Short latency somatosensory evoked potentials to peroneal nerve stimulation in normal Japanese children

Short latency somatosensory evoked potentials (SSEP) were elicited by stimulation of the peroneal nerve in 68 normal children of 39 weeks to 15 years old. In all subjects, three positive potentials (P1, P2 and P3) and one negative potential (N1) were consistently recorded. A further positive potential (P4) after N1 was not always observed. There was no change of wave form with development. P1, P2, P3 and N1 might be generated in subcortical structures; caudal cervical spine, brainstem, thalamus and thalamocortical pathway, respectively. The latency of each peak per one meter body length decreased with age until 5 or 6 years of age. Moreover, the latency between peaks per one meter body length also decreased with age until 5 to 6 years of age. These findings are consistent with the development of SSEP on median nerve stimulation and with the developmental phenomenon of spinal conduction velocity, and might be related to the increase in the diameter and the progressive myelination of nerve fibers.     

Short latency somatosensory evoked potential in children

The short latency somatosensory evoked potential was studied in 90 normal children of 1 month to 16 years old and 7 adults. Somatosensory stimuli were delivered through a disc electrode placed over the median nerve at the wrist joint. The uniform recording sites used were the central region of the scalp, and the seventh cervical spine or Erb's point. Reference electrodes were placed on the hand contralateral to the median nerve stimulated. Three positive peaks (P1, P2 and P3) and one negative peak (N1) were consistently recorded, a further positive peak (P4) after N1 was not always observed. The latency of each peak per 1 m body length decreased with age until 2 or 5 years of age. The latency of each peak after 2 years of age was positively correlated with the body length and arm length. The value of P1 peak latency per 1 m body length reaches adult values at an earlier rate than the value of P3 peak latency and P2-P3 latency per 1 m body length. This suggests that central lemmiscal pathways mature at a slower rate than peripheral nerve fibers. The wave form pattern of the short latency somatosensory evoked potential changed to the adult pattern at 10 years of age. The peak latency of P4 during deep sleep was slightly prolonged. In recording on infants during sleep, the EEG should be monitored to determine the stage of sleep.     

Dectection of spinal cord lesion using skin electrode recordings of spinal evoked potential

The multi-channel recording of somatosensory spinal evoked potential (SSEP) was carried out on 30 patients with various neurological disorders. In some cases, SSEP changes corresponded well with the lesioned level. In general, the lesions of thoraco-cervical level were difficult to detect, because the appearance rate of SSEP peaks are reduced over the thoraco-cervical spine even in normal controls. In cases with spinal type of MS, SSEP revealed marked changes and subclinical sensory demyelinating lesions were detectable. Chronological SSEP recording in patients with acute transverse myelitis revealed functional improvements corresponding with clinical recovery. Surface and non-invasive SSEP recording is useful for detecting lesions in the spinal cord or peripheral nerves. It also offers valuable information about chronological modification of the lesions, and may reveal subclinical changes in certain neurological disorders.     

A study of the maturation of the somatosensory pathway by evoked potentials

We investigated the somatosensory evoked potentials (SSEPs) in 62 healthy children, ten days to twelve years old. Our control group consisted of ten healthy adults, sixteen to thirty-six years old. The stimulus was applied at the median nerve at the wrist and the cerebral SSEPs were recorded by electrodes placed on the contralateral parietal scalp region, while for the cervical SSEP recording the electrodes were placed over the skin at the C6-C7 vertebral region. The reference electrode was placed at the FZ according to the 10-20 system. Our study revealed a significant change in the early components of the SSEPs (NI and PI) between groups of different ages. The latency and duration of the NI wave form and the latency of PI were inversely correlated with age. These changes in the early components of the SSEPs are most likely due to the gradual maturation of the afferent nervous system with age. From the difference in latencies between the peak of NI and the cervical SSEP we were able to calculate the sensory conduction time in the central nervous system and found a progressive decrease in relation to the increase of age. This is most likely due to the development of postnatal myelination of the sensory fibres of the central somatosensory pathway.     

