Bilateral periventricular nodular heterotopia. PET and MRI of a patient with focal seizures

Three Different FDG Patterns in Periventricular Nodular Heterotopia Correlated to Video Stereoelectroencephalography

ABSTRACT

A 40-year-old woman with a drug-resistant focal epilepsy underwent cerebral FDG PET in phase 1 presurgical epilepsy study. MRI essentially showed multiple periventricular nodular heterotopias. The stereoelectroencephalography coupled to MRI and FDG PET helped to define the anatomofunctional correlation of the epileptogenic zone network. This procedure brought to light 3 distinct patterns of FDG consumption, corresponding to different anatomoelectroclinical features. This pattern was already found in a previous FDG PET reflecting a "stable" permanent intralesional intercritical stereoelectroencephalography activity, an electrical "signature" of the lesion. Finally, functional imaging improved thermocoagulation in this patient and emphasized the use of FDG in drug-resistant epilepsy.

The Role of FDG-PET in Patients with Epilepsy Related to Periventricular Nodular Heterotopias: Diagnostic Features and Long-Term Outcome

BACKGROUND AND PURPOSE

Periventricular nodular heterotopias (PNHs) are frequently associated with drug-resistant epilepsy (DRE). Although magnetic resonance imaging (MRI) can define the morphological features of PNHs, still there is a need to assess their metabolic activity in order to provide useful information on epileptogenicity and long-term outcome. To that end, we investigated the ability of ¹⁸ F-FDG PET to identify seizure onset zone in order to assess the metabolic activity of the ectopic neurons and to provide prognostic information on the postsurgical outcome.

METHODS

Sixteen patients (6 men and 10 women; ranging between 24 and 53 years of age) with PNHs-related DRE were evaluated. All patients underwent clinical evaluation, Stereo-electroencephalogram (SEEG), brain MRI, and ¹⁸ F-FDG brain PET/CT. PET images were superimposed on the patient-specific 3-dimensional-brain MRI. The metabolic activity of each nodule and of their cortex was visually and semiquantitatively assessed. The outcome after intervention was assessed in all patients using Engel classification.

RESULTS

Thirty-one heterotopic sites were identified. Twenty-one of 23 nodules with detectable electric activity on SEEG were identified by PET (91.3%), while 5 of 8 of nodules without electric activity showed no metabolism on PET (62.5%). Overall, the concordance between SEEG and FDG-PET was 26/31 (83.9%). Furthermore, cortical metabolic alterations were depicted, correlating with epileptogenic areas. A favorable postsurgical outcome was reported in 13 patients (81.3%). The presence of a hypometabolic nodule significantly correlated with a worse outcome after surgical therapy (P = .036).

CONCLUSIONS

In PNHs-related epilepsy, FDG-PET more accurately identifies epileptogenic foci, which aids surgical planning and in postoperative seizure control.