Clinical interpretation of brainstem evoked response audiometry abnormalities in cochlear pathology

This investigation involved 45 patients with sensorineural hearing loss (SNHL): 24 with Meniere's disease, 18 with acoustic trauma, and 3 with SNHL due to ototoxic drugs. They all underwent pure tone audiometry and standard brainstem evoked response audiometry (BERA). In patients without wave I in auditory brainstem response, electrocochelography (ECochG) was performed. The findings are presented showing that cochlear lesions (beside threshold elevation) cause latency prolongation of wave I, III and V relative to normal latencies at the actual click hearing level. At high stimulation levels, this effect is almost completely compensated for by the fact that cochlear recruiting ears exhibit steeper latency-intensity curves than do normal ears. But, at the same time this pathology does not cause latency prolongation of central conduction time (CCT). Beside this, cochlear lesions will cause, in some cases, deterioration of replicability (poor waveform resolution) of waves preceding wave V. In such cases, the authors strongly recommend electrocochleography (ECochG) to make wave I visible, because they think that it is the best way to verify the diagnosis of cochlear lesion using BERA.     

Median nerve F wave conduction in healthy subjects over age sixty-five

Parameters of the median nerve F wave and peripheral motor nerve conduction in 51 healthy male and female human subjects 67 to 89 years of age are described. F wave responses were elicited by stimulation of the nerve at the wrist. Motor nerve conduction velocity (MNCV) was determined for the forearm segment. Major results of this study of an older group of subjects demonstrate that: 1) the shortest F wave latency (SFWL) and the MNCV were slower in our older subjects than values in younger subjects; 2) there was no significant correlation between SFWL and age within the age group examined; 3) distal motor conduction latency was significantly slower in subjects age 75-89 years than in those age 67-74 years; 4) SFWL and MNCV of females were significantly faster than that of males; 5) a positive correlation was found between SFWL and arm length and a predictive formula is derived. An upper limit of normal F wave wrist latency of 31 msec for females and 34.4 msec for males over 65 years of age is proposed as a guideline.     

Maturation of lower extremity EMG responses to postural perturbations: relationship of response-latencies to development of fastest central and peripheral efferents

Summary EMG responses to toe-up tilt perturbations on a movable platform system were analysed in 86 children between the age of 12 months and 13 years. To assess the relative contribution of peripheral and central nerve conduction properties, a concomitant recording of the fastest efferent pathways in the central and peripheral motor system was made using non-invasive transcranial magnetic stimulation of motor cortex and peripheral nerve roots. This allowed the determination of the fastest downstream efferent connection times from motor cortex to lumbar motor neuron pools and to measure the fastest efferent conduction from these motor neuron pools to effector muscles in the lower leg. The sequence observed for stance stabilizing EMG responses was similar to that obtained in earlier studies with short latency (SL) and middle latency (ML) components occurring in the stretched triceps surae muscle and long latency (LL) responses occurring in the non-stretched tibialis anterior muscle. Homologous responses were also obtained in upper leg muscles, being recruited consistently later than those in lower leg muscles across all age groups. In the short latency range two different SL1- and SL2-responses were obtained in children of all age groups as well as in adult controls. Both the SL1- and the SL2-responses showed a flat developmental profile, reaching adult values between 20 and 30 months of age which correlated with that of the fastest efferents from lumbar motor neuron pools to leg muscles, i.e. the final motor path. ML-responses showed a steeper developmental profile. The LL-responses in TA muscle showed an even more prolonged maturational profile which fitted well with the development of central conduction times between motor cortex and the spinal motor neuron pools. The sum of the fastest possible afferent conduction times as estimated from somatosensory evoked potentials, and the fastest downstream efferent conduction times from motor cortex to effector muscles was smaller than the onset latencies of LL-responses. The resulting transcerebral processing time exceeded the sum of the fastest up- and downstream conduction times by up to 70 ms. This suggests a prolonged transcerebral processing loop for the proprioceptive input to LL-responses rather than a transcortical loop.     

