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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The purpose of this study was to report the effects of spinal cord compression, ischemia, and distraction on clinical status, and somatosensory (SEP) and neurogenic-motor evoked potentials (NMEPs) in animals. The authors also reported their clinical experience with NMEPs elicited from humans undergoing surgery for spinal deformities. Results from the animal studies indicate that NMEPs are more sensitive and specific to the effects from spinal cord compression, ischemia, and distraction than SEPs. In every situation, NMEPs always correlated with the animal's post-surgical clinical status, while SEPs demonstrated an unacceptable false positive and false negative rate. In the 111 clinical cases in which NMEPs were administered, reliable NMEPs were easily elicited in more than 90% of the cases. In the remaining cases, no reliable NMEPs could be recorded because of procedural errors, which have been resolved. The results from this study suggest that the use of NMEPs should be considered as an adjunct to SEPs when monitoring spinal cord function during surgery.
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PMID:Sensitivity and specificity of somatosensory and neurogenic-motor evoked potentials in animals and humans. 306 Oct 24

Short latency SEP were investigated in 140 patients suffering from various cerebrovascular ischemic disease (CVD). CCT,AR and number of cortical phases of each stimulation side, as well as AR left to right side (AR l/r) were correlated to patient's age and sex, to diagnosis and vascular supply, to clinical symptoms, duration between stroke and investigation, SPECT, TCT and EEG. Significant correlations were found between CCT and diagnosis, vascular supply, clinical symptoms, duration, SPECT and TCT findings. CCT was prolonged in patients with completed stroke, MID, ischemia of the A.C.M., sensomotor hemiparesis or monoparesis of the upper extremity and lesions in SPECT and TCT located within thalamus and/or postcentral gyrus. Decreased perfusion in SPECT was only of statistical significance when it was combined with clinical symptoms and/or lesions in TCT. Significant correlations were found between AR l/r and all variables except age and sex. Differences in sub-groups corresponded to those found for the CCT. AR was lower at the affected side. Deviations of AR were also found in patients with focal lesions both in the EEG and in the TCT. Significant correlations were found between number of phases, clinical findings and SPECT, but no correlation was seen to TCT. Patients with CVD showed significant abnormalities of CCT and AR only in cases presenting neurological deficit and structural lesion in TCT. The abnormalities were more prominent in patients with an interval stroke-investigation over one year. No abnormalities were seen in patients with reversible symptomatology investigated after cessation of symptoms. A direct correlation may be suspected between number of phases and tracer uptake in SPECT.
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PMID:[Early somatosensory evoked potentials in cerebrovascular ischemic diseases. III. Correlations with age, sex, clinical data, EEG, emission and transmission computed tomography]. 313 95

The findings of AEP and SEP in the cases with brain death confirmed by the apnea test had not been reported. We studied the features and the characteristic changes of those evoked potentials in 7 cases of brain death. The etiology of brain death in those cases were the primary intracranial lesions in six and the brain ischemia secondary to cardiac arrest in the others. The apnea test and the recordings of AEP and SEP were performed in the same day in most cases. The mean intervals from the application of the respirator to the apnea test and to cardiac arrest were 5.8 +/- 7.1 days and 5.9 +/- 7.2 days, respectively. Cardiac arrest occurred with mean of 11.8 +/- 8.0 days after the application of the respirator. AEP showed absent responses in six cases (86%) and wave I only in the other (14%). SEP showed P 1-N 1 in four cases (57%) and no responses in three (43%). The components of AEP were disturbed earlier than those of SEP and cases were classified into three types according to those findings. Type I (one case, 13%): wave I only in AEP and P 1-N 1 in SEP. Type II (three cases, 28%): no wave in AEP and P 1-N 1 in SEP. Type III (three cases, 28%): no wave in AEP and SEP.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[The findings of auditory and somatosensory evoked potentials in brain death confirmed by the apnea test]. 322 32

