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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In an attempt to determine the usefulness of evoked potentials as a measure of focal cerebral ischemia, we examined somatosensory evoked potentials (SEP's) and morphological neuronal changes in cats following unilateral middle cerebral artery (MCA) occlusion. Fifteen adult cats underwent transorbital occlusion of the MCA under halothane anesthesia. In seven cats the ipsilateral SEP's were abolished after middle cerebral artery occlusion, and did not show any recovery after 6 hours. The same seven cats showed the greatest area of moderate and severe ischemic neuronal changes, ranging from 21 to 64% (mean 39 +/- 14%) of the total ipsilateral cortical area. The remaining eight cats showed a complete flattening or decreased amplitude of the SEP after occlusion, but demonstrated a considerable recovery in the amplitude of the primary cortical potential during the six hours of the study. All these cats had ischemic areas of less than 15% (mean 9 +/- 3%) of the total ipsilateral cortex. These results demonstrate that the disappearance of the SEP and their failure to recover correlate with the extent and degree of histological cerebral ischemia.
Stroke
PMID:Correlation between somatosensory evoked potentials and neuronal ischemic changes following middle cerebral artery occlusion. 381 Jul 20

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)
Stroke
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

Changes in multimodality evoked potentials (MEP's), consisting of somatosensory evoked potentials (SEP's), visual evoked potentials (VEP's), and auditory evoked brainstem responses (AEBR's), were studied in 36 patients with hypertensive putaminal hemorrhage to ascertain the relation among areas and distribution of brain dysfunction, the size of hemorrhage on computerized tomographic scan, and the clinical outcome. Among MEP's, SEP's were most significantly involved in all patients. Abnormalities in VEP's and AEBR's remained mild or moderate when the hemorrhage did not extend to the diencephalon. If SEP's were normal or mildly abnormal, they improved early the ictus. These patients did well clinically. If SEP's were absent, the patients had poor outcome even when the hemorrhage was small and located outside the internal capsule. In contrast, deterioration or persistence of MEP's indicated secondary insult to the brain and poor patient outcome. Early and serial MEP studies are useful in evaluating primary and secondary brain dysfunction and in predicting patient outcome in hypertensive putaminal hemorrhage.
Stroke
PMID:Evaluation of brain dysfunction in hypertensive putaminal hemorrhage with multimodality evoked potentials. 381 Jul 73

Somatosensory evoked potentials (SEP's) reflect the integrity of the central neuronal pathway, and as such may be used to assess function that remains during a variety of cerebral insults. To evaluate the natural history and utility of SEP's during experimental cerebral ischemia and infarction, SEP's were measured in 17 adult cats at 24 hours and 1 hour prior to right middle cerebral artery (MCA) occlusion, and again immediately afterward and at either 6 hours (five cats) or 24 hours (six cats) post-occlusion. Before occlusion of the right MCA, the SEP's were identical in the right and left hemispheres. After occlusion, there was a significant slowing of the interpeak latency of the first positive peak (P1) in the right hemisphere (3.53 +/- 0.6 msec before compared to 3.99 +/- 0.6 msec after occlusion, p less than 0.001). Maximal slowing in right hemisphere P1 latency was seen in those animals in which the stroke extended into the thalamus (4.38 +/- 0.1 msec). This was significantly slower than left hemisphere values (3.92 +/- 0.32 msec, p less than 0.01). The ipsilateral cortical components of the SEP's, the second positive peak (P2), and the major negative deflection (MN) were slowed in all cats immediately after right MCA occlusion compared to preocclusion measurements (p less than 0.001). Severe infarcts in the mid-suprasylvian and posterior ectosylvian gyri (including the somatosensory cortex) resulted in a greater slowing of the latency of MN compared to less severe infarcts in that region (20.6 +/- 3.9 msec versus 16.4 +/- 1.1 msec, p less than 0.05). There was a precipitous decrease in the amplitude or voltage of the ipsilateral P2-MN complex immediately after occlusion (5.32 +/- 0.4 microV before compared to 0.98 +/- 0.3 microV after occlusion, p less than 0.001). Therefore, the central latencies and cortical amplitudes of the SEP's are sensitive experimental tools as indicators of the onset and extent of a cerebral ischemic insult.
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PMID:Somatosensory evoked potentials as a measure of experimental cerebral ischemia. 396 67

