¹⁸F‐fluorodeoxy‐glucose positron emission tomography pattern and prognostic predictors in patients with anti‐GABAB receptor encephalitis

Abstract

Aims To identify the metabolic pattern and prognostic predictors in anti‐gamma‐aminobutyric‐acid B (GABAB) receptor encephalitis using 18F‐fluorodeoxy‐glucose positron emission tomography (18F‐FDG‐PET). Methods Twenty‐one patients diagnosed anti‐GABAB receptor encephalitis who underwent 18F‐FDG‐PET at first hospitalization were retrospectively reviewed. 18F‐FDG‐PET images were analyzed in comparison with controls. Further group comparisons of 18F‐FDG‐PET data were carried out between prognostic subgroups. Results 18F‐FDG‐PET was abnormal in 81% patients with anti‐GABAB receptor encephalitis and was more sensitive than MRI (81% vs. 42.9%, p = 0.025). Alter limbic lobe glucose metabolism (mostly hypermetabolism) was observed in 14 patients (66.7%), of whom 10 (10/14, 71.4%) demonstrated hypermetabolism in the medial temporal lobe (MTL). Group analysis also confirmed MTL hypermetabolism in association with relative frontal and parietal hypometabolism was a general metabolic pattern. After a median follow‐up of 33 months, the group comparisons revealed that patients with poor outcome demonstrated increased metabolism in the MTL compared to those with good outcome. Conclusion 18F‐FDG‐PET may be more sensitive than MRI in the early diagnosis of anti‐GABAB receptor encephalitis. MTL hypermetabolism was associated with relative frontal or parietal hypometabolism and may serve as a prognostic biomarker in anti‐GABAB receptor encephalitis.

Positron emission tomography in autoimmune encephalitis: Clinical implications and future directions

“…Patients with increased metabolism in the MTL tend to have poor outcomes after a median follow-up of 33 months. 31 In a study of five patients with anti-GABA B receptor encephalitis, three patients showed abnormalities on PET, including two temporal hypermetabolism and one cortical hypometabolism. 32 Another patient with small cell lung cancer who presented with 3 weeks of progressive seizures, memory impairment, and behavioral disorder was diagnosed with anti-GABA B receptor encephalitis.…”

“…Group analysis also confirmed MTL hypermetabolism and frontal–parietal hypometabolism (Figure 3). Patients with increased metabolism in the MTL tend to have poor outcomes after a median follow‐up of 33 months 31 . In a study of five patients with anti‐GABA B receptor encephalitis, three patients showed abnormalities on PET, including two temporal hypermetabolism and one cortical hypometabolism 32 .…”

FDG-PET-Bildgebung der limbischen Enzephalitis

“…Die zerebrale MRT mit T1-, T2, FLAIR-und diffusionsgewichteten Sequenzen ist Teil der Basisdiagnostik bei Verdacht auf eine LE [16,20,38], wobei nur die FLAIR-Sequenz Bestandteil der o. g. diagnostischen Kriterien ist [16]. Initial zeigen etwa 50-75% der Patienten mit limbischer Enzephalitis eine unilaterale oder bilaterale Hyperintensität in der T2/FLAIR-MRT [13,41,46,47], meist ohne Kontrastmittelaufnahme. Mittels Volumetrie des Hippocampus und hippocampler Subfelder sowie voxelbasierter Volumetrie der grauen Substanz anhand T1w-MRT konnten auch strukturelle Veränderungen (Atrophie) nachgewiesen werden, die möglicherweise als Hinweise für das Auftreten und Fortschreiten eines Neuronenverlustes dienen können [41].…”

“…2, Abb. 3) [47,48,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80]. Dabei kann sowohl ein Hyper-, seltener auch ein Hypometabolismus mesiotemporal auftreten [76,77,81].…”

“…Insbesondere für den Nachweis extratemporaler Befunde wird der Einsatz voxelbasierter statistischer Verfahren zusätzlich zur rein visuellen Beurteilung der FDG-▶ Abb. 5 Typischer Befund in der zerebralen FDG-PET bei Anti-NMDA-Rezeptor-Enzephalitis PR A XIS Tipp Durch den Nachweis einer extratemporalen Beteiligung bei der limbischen Enzephalitis liefert die FDG-PET bei etwa 50% der Patienten eine Zusatzinformation über die strukturelle MRT hinaus [47,75,78,81,88].…”