Abstracts

Rationale: Thalamic relay nuclei receive input from numerous pathways and reciprocate with complex cortical projections; thereby serving as important propagation centers for seizures. We reported blood flow increases in the thalamus in secondarily generalized tonic-clonic (SGTC) seizures by subtraction ictal SPECT co-registered to MRI (SISCOM). Recent studies have shown efficacy of deep brain stimulation of the anterior nuclei of the thalamus in the treatment of refractory epilepsy patients. The aim of this study is to investigate the relationship between thalamic ictal SPECT hyperperfusion and seizure type. Methods: We previously reviewed all SISCOM data from the Medical College of Georgia from 1998 to 2009. We selected a cohort of SISCOM studies which included only thalamic hyperperfusion. Using Analyze 8.1 (Mayo BIR, Rochester, MN), we reviewed coronal, axial, and sagittal images. Based upon the relationship to the third ventricle, lateral ventricles, and basal ganglia, we identified ictal hyperperfusion in three thalamic regions: the anterior, medial-dorsal, and lateral regions. Using Chi-square test, we analyzed the frequency of thalamic hyperperfusion in SGTC and complex partial (CP) seizures. Results: We reviewed 128 cases: 76 cases of CP seizures and 52 cases of SGTC seizures. Among the CP seizure cases, there was greater frequency of medial-dorsal thalamic hyperperfusion (42%, 32/76) as compared to anterior (20%, 15/76), or lateral (38%, 29/76) thalamic hyperperfusion. Among the SGTC seizure cases, there was a greater frequency of lateral thalamic hyperperfusion (40%, 21/52) as compared to anterior (25%, 13/52), or medial-dorsal (35%, 18/52) thalamic hyperperfusion; the relationship between regional thalamic hyperperfusion and seizure type was statistically non-significant (Chi-Squire statistics=0.87, Degree of freedom=2, and p=0.64). A second analysis investigated the relationship between the side of thalamic hyperperfusion, and the side of seizure onset. Among CP seizure cases, thalamic hyperperfusion was contralateral to the side of seizure onset in 44/76 (58%) cases; among SGTC cases, thalamic hyperperfusion was contralateral to the side of seizure onset in 33/52 (63%) cases; the relationship between lateralization of thalamic hyperperfusion and seizure type was statistically non-significant (Chi-Squire statistics=0.40, Degree of freedom=1, and p=0.52). Conclusions: Multiple thalamic regions are involved in CPS and SGTC seizures. Our study indicates that CP and SGTC seizures do not have distinct regional patterns of ictal thalamic hyperperfusion. More investigation is warranted including investigating the relationship between time of SPECT injection and region of thalamic hyperperfusion. This would help to further delineate the subcortical network involved with CP and SGTC seizures.