve as a noninvasive measure of myelin defect.     

Brain stem auditory evoked response development in the kitten

The development of brain stem auditory evoked responses (BAERs), recorded from a surface electrode as short-latency, volume-conducted potentials, was studied in a series of kittens over a postnatal period ranging from birth to 60 days. Repeated, longitudinal observations on particular kittens were supplemented with observations on additional kittens during the first and second postnatal week to determine age of onset of the BAERs. The position of the animal and sound source within the recording chamber were held constant across recording sessions, as was click intensity except during recordings in which intensity effects were specifically studied. Click rates of 1, 10, 50 and 100/sec were routinely presented. Reference electrodes at the tongue, pinna and neck showed volume-conducted responses to the click stimuli and resulted in considerable distortion of the activity recorded by the vertex electrod; the forepaw, in contrast, showed no activity and a vertex-forepaw electrode configuration provided good resolution of the BAERs across development.A number of new observations were made. BAERs were first observed at 4 days of age, approximately the same age at which depth evoked potentials are first recorded in brain stem auditory nuclei. Initially the BAERs were diffuse, high threshold and fatigued rapidly, characteristics shared with depth evoked potentials in the early postnatal period. Over the first two weeks, the potentials showed marked decrease in threshold, increased resistance to fast click rates, and better definition of wave forms. All BAER components showed exponential decreases in latency. Because all of the brain stem evoked potentials could be recorded concurrently and longitudinally in the same subject a number of developmental comparisons were possible among the BAER components. Wave 1, related to the acoustic nerve in the adult cat, showed a developmental time course and adult latency similar to that reported for N₁. Wave 2, related to the cochlear nucleus in the adult, showed a marked bimodality over the first month; wave 2a was a large amplitude clearly separated wave which gradually fused as an inconspicuous conspicuous leading shoulder on wave 2b. Wave 2b developed with a time course and adult latency similar to that reported for the ventral cochlear nucleus. Wave 3, related to the region of the superior olivary complex in the adult, showed a clear but transient bimodality during the third week of development. Wave 5, related to the inferior colliculus in the adult, appeared later than waves 1–4 and showed a significantly slower rate of development than waves 1–4. These data indicate that differential developmental changes occur within the brain stem auditory pathway and that the BAERs provide a dynamic probe of concurrent maturational interactions.     

Auditory brain stem responses in the cat. I. Intracranial and extracranial recordings

A spatial and temporal analysis of auditory evoked potentials within the brain stem were performed in cats to determine the areas of the brain stem having large amplitude voltage fields, corresponding in latency to each of the components of the scalp-recorded auditory brain stem response (ABR). On the basis of this criterion, the first few components (occurring within 2 msec post-stimulus) were attributed to activity in a single structure, the eighth nerve. In contrast, each of the other components was correlated with large amplitude fields in at least two sites within the brain stem auditory pathways. The findings demonstrate a complex spatial and temporal distribution of electrical events within the auditory brain stem pathways, which preclude any simple one-to-one relationship between a given anatomical site and a particular component of the ABR. The possibility that the determination of the generators might be influenced by filtering of the evoked potentials was also examined. High-pass filtering of the evoked potentials resulted in a modification of the defined generators for only one of the components studied (P4). Filtering had little effect on the components of the scalp-recorded ABR.     

Monitoring of antidromic facial nerve action potentials in cerebello-pontine angle tumor operations

