Brain molecular imaging in pharmacoresistant focal epilepsy: Current practice and perspectives

Abstract

This review aims to synthesize all the available data on brain molecular imaging, such as single-photon emission computed tomography (SPECT) and interictal fluorodeoxyglucose positron emission tomography (FDG-PET), in focal epilepsies. SPECT imaging is able to measure regional cerebral blood flow and its major innovation remains its ictal imaging value. On the other hand, FDG-PET, which has higher spatial resolution and lower background activity than SPECT, enables glycolytic metabolism to be identified in interictal states. Therefore, interictal FDG-PET has greater sensitivity than interictal SPECT, especially in temporal lobe epilepsies (TLEs). Thus, F-FDG-PET is a necessary step in the presurgical evaluation of TLEs, but also of extratemporal epilepsies (ETEs), contributing to>30% of the decision to undertake surgery. In addition, FDG-PET has particular diagnostic value in focal epilepsies showing normal magnetic resonance imaging (MRI). PET also has good prognostic value for post-surgical outcomes as well as cognitive impairment, especially in cases where the hypometabolism extent is limited. Moreover, the notion of an epileptic network is well highlighted by functional PET imaging, allowing better understanding of the pathological substrates of these disorders. Future development of quantitative analysis software and of novel radiotracers and cameras will certainly enhance its clinical usefulness.

Interregional metabolic connectivity of 2‐deoxy‐2[18F]fluoro‐D‐glucose positron emission tomography in vagus nerve stimulation for pediatric patients with epilepsy: A retrospective cross‐sectional study

“…Its predictive value for epileptogenic zone and surgical outcome has been reported, especially for temporal lobe epilepsy . Studies of PET data from epilepsy patients have shown correlation of hypometabolism and epileptogenicity, or the topography of abnormal metabolism, which can imply a dysfunctional neural network . However, how PET scans often show hypometabolism beyond the presumed epileptogenic zone 8 and how they are relatively less sensitive in analyzing extratemporal lobe epilepsies can be confounding for patients with intractable epilepsy.…”

PET and ictal SPECT can be helpful for localizing epileptic foci

“…Several reviews on PET and SPECT in presurgical evaluation were published during this period [ 31 ▪▪ , 56 ▪▪ – 59 ▪▪ , 60 ▪ ].…”

High-quality brain perfusion SPECT images may be achieved with a high-speed recording using 360° CZT camera

“…Today, brain perfusion SPECT is considered to be highly indicated (i) to image and localize the foci of epilepsy after injection of a perfusion tracer in the ictal state, whereas such ictal imaging is impossible with FDG PET [ 3 ]; (ii) to evaluate chronic cerebral ischemia with acetazolamide challenge, in order to detect areas of critically reduced perfusion [ 35 ]; and (iii) as an alternative to FDG PET for assessment of neurodegenerative disorders, particularly in diabetic patients for whom brain FDG-PET should be acquired in normal glycemia conditions [ 36 , 37 ]. The new CZT cameras have also potential for new indications that may not be achievable with brain PET imaging.…”