Making the Case for Brain ¹⁸F-FDG PET Subtraction in Medically Refractory Epilepsy: A Novel, Useful Tool—Practical Points?

Abstract

¹⁸F-FDG PET plays a major role in the presurgical evaluation of medically refractory epilepsy patients. The current standard of care is performing interictal evaluations of glucose metabolism. Use of this method is related mostly to the tracer kinetics of ¹⁸F-FDG because of a long uptake phase that would translate into ictal injections that have low sensitivity and low specificity and demonstrate not only ictal but postictal changes. This limitation can be overcome in some status epilepticus scenarios in which prolonged seizures can then correlate better with ¹⁸F-FDG uptake kinetics. In these cases, focal visual qualitative hot spots are suggestive of the seizure-onset zone. However, by using advanced subtraction techniques, the prolonged ¹⁸F-FDG uptake phase can be overcome in a variety of other cases as well, opening the door to a slightly larger set of patients who may benefit from this higher-resolution PET method. This article presents 4 cases in which a novel subtraction ¹⁸F-FDG PET technique was used and elucidates its impact in these specific cases.