Topographic analysis and dipole modelling of spikes in focal epilepsy

Topographic analysis and dipole modelling of spikes in focal epilepsy

S156 efferent sympathetic fibres have been selectively tested in distal segments of the limbs by recording the sympathetic skin response simultaneousl...

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S156 efferent sympathetic fibres have been selectively tested in distal segments of the limbs by recording the sympathetic skin response simultaneously at the palm of the hand and at the finger tip. Our results show that, in some patients. the response was absent in the finger tip while present in the palm of the hand. This finding Indicates a predominantly distal involvement of sympathetic fibres. Patients with absent sympathetic akin responses were also those with a more severe neuropathy.

IN FOOT MUSCLES

FASCICULATIONS YOUNG ADULTS. A. Van Der Heyden (University

OF HEALTHY

Maastricht,

The Netherlands)

Thirty young adults were investigated with surface electrodes for the occurrence of fasciculation potentials in intrinsic foot muscles (abd. hallucis, abd. dig. V, ext. dig. brevis). All subjects appeared to have fasciculations in at least one muscle, the amount varying from 1 to 35 per minute. The abd. hallucis was the muscle with most fasciculations. Effects of local temperature changes were studied. In subjects with a large amount of fasciculations this spontaneous activity was further analyzed, using SFEMG as well as CNEMG, in order to determine its site of origin.

TOPOGRAPHIC ANALYSIS AND DIPOLE MODELLING OF SPIRES IN FOCAL EPILEPSY. W. Van Der Meij, B.W. Van Dijk, G.H. Wieneke (University

Hospital,

Utrecht,

‘ABNORMAL’ AND ‘EPILEPTIFORM’ TRANSIENTS IN THE SLEEP EEG IN HEALTHY ADULTS: QUANTITATIVE ASSESSMENT. W. Van Emde Boas, A.M. Beun and E. Dekker (Instituut lands)

and F. Spaans

of Limburg,

lepsy could be made. A statistically significant difference between the 2 groups was found in the localization of the spike maxima inside or outside the centrotemporal quadrangle and in the orientation of the equivalent dipole.

A.C.

Van Huff&n

and

the Netherlands)

The problem of how to differentiate between symptomatic and idiopathic epileptiform spikes in the EEG has not yet been solved. We studied 19 patients with seizures and epileptiform spikes in the centrotemporal region: 4 patients with cerebral palsy, 5 with temporal lobe epilepsy and 10 with benign focal epilepsy of childhood with centrotemporal spikes. The EEG was recorded with the 32 electrode system designed by Buchsbaum (Buchsbaum, MS. et al., In: F.H. Duffy (Ed.), Butterworths, 1986: 325). in addition to the lo-20 system. Spikes were selected visually and signal averaging was applied. A topographic brain map was made at the peak of the averaged spike. The topography of the potential fields of the spikes could thus be studied. To localize the source of the equivalent dipole a stationary dipole model was used and the head was modelled as a standard three sphere volume conductor (Ary, J.P. et al., IEEE Trans. Biomed. Eng., 1981, BME 28: 447). On the basis of EEG data thus obtained a differentiation between idiopathic focal epilepsy and symptomatic focal epi-

voor

Epilepsiebestrijding,

Heemstede,

The Nether-

Short lasting sleep EEG recording is a routine procedure in the diagnostic work-up in epilepsy, notably in patients with an ambiguous clinical history in whom regular recordings have yielded negative results. However, recent studies have shown that, contrary to findings during wakefulness, recordings during drowsiness or sleep will yield a number of ‘abnormal’ paroxysmal, sharp transients, even in healthy human adults. In our present series of 60 whole night sleep EEG recordings obtained from healthy adult volunteers, using the identical recording methodology as in the diagnosis of epilepsy, all but two of the records showed one or more ‘abnormalities’. usually of a transient character and often quite ‘epileptiform’. With lack of proper experience, such phenomena could easily result in a false positive diagnosis of epilepsy and a quantitative assessment of these transients is needed in order to establish their clinical significance. Our quantitative assessment shows that these abnormalities in healthy adults are more limited to drowsiness and light sleep early during the night (the stages most frequently studied in the regular EEG laboratory!), than in the records of patients with an established diagnosis of epilepsy; also they occur less frequently in healthy subjects than in epileptic patients. Typical EEG examples and quantitative data will be presented.

INTERICTAL AND ICTAL FINDINGS IN SCALP VERSUS INTRACRANIAL EEG: A RETROSPECITVE COMPARATIVE STUDY. W Van Emde Boas, D.N. Velis, J. Overweg, J. De Vries and C.W. Van Veelen (Instituut lands)

voor

Epilepsiebestrijding,

A. Van Wielingen,

Heemstede,

The Nether-

For all patients studied with subchronic corticography and stereo-encephalography during presurgical evaluation for intractable complex partial seizures in the period 1982-1988, the occurrence, lateralization and localization of interictal and ictal epileptiform activity in the records, obtained during prolonged