气功所致精神障碍患者脑诱发电位系列实验研究

目的 研究气功所致精神障碍患者与正常人在诱发了诱发电位的检测中的不同特点。方法 应用美国仪器和四种方法，对１２例气功偏差所致精神障碍患者和５２例正常人的诱导电位作了检测。结果 与正常人比较，患者组ＡＥＰ的Ｐ１、Ｐ２、Ｎ２、Ｐ３；ＶＥＰ的Ｎ１、Ｎ２、Ｐ３和ＳＥＰ的Ｐ２潜伏期均明显延迟ＡＥＰ、ＶＥＰ和ＳＥＰ的若干波幅同时明显改变。另在ＣＮＶ中机见Ｐ１ＮＶ和Ａ－Ｃ潜伏期延迟，波畅Ｂ增大，Ａ－Ｓ２＾－和Ｓ     

Re-evaluation of short latency somatosensory evoked potentials (P13, P14 and N18) for brainstem function in children who once suffered from deep coma

One of the major clinical features of brain death is deep coma. Therefore, we re-evaluated retrospectively electrophysiological examinations of brainstem function in about 31 children who had once suffered from deep coma in order to reveal its pathophysiological characteristics. The patient age at coma ranged from 1 month to 10 years (mean 2 years 1 month). The electrophysiological examinations were performed, including any of short-latency somatosensory evoked potential (SSEP), brainstem auditory evoked potential (BAEP) and blink reflexes. We first compared results between the fair and poor prognostic groups, and then re-evaluated SSEP results on a few severely impaired patients with persistent vegetative state (PVS). Subsequently, SSEP clarified more specific findings for a deep coma condition than BAEP and blink reflex. A lack of P14, N18 and N20, and an amplitude reduction or vagueness of P13 in SSEP in these children strongly suggested high risk in their future neurological prognosis. In conclusion, electrophysiological examinations, especially SSEP (P13, P14 and N18), might be very useful in obtaining a long-term neurological prognosis after deep coma in children.     

Lumbar spinal cord and early cortical evoked potentials after tibial nerve stimulation: effects of stature on normative data

Short-latency somatosensory evoked responses to tibial nerve stimulation were recorded simultaneously over the spinous processes of the lumbar vertebrae and scalp in normal young subjects. This non-invasive test revealed values which are highly reproducible and could be closely correlated with subject-related variables such as height and leg length. A nomogram describing the close relationship between absolute latency of various response components and stature was derived and shown to be an important variable in the establishment of normative data nad interpretation of SSEP in relation to disorders affecting the peripheral and central nervous system. In contrast, central conduction times of interpeak intervals (N22-P37 and N22-N45) were unrelated to variations in the subjects, stature providing a reliable clinical measure in the assessment of the central somatosensory pathway.     

Effects of stimulus intensity on latency and conduction time of short-latency somatosensory evoked potentials.

We studied the effect of stimulus intensity on latencies of short-latency somatosensory evoked potentials (SSEP) by measuring both onset and peak latencies individually. The latencies of N9, N13, N20 and N9-N13 peripheral conduction time (PCT) of median nerve (MN) SSEP, and N8, N23, P37 and N8-N23 PCT of tibial nerve (TN) and sural nerve (SN) SSEP significantly shortened with increasing stimulus intensity by onset latency measurement. However, those latencies by peak latency measurement were less significantly shortened or had only a trend of latency shortening without statistical significance. In contrast to PCT, N13-N20 central conduction time (CCT) of MN-SSEP and N23-P37 CCT of TN- or SN-SSEP showed no latency changes with the increased stimulus intensity by both onset and peak latencies measurement. As peak latencies had greater interindividual variability than onset latencies shown by larger standard deviation, shortening of onset latencies were more consistent than that of peak latencies. We think shortening of onset latencies indicates the recruitment of faster conduction fiber along with increased stimulus intensity. As the degree of latency shortening was less if stimulus intensity was above 2.5 times sensory threshold, the stimulus intensity greater than 2.5 times the sensory threshold should be used for clinical application.     

Short latency somatosensory evoked potentials following the peripheral nerve stimulation of lower extremities in children

We have evaluated the short latency somatosensory evoked potentials (SSEPs) following peroneal and posterior tibial nerve stimulation in 27 normal children and adults, and then applied SSEPs examination following peroneal nerve stimulation to 6 children with neurological deficits. Features of the evoked potentials following peroneal nerve stimulation in normal children were almost similar to those in adults, but we found several points characteristic in children; a higher incidence of evoked potentials and a clearer appearance of "standing potential" at the lower thoracic vertebral level than in adults. Spinal afferent conduction velocity reached at a maximum at 3-4 years of age. The SSEPs following peripheral nerve stimulation in lower extremities are useful in pediatric neurology to determine the level of the spinal lesion, to reveal the distribution and pathophysiology of the spinal dysfunction, and to analyze the process of the disease progression.     