Effect of body temperature changes on evoked potentials

Short-latency somatosensory (SSEPs) and brainstem auditory evoked potentials (BAEPs) were recorded in 12 patients with fever due to respiratory infection (age, 44.3 +/- 20.9 years, mean +/- SD) to clarify the effect of body temperature change on conduction in the central somatosensory and brainstem auditory pathways. Subjects were studied during episodes of fever (37.9 +/- 0.8 degrees C) and after their body temperature had decreased (36.6 +/- 0.3 degrees C). The central conduction time (CCT), which is the peak latency between N 13 and N 20, was significantly longer after body temperature had decreased than during fever. Likewise the interpeak latency between waves I and V (I-V IPL) was significantly prolonged following decrease in body temperature. These results suggest that increases in body temperature have an effect upon conduction in the central somatosensory and brainstem auditory pathways.     

The usefulness of the brainstem auditory evoked potential in the early diagnosis of cranial nerve neuropathy associated with diabetes mellitus

BACKGROUND: An evaluation of the extent and mechanism of damage of the central nervous system in diabetes mellitus is of high value in current neurological research. Electrophysiological abnormalities are frequently present is completely asymatomatic diabetes mellitus (DM) patients. Limited data is available in the use of brainstem auditory evoked potential (BAEP) in DM. AIM: Is to evaluate the efficacy of BAEP as a method useful in the diagnosis of subclinical damage of the central nervous system in DM. MATERIAL AND METHOD: 67 diabetes and 32 healthy controls - age and sex matched - were chosen. The diabetes were of type I and II and more than or less than 10 years duration. The BAEP was elicited by using auditory stimulus by using Dantec Evomatic 4000 evoked potential machine. The latency of component response recored as waves I, III and V, interpeak latency (IPLs) I - III, I - V, III - V and amplitude of waves V. RESULTS: The difference was highly significant in the increased latency of waves I, III and V, interpeak latency (IPLs) I - III, I - V, III - V and amplitude of waves V of each type of diabetes as compared to control. Comparison of the type and duration of diabetes between each other showed no significant difference. CONCLUSION: BAEP recording can represent an objective, clinically useful and non invasive procedure to stress the early impairment both of the auditory nerve and of brainstem function.     

Central auditory conduction time in the rat

Summary Central conduction time is the time for an afferent volley to traverse the central pathways of a sensory system. In the present study, central auditory conduction time (CACT) was calculated for the rat, the first such formal measurement in any animal. Brainstem auditory evoked potentials (BAEPs) were recorded simultaneously with the primary response of the auditory cortex (P1). The latency of wave II of the BAEP, which arises in the cochlear nucleus, was subtracted from that of P1. This yielded a mean CACT of 6.6 ms. The results confirm a previous theoretical estimate that CACT in the rat is at least twice as long as central soma-tosensory conduction time.     

Somatosensory evoked potentials in children with brain ventricular dilatation

Aim

To determine possible nerve conduction changes in the somatosensory pathway in children with brain ventricular dilatation and to estimate the relation between the ventricular size and somatosensory evoked potentials (SEP).

Methods

Twelve children with ventricular dilatation (frontal and occipital horn ratios >0.44) and 19 children without ventricular dilatation (control group), aged between 2 and 15 years, were included in the study. Somatosensory evoked responses to median nerve stimulation were recorded in both groups. Evoked potentials were recorded by silver/silver-chloride cup electrodes from Erb’s point in the supraclavicular fossa (wave N9), the cervical spine at the C7 vertebral prominence (wave N13), and the scalp above the contralateral sensory cortex at the point C3’ or C4’, 1 cm behind the C3 or C4 site in the standard 10-20 system (wave N19). Computed tomography scanning was performed to estimate ventricular dilatation.

Results

The conduction time of the central somatosensory pathway (N19-N13 interwave latency) was significantly longer in the children with ventricular dilatation than in the control group (P = 0.046). A statistically significant but weak correlation was found between the frontal and occipital horn ratio values and the N19-N13 interwave latencies in the subjects with enlarged ventricles (r = 0.579, P = 0.045)

