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P195 Dipole reconstruction as a method for identifying patients with mesolimbic epilepsy
Poster Session: EEG and EEG Related Techniques - Epilepsy different frequency bands of the EEG was integrated. Statistical analysis revealed significant enhancement of alpha-activity over the occipital lobes in 10 of 15 subjects for microwave exposition, compared to the placebo run. The increased alpha-activity remained always within the physiological range. We propose a modulation of cerebral activity due to exposition with pulsed microwaves to be responsible for the measured effect. ~-~
INHIBITORY EFFECTS OF TRANSCRANIAL MAGNETIC STIMULATION IN PATIENTS WITH PARTIAL EPILEPSY
M. Cincotta, S. Lori, A. Borgheresi, M. Fabbri, G. Zaccara. Servizio di Neurofisiopatologia U.S.L. 10, Florence, Italy The motor evoked potential is followed by a transient silence in the electromyogram, when transcranial magnetic stimulation (TMS) of the motor cortex is delivered during a tonic muscle contraction. The late part of this silent period (SP) is thought to be due to cortical inhibitory mechanisms. We studied the TMS-induced SP in 8 patients with cryptogenic partial epilepsy with clonic seizures, in 11 patients with partial seizures without clonic jerks and in 16 age- and sex-matched normal subjects. A Magstim 200 magnetic stimulator with a standard circular coil was employed. The SP in the first dorsal interosseous muscles was bilaterally longer (p < 0.05) in the patients with clonic seizures when compared with the other two groups of subjects. Our findings could indicate an interictal hyperactivity of cortical inhibitory neurons projecting onto the piramidal cells, when the focus involves the primary motor cortex. FP~
319
ictal electrographic findings (EEG/EMG) do not differ from those seen in atonic seizures from patients with other forms of epilepsy.
[--P-~
SPIKE PROPAGATIONIN ROLANDIC EPILEPSY
C. Baumgarmer, M. Graf, A. Doppelbauer, A. Lischka. Universitgitsklinik fiir Neurologie, Vienna, Austria We studied the functional organization of the interictal spike complex in 12 patients with benign rolandic epilepsy of childhood (BREC). In order to provide a biological marker for the location of epileptic activity we recorded somatosensory evoked potentials in response to median nerve stimulation in all patients. We used multiple dipole modeling to assess the number, the three-dimensional intracerebral location and the time activity of the underlying neuronal sources. Whereas in 7 patients the interictal spike complex could be modeled by a single tangential dipolar source (group 1), in the remaining 5 patients two sources - a radial and a tangential dipole - were necessary to adequately explain the interictal spikes (group 2). The tangential source was characterized by a frontal positivity and a parietal negativity with a phase reversal following central sulcus suggesting epileptic activity in the anterior wall of central suleus. The radial source showed a single electronegativity over the ipsilateral central region which would be compatible with involvement of the top of either preor postcentral gyrus. Both sources showed biphasic time patterns with an average latency difference of 30 msec suggesting propagation of epileptic activity within the central region during interictal spikes in BREC. Acknowledgment: This research was supported by the Fonds zur Ftrderung der wissenschaftlichen Forschung (~sterreichs (project P10302MED).
CONTINUOUS FOCAL SPIKES ASSOCIATED WITH FOCAL CORTICAL DYSGENESIS
Kjeld Andersen, G. Myhr, G. Nilsen. Lab. of Clinical Neurophysiology, University Hospital, Trondheim, Norway A 25 year old woman presented with continuous high amplitude spikes within the alfa frequency range over the right occipito-posttemporal area. A MR/was recommended to the neurologist and revealed a cortical heterotopia in the same area. Review of older EEGs showed continuous delta activity in every EEG from the first at one month of age and continuous spikes in all 27 EEGs from five months of age. A similar pattern was found over the right occipital region in a 38 year old woman. Fourteen EEGs from two years of age had all shown the same continuous focal spikes. A MR/was also advised and disclosed pachygyria/polymicrogyria in the right parieto-occipital region and slight hemimegalencephaly. Both patients are slightly mentally retarded and have had epileptic seizures from the first month of life, myoclonia with secondary generalisation or other focal manifestations. The epilepsy is controlled on standard medication. No sleep EEGs were recorded. In large series of neuronal migration disorders this consistent focal EEG pattern has not been a frequent finding in awake EEGs in infants or small children. ATONIC SEIZURES ARE ONE OF THE MAIN SEIZURE TYPES IN PATIENTS WITH PROGRESSIVE MYOCLONUS EPILEPSIES H. Vogt, I.W. Mothersill, M. Cenusa, G. Kr~imer. Swiss Epilepsy Center, Zi~rich/Switzerland
Rationale: Negative myoclonias have occasionally been reported in patients with progressive myoclonus epilepsies (PME's). In our experience this atonic seizures are one of the main clinical manifestations in this rare epilepsy type. They often remain unrecognized and for their identification and definition require ictal polygraphic recordings in freely moving patients. Methods: Ictal polygraphic video-EEG-recordings were performed (16 channel EEG, 8 channel surface EMG) in all our known 21 patients with progressive myoclonus epilepsies (12 Unverricht, 4 Lafora, 4 CLF, 1 MERRF). Results: All 21 patients presented atonic seizures of short duration (100-300 ms) either isolated or in combination with myoclonus. The epileptic atonic seizures were provoked by voluntary movement. The duration of the muscular atonia was between 100 and 300 ms. In 13 patients the atonic seizures correlated with bilateral spikes or spike-and-waves with in the majority of a central-postcentral amplitude maximum. Their