Developmental assessment of spinal cord and cortical evoked potentials after tibial nerve stimulation: effects of age and stature on normative data during childhood

Somesthetic information from lower extremities is processed by cerebral cortex after traversing the sensory pathways of peripheral nerve, spinal cord, brain-stem and thalamus. Clinical utility of somatosensory evoked potentials (SSEPs) during human development requires systematic analysis of normative data acquired during various stages of body growth and nervous system maturation. Accordingly, SSEPs after tibial nerve stimulation were studied in 32 normal awake children (1-8 years old) and compared with values obtained in young adults (18-40 years old). Potentials were recorded from the tibial nerve (N5), first lumbar spinous process (N14), seventh cervical spinous process (N20) and from the scalp, 2 cm behind the vertex (P28). In all children studied, the N5, N14 and N20 latencies were positively correlated with age and height yielding a predictive nomogram. An extremely variable electropositive cortical SSEP was recorded from Cz' which did not show a highly predictable linear relationship in association with a relatively poor correlation coefficient for height and age. It may be concluded that between 1 and 8 years of normal postnatal development, latencies reflecting peripheral nerve and lumbar spinal cord vary directly with height and age and can be represented by a simple cable model of a lengthening myelinated pathway. In contrast, the latency of the cortical SSEP reflects asynchronous maturation of elongating polysynaptic pathways and apparently requires a more complex model for prediction in order to enhance its clinical utility.     

Prevention of spinal cord injury with time-frequency analysis of evoked potentials: an experimental study

OBJECTIVES: To verify the applicability and validity of time-frequency analysis (TFA) of evoked potential (EP) signals in detecting the integrity of spinal cord function and preventing spinal cord injury. METHODS: The spinal cord was simulated during surgery in 20 mature rats by mechanically damaging the spinal cord. Cortical somatosensory evoked potential (CSEP), spinal somatosensory evoked potential (SSEP), cortical motor evoked potential (CMEP), and spinal cord evoked potential (SCEP) were used to monitor spinal cord function. Short time Fourier transform (STFT) was applied to the CSEP signal, and cone shaped distribution (CSD) was used as the TFA algorithm for SSEP, CMEP, and SCEP signals. The changes in the latency and amplitude of EP signals were measured in the time domain, and peak time, peak frequency, and peak power were measured in the time-frequency distribution (TFD). RESULTS: The TFDs of EPs were found to concentrate in a certain location under normal conditions. When injury occurred, the energy decreased in peak power, and there was a greater dispersion of energy across the time-frequency range. Strong relations were found between latency and peak time, and amplitude and peak power. However, the change in peak power after injury was significantly larger than the corresponding change in amplitude (p<0.001 by ANOVA). CONCLUSIONS: It was found that TFA of EPs provided an earlier and more sensitive indication of injury than time domain monitoring alone. It is suggested that TFA of EP signals should therefore be useful in preventing spinal cord injury during surgery.     

Brain stem auditory, pattern-reversal visual, and short-latency somatosensory evoked potentials: latencies in relation to age, sex, and brain and body size

To determine standards of normality for auditory, somatosensory and visual evoked potentials commonly used in the assessment of neurological disease, 8 AEP, 1 VEP and 12 SEP components were recorded to stimulation of left and right ears, eyes, and median nerves in 286 normal subjects ranging in age from 4 to 95 years. Peak and interpeak latencies, and left-right differences in latency, were analyzed as a function of age, sex, and estimates of brain and body size. Major features of the results were: (1) Peak latencies of all components showed statistically significant increases in latency with age except that VEP P100 latency decreased significantly between 4 and 19 years and did not change between 20 and 59 years. (2) In adults the peak latencies of all components were significantly later in males than in females. For AEPs and VEPs these differences were explained by sex differences in brain size, and for adult SEPs were explained by sex differences in arm and shoulder dimensions. No significant sex differences in VEP and SEP latencies were seen in children. (3) Most interpeak latencies showed significant differences in relation to age or sex. (4) Age and sex are useful predictors of latency for nearly all peak and interpeak latencies; in addition, height is a useful predictor of SEP peak latencies. (5) Left-right latency differences showed little age-related, and no sex-related, change. The interlaboratory use of these or other normative data was discussed. It was concluded that these AEP and SEP norms can probably be used in other laboratories if stimulating and recording conditions are similar. However, VEP results are difficult to transfer due to the poorly understood effects of variation in stimulus conditions. Some issues regarding the optimal characterization of norms were also discussed.     

