Original articlePediatric Epilepsy Surgery in Focal Lesions and Generalized Electroencephalogram Abnormalities
Introduction
During evaluation for epilepsy surgery, patients with exclusively generalized and bilaterally multiregional interictal and ictal scalp electroencephalogram (EEG) epileptiform abnormalities and cognitive delay are not usually considered surgical candidates, because such findings are presumed to suggest generalized epilepsy. However, this paradigm does not hold true in infants with generalized scalp EEG patterns such as hypsarrhythmia, and in infantile spasms where seizure freedom has been obtained after resection of the cortical lesion that was apparent on the brain magnetic resonance imaging (MRI) or positron emission tomography [1], [2], [3].
It is not clear if some children beyond infancy who have exclusively generalized and multiregional EEG abnormalities in the presence of a focal brain lesion could benefit from epilepsy surgery. In this case series, we report on 10 such children with catastrophic epilepsy who became seizure-free or who significantly improved after surgery. We also discuss the potential mechanisms of generalized EEG abnormalities and the masking of focal epileptiform abnormalities on scalp EEG.
Section snippets
Materials and Methods
Of 176 children (less than 16 years of age) who underwent epilepsy surgery at the Cleveland Clinic during 2001-2003, we identified 10 children, aged 3-16 (mean age, 8.5) years, who under went surgical resection of a focal lesion apparent on brain MRI and fluorodeoxy glucose-positron emission tomography, despite the presence of generalized and multiregional scalp EEG abnormalities and a lack of a predominant EEG focus. All children were desperately sick, and had catastrophic epilepsy. Six
Demographic and Seizure Data
In 10 children (6 females), the age of seizure onset was 1 day to 4 years (mean, 22 months; median, 18 months; for a summary of data, see Table 1). The range of ages at surgery was 3-16 (mean, 8.5) years. The interval between seizure onset and surgery was 3-16 (mean, 6.75) years. All patients were previously rejected as epilepsy surgery candidates after one (five patients) or two (five patients) presurgical evaluations at our center and other centers. At the time of their final presurgical
Epilepsy Surgery Despite Generalized EEG Findings
Our surgical series indicates that even in older children with surgically remediable epilepsy, interictal and ictal scalp EEGs may reveal generalized and multiregional abnormalities with no dominant EEG focus. In these patients, freedom from seizures, or significant improvement after complete resection of a lesion seen on MRI, suggests that the localized epileptogenic process was preoperatively masked by generalized EEG abnormalities. In addition to the evidence of a focal lesion (presumed to
Conclusions
The exclusively generalized expression of EEG abnormalities in the presence of a focal cortical lesion (congenital or acquired during infancy) may occur beyond infancy. Freedom from seizures is possible in some older children after resection of a brain lesion seen on MRI, despite the presence of generalized scalp EEG abnormalities and the absence of dominant or concordant focal EEG abnormalities. When present, focal motor deficits such as hemiparesis, carefully observed focal features of
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