We believe that somatosensory and brainstem auditory evoked response studies help in the understanding of the dysfunction of the ascending sensory pathyways at various levels. In some patients where EEGs showed a significant contamination of muscle and background noise, the SEP studies helped to identify the level of dysfunction. The severity of the clinical condition (GCS score) correlated significantly (p = 0.003) with the prolongation of the CCT. Asymmetries in CCTs were more frequent in the stroke group than in the other groups. The presence of asymmetries in CCT in diffuse encephalopathies indicated a variable degree of dysfunction in the ascending sensory pathways, which clinically were not easily identifiable. This fact raised the possibility of either pre-existing lesion(s) or recent insult(s) such as ischemia. The presence or absence of N20 appeared to influence the duration of survival in subgroups. Some degree of difference in duration of survival was noted among the metabolic group with and without N20 potential. The subset of patients with N20 potential survived relatively longer than the group without it. A suggestion of influence was seen in the stroke group, but caution must be exercised because the absence of N20 was compatible with survival. The hypoxic group did not show any difference. A combination of prolonged interpeak EP-N13 and N13-N20 indicated a poor prognosis. A distinct absence of Wave I in BAER limited its usefulness on some occasions. A combination of abnormal interpeak III-V and abnormal CCT seemed to suggest a poor prognosis. Although death generally occurred earlier in the stroke group, age did not seem to influence the mortality in the first 10 days. Similarly, the cause of death also did not seem to influence the course in those 10 days. None of the adult patients survived.
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PMID:Somatosensory and brainstem auditory evoked potential studies in nontraumatic coma. 339 8

Somatosensory and auditory evoked cortical potentials (SEP's and AEP's), regional cerebral blood flow, regional brain water content, and alteration of the blood-brain barrier were investigated in 3 cortical areas during permanent and 1- and 2-hour transient occlusion of the left middle cerebral artery and after restoration of blood flow in cats. During occlusion, blood flow in the auditory cortex was severely suppressed. In the fore limb projection area of the somatosensory cortex, blood flow was moderately reduced while it was nearly unaffected in the hind limb projection area. Despite different degrees of ischemia in the 3 cortical areas, all evoked responses were completely abolished within 10 minutes after occlusion. During permanent occlusion, the pattern of blood flow reduction persisted, and all evoked potentials stayed abolished. Recirculation after occlusion restored blood flow rapidly. AEP's recovered poorly after both 1 and 2 hours of ischemia. SEP's regained normal amplitudes soon after recirculation in the group with 1-hour occlusion. After 2 hours of ischemia, the recovery of SEP's was variable but better than that of the AEP's. Remarkable water accumulation was observed in the auditory cortex of all 3 groups and was accompanied in the 2-hour ischemia group by a disruption of the blood-brain barrier. In the 2-hour group, water accumulation was also found in the subcortical white matter radiation, whereas significant changes in regional water content were not observed in the somatosensory areas. The present study indicates that abolition of SEP's during middle cerebral artery occlusion in cats is caused by lesions in the afferent pathway leading to cortical deafferentation rather than by cortical ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Experimental focal ischemia in cats: changes in multimodality evoked potentials as related to local cerebral blood flow and ischemic brain edema. 381 Jul 52

A review of current techniques and results of monitoring spinal cord function by the intraoperative testing of somatosensory evoked potentials is given. The criteria for an ideal monitoring method are defined: (1) potential alterations occur before the lesion is irreversible, (2) monitoring itself does not harm the patient, (3) there are no false-positive or false-negative results, (4) warning criteria are defined by objective and quantifiable parameters. In recording and stimulation, two different approaches are applied: cortical or spinal recording and peripheral or spinal stimulation. Spinal stimulation techniques are considered more invasive, but an averaged potential is obtained quicker and more reliably by spinal methods. Failure rates in establishing useful monitoring procedures vary between 2.85 and 5%. The N2O-analgesic-relaxant-type of anesthesia is recommended. A precise definition of criteria indicating spinal cord damage has been difficult because of the natural variability of intraoperative evoked potentials. Wide ranges of physiologic, anesthesiologic, and technical and surgical factors have been found to influence intraoperative potential monitoring adversely. The so-called warning criteria drawn from evoked potential changes have so far been set arbitrarily: amplitude reductions of 30-50% for several recordings or at least 15 minutes have mostly been used. It has become clear, however, that warning criteria should be different for healthy or impaired spinal cord function and for cortical and spinal recordings. The value of a lesion-specific spinal cord potential for monitoring remains to be clarified. SEPs are sensitive for demonstrating ischemic changes to the spinal cord, but the limited experience with these lesions does not allow firm conclusions regarding the reversibility of clinical and evoked potential changes in spinal cord ischemia in man. The limited experience with multilevel recording, i.e., simultaneously recording at spinal and cortical level, indicates that epidural recordings are less variable and less failure-prone than cortical recording. Simultaneous multilevel recording also gives more information and allows easier recognition of false-positive or false-negative results. Poor preoperative SEP nearly always preclude useful monitoring. The results obtained so far point out areas where further development is necessary in order to increase the efficacy of this method. Major unsolved problems are (1) definition of warning criteria, (2) incidence of false-positive and false-negative findings, and (3) improvement of data acquisition.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Spinal cord monitoring: current status and new developments. 391 21