Electrophysiological studies in siblings of De Sanctis-Cacchione syndrome

Multi-modality evoked potentials in two cases, who were siblings, of De Sanctis-Cacchione syndrome were reported. The case 1, who was elder sister of the case 2, was a 25-year-old female. And the case 2 was a 23-year-old female. They have the history of consanguinity. They were first noted to have skin erythema on exposure to sunlight, and a diagnosis of xeroderma pigmentosum was made. At the childhood neurological manifestation, such as mental retardation, deafness and muscular weakness developed gradually. The case 2, who was a elder sister, was operated on for squamous cell carcinoma of the eyelid at the age of 20 and 21 years old. Motor conduction velocity obtained from lower limbs were severely reduced and that from upper limbs were moderately delayed. Sensory conduction velocity of median nerve were severely diminished. Auditory brainstem responses (ABR) of the case 1 showed the prolongation in interpeak latency of I-V. ABR of the case 2 could not be obtained. N19 and N13 of short-latency somatosensory evoked potentials (SSEP) to median nerve stimulation with case 2 could not be obtained too. N13-N19 latency of case 1 was remarkably prolonged compared to the normal subjects. Central motor conduction time (CMCT) was studied in case 2 by using the magnetic stimulator. CMCT of case 2 was within the upper limit of normal control. Interpeak latency of I-V in ABR represents the brainstem dysfunction in auditory pathway, and interpeak latency of N13-N19 in SSEP was recognized as central conduction time from medial lemniscus to primary sensory area of cortex. So the prolongation of these interpeak latency in this cases may mean the dysfunction in the central nervous system.(ABSTRACT TRUNCATED AT 250 WORDS)     

Approach to dorsal pontine lesions via the fourth ventricle with SSEP monitoring: a report of two cases

Operative morbidity is a limiting factor for the trans-fourth ventricular approach to brain stem lesions. The usefulness of somatosensory evoked potentials (SSEP) in this approach has not been established. Two patients with pontine lesions were operated on with SSEP monitoring using the trans-fourth ventricular approach. One patient had a cavernous haemangioma and the other had a chordoma invading the pons. SSEP remained normal in the first, and a slight transitory decrease of the amplitude was observed in the second patient. The lesions were macroscopically totally removed with minimal postoperative neurological deterioration. In this approach it is assumed that SSEP monitoring was especially helpful for removal of the lesions extending deeply in the pons.     

The relationship between median nerve somatosensory evoked potential latencies and age and growth parameters in young children

Median nerve somatosensory evoked potentials (SEPs) were recorded in a group of 35 normal children aged 6-36 months and related to body length, body weight and head circumference. Recordings were made while the child was awake using the following derivations: ipsilateral clavicle--Fpz; seventh cervical vertebra (CV7)--Fpz; contralateral C'--Fpz. The clavicular-Fpz response was bilobed in 77% of the recordings, the initial negativity being designated CL1 and the following negativity, CL2. Early negativities, coincident in latency with CL1 and CL2, were often present in CV7-Fpz recordings, however, a negativity longer in latency than CL2 was always present, was designated CVN, and preceded a prominent positivity. A scalp-recorded early negativity (N1) and a following positivity (P1) were well defined in all recordings. The latency of CL1, CL2 and CVN increased with an increase in age and stature. In contrast, significant negative correlations were found between the latency of N1, P1, age and stature. The CL1-CVN interpeak latency did not correlate significantly with age, while the central conduction time (CVN-N1) declined significantly with an increase in age and stature. These findings confirmed the complexity of SEP absolute and interpeak latency changes with an increase in age and stature in young children.     