Conclusion

Ventricular dilatation is associated with prolonged conduction of the central part of the somatosensory pathway in children. Early detection and treatment of hydrocephalus could be useful in preventing long-term consequences of high intraventricular pressure.Testing of somatosensory evoked potentials (SEP) is a noninvasive, objective method for evaluating the central and peripheral nervous systems, and can also generate information about the maturation of the human afferent sensory system (1,2). This testing is particularly useful in infants and children because the clinical sensory neurological examination in these patients is often difficult and unreliable. In infants with hydrocephalus, both visual and auditory brainstem evoked potentials have already been studied (3,4). However, a limited number of studies have been done to assess SEPs in such infants (5).Hydrocephalus is characterized by diffuse cortical and subcortical damage and therefore differs from other pathologies that result from discrete lesions. Neurophysiological consequences of hydrocephalus and their influence on the function of different neuroanatomic structures are not well known. In children, hydrocephalus compromises normal neurological development and can also cause permanent neurocognitive sequels (6). Therefore, special attention should be paid to the early detection and timely treatment of hydrocephalus.The aim of our study was to determine the possible nerve conduction changes in the somatosensory pathway in children with ventricular dilatation and to estimate the relation between the ventricular size and SEPs latencies.     

The Effects of Age on Human Event-Related Potentials

Event-related brain potentials were recorded from 72 normal subjects aged 20-79 yrs. The event-related potential to a detected improbable signal contained a large late positive component or P3 wave. The latency of the P3 wave in the response to an auditory signal increased regularly with increasing age at a rate of 1.36 ms per year, and its amplitude decreased at a rate of 0.18 μV per year. Similar age-related changes in the P3 wave occurred in the visual and somatosensory modalities. The change in the latency of the P3 wave occurred independently of any change in the reaction time, which showed no significant age-related change. The latency of the P3 wave associated with the detection of an omitted auditory stimulus did not change significantly with age.     

Involvement of central nervous system in patients with diabetes mellitus detected by evoked potentials

Somatosensory (SSEPs) and brainstem auditory evoked potentials (BAEPs) were recorded for 44 patients with diabetes mellitus (age, 63.0 +/- 9.3 years, mean +/- SD) and 20 age-matched healthy controls (age, 67.3 +/- 9.1 years) to elucidate the involvement of the central nervous system (CNS) in diabetes mellitus. Furthermore, relationships between SSEP or BAEP and clinical variables such as autonomic nervous function, peripheral nerve conduction velocity, duration of diabetes, metabolic control (fasting blood sugar level, HbA1 and HbA1c levels) and therapeutic method, were studied. The central conduction time (CCT), which represents the peak latency between N13 and N20, in patients with diabetes mellitus was significantly longer than that of the healthy controls (p less than 0.005). Likewise, diabetic patients showed significant prolongation of interpeak latency between waves I and V (I-V IPL) compared to the healthy controls (p less than 0.005). Significant correlations between CCT and motor conduction velocity of median nerve (p less than 0.05) were observed although the correlation between CCT and sensory nerve conduction velocity was not found to be significant (p less than 0.1). Furthermore, I-V IPL was significantly correlated with the duration of illness (p less than 0.05). There were no significant correlations between CCT or I-V IPL and autonomic nervous dysfunction as determined by orthostatic hypotension and the coefficient variation of the R-R interval or metabolic control or therapeutic method. From the present results, it would appear that there is CNS involvement even in diabetic patients not manifesting overt CNS signs and symptoms and that it is correlated somewhat with impairment of the peripheral nervous system and duration of illness.     

H-reflex latency and sensory conduction in the assessment of neuropathy in patients of chronic obstructive lung disease.

H-reflex latency, proximal conduction velocity and distal proprioceptive conduction velocity were studied along with distal motor and sensory conduction in 38 patients of chronic obstructive lung disease grouped according to age and duration of the disease, as well as in 35 age-matched smoker controls and 14 non-smoker controls. The mean values of all the parameters studied in all the patient groups were significantly different from those of the non-smoker control group. Smoker controls also showed significant abnormality in all the parameters except motor conduction velocity. Among the patients, significant abnormality (mean +/- greater than 2 SD) was seen in 44.7% in motor conduction, 86.8% in sural nerve distal latency, 97% in Ia conduction velocity, 78.9% in H-reflex latency and 60.5% in proximal conduction velocity, as compared to the non-smoker control values. Among the old patients with more than 10 years of the disease, 62.5% had all the parameters significantly abnormal. More than one parameter was affected in 97.4% of the patients. The intra-group and inter-group differences in all the parameters studied, except motor conduction velocity, were statistically significant indicating that age, chronicity of the disease and smoking can produce nerve conduction defects independently and collectively. It is suggested that though all parameters studied are highly sensitive to neuropathies, proximal H-latency studies are best suited for grading conduction defects in patients of chronic obstructive lung disease, since in many patients sural nerve action potential (52.63%) and distal H-reflex response for Ia conduction studies (81.52%) could not be elicited.(ABSTRACT TRUNCATED AT 250 WORDS)     

