Interictal Brain FDG PET evaluation of chronic refractory seizures in a patient with Tuberous Sclerosis.
History:
11 y/o boy with known history of Tuberous Sclerosis and chronic refractory seizures since 8 years, underwent video EEG evaluation as epilepsy surgery evaluation. The findings were suggestive of possible epileptogenesis in the right lateralization localizing to right posterior head region (regions T4/O2). MRI brain and interictal FDG PET/CT were performed. Relevant images for the PET/CT and MRI (slice registered) are provided.
Management flowchart for Epilepsy surgery evaluation:
Rugg-Gunn F, Miserocchi A, McEvoy A. Epilepsy surgery.
Practical Neurology 2020;20:4-14.
Phases of the evaluation
Young, C. C., Williams, J. R., Feroze, A. H., et al. Pediatric functional hemispherectomy: operative techniques and complication avoidance. Neurosurgical Focus FOC, 2020;48(4), E9.
Purpose of individual components
Baumgartner C, Koren JP, Britto-Arias M, Zoche L, Pirker S. Presurgical epilepsy evaluation and epilepsy surgery. F1000Res. 2019 Oct 29;8:F1000 Faculty Rev-1818.
Anatomical MRI
- T1, T2, FLAIR and SWI
- Lesion/congenital abnormality detection, hippocampal volume assessment and ventricles assessment.
Video EEG
- Lateralization, and if possible, region-localization.
- Other less common tests: Electrical source imaging, magneto-encephalography.
Nuclear imaging
- Localization of epileptogenic-zone.
- Preferable if fused with MRI.
- Interictal perfusion (ECD, HMPAO) and metabolic (FDG) imaging: Hypo-perfused-metabolic regions.
- Ictal perfusion imaging: Hyper-perfused region.
Software-based technique for analyzing images:
- Subtraction ictal SPECT co-registered to MRI (SISCOM)
- Originally developed for ictal-interictal SPECT studies.
- Based on voxel-by-voxel analysis of functional images to provide EPZ localization.
- Has higher sensitivity and specificity than only visual analysis.
- Results have good correlation with post-surgical outcomes.
FMRI and Tractography
- Language function localization
- Prediction of post-Sx memory decline
- Post-Sx visual defects (Meyer’s loop)
- Post-Sx motor defects
Intra-cranial EEG
- Through open craniotomy (CEEG), or
- Stereotactic with neuroimaging guidance (SEEG)
- IEEG is used if non-invasive methods yield contradictory results.
- A combination of subdural and deep electrodes are used to delineate irritative zone.
