FDG-PET and MRI in the Evolution of New-Onset Refractory Status Epilepticus

Abstract

BACKGROUND AND PURPOSE: New-onset refractory status epilepticus is a clinical condition characterized by acute and prolonged pharmacoresistant seizures without a pre-existing relevant neurologic disorder, prior epilepsy, or clear structural, toxic, or metabolic cause. New-onset refractory status epilepticus is often associated with antineuronal antibodies and may respond to early immunosuppressive therapy, reflecting an inflammatory element of the condition. FDG-PET is a useful diagnostic tool in inflammatory and noninflammatory encephalitis. We report here FDG-PET findings in new-onset refractory status epilepticus and their correlation to disease activity, other imaging findings, and outcomes. MATERIALS AND METHODS:Twelve patients who met the criteria for new-onset refractory status epilepticus and who had FDG-PET and MR imaging scans and electroencephalography at a single academic medical center between 2008 and 2017 were retrospectively identified. Images were independently reviewed by 2 radiologists specialized in nuclear imaging. Clinical characteristics and outcome measures were collected through chart review. RESULTS:Twelve patients underwent 21 FDG-PET scans and 50 MR imaging scans. Nine (75%) patients were positive for autoantibodies. All patients had identifiable abnormalities on the initial FDG-PET in the form of hypermetabolism (83%) and/or hypometabolism (42%). Eight (67%) had medial temporal involvement. All patients (n ϭ 3) with N-methyl-D-aspartic acid receptor antibodies had profound bilateral occipital hypometabolism. Initial MR imaging findings were normal in 6 (50%) patients. Most patients had some degree of persistent hyper-(73%) or hypometabolism (45%) after immunosuppressive therapy. FDG-PET hypometabolism was predictive of poor outcome (mRS 4 -6) at hospital discharge (P ϭ .028). CONCLUSIONS:Both FDG-PET hypometabolism and hypermetabolism are seen in the setting of new-onset refractory status epilepticus and may represent markers of disease activity. ABBREVIATIONS: ALE ϭ autoimmune limbic encephalitis; EEG ϭ electroencephalography; GABA-B ϭ ␥-aminobutyric acid B; LGI1 ϭ leucine-rich glioma inactivated 1; NMDA ϭ N-methyl-D-aspartate; NMDA-R ϭ N-methyl-D-aspartate receptor; NORSE ϭ new-onset refractory status epilepticus; VGKC ϭ voltage-gated potassium channel

The timelines of MRI findings related to outcomes in adult patients with new‐onset refractory status epilepticus

“…In our study, MTL signal abnormality was the most common finding (51.3%), similar to previous studies (45%‐100%) 7–10 . All patients with diffusion restriction exhibited persisting lesions, and 67% of NORSE patients with MTL signal abnormality during the acute phase had persisting lesions on follow‐up MRI, as was the case in other studies 24,25 …”

“…As in previous reports, 4,6 we found that all patients with claustrum involvement had FIRES with cryptogenic etiology. In our patients, the percentage of cryptogenic etiology in NORSE patients was 87%, which was rather high compared with previous studies (25%‐100%) 2,7–10,46 . This was likely due to the inclusion of 19 patients who visited our hospital before 2012, when autoimmune antibody tests were not yet performed.…”

“…This retrospective long‐term follow‐up MRI study evaluated the timeline of MRI abnormalities in adult NORSE patients. The percentage of MRI abnormalities in NORSE patients in our study (82%) and other, previous studies (62%‐100%), 2,6–10 was higher than in the general population of SE patients (25%) 11 …”

“…This study demonstrated initial diffuse leptomeningeal enhancement in 43% of NORSE patients, which was higher than in previous studies (6%‐25%) 2,8–10 . The higher percentage can be explained by our different method for calculating the percentage, which used the number of contrast‐enhanced MRIs performed within 16 days of seizure onset, not just the total number of MRIs without consideration for the use of contrast enhancement or the time at which the MRI was performed after seizure onset, as has been described in previous studies.…”

Morphological and Advanced Imaging of Epilepsy: Beyond the Basics

“…The search for an underlying etiology in cases of drug-resistant epilepsy is of vital importance because it may guide surgical treatment and thereby allay some of the negative psychological, cognitive and socioeconomic consequences of persistent seizures [3], especially in seizures with presentation during childhood. Therefore, there is an increased interest among researchers in investigation of newly acquired tools such as machine learning and automated methods [4,5,6,7,8], as well as a multidisciplinary approach combining electroencephalography (EEG) and MRI findings [9,10,11], with nuclear medicine techniques and genetics/molecular biology’s analysis [12,13,14,15].…”