Facilitation and inhibition of synaptic transmission in the spinal cord: an electroneurographic study in humans

Summary The neurographic activity evoked either by stimulation of the tibial nerve at the popliteal fossa or by percussion of the Achilles tendon has been recorded at lumbar and thigh levels, in order to find out whether conduction time, temporal dispersion and central delay of the neural volleys underlying the monosynaptic reflex (H or T) may change (a) as a function of stimulus intensity; (b) under facilitatory or inhibitory experimental conditions; (c) “spontaneously”, i.e. during the steady state. The reflexly evoked ventral root discharge (VRD) decreases in latency with increasing stimulus intensity up to the maximum reflex response in the absence of changes in afferent (thigh to spine) or efferent (spine to thigh) conduction times. Reduction of the central delay was greater with mechanical than electrical stimulation, probably due to the combined effect of spatial and temporal summation under the former experimental condition. The latency of the VRD related to the maximal H response was not further modified by supramaximal stimulus strengths. The Jendrassik manœuvre caused a significant decrease in latency of the VRD, the opposite effect being observed during calf muscle vibration. A significant relationship between amplitude and latency of single VRD s could be demonstrated during the “steady state”. Our data point to the existence of a positive correlation between the size of the motoneuronal pool activated by an afferent volley and speed of transmission in the reflex pathway, both during the “steady state” and under either facilitatory or inhibitory experimental conditions, provided that the test stimulus strength does not exceed the maximum reflex response (H or T). No detectable signs of peripheral dispersion of the VRD could be demonstrated, irrespective of the stimulus employed: this suggests that the axon diameters of the moto-neurones contributing to the monosynaptic reflex fall within a fairly narrow distribution     

Long-latency spinal reflexes in humans

Stretching human muscles with a mechanical device gave rise to multiple peaks in the rectified and averaged electromyogram. In the first dorsal interosseous the latency of the first peak (M1) was 32.4 +/- 2.4 ms (SD) and the latency of the second peak (M2) was 55.1 +/- 11.3 ms, in both cases measured from the time of the stimulus to the take-off point of the peak. Often a third peak (M3) was seen, having a considerably longer latency. The origin of peak M1 was considered to be in the stretch reflex arc because of its latency and its invariable association with muscle movement. Peak M2 was due to stimulation of afferent terminals in the skin and/or subcutaneous tissues by the mechanical device producing the muscle stretch. The conduction velocity of the pathway involved in the generation of the M1 component is the same as that for M2. This implies that central processing in the spinal cord delays the M2 response. The M2 mechanism does not involve a transcortical (long-loop) pathway because in foot muscles the M1-M2 delay remains the same as is found for hand muscles, although M1 latency is prolonged (to 39.4 +/- 6.2 ms for extensor digitorum longus). This indicates that there is not time for M2 impulses to traverse a pathway any longer than that passing to and from the spinal cord.     

Physiological properties of individual cerebral axons studied in vivo for as long as one year