Thirty patients with unilateral lesions of the cerebral hemisphere and clinical signs of an affected somatosensory system (mainly disturbances of kinesthesia and stereoesthesia) were investigated. SEP recordings were abnormal in 27. The degree of sensory loss (especially kinesthesia) correlated well with the SEP abnormalities in 26. These SEP abnormalities could be segregated into 4 groups (types 1-4). A type 1 SEP with pathological evoked potentials from P15 on (but a normal P13/14 complex with ear- or extracephalic reference recordings) correlated with lesions of the thalamus, the internal capsule, and the centrum semiovale. A type 2 SEP characterized by loss or severe attenuation of N20 and the following components was found in patients with lesions of the postcentral gyrus. A variant (type 2a) showed isolated loss of N20, but preserved subsequent components and may be due to lesions restricted to area 3b. A third pattern of SEP abnormality is characterized by a preserved primary cortical response and loss of all the subsequent potentials. It is assumed to correlate with lesions of the parietal association cortex. In only 1 case was a type 4 SEP found, with pathological features from N3 (N55) on, caused by an ischemic stroke in area 39. Loss of all evoked responses after P13/14, including P15, suggests a lesion between thalamus and centrum semiovale. Lesions located close to the postcentral cortex lead to a loss of N20 and a variable cut off of the rising negativity following P15. Preservation of the primary cortical complex and distortion or loss of the later components point to a parietal lesion. Severe disturbances of kinesthesia and stereognosia in patients with a normal primary cortical complex and isolated abnormality of the following potentials suggests that the adjacent association cortex may be important for the perception of this complex somatosensory information. Thus the neuronal activity underlying the primary cortical response does not suffice for perception of motion and for stereoesthesia.
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PMID:The significance of somatosensory evoked potentials for localization of unilateral lesions within the cerebral hemispheres. 663 52

Dissociated sensory impairment in brain-stem disorders suggests a lateral lesion involving the spinothalamic tract. Evoked potential studies of the somatosensory system with standard electrical stimulation (SEP) generally fail to establish objective correlates of such sensory deficits, because electrical stimuli predominantly activate large myelinated fibers that project into the medial lemniscal system. In contrast, laser-evoked potentials (LEPs), in response to brief radiant heat pulses, stimulate nociceptive afferents of the superficial skin and allow evaluation of thin fiber and spinothalamic tract function. We describe the recovery of deficits in pain sensitivity in five patients with isolated lateral brain-stem lesions that could be successfully monitored by LEP recordings in the acute stage and after intervals ranging from 7 months to 4 years. Upon first examination, LEPs were abnormal on the affected body side in all five cases of lateral medullary syndrome, irrespective of whether the etiology was vascular or inflammatory. The degree of recovery of pain sensitivity upon reexamination was reflected by the extent of normalization of the LEP. A control patient with vascular pontine lacunar stroke had normal LEPs on both sides, suggesting preserved spinothalamic conduction. The peak-to-peak amplitude of the main LEP component (N250-P400) correlated significantly with clinical pain sensitivity scored by standardized sensory testing (r = 0.76, p < 0.01). In contrast, early and late SEPs, after standard electrical median or tibial nerve stimulation, were normal in all patients, consistent with their intact mechanosensitivity. In conclusion, LEP studies allow the status of nociceptive function to be objectively and reliably documented on repeated examinations and therefore provide a useful supplement to multimodal sensory assessment in brain-stem disorders.
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PMID:Recovery from brain-stem lesions involving the nociceptive pathways: comparison of clinical findings with laser-evoked potentials. 885 95

1. The role of cutaneous mechanoreceptors in the tactile perception of shape was investigated. Objects whose surfaces were shaped as a pattern of smooth, alternating convex and concave cylindrical surfaces of differing radii of curvature were constructed such that there were no discontinuities in the slope of the surface. These "wavy surfaces" were stroked across the fingerpad of the anesthetized monkey and electrophysiological responses of slowly adapting type I mechanoreceptive afferents (SAs) and rapidly adapting type I mechanoreceptive afferents (RAs) were recorded. 2. For both SAs and RAs, each convexity indenting the skin evoked a burst of impulses and each concavity of the same curvature that followed elicited a pause in response. "Spatial event plots" (SEPs) of the occurrence of action potentials as a function of the location of the object on the receptive field were obtained and interpreted as the responses of a spatially distributed population of fibers. With increasing magnitude of curvature (equivalently, decreasing radius of curvature) of convexity, the mean width of the burst in the SEPs for each fiber type (representing the width of a region of skin containing active fibers) decreased and the mean discharge rate during the burst increased. Over a range of velocities of stroking from 1 to 40 mm/s, the number of RAs activated increased with velocity, whereas SAs were active at all velocities. For both SAs and RAs, the burst rates increased with velocity, whereas the widths of the bursts and pauses remained approximately invariant. Thus the spatial measures of burst or pause width provide a robust representation of the size of a feature on the object surface. 3. For a given velocity of stroking, the spatially distributed pattern of averaged discharge rates (spatial rate profile, SRP) provided a representation of the shape of the wavy surface. The distance between neighboring peaks in the SRP for individual RAs and SAs was approximately the same as the distance between the peaks of the wavy surface. The averaged SRP for a population of SAs provided a better representation of shape than that for RAs. Whereas active regions in the SEP can be isomorphic to the two dimensional form of the stimulus "footprint" in contact with the skin surface, the SRP, which in addition encodes the features of the stimulus in the third dimension normal to the skin surface, is not isomorphic to the stimulus shape. 4. When the sizes as well as the shapes of objects are varied, it is hypothesized that a central processing mechanism extracts the invariant property of shape from the slopes of the rising and falling phases of an SRP that has been normalized for overall differences in discharge rates. These differences would be expected to occur with variations in the parameters of stimulation such as compressional force, stroke trajectory, and stroke velocity. It was shown that a common feature of the mean SRP for SAs evoked by each wavy surface convexity, regardless of its radius, was the constancy of the slope from the base to the peak and from the peak to the base. Thus a possible code for the constant curvature of a cylinder is the constancy of the slopes along the rising and declining phases of the triangular-shaped spatial response profile evoked in the SA population by the cylindrical convexity.
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PMID:Neural encoding of shape: responses of cutaneous mechanoreceptors to a wavy surface stroked across the monkey fingerpad. 898 76

