Giant somatosensory evoked potentials in children without myoclonic epilepsy

Sixteen of 1093 children 5-14 years of age with various neurological problems were detected showing giant somatosensory evoked potentials (GSSEP). These potentials were analysed and their enlarged components described. None of the 16 children had evidence of myoclonic epileptic seizures. Nine children had epileptic seizures, but 7 did not. The characteristics of GSSEPs in patients without myoclonic seizures are described. We conclude that in patients without myoclonic seizures GSSEPs occur and bear some similarity with those elicited in patients with myoclonic seizures. They may represent a form of hyperexcitability of the CNS.     

Evoked spikes and giant somatosensory evoked potentials in a patient with fragile-X syndrome

We report the case of a 7 year old boy with fragile-X syndrome and epilepsy. In this patient, the detection of rolandic epileptiform potentials during sleep and hand tapping-evoked rolandic EEG spikes, together with giant somatosensory evoked potentials, further support the already suggested neurophysiological similarities between fragile-X syndrome and benign childhood epilepsy with centrotemporal spikes.

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Sommario Descriviamo il caso di un bambino di 7 anni affetto da sindrome del cromosoma X fragile ed epilessia. L'osservazione di potenziali epilettiformi rolandici durante il sonno, di punte rolandiche evocate dalla percussione della mano destra e di potenziali evocati somatosensoriali giganti, in questo paziente, fornisce unulteriore supporto alle somiglianze neurofisiologiche, già ipotizzate, tra sindrome del cromosoma X fragile ed epilessia a punte centrotemporali.

     

Subcortical nodular heterotopia: a functional MRI and somatosensory evoked potentials study

Abstract. Subcortical nodular heterotopia (SNH) associated with refractory epilepsy may be surgically treated, and a positive outcome can be expected following the complete excision of the malformed tissue. Recent functional neuroimaging studies have suggested the possible functional relevance of cerebral malformations, and may make it possible to improve presurgical planning, thus allowing extended resections and minimising post–operative deficits. We here report the case of a 19–year–old man with epilepsy and a giant SNH associated with diffused abnormal gyrations of the right temporal–parietal regions. Cortical functional organisation was investigated by means of functional magnetic resonance imaging (MRI) during sensory and motor tasks, and somatosensory evoked potentials. The results revealed enlarged and displaced motor and sensory cortical areas with heterotopic tissue functional activation. The relevance of these findings is discussed in the light of the possible surgical treatment of drug–refractory epilepsy associated with cerebral malformations: surgical treatment based on conventional MRI studies alone, without taking the functional nature of dysplastic tissues into account, may lead to considerable side effects.     

Valproate lowered the amplitude of visual and somatosensory evoked potentials in two cases of untreated juvenile myoclonic epilepsy

Abstract  The amplitude of flash visual evoked potential (F-VEP) and somatosensory evoked potential (SEP) was found to be initially slightly higher in two untreated patients with juvenile myoclonic epilepsy (JME). Patients were studied before and after complete control of seizures with valproate. In both patients valproate prolonged the latencies of the waves IV and V and lowered the amplitudes of waves V and VI of the F-VEP. The N20–P25 amplitude in SEP in both patients was also lowered by valproate. These results may suggest that slightly higher cortical excitability in untreated JME was controlled by valproate.     

Magnetoencephalographic study of giant somatosensory evoked responses in patients with rolandic epilepsy

We report five patients with rolandic epilepsy associated with giant somatosensory responses to median nerve stimulation, in whom we analyzed the pathophysiologic relationship between rolandic discharges and the somatosensory responses using magnetoencephalography. Four of the five patients showed giant P30m, the current source of which was localized in the primary somatosensory cortex, while the first cortical response, N20m, was not enhanced, except in one patient. The current source of the giant middle-latency component, N70m, was localized posterior to that of N20m, possibly in the posterior parietal cortex, in all patients. The initial positive peak and large negative peak of rolandic discharges were identical to P30m and N70m with respect to the current source localization, wave form, topographic pattern, and time relationship in the electroencephalogram and magnetoencephalogram, and somatosensory evoked magnetic field and somatosensory evoked potential records, respectively. In addition, the secondary sensory cortex was considered to be the generator of the middle-latency component in one patient. In one patient, the current intensity of the N70m was normalized along with clinical improvement and the disappearance of rolandic discharges, whereas those of other somatosensory evoked magnetic field components remained unchanged. Our data suggest that the rolandic discharge generator mechanism in these patients could be closely related to the developmental alteration of excitability in the primary somatosensory cortex, posterior parietal cortex, and secondary somatosensory cortex, which decreased with age, and it could share a common neuronal pathway, at least in part, with the giant P30m-N70m (N90m) in the somatosensory evoked magnetic field through the sequential and parallel processing of somatosensory information.     

Giant somatosensory evoked potentials in a patient with the anterior spinal artery syndrome

We studied a previously healthy 25-year-old woman with the anterior spinal artery syndrome, a rare thoracocervical myelopathy with multiple potential etiologies. Quantitative and clinical sensory examination showed dissociated loss of pin-prick and temperature discrimination below the level of the lesion, with normal light touch, vibratory, and position sense. Magnetic resonance imaging was consistent with cervical spinal cord infarction. Median SEPs showed normal Erb's potential with absent spinal N—₁₃ and normal scalp N—₂₀ latency. Tibial SEPs showed normal lumbosacral responses and normal scalp P—₃₀ latency. Both median and tibial nerve stimulation produced cortical responses of unusually large amplitude (median 38 m?V, tibial 17 m?V). We hypothesize that large SEP amplitudes in this patient resulted from loss of anterolateral inhibitory influences on the dorsal column–medial lemniscal system. © 1993 John Wiley & Soncs, Inc.     