The long-term stability of conduction velocity and recovery processes were studied in a fast-conducting (corticotectal) and in a more slowly conducting (visual callosal) axonal system. Chronic microelectrode recording methods were used in conjunction with antidromic activation via electrical stimulation at one or more axonal site. These methods enabled 54 axons to be studied for greater than 20 days and seven of these cells to be studied for 101-448 days. The conduction velocities of corticotectal axons were characteristic of myelinated axons and were very stable over time. The conduction velocities of most callosal axons were characteristic of nonmyelinated axons, and 68% of callosal axons had conduction velocities that were stable over long periods of time. Of the remaining callosal axons, approximately one third showed an increase in conduction velocity (8-14%), whereas two thirds showed a progressive and systematic decrease in conduction velocity (6-81%). These changes in conduction velocity were distributed along the callosal axon, rather than limited to a single segment of axon. Although the refractory period of callosal and corticotectal axons showed considerable variability over time, the minimal interval between two conducted impulses was stable. The stability of this property was remarkable because the minimal interspike intervals of different axons with similar conduction velocities often differed greatly. Callosal axons show a supernormal period of increased conduction velocity following the relative refractory period and a subsequent subnormal period of decreased conduction velocity following a burst of prior impulses. In different callosal axons the magnitude of the velocity changes (percent change) differs greatly, even among axons of the same conduction velocity. For a given axon, however, these properties are very stable over time. These results on axonal properties may be useful in studies requiring the examination of extracellular responses of individual neurons over long periods of time. Antidromic latency provides a useful means of identifying a cell, particularly when conduction times are long. The stability of the minimal interspike interval and the supernormal period within individual axons make them suitable as ancillary criteria in identifying individual neurons. These three measures are independent of spike amplitude and waveform, and together they provide a "signature" by which individual cortical neurons can be identified over periods that represent a significant portion of the lifespan of adult mammals.     

Acoustic startle response in young and aging C57BL/6J and CBA/J mice

C57BL/6J (C57) mice demonstrate progressive age-related hearing loss during the first year of life, whereas CBA/J (CBA) mice lose little sensitivity through 18 months of age. The acoustic startle response (ASR) was measured in these strains to determine behavioral correlates of aging with and without presbycusis. The stimuli were tone pips (10-ms duration, 1-ms rise-fall) with frequencies of 4, 8, 12, 16, or 24 kHz at intensities of 70, 80, 90, or 100 dB SPL. ASR "thresholds" (the minimum SPL required to elicit ASRs more than 50% of the time) increased with age, and startle amplitudes became smaller in both strains. However, the changes in these startle parameters were much more pronounced in C57 mice, with middle to high frequencies (12-24 kHz) severely affected. The startle latencies at and above ASR "threshold" increased with age in C57 mice, but did not change in CBA mice. The CBA data indicate that aging, per se, has little effect on ASR parameters; the C57 data show that hearing loss is a cogent factor. However, ASR parameters of C57 mice are altered to a greater extent than expected, on the basis of the elevations of absolute sensory thresholds, particularly for middle frequencies (12-16 kHz). Both peripheral and central mechanisms are proposed to account for the discrepancy.     

Acoustic phenomena in the latent period of skeletal muscle: a simple method for in-vivo measurement of the electro-mechanic latency (EML)

An in-vivo method for the assessment of the latency of muscular contraction is presented. It is based on acoustic registration of musclar thickening by a microphone. It was found that the recorded sound wave is often preceded by a small wave of opposite polarity (flattening of the muscle belly) which is an acoustic correlate of the latency relaxation. Strong direct stimulation produced another small sound wave at the beginning of the latent period. The physiological significance of these findings is discussed.This work was supported by the Deutsche Forschungsgemeinschaft (SFB 70)     

Low voltage bifocal electrical stimulation of the motor cortex

Currently, non-invasive cerebral motor area stimulation is performed by magnetic or high voltage bifocal electrical stimulation. These techniques require non-conventional stimulators. The present study, performed on 28 normal subjects between 18 and 73 years of age, was designed to standardize a method of bifocal stimulation of motor cortex which uses low voltage conventional stimulators and therefore can be routinely used in electrophysiological laboratories. The hand motor area was stimulated by surface electrodes applied in Cz (cathode) and 8 cm lateral on the bimetal line (anode). Under the electrodes infiltration with Xylocaine 2% was made. Duration and intensity of the rectangular pulses were 150 microseconds and 200-250 Volts, respectively. The motor evoked potential (MEP) was recorded from opponens pollicis muscle by concentric needle electrodes and a slight voluntary contraction was made to facilitate the motor response. MEP latency and central motor conduction time (CMCT) were calculated for both sides. A significant relation with age and height in normal subjects was found only for the MEP latency. We computed also the equations expressing the normal variability between the sides of MEP latency and of CMCT.     

