Abstracts

Rationale: Focal cortical dysplasias (FCDs) are a malformation of cortical development (MCD) frequently associated with drug resistant epilepsy in children and adults.  Scalp EEG can show focal epileptiform discharges over the lesion, but this is often dependent on the lesion location. MRI Brain findings can include cortical thickening, blurring of the cortical grey-white junction, increased T2 signal, a T2 hyperintense transmantle stripe, or localized volume loss.  The diagnosis is tissue-based, and the most widely accepted classification system is the Palmini classification scheme, which organizes FCDs into Type I and II, with subtypes IA, IB, IIA and IIB. Methods: Here we report the case of a healthy 19 year-old male university student, who came to medical attention after his first focal to bilateral tonic-clonic seizure, occurring out of sleep. Detailed questioning revealed that he had 2 focal (non-motor, cognitive) seizures in the prior week that consisted of a perception that he suddenly felt as though he was outside his body and watching himself for 10 seconds.  He was started on levetiracetam. Results: Ambulatory EEG revealed rare left anterior temporal sharp waves. Brain MRI revealed a slightly expansile, nonenhancing low blood volume, low cellularity cortical and subcortical lesion in the inferolateral left temporal lobe, concerning for a glioma/glial neuronal neoplasm or a focal cortical dysplasia. The indistinctness of the adjacent gray-white junction, unusual sulcation of the left inferolateral temporal lobe and slight thickening of the cortex favored a focal dysplasia, but the prominence of the abnormal signal intensity and slightly expansile appearance were unusual.  No transmantle sign was present. The lesion was resected using image-guided resection with intraoperative electrocorticography (ECoG), which revealed frequent spikes and polyspikes over the anterior temporal lobe along the inferior>middle temporal gyri and the basal region over the lesion. The neurosurgeon noted an extremely thin skull over the lesion, consistent with a chronic lesion.Pathology was consistent with FCD IIB and showed disorganized cortical lamination, increased neurons in Layer I, blurred grey-white junction with extensions of pyramidal neurons into the white matter, mal-oriented and clustered neurons, dysmorphic-appearing neurons and scattered balloon cells (primarily within the white matter), mild-moderate gliosis and extensive corpora amylacea.  Tumor markers were negative.  He remains seizure free on medications after the short post-op interval. Conclusions: This case illustrates some but not all of the typical FCD imaging findings; pathology was definitively diagnostic for FCD IIB. The electrocorticography furthermore illustrates the highly epileptogenic nature of FCDs.  The case is of interest due to the somewhat atypical imaging that created a diagnostic challenge, and because of the relatively late onset of seizures in this patient. Early surgery may have prevented this young man from social- educational decline while waiting to establish if he would become drug-resistant. Funding: None