A method of recording the antidromic facial nerve compound potential (AFNAP) is presented. When the facial nerve is stimulated, a compound action potential is propagated in both directions from the stimulating site. We recorded AFNAP's in 6 cases of cerebello-pontine angle (CP angle) tumors (5 acoustic neuromas and one epidermoid) using a bipolar silver ball-type electrode directly put on the facial nerve in CP angle by stimulation of the peripheral facial nerve at the stylomastoid foramen. It was necessary to use needle electrodes instead of surface ones for stimulation to keep the artefacts from stimulating currents within reasonable bounds. Good contact of the electrode tips with facial nerve was required to get clear action potential. By stimulation with needle electrodes AFNAP's were recorded without averaging and had a good reproducibility. AFNAP's were typical triphasic potentials and the major negative peak latencies were observed from 1.5 to 3.4 msec except one case of recurrent epidermoid whose major negative peak latency was 7.6 msec. It was verified that these potentials were the results of facial activity, because they were recorded exclusively on the facial nerve, they could not be recorded at the proximal end of the sectioned facial nerve, and alterations of latency were observed with changing the position of recording electrode along the facial nerve. A calculated conduction velocity was about 50 m/sec. It was thought that recording AFNAP facilitated the identification of the facial nerve on the surface of the CP angle tumor, because the amplitude of AFNAP decreased immediately when the recording electrodes were off from the facial nerve.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cognitive evoked potentials to anticipated oesophageal stimulus in humans: quantitative assessment of the cognitive aspects of visceral perception

Evoked potential studies provide an objective measure of the neural pathways involved with perception. The effects of cognitive factors, such as anticipation or awareness, on evoked potentials are not known. The aim was to compare the evoked potential response to oesophageal stimulation with the cortical activity associated with anticipation of the same stimulus. In 12 healthy men (23.5 +/- 4 years), oesophageal electrical stimulation (15 mA, 0.2 Hz, 0.2 msec) was applied, and the evoked potentials recorded using scalp electrodes. A computerized model of randomly skipped stimuli (4:1 ratio) was used to separately record the evoked potentials associated with stimulation and those associated with an anticipated stimulus. The electrical stimulus represented the nontarget stimulus and the skipped impulse the target (anticipatory) stimulus. This anticipatory evoked potential was also compared to auditory P300 evoked potentials. Reproducible evoked potentials and auditory P300 responses were elicited in all subjects. Anticipatory evoked potentials (peak latency 282.1 +/- 7.9 msec, amplitude 8.2 +/- 0.7 microV, P < 0.05 vs auditory P300 evoked potential) were obtained with the skipped stimulus. This anticipatory evoked potential was located frontocentrally, while the auditory P300 potential was located in the centro-parietal cortex. The anticipatory evoked potential associated with expectation of an oesophageal stimulus, although of similar latency to that of the auditory P300 evoked response, originates from a different cortical location. The recording of cognitive evoked potentials to an expected oesophageal stimulus depends on attention to, and awareness of, the actual stimulus. Anticipatory evoked potentials to GI stimuli may provide an objective electrophysiological tool for the assessment of the cognitive factors associated with visceral perception.     

Neural generators of the brain-stem auditory evoked potentials (BAEPs) in the rhesus monkey

Brain-stem auditory evoked potentials (BAEPs) were recorded from rhesus monkeys in response to click stimuli. The BAEPs in the monkey have only 4 major peaks, while 5 major peaks can be identified in the human BAEP. The responses from electrodes placed at the vertex and the mastoid recorded either differentially or separately using non-cephalic references were compared to concomitant recordings from the auditory nerve, the cochlear nucleus, and the inferior colliculus, including the lateral lemniscus and the brachium of the inferior colliculus. It was found that the response from the intracranial portion of the auditory nerve lags behind the far-field response recorded from the mastoid by about 0.2 msec. The major component of the potentials recorded from the lateral lemniscus appeared with a latency that was close to that of the fourth peak in the BAEP. Deafferentation of the inferior colliculus resulted in only small changes in the BAEP, indicating that the contributions to the BAEP from the inferior colliculus and more central structures of the ascending auditory pathway are insignificant. It is concluded that the main reason for the difference between the human BAEP and the BAEP in the rhesus monkey is the smaller size of the monkey's head and the resulting shorter auditory nerve. The result is that the auditory nerve in the monkey only generates one peak in the far-field response, while in man the auditory nerve gives rise to both of the two earliest peaks in the BAEP; thus, the BAEP in man has 5 peaks while that in the monkey has only 4 peaks.