国人大脑皮层与脊髓电刺激多导联描记MEP正常值

报告国人上、下肢共２４块肌于大脑皮层与脊髓电刺激时的运动诱发电位（ＭＥＰ）正常值。无论上肢或下肢，ＭＥＰ潜伏期均因肌肉所在位置而异，越是远端肌潜伏期越长，认为此乃脊神经长度不同所致。但中枢运动传导时间（ＣＭＣＴ）则与脊神经长度、肢长及身高无关，此为锥体束功能的最重要指标。肌肉轻度收缩时，皮层刺激的ＭＥＰ潜伏期缩短，波幅增高，认为系上运动神经元的易化所致。作者认为，ＭＥＰ的多导记录能减少刺激次数，一次性刺激即能同时获得多块肌的ＥＭＰ记录；有利于髓内和神经根病变的定位诊断。     

Analysis of muscle receptor connections by spike-triggered averaging. 2. Spindle group II afferents.

1. The spike-triggered averaging (STA) method has been used to study synaptic connections of nine spindle group II afferents from medial gastrocnemius to 151 motoneurons of leg muscles in the cat. 2. EPSPs were found in 40 cells, predominantly of triceps surae with latency from cord entry ranging from 0.3 to 4.2 ms. Those with latency less than or equal to 1.4 ms were deduced to be monosynaptic in confirmation of Kirkwood and Sears (13). Mean amplitude for MG-LGS cells was 30.1 muV and mean rise time 1.0 ms (compared with 65.4 muV and 1.0 ms for monosynaptic Ia EPSPs from the preceding report (26)). It is argued that monosynaptic latency for spindle group II afferents could be as large as 1.65 ms. 3. The occurrence of a presynaptic spike permitted the division of EPSP latencies into central conduction time and synaptic delay components. Sindle group II central conduction times were significantly longer than those of Ia afferents, while there were no differences in the synaptic delays associated with the two afferent types. 4. EPSPs of longer latency were judged to be di- or trisynaptic. They were smaller and had longer rise times than the monosynaptic effects. Evidence is presented to show that short rise time of an individual PSP does not guarantee that it is monosynaptic. Rise times are different only on a population basis. 5. Inhibitory responses were found with latencies and mean rise times appropriate for di- and trisynaptic connections. Their mean amplitude was 4.6 muV. 6. The distribution of EPSPs and IPSPs was generally consistent with their exerting stretch reflex effects similar to that of Ia afferents and inconsistent with the inclusion of them in the grouping known as "flexor reflex afferents."     

The effect of parathyroid hormone and 1,25 (OH)2D3 on nerve conductance in patients on maintenance hemodialysis

In 30 uremic patients on chronic maintenance hemodialysis the sensory and motor fiber conduction and the motor distal latency were measured in the left tibial nerve, in order to evaluate if a correlation between their values and the serum IPTH or 1.25(OH)2D3 can be found. The sensory and motor fiber conduction velocities were found to be significantly lower in hemodialysis patients than in a group of healthy controls. The motor distal latency time did not differ significantly from that found in healthy persons. A markedly increased serum C-terminal and mid-region (44-68) iPTH, and a very low serum 1.25(OH)2D3 were found in uremic patients. Regression analyses demonstrated the significant negative correlations between the serum C-terminal iPTH and the sensory (r = -0.441, p less than 0.05) and motor nerve (r -0.471, p less than 0.01) conduction velocities. A significant positive correlation between serum 1.25(OH)2D3 levels and the motor distal latency time was also observed (r = 0.3639, p less than 0.05). The results obtained suggest a role of the increased concentration of IPTH fragments in the development of uremic polyneuropathy. A significant decrease of 1.25(OH)2D3 obviously has no negative effect upon the nerve conductance in patients on maintenance hemodialysis.     

磁刺激运动诱发电位对S_1神经根病的诊断价值

采用磁刺激腰骶部运动神经传导时间（ＭＮＣＴ）与磁刺激窝Ｆ波相结合测定运动神经根传导时间（ＭＲＣＴ）的方法，无痛无创地评估Ｓ１神经根功能。研究对象为５０名正常受试者和３０名Ｓ１神经根受损病人。结果表明：磁刺激ＭＮＣＴ在病人组均正常，而ＭＲＣＴ却明显异常，异常率为８７％，明显高于Ｆ波潜伏期的异常率７３％。因此，磁刺激运动诱发电位（ＭＥＰ）是诊断Ｓ１神经根病的一种有很大应用价值的方法。