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DIPOLE RECONSTRUCTION AS A METHOD FOR IDENTIFYING PATIENTS WITH MESOLIMBIC EPILEPSY
G. Lantz, E. Ryding, I. Ros~n. Dept of Clinical Neurophysiology, Lund University Hospital, Lund, Sweden The aim of the study was to evaluate if dipole analysis of extracranially recorded epileptiform activity, using a spherical 3-shell head model, may distinguish epilepsy of mesolimbic origin from origins of other locations. Dipole analysis was performed on previously extra-cranially recorded epileptiform discharges, in 22 patients investigated for ictal onset patterns with subdural electrodes over one or both subtemporal areas. The dipole results in two groups of patients were compared. Group A contained patients, in whom the subdural investigation showed subtemporal seizure onset (indicating mesolimbic epilepsy) ipsilateral to the dipole locations. Group B contained patients in whom seizure onset was other than ipsilateral subtemporal, or in whom seizure onset could not be determined. Group A patients had uniform dipole results, with an oblique posterior, slightly elevated dipole orientation, and an anterior temporal dipole location. Group B patients had more variable dipole results. We conclude that, if dipoles with anterior temporal location, and oblique posterior and elevated orientation are obtained, epilepsy of mesolimbic origin should be suspected. If the dipole locations or orientations markedly deviate from this pattern, the epileptogenic region is likely to be other than mesolimbic.
~-~-~
THE DIAGNOSIS OF PSEUDOSEIZURES IN EPILEPTIC AND NON-EPILEPTIC PATIENTS
A. Martins, M. Sande Lemos, T. Paiva. Laboratorio de EEG, Centro de Estudos Egas Moniz, Hospital Santa Maria, Lisbon, Portugal Suggestion with intravenous saline placebo has been used to induce pseudoseizures. We analyzed the relative contribution of a positive or negative response and the presence or absence of interictal epileptiform activity in establishing a final diagnosis in epileptic and non-epileptic patients with clinical suspicion of pseudoseizures. 49 patients in whom intravenous saline was given to induce or stop seizures were studied. They were all referred through the Epilepsy Clinic either as known epileptic patients or with no established diagnosis. Prolonged video EEG monitoring was performed during which intravenous saline was given in an attempt to induce episodes similar to the patient's clinical attacks. A positive response was achieved in 53% of the cases. The presence of epileptiform activity in positive and negative response groups was not statistically significant.
INHIBITORY EFFECTS OF TRANSCRANIAL MAGNETIC STIMULATION IN PATIENTS WITH PARTIAL EPILEPSY
M. Cincotta, S. Lori, A. Borgheresi, M. Fabbri, G. Zaccara. Servizio di Neurofisiopatologia U.S.L. 10, Florence, Italy The motor evoked potential is followed by a transient silence in the electromyogram, when transcranial magnetic stimulation (TMS) of the motor cortex is delivered during a tonic muscle contraction. The late part of this silent period (SP) is thought to be due to cortical inhibitory mechanisms. We studied the TMS-induced SP in 8 patients with cryptogenic partial epilepsy with clonic seizures, in 11 patients with partial seizures without clonic jerks and in 16 age- and sex-matched normal subjects. A Magstim 200 magnetic stimulator with a standard circular coil was employed. The SP in the first dorsal interosseous muscles was bilaterally longer (p < 0.05) in the patients with clonic seizures when compared with the other two groups of subjects. Our findings could indicate an interictal hyperactivity of cortical inhibitory neurons projecting onto the piramidal cells, when the focus involves the primary motor cortex. FP~
319
ictal electrographic findings (EEG/EMG) do not differ from those seen in atonic seizures from patients with other forms of epilepsy.
[--P-~
SPIKE PROPAGATIONIN ROLANDIC EPILEPSY
C. Baumgarmer, M. Graf, A. Doppelbauer, A. Lischka. Universitgitsklinik fiir Neurologie, Vienna, Austria We studied the functional organization of the interictal spike complex in 12 patients with benign rolandic epilepsy of childhood (BREC). In order to provide a biological marker for the location of epileptic activity we recorded somatosensory evoked potentials in response to median nerve stimulation in all patients. We used multiple dipole modeling to assess the number, the three-dimensional intracerebral location and the time activity of the underlying neuronal sources. Whereas in 7 patients the interictal spike complex could be modeled by a single tangential dipolar source (group 1), in the remaining 5 patients two sources - a radial and a tangential dipole - were necessary to adequately explain the interictal spikes (group 2). The tangential source was characterized by a frontal positivity and a parietal negativity with a phase reversal following central sulcus suggesting epileptic activity in the anterior wall of central suleus. The radial source showed a single electronegativity over the ipsilateral central region which would be compatible with involvement of the top of either preor postcentral gyrus. Both sources showed biphasic time patterns with an average latency difference of 30 msec suggesting propagation of epileptic activity within the central region during interictal spikes in BREC. Acknowledgment: This research was supported by the Fonds zur Ftrderung der wissenschaftlichen Forschung (~sterreichs (project P10302MED).
