JNM: PET used to evaluate pediatric epileptic condition
PET may offer one of the first clinical evaluations of fever-induced refractory epileptic encephalopathy in school-age children (FIRES), a new and poorly understood condition that results in severe cognitive dysfunction, according to a study published in the January issue of the Journal of Nuclear Medicine.

FIRES occurs in previously healthy children who experience a brief fever followed by several weeks of acute, pharmaceutical-resistant seizures. Once the seizures desist, FIRES patients are left with severe cognitive dysfunction, mainly in language, memory and behavior. Relatively little information is known about FIRES.

The authors, who named the severe epileptic encephalopathy FIRES in 2006, studied eight patients with the condition (mean age 9.3 years). Patients underwent a neuropsychological exam as well as MRI and 18F-FDG PET. The FIRES group was age-matched to a pseudo-control group of epilepsy patients.

All eight FIRES patients disclosed several significant hypometabolic areas on visual PET analysis, seven of which were severe. All the hypometabolic areas corresponded to significant hypometabolic clusters as viewed by statistical parametric mapping (SPM). "The more extensive was the metabolic deficit (number of voxels), the worse the cognitive impairment (IQ): correlation coefficient, -0.45," wrote Catherine Chiron, MD, PhD, pediatric epileptologist and head of the Research Program on Epilepsy at Hospital Necker – Enfants Malades in Paris, and co-authors.

"On the basis of an original pediatric-based methodology, PET group analysis highlighted a robust widespread hypometabolic cortical network. Such extensive hypometabolism in previously healthy children suggests a functional defect related to the acute epileptic storm—that is, status epilepticus," continued Chiron and colleagues. The researchers pointed out that the hypometabolic areas common to all patients, which involved symmetrically associative temporoparietal and orbitofrontal cortices, were present even in patients with negative MRIs.

"The fact that the dysfunctional network is superimposed over the epileptic network is a strong argument that FIRES is the cause of cognitive deterioration in these previously normal children. Moreover, localizing such a dysfunction may help to specify the re-adaptation more accurately," Chiron stated.

The researchers expressed encouragement that their research could make headway in understanding and eventually treating the little-understood FIRES. "These findings may open the way for using 18F-FDG PET more extensively and more accurately in pediatric imaging, as this methodology allows us to investigate not only unilateral but also bilateral diseases, and to interpret PET images in an objective and sensitive manner."