Abstracts

RATIONALE: With prolonged status epilepticus, neuronal loss and gliosis has been reported in multiple subcortical structures including the hippocampus. The thalamus relays information in various sensory modalities, as well as from the basal ganglia and cerebellum. Significant neuronal loss in the thalamus would be expected to affect learning and higher motor and cognitive functions, and therefore be linked with long-term disabilities associated with chronic medically intractable epilepsy.
Learning Objective: At the end of this activity the participants are expected to be able to discuss volume changes of the thalamus on MRI in pediatric patients with intractable epilepsy.
METHODS: (Patients): 11 patients were studied (3 male, 8 female) with partial epilepsy, defined both on clinical and EEG grounds. The age of onset of seizures was 1.5-14 years (mean 6.1 +/- 4.1), and the age at evaluation was 2-22 years (mean 11.6 +/- 6.3). All patients had more than 1 seizure per week on average for the three months preceding evaluation, and had failed three or more antiepileptic drugs.
(Magnetic resonance imaging): Coronal IR-Prepped FAST-SPGR T1-weighted images of 124 contiguous 1.5mm coronal slices were obtained and analyzed with a custom-made software CARDVIEWS (Center for Morphometric Analysis, Massachusetts General Hospital, Boston, MA) for volumetric measurements. Each image was segmented into various substructures of the brain including the thalami, cerebral cortex, and basal ganglia according to semi-automatic signal intensity with manual corrections. Volume of the substructures was calculated based on the number of voxels included (Caviness et al. J Cog Neurosci. 1996;8:566-88).
RESULTS: On EEG video telemetry, 6 patients had left-sided predominance of the epileptiform activity (ictal EEG in 5, 1 had only interictal EEG recordings), and 5 patients had right-sided predominance (all had ictal EEG). No change in thalamic volume was detected when comparing left vs. right, in patients with both predominantly left-sided and right-sided EEG activity (surface monitoring, ictal EEG in 10/11, only interictal EEG in 1/11).
CONCLUSIONS: Volumetric MRI studies provides a sensitive tool to closely monitor subtle changes in brain volume in patients with epilepsy. No asymmetries in thalamic volumes were detected in patients with either predominately left-sided or right-sided epileptiform activity. Despite frequent seizures, we found no evidence for thalamic volume loss in this selected group of patients. These results suggest that the thalamus is a low risk for injury with recurrent seizures.
[Supported by: The National Epifellows Foundation (Research Grant) and the Epilepsy Foundation (Research Clinical Fellowship, with support from Pfizer).]