18F-FDG PET in drug-resistant epilepsy due to focal cortical dysplasia type 2: additional value of electroclinical data and coregistration with MRI
To assess the localizing value of 18F-FDG PET in patients operated on for drug-resistant epilepsy due to focal cortical dysplasia type 2 (FCD2).
We analysed 18F-FDG PET scans from 103 consecutive patients (52 males, 7–65 years old) with histologically proven FCD2. PET and MRI data were first reviewed by visual analysis blinded to clinical information and FCD2 location. The additional value of electroclinical data and PET/MRI coregistration was assessed by comparison with pathological results and surgical outcomes.
Visual analysis of PET scans showed focal or regional hypometabolism corresponding to the FCD2 in 45 patients (44%), but the findings were doubtful or misleading in 37 patients and negative in 21. When considering electroclinical data, positive localization was obtained in 73 patients, and this increased to 85 (83%) after coregistration of PET and MRI data. Under the same conditions, MRI was positive in 61 patients (59%), doubtful in 15 and negative in 27. The additional value of PET was predominant in patients negative or doubtful on MRI, localizing the FCD2 in 35 patients (83%). Interobserver agreement correlated with the grade of hypometabolism: it was good in patients with mild to severe hypometabolism (82–95%), but moderate in those with subtle/doubtful hypometabolism (45%). The main factors influencing positive PET localization were the grade of hypometabolism and the size of the FCD2 (P < 0.0001). Misleading location (nine patients) was associated with a small FCD2 in the mesial frontal and central regions. Following limited cortical resection mainly located in extratemporal areas (mean follow-up 5.6 years), a seizure-free outcome was achieved in 94% of patients, including Engel’s class IA in 72%.
In this series, 18F-FDG PET contributed to the localization of FCD2 in 83% of patients. This high localizing value was obtained by integration of electroclinical data and PET/MRI coregistration. This approach may help improve the surgical outcome in extratemporal epilepsy, even in patients negative on MRI.
KeywordsFocal cortical dysplasia 18F-FDG PET MRI Epilepsy surgery
The authors thank the team of SHFJ, Patrick Bodilis, Christine Baron, Brigitte Jouve, Vincent Brulon, Philippe Gervais and Thierry Le Kieffre, for performing the PET scans.
All authors were involved in drafting and revising the article.
Compliance with ethical standards
Conflicts of interest
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the principles of the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards.
Informed consent was obtained from all individual participants included in the study.
- 8.Engel J Jr, Van Ness PC, Rasmussen TB, Ojemann LM. Outcome with respect to epileptic seizures. In: Engel J Jr, editor. Surgical treatment of the epilepsies. 2nd ed. New York: Raven; 1993. p. 609–21.Google Scholar
- 10.Rivière D, Geffroy D, Denghien I, Souedet N, Cointepas Y. BrainVISA: an extensible software environment for sharing multimodal neuroimaging data and processing tools. In: Proceedings of the 15th Annual Meeting of the Organization for Human Brain Mapping, 18–23 June 2009, San Francisco, California. http://brainvisa.info.
- 17.Urbach H, Scheffler B, Heinrichsmeier T, von Oertzen J, Kral T, Wellmer J, et al. Focal cortical dysplasia of Taylor's balloon cell type: a clinicopathological entity with characteristic neuroimaging and histopathological features, and favorable postsurgical outcome. Epilepsia. 2002;43:33–40.CrossRefPubMedGoogle Scholar
- 37.Mendes Coelho VC, Morita ME, Amorim BJ, Ramos CD, Yasuda CL, Tedeschi H, et al. Automated online quantification method for 18F-FDG positron emission tomography/CT improves detection of the epileptogenic zone in patients with pharmacoresistant epilepsy. Front Neurol. 2017;8:453.CrossRefPubMedPubMedCentralGoogle Scholar