Tumours arising in the setting of paediatric chronic epilepsy

Along with malformations of cortical development or cortical dysplasia, hippocampal sclerosis, and remote ischaemic damage, tumours are among the more commonly identifiable causes of medically intractable seizures in paediatric age patients. This study reviews one institution's 20 year experience with tumours arising in this clinical setting.

Retrospective review of 129 paediatric patients [less than 19 years of age, 65 females (50.4%)] with tumours and medically intractable seizures encountered during a 20 year period of time (1989-2009). Using the most recent World Health Organization (WHO) classification of brain tumours, tumour type and grade were assessed.

The most common sites of origin included temporal lobe (n = 77, 59.7%), parietal lobe (n = 20, 15.5%), and frontal lobe (n = 15, 11.6%). WHO grade included 73 (56.6%) grade I tumours, 32 (24.8%) grade II tumours, and 18 (14%) grade I/II tumours. In six cases (4.7%), a WHO grade was not associated with mass. Tumour types included: ganglioglioma (n = 48, 37.2%), dysembryoplastic neuroepithelial tumour (n = 17, 13.2%), low grade astrocytoma (n = 15, 11.6%), low grade mixed glioma (n = 8, 6.2%), low grade oligodendroglioma (n = 5, 3.9%), meningioangiomatosis (n = 4, 3.1%) angiocentric glioma (n = 3, 2.3%), and dysembryoplastic neuroepithelial tumour/ganglioglioma composite tumour (n = 3, 2.3%). Less frequently observed lesions (n = 1 or 2) included pilocytic astrocytoma, protoplasmic astrocytoma, pleomorphic xanthoastrocytoma, and glioneuronal hamartoma. In 18 cases, distinction between low grade glioma and low grade glioneuronal tumour could not be definitively made. Coexisting malformation of cortical development/cortical dysplasia was noted in 29.8% of evaluable cases. In four tumours, coexistent hippocampal sclerosis was identified. Ki-67 labelling indices were less than 5% in all (n = 51) cases assessed. Of 25 tumours evaluated for chromosome 1p status, only one low grade mixed glioma demonstrated evidence of deletion; only one of 22 evaluated tumours (a low grade mixed glioma) showed evidence of chromosome 19q deletion.

Collectively, WHO grade I glioneuronal tumours account for slightly more than half of all neoplasms which cause intractable epilepsy in paediatric patients. A significant minority of tumours (n = 18, 14%) were difficult to definitively classify as glioma versus glioneuronal tumour, due to extent of sampling. Coexistent pathologies including malformation of cortical development/cortical dysplasia may be observed in a significant minority of tumours, suggesting a possible developmental origin for some tumours arising in this setting.