Abstracts

Dysembryoblastic Neuroepithelial tumors (DNT) are a pathologically distinct group of tumors commonly associated with medically intractable chronic epilepsy and a favorable prognosis after surgical resection. We describe the clinical, MRI and pathological characteristics and outcome in children after surgical resection of pathologically confirmed DNT to ascertain prognostic features for seizure free outcome.
Neurology, neurosurgery and pathology databases from 1993 to 2002 were used to retrospectively identify children with confirmed DNT who presented with seizures and had a minimum of 12-month follow-up. Clinical, radiological and pathological features were examined.
Twenty-six children, with mean seizure duration 2.6 years (range 0-10.4) prior to surgery, were identified. Mean age at surgery was 10.0 years (4.0-18.0). DNTs were found in the temporal lobe (39%), frontal lobe (31%), parietal lobe (23%) and occipital lobe (8%). Pre-operatively, the majority of DNT (77%) had a typical MRI appearance, with a well defined, cortically based, multicystic mass. Enhancement was identified in 50%. Residual DNT was evident in 15 of the 22 children where pre- and post-operative MRI was available. Three children demonstrated recurrence of tumor. Pathologically the majority of DNTs had complex glioneuronal features, and some degree of cortical dysplasia was found in surrounding tissue of all tumors where sufficient tissue was available for examination (18/26). Seizure outcome was good in 85% of children at 12 months (Engel class 1) however at longer follow-up (mean 4.3, range 1.0-14.4 years) only 65% remained seizure-free. Seven children had further surgical resection because of continued medically intractable seizures. Risk factors for seizure recurrence (age at onset, duration of seizures pre-operatively, MRI appearance of DNT, location of tumor, residual spikes on electrocorticography, residual tumor on MRI post-operatively, pathological classification of DNT, degree of associated cortical dysplasia) were examined with respect to seizure outcome at 12 months and at long-term follow-up. Only the presence of residual tumor was a significant risk factor for seizure recurrence at long-term follow-up (p=0.015). Although not statistically significant, all four children with continuing seizures at 12 months had residual DNT on MRI.
Children with DNT represent a group with surgically treatable epilepsy, however outcome is not always favorable. Residual tumor is a risk factor for continued or recurrent seizures, and some children may require multiple surgical resections. Cortical dysplasia commonly coexists with DNT. Recurrent tumor can occur despite the low grade nature of this neoplasm. Although the majority of children remain seizure free after surgical excision of DNT without recurrence, a considerable number fail to respond or have recurrent seizures after a brief seizure-free period.