Comparative investigations of somatosensory evoked potentials in 23 patients with hemisyndromes following acute ischemia of the middle cerebral artery region and in 12 patients with similar hemisyndromes on the base of cerebral neoplasms revealed marked differences. Whereas in 87% of the patients with ischemic lesions the primary cortical complex of the SEP was severely altered there were similar abnormalities in only one of the patients with neoplasm. The SEP changes were not dependent on the neurologic (sensory) symptoms nor on focal or diffuse EEG abnormalities.
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PMID:[Somatosensory cortical stimulus response evoked potentials in unilateral symptoms caused by cerebrovascular disorders or brain tumors]. 641 14

The dynamic changes of cortical somatosensory evoked potential during occluding bilateral common carotid arteries and electroacupuncturing "Hegu" point were recorded and observed IN 30 wistar rats anesthetized with chloralose and urethane, The main results were as follows: After brain ischemia, P. N. amplitudes of SEP were significantly depressed, and the spike latency of SEP is obviously increased. The decreased amplitude of SEP during brain ischemia could be obviously increased by electroacupuncturing "Hegu" point. It is suggested that SEP may be an indicator to show brain ischemia and acupuncturing "Hegu" point could improve brain ischemia.
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PMID:[The effects of brain ischemia and electroacupuncture on cortical somatosensory evoked potential in rats]. 775 Jan 70

Transcranial magnetic stimulation (TMS) is a non-invasive diagnostic method particularly suited to investigation of the long motor tracts. The clinical value of this method in many cortical and subcortical diseases has been well established, but comparable studies for most spinal cord diseases have still to be made. Forty patients in whom spinal cord disease was established by clinical examination, cerebrospinal fluid examination, and magnetic resonance imaging (MRI) were studied by means of somatosensory evoked potentials (SEP, median and tibial nerve stimulation) and magnetic motor evoked potentials (MEP, first dorsal interosseus and tibialis anterior muscle recordings after transcranial and spinal stimulation). The underlying pathology was neoplastic (n = 16), inflammatory (n = 15) or ischemic (n = 9). Clinical signs and symptoms ranged from slight sensory disturbances to complete paraplegia and had developed within minutes (ischemia) or over many years (benign neoplastic disease). The overall frequency of pathological SEP was slightly higher than that of MEP (78% vs 68%) which was statistically not significant (p > 0.05). This was also true for the subgroups, except for pure motor disorders, which gave the same yield for both methods. Decreased amplitudes or absence of MEP were more frequent in neoplastic than in inflammatory lesions (75% vs 33%, p < 0.05). In the latter, however, MEP more often occurred with increased latencies (40% vs 31%, p > 0.05, n.s.). Pathological SEP were found in 75% of patients presenting with pure motor abnormalities, while pathological MEP were found in 30% of patients with pure sensory disturbances.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Magnetic motor evoked potentials (MEP) in diseases of the spinal cord. 788 35

Intraoperative neurophysiological monitoring is of benefit in protecting tissue at risk for trauma or ischemia during surgical procedures. Monitoring modalities include EEG, computer processed EEG, somatosensory (SEP), auditory (BAEP), and visual evoked potentials (VEP), and cranial nerve monitoring. The efficacy of monitoring is controversial, because no properly controlled prospective study of outcome with and without monitoring has been done. The weight of evidence suggests that loss of spontaneous EEG and SEP correlate well with critical reductions of cerebral blood flow. Meta-analysis of series comprising 3,028 patients undergoing carotid endarterectomies shows that SEP deteriorated in 5.6% of cases, with 20% of these having postoperative deficits, but more might have had deficits if they had not been shunted. SEP monitoring can be useful in surgery affecting brain and cord vasculature. Monitoring is not indicated for routine lumbosacral spine surgery. BAEPs have predictive value for preservation of hearing after acoustic neuroma surgery, and other surgery near the brainstem. VEPs have been too variable to be of major use in the operating room. For neurophysiologic monitoring to be useful, it must be performed by an experienced team, and the surgeon must be willing to act on the findings. Under these circumstances, monitoring can reduce surgical complications in selected cases.
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PMID:Efficacy of intraoperative neurophysiological monitoring. 789 14


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