CONTINUOUS FOCAL SPIKES ASSOCIATED WITH FOCAL CORTICAL DYSGENESIS
Kjeld Andersen, G. Myhr, G. Nilsen. Lab. of Clinical Neurophysiology, University Hospital, Trondheim, Norway A 25 year old woman presented with continuous high amplitude spikes within the alfa frequency range over the right occipito-posttemporal area. A MR/was recommended to the neurologist and revealed a cortical heterotopia in the same area. Review of older EEGs showed continuous delta activity in every EEG from the first at one month of age and continuous spikes in all 27 EEGs from five months of age. A similar pattern was found over the right occipital region in a 38 year old woman. Fourteen EEGs from two years of age had all shown the same continuous focal spikes. A MR/was also advised and disclosed pachygyria/polymicrogyria in the right parieto-occipital region and slight hemimegalencephaly. Both patients are slightly mentally retarded and have had epileptic seizures from the first month of life, myoclonia with secondary generalisation or other focal manifestations. The epilepsy is controlled on standard medication. No sleep EEGs were recorded. In large series of neuronal migration disorders this consistent focal EEG pattern has not been a frequent finding in awake EEGs in infants or small children. ATONIC SEIZURES ARE ONE OF THE MAIN SEIZURE TYPES IN PATIENTS WITH PROGRESSIVE MYOCLONUS EPILEPSIES H. Vogt, I.W. Mothersill, M. Cenusa, G. Kr~imer. Swiss Epilepsy Center, Zi~rich/Switzerland
Rationale: Negative myoclonias have occasionally been reported in patients with progressive myoclonus epilepsies (PME's). In our experience this atonic seizures are one of the main clinical manifestations in this rare epilepsy type. They often remain unrecognized and for their identification and definition require ictal polygraphic recordings in freely moving patients. Methods: Ictal polygraphic video-EEG-recordings were performed (16 channel EEG, 8 channel surface EMG) in all our known 21 patients with progressive myoclonus epilepsies (12 Unverricht, 4 Lafora, 4 CLF, 1 MERRF). Results: All 21 patients presented atonic seizures of short duration (100-300 ms) either isolated or in combination with myoclonus. The epileptic atonic seizures were provoked by voluntary movement. The duration of the muscular atonia was between 100 and 300 ms. In 13 patients the atonic seizures correlated with bilateral spikes or spike-and-waves with in the majority of a central-postcentral amplitude maximum. Their
~-~
DIPOLE RECONSTRUCTION AS A METHOD FOR IDENTIFYING PATIENTS WITH MESOLIMBIC EPILEPSY
G. Lantz, E. Ryding, I. Ros~n. Dept of Clinical Neurophysiology, Lund University Hospital, Lund, Sweden The aim of the study was to evaluate if dipole analysis of extracranially recorded epileptiform activity, using a spherical 3-shell head model, may distinguish epilepsy of mesolimbic origin from origins of other locations. Dipole analysis was performed on previously extra-cranially recorded epileptiform discharges, in 22 patients investigated for ictal onset patterns with subdural electrodes over one or both subtemporal areas. The dipole results in two groups of patients were compared. Group A contained patients, in whom the subdural investigation showed subtemporal seizure onset (indicating mesolimbic epilepsy) ipsilateral to the dipole locations. Group B contained patients in whom seizure onset was other than ipsilateral subtemporal, or in whom seizure onset could not be determined. Group A patients had uniform dipole results, with an oblique posterior, slightly elevated dipole orientation, and an anterior temporal dipole location. Group B patients had more variable dipole results. We conclude that, if dipoles with anterior temporal location, and oblique posterior and elevated orientation are obtained, epilepsy of mesolimbic origin should be suspected. If the dipole locations or orientations markedly deviate from this pattern, the epileptogenic region is likely to be other than mesolimbic.
~-~-~
THE DIAGNOSIS OF PSEUDOSEIZURES IN EPILEPTIC AND NON-EPILEPTIC PATIENTS
A. Martins, M. Sande Lemos, T. Paiva. Laboratorio de EEG, Centro de Estudos Egas Moniz, Hospital Santa Maria, Lisbon, Portugal Suggestion with intravenous saline placebo has been used to induce pseudoseizures. We analyzed the relative contribution of a positive or negative response and the presence or absence of interictal epileptiform activity in establishing a final diagnosis in epileptic and non-epileptic patients with clinical suspicion of pseudoseizures. 49 patients in whom intravenous saline was given to induce or stop seizures were studied. They were all referred through the Epilepsy Clinic either as known epileptic patients or with no established diagnosis. Prolonged video EEG monitoring was performed during which intravenous saline was given in an attempt to induce episodes similar to the patient's clinical attacks. A positive response was achieved in 53% of the cases. The presence of epileptiform activity in positive and negative response groups was not statistically significant.