Spinal myoclonus with giant somatosensory evoked potentials and enhanced long-loop reflex: a case report

We describe a patient with an ischaemic lesion of the cervical spinal cord who presented with clinical evidence of stimulus-sensitive, multisegmental myoclonic jerks restricted to the truncal and proximal limb muscles and accompanied by electrophysiological features (giant somatosensory evoked potentials and enhanced long-loop reflex) of cortical myoclonus. We hypothesize that these features might result from a loss of inhibitory influences on the sensory input to cortical structures: a concomitant contribution of spinal and cortical hyperexcitability seems to have played a crucial role in inducing myoclonus in our patient.     

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.     

Short-latency somatosensory evoked potentials to median nerve stimulation in patients with diffuse neurologic disease

Short-latency somatosensory evoked potentials were found to be abnormal in 15 of 28 patients with diffuse neurologic disease of varying etiology and severity. These abnormalities often did not directly correlate with the presence or degree of clinical sensory impairment. They were similar to findings in patients with demyelinating and focal lesions of the nervous system. This suggests that the interpretation of these potentials can be done only in the context of the patient's clinical assessment.     

Late-onset temporal lobe epilepsy in a patient with juvenile myoclonic epilepsy

We report a patient with longstanding, severe juvenile myoclonic epilepsy who subsequently developed features of temporal lobe epilepsy, which gradually became clinically dominant. Over the years, there was an electrographic evolution from the typical generalised epileptiform patterns, characteristic of juvenile myoclonic epilepsy, to the novel appearance of interictal temporal spikes immediately preceding bisynchronous discharges, and subsequently to temporal intermittent rhythmic delta activity and temporal lobe-onset seizures. In this rare case of coexistent primary generalised epilepsy and focal epilepsy, the epileptic networks of the two forms of epilepsy appear to overlap.     

The effects of focal epileptic activity on the somatosensory evoked potentials in the rat

Summary The cortical somatosensory evoked potential (SEP) of the rat, evoked by contralateral forepaw stimulation, consisted of early (P 1 and N 1) and late components (P 2 and N 2). Microelectrode recording yielded evoked unitary responses of short latencies in the range of the early components and responses of longer latencies in the range of P 2. During the development of focal epilepsy after topical application of penicillin, the late components of SEP were enhanced and the enhanced late negativity corresponded to a surface negative cortical spike. The prominent enlargement of later components was associated with prolonged, often recurrent discharges of longer latency unitary responses and with enlarged local field potentials. Early components of SEP remained relatively unaffected and so did unitary responses with short latencies.Epileptic spike-conditioned SEPs in the cuneate nucleus, thalamic sensory relay nucleus and sensory cortex were depressed from 100 ms (cuneate nucleus) to about 300 ms (thalamus and cortex) subsequent to spike discharge. Transmission in the cuneate nucleus was least affected. Thalamic and cortical early components of SEP had similar time courses of recovery, which differed markedly from that of cortical late components. Our findings suggest that two different neuronal activities generate different components of SEP and are differentially involved in the epileptic activities, which results in the different amplitude recovery following spontaneous epileptic spike discharges.This work was supported by the Deutsche Forschungsgemeinschaft (German Research Council)     

Evaluation of cognition, structural, and functional MRI in juvenile myoclonic epilepsy

Purpose:  Previous studies using advanced imaging techniques have suggested subtle structural and functional changes in patients with juvenile myoclonic epilepsy (JME), mainly associated with the frontal lobes. In addition, it has been reported that these patients show neuropsychological deficits, often summarized as frontal lobe dysfunction. The aim of this study was a comprehensive analysis of neuropsychological parameters, and functional and structural magnetic resonance imaging (MRI) in an independent cohort of patients with JME.
Methods:  We studied 19 JME patients and 20 age-, sex-, and education-matched controls using a battery of standardized neuropsychological tests, optimized voxel-based morphometry (VBM), and two domain-specific working-memory paradigms combined with functional MRI (fMRI).
Results:  Our investigations did not reveal statistically significant differences between the groups of JME patients and normal controls in either the VBM or the fMRI study of working memory. The neuropsychological examination showed a slightly worse performance for the JME patients across most tests used, reaching statistical significance for semantic and verbal fluency.
Conclusions:  In our cohort of JME patients, we could not reproduce the findings of frontal gray matter changes from previous studies, and we could not detect an fMRI correlate of previously reported differences in working memory in JME. The neuropsychological deficits may be attributed partially to antiepileptic medication. We conclude that structural and functional frontal lobe deficits in JME patients have to be interpreted with care. One reason for a variation between different cohorts may be the genetic heterogeneity of the disease.     

Visual evoked potentials in a patient with prosopagnosia

Visual evoked potentials (VEPs) were recorded from a 53-year-old man with prosopagnosia during presentation of slides of known and unknown faces and under two control conditions. ANOVA comparisons with a normal male group showed no differences in P100 amplitude, P300 amplitude or P300 latency. There were no significant evoked potential differences between the patient and controls specifically related to the face conditions. There was, however, a significant delay in the latency of P100 from both hemispheres during all types of stimuli. This prolonged latency was asymmetrical, showing a right sided emphasis with the control conditions: pattern reversal and slides of geometric designs. This finding, of a dissociation in the interhemispheric delay, provides physiological evidence of stimulus-specific organisation at an early, sensory level. The fact that the P100 component showed a marked delay, yet P300 fell within normal limits for amplitude and latency, suggests that this patient's problem lies at a perceptual level.