In order to compare the sensitivity of multichannel derived median nerve SEP with EEG in vascular cerebral lesions we examined 22 normals and 23 patients. SEP components within the first 50 ms could be divided into main waveform patterns: (1) a W-shaped parietal pattern consisting of N20, P25, N35 and P45 in most cases. (2) a frontal pattern with P20 and N30 as well as possibly detectible N24, P28, P33, N40 and P50. (3) a central P22. Two younger normals showed a V-shaped parietal pattern with N20 and P35, a frontal pattern with P20 and N36, and central P22 with a remarkably long latency. All components could be analysed sufficiently by means of three representative electrode positions (stimulation right/left): P3/P4, C3/C4, and F3/F4, which reduces the expense of recording and analysing considerably. 21 patients (91.3%) showed abnormal results in SEP, whereas 14 patients (60.9%) in EEG. A three channel electrode array can increase the usefulness of SEP and detect cerebral dysfunctions in cerebral lesions in spite of normal EEG under routine examination conditions. Analysis of multichannel derived SEPs during treatment and recovery after stroke and search for the prognostic value in the acute stage of the disease should be done in future.
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PMID:Multichannel derived median nerve SEP compared to EEG in patients with vascular cerebral lesions. 1144 39

The CNS neuron excitability and plasticity are objective and measured on the basis of the somatosensory (SEP) and motor (MEP) evoked potential (EP) findings. The EP examinations are performed in acute stroke (ac-sk) and comatose patients (pts) after brain injury. It was tried to check publication frequency of the reports in the 1988-1999 years, in Neurologia i Neurochirurgia Polska and in the journals registered in the MEDLINE system. The screening meta-analysis was conducted of the reported findings. The authors of 23 publications from 16 countries performed SEP and/or MEP examinations in the 802 ischeamic and 140 haemorrhagic acute stroke patients. The lesion was accurately localized, the immediate and late plasticity was identified and the influence of mannitol on penumbra neurons was assessed. The time of active movement recovery and the functional improvement of the patients were early and accurately prognosticated.
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PMID:[Changes in evoked potentials caused in patients with acute stroke (based on literature review 1988-1999]. 1205 2

Twenty-one children and young adults with sickle/beta-thalassemia without overt stroke were examined with magnetic resonance imaging and angiography (MRA), transcranial Doppler (TCD), visual (VEP) and median nerve somatosensory (SEP)-evoked potential recordings, and neuropsychological testing (Wechsler Intelligence Scale [WISC-III]). Eight (38%) had silent infarction in the parietooccipital cortex, deep white matter, or basal ganglia, including two of three with previous seizures. Of 17 undergoing TCD, none had maximum middle cerebral artery (MCA) velocities greater than 126cm/sec, but 9 were abnormal, with low velocities and difficulty in tracking the MCA and/or asymmetry. Three patients had abnormal MRA, one of whom also had silent infarction. One patient had pathological VEP recordings, whereas all SEP recordings were normal. WISC-III was performed in all 11 children, 4 with silent infarction: all but 1 had IQ scores greater than 85 (mean, 97.7; standard deviation, 14.2). We conclude that Greek children and young adults with Sbeta-thalassemia and no history of clinical stroke have TCD abnormalities and silent infarction similar to those reported in children and adolescents with sickle cell anemia, but cognitive function is not necessarily compromised. International collaboration is needed to establish the risk factors for central nervous system sequelae in patients with sickle cell disease, including Sbeta-thalassemia, leading to evidence-based prevention.
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PMID:Central nervous system abnormalities in asymptomatic young patients with Sbeta-thalassemia. 1517 17


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