Experimental study of brain stem infarction in dogs--effect on BAEP, SSEP, blink reflex and EEG of perforator occlusion

Assessment of the lesion in the brain stem by evoked potentials has not been well established. We have already developed a model of brain stem ischemia by occluding the perforators of the posterior cerebral arteries of the dog. The ischemic lesions locates mainly in the ventral side of the midbrain. Using this model, we assessed brain stem function by brain stem auditory evoked potential (BAEP), surface- and depth-recorded (in medial lemniscus) short latency somatosensory evoked potential (SSEP), blink reflex (BR) and electroencephalography (EEG), and investigated the correlation between the electrophysiological abnormalities and the lesion in the brain stem. The studies were performed for 6 hours after perforator occlusion. Furthermore, depth-recorded SSEP and regional cerebral blood flow (rCBF) were measured under induced hypotension by withdrawal of arterial blood. BAEP did not change in 13 of 16 animals. Surface-recorded SSEP remained unchanged in all 6 animals. The results are probably due to the fact that the lesion does not involve the auditory and somatosensory pathways and the accompanying events such as edema does not affect the both pathways. Depth-recorded SSEP remained unchanged after occlusion and did not disappear even when rCBF fell below 10 ml/100 g/min. It may be suggested that the threshold for electrical failure in the brain stem is much lower than that in the cortex. In BR, R1 did not change but ipsilateral R2 became nearly invisible immediately after perforator occlusion in all animals. The fact that the ischemic lesion did not involve the pons and disturbed reticular formation in the midbrain may probably account for the remaining of R1 and the disappearance of ipsilateral R2.(ABSTRACT TRUNCATED AT 250 WORDS)     

Correlation between morphological abnormalities of Chiari malformation and evoked potentials]

We studied correlation between morphological abnormalities of Chiari malformation and evoked potentials (short-latency somatosensory evoked potential [SSEP] and auditory brainstem response [ABR]). On SSEP the inter-peak latency prolongation of P3-N1 was revealed in 6 out of 8 cases with Chiari malformations. The feature of positive wave between P3 and N1 was divided into 2 groups. The tendency of the positivity between P3 and N1 was more marked in cases of prolonged P3-N1 latency and correlated with the medullary kink. On ABR the prolongation of III-V inter-peak latency was revealed in one side in 3 patients Chiari malformations with malformed pons and tegmentum.     

Evoked potentials in Huntington's disease. A comparative and longitudinal study

Pattern-reversal visual (PRVEPs), brain-stem auditory (BAEPs), and somatosensory (SSEPs) evoked potentials were studied in 12 patients with Huntington's disease (HD) and were repeated in eight at one and two years. The mean cortical SSEP amplitude was decreased compared with that of age-matched controls, with a trend of decreasing amplitude with increasing duration and severity of illness. The SSEP latency was not significantly different from that of controls. The PRVEPs and BAEPs were normal. The serial studies showed a progressive decrease in amplitude of the SSEP over a two-year period. These neurophysiological findings may reflect the pathological involvement of the thalamus reported for HD. While evoked potentials are not of use in individual case diagnosis, the SSEP may be an objective physiological method for following the course of the disease in HD and the effects of therapeutic intervention in patient populations.     

Electrophysiological studies on hydranencephaly

Electrophysiological studies were performed on two children with hydranencephaly that was diagnosed by CT and/or magnetic resonance imaging (MRI). Case 1 was a 4-months-old boy who had no rostral tissue above the midbrain. Case 2 was a 5-years-old boy in whom CT showed the presence of the thalamus. Short latency somatosensory evoked potentials (SSEP) in both cases exhibited the absence of cortical activity (N1 and P4) with the preservation of waves of brainstem origin. However, in case 1, the wave component N0 was not observed, while N0 was seen in case 2. Thus, the N0 was component of SSEP on median nerve stimulation in children, which corresponds to N16 in adults, may originate in the thalamus.     

Short latency somatosensory evoked potentials in patients with neurological lesions

Short latency somatosensory potentials following median nerve stimulation were recorded in patients grouped according to anatomic location of neurological lesion. Patients with cerebral lesions causing severe sensory deficit lacked a major positive wave of cortical origin that in normal subjects peaked at a mean latency of 20.5 ms. Patients with severe cervical spinal cord disease lacked all of the normal somatosensory response except for the earliest component attributed to peripheral nerve activity. Patients with brain-stem lesions showed delayed latencies of later waves and prolonged interwave latencies. However, auditory evoked potentials measured in the group with brain-stem lesions were more helpful in localization. Analysis of short latency somatosensory potentials can discriminate between peripheral nerve, spinal cord, brain-stem, and cerebral lesions. Further experience and refinement of technique of measurement should increase the value of this procedure.