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Arthur Cukiert, Cassio Forster, Viviane Ferreira, Leila Frayman, Jose Buratini.
Epilepsy Surgery Program- Hospital Brigadeiro and Sao Paulo Epilepsy Clinic, Sao Paulo SP, Brazil
RATIONALE- Secondary bilateral synchrony (SBS) can be generated from mesial foci. Scalp EEG is often misleading or misdiagnostic in these cases and focus localization is virtually impossible in many patients. MRI is capable of detecting very small cortical malformations and lesions but many patients with refractory epilepsy have normal high-resolution MR scans. This paper describes a patient who had normal high-resolution MRI and clinically suspected frontal lobe epilepsy and proved to have a very small fronto-mesial cortical displasia after invasive recording and cortical resection.
MATERIAL- E.J.T., a 14 years old girl, started with seizures at the age of eight years. Seizures occurred basically during sleep and very sporadically during wakefulness. Seizure frequency ranged from 1 to 6 per night. Her scalp EEG disclosed bilateral spike-and-wave discharges with frontal predominance and isolated bifrontal discharges. No independent spiking was noted. Ictal EEG was generalized from onset and non-localizatory. Clinically, seizures were of the hypermotor type with pedalling and boxing. Diagnostic and high-resolution MRI directed to the frontal lobes were normal. Subdural plates were implanted covering both frontal lobe convexities and mesial surfaces (Figures 1 and 2).
RESULTS- Five typical seizures were recorded. All arised from the right mesial frontal lobe 1 cm ahead of the supplementary motor area (Figure 3). Interhemispheric latency for spread of the discharges was 15-20 msec to the contralateral mesial surface, 25 msec to the ipsilateral lateral frontal cortex and 30 msec to the contralateral one (Figures 4 and 5). She was submitted to a frontal lobe resection. Pathological examination disclosed a 3 mm area of cortical displasia. She has been seizure-free after surgery (6 months).
CONCLUSION- Highly diffuse secondary bilateral synchrony can be generated from discrete mesio-frontal areas. Patients in whom fronto-mesial epilepsy is highly suspected on clinical grounds, even with normal neuroimaging, can benefit from intensive neurophysiological monitoring, including invasive recording and cortical resections in selected cases.