Mechanisms involved in the conduction of anterior temporal epileptiform discharges to the scalp.
OBJECTIVE
To evaluate the mechanisms involved in the conduction to the scalp of anterior temporal epileptiform discharges in temporal lobe epilepsy.


METHODS
During electroencephalographic recordings extra electrodes were applied around the eyes and on the cheeks in 13 patients with anterior temporal discharges. The amplitude of at least 34 discharges per patient was compared.


RESULTS
Five hundred and twenty epileptiform discharges were studied. Among standard electrodes, most discharges from all patients were maximal at anterior temporal electrodes. They were always also seen over the ipsilateral outer canthus and inferior orbital electrodes with similar amplitudes, and with lower amplitudes at other ipsilateral facial electrodes (67.7-57.6%). Ipsilateral cheek and mid-temporal electrodes showed amplitudes within similar range (66.3-67.7%) despite being at different distance from the temporal lobes. At least 40% of discharges were also recorded by facial electrodes contralaterally to the hemisphere where discharges were largest ('cross over') with no clear latency difference.


CONCLUSIONS
The topography of anterior temporal discharges is most readily explained by volume conduction through high conductivity skull foramina.


CONCLUSIONS
The role of skull holes should be incorporated in EEG and possibly in MEG source localisation models and additional facial electrodes can be useful in the evaluation of bitemporal discharges in temporal lobe epilepsy.
Department of Clinical Neurophysiology, King's College Hospital, Denmark Hill, London, United Kingdom.
Matthew
M
Sparkes
Department of Clinical Neurophysiology, King's College Hospital, Denmark Hill, London, United Kingdom; Department of Clinical Neuroscience, Institute of Psychiatry, King's College London, London, United Kingdom.
Antonio
A
Valentin
Department of Clinical Neurophysiology, King's College Hospital, Denmark Hill, London, United Kingdom; Department of Clinical Neuroscience, Institute of Psychiatry, King's College London, London, United Kingdom. Electronic address: gonzalo.alarcon@iop.kcl.ac.uk.
Gonzalo
G
Alarcón
D000293:Adolescent; D000328:Adult; D000368:Aged; D004566:Electrodes / Q000592:standards; D004569:Electroencephalography / Q000295:instrumentation / Q000379:methods* / Q000592:standards; D004833:Epilepsy, Temporal Lobe / Q000175:diagnosis / Q000503:physiopathology*; D006801:Humans; D008875:Middle Aged; D011930:Reaction Time / Q000502:physiology; D012535:Scalp / Q000502:physiology*; D013702:Temporal Lobe / Q000502:physiology*; D055815:Young Adult