LATERALIZING AND LOCALIZING VALUE OF DIFFERENT IMAGING MODALITIES IN CHILDREN WITH CORTICAL MALFORMATIONS

Objectives: To determine the benefit of nuclear medicine in preoperative evaluation of malformations of cortical development (MCD) with respect to the epileptic focus.

Methods: 17 patients (pts; 12m, 3–17y) with intractable partial seizures were investigated during preoperative evaluation with either 99mTc HMPAO SPECT (ictal: 7, interictal: 10) or 18F FDG (n=4) and 11C Methionine (MET) PET (preoperative n=5, postoperative n=3). MRI led to diagnosis initially, which was confirmed histologically in 5 pts. Focal cortical dysplasia (FCD) was evident in 12 children, polymicrogyria in 3 and band heterotopia in 2 children. Studies were evaluated visually and compared with MRI retrospectively. Postoperative outcome was classified according to Engel criteria.

Results: Excellent results were obtained for ictal SPECT. A correct lateralization was found in all investigated pts (with FCD), showing an extended area of increased tracer uptake with relative maximum in the region of the MCD. -Interictal SPECT allowed a focus lateralization in 9 pts demonstrating extended areas with hypoperfusion. A correct focus localization, defined by region with maximal reduced HMAPO uptake in comparison with MRI, as possible in 5 pts with FCD. Heterotopia could be clearly delineated within white matter region one pt, 2/3 pts with polymicrogyria demonstrated abnormal cortical configuration. -FDG PET was normal in one child, revealed extended areas of hypometabolism surrounding the MCD in 2 pts. Displaced activity of normal gray matter could be seen in one pt with heterotopia, in accordance with MRI. -MET PET demonstrated elevated aminoacid transport in 3/5 pts (with FCD) and was normal in the remaining. Postoperative MET PET revealed no abnormal MET uptake postoperatively in 3 pts with unclear hyperintensities on MRI, but excellent outcome measures (grade IA). Conclusion: In a very high percentage important information concerning the epileptic focus could be obtained from all applied nuclear medicine methods. But in the majority of the cases abnormalities exceeded the boundaries of the MRI lesion clearly. Only MET PET delineated an epileptogenic area in more than half of the pts. Therefore the importance of MET PET in MCD has to be investigated in further studies more intensively.