Magnetic resonance imaging and positron emission tomography in anti-NMDA receptor encephalitis: A systematic review

Abstract

Due to a variety of clinical manifestations anti-N-methyl-d-aspartate (NMDA) receptor encephalitis may be difficult to diagnose. Magnetic resonance imaging (MRI) may be used as a component of the workup for encephalopathy. However, the use of MRI in anti-NMDA encephalitis is complicated by wide-ranging reports regarding the frequency of normal MRI findings in this disease. Positron emission tomography (PET) is a modality of imaging that may assess functional rather than structural disturbances. Therefore, this review was conducted to summarise published studies regarding the use of MRI and PET in the diagnosis of anti-NMDA receptor encephalitis. The terms (MR OR magnetic resonance OR PET OR positron emission tomography) AND (NMDA encephalitis OR N-methyl-d-aspartate encephalitis) were used to search the databases PubMed, EMBASE and Scopus on 10/5/2017. These searches returned 1534 results. Sixty studies met the inclusion criteria. The results indicated that fewer than half of MRIs in anti-NMDA receptor encephalitis show abnormal findings. When abnormal findings are present they most commonly include T2/FLAIR medial temporal and frontal hyperintensity, and leptomeningeal contrast enhancement. Cortical grey matter changes were reported in the same number of patients as subcortical white matter changes. The only MRI finding with prognostic significance at this stage is progressive cerebellar atrophy. FDG-PET has been assessed in a few small studies and can demonstrate abnormalities in cases where MRI does not. Further research should aim for larger sample sizes and to report (and attempt to control for) the time between symptom onset and the scan being conducted, and pre-imaging treatments.

Recognizing psychiatric presentations of anti‐NMDA receptor encephalitis in children and adolescents: A synthesis of published reports

“…Even higher rates of this pattern have been observed in children, and non‐specific EEG abnormalities, such as diffuse slowing, are common . Neuroimaging is rarely helpful in making an early diagnosis of anti‐NMDArE, although magnetic resonance imaging may be abnormal in more than half of patients within 3 months of illness onset, and a magnetic resonance imaging measure of large‐scale brain network connectivity shows promise as a diagnostic tool …”

“…10,18,31 Even higher rates of this pattern have been observed in children, [32][33][34] and non-specific EEG abnormalities, such as diffuse slowing, are common. 31,32 Neuroimaging is rarely helpful in making an early diagnosis of anti-NMDArE, 22,24,35 although magnetic resonance imaging may be abnormal in more than half of patients within 3 months of illness onset, 14 and a magnetic resonance imaging measure of large-scale brain network connectivity shows promise as a diagnostic tool. 36 Another potential diagnostic challenge for clinicians managing these patients is the degree to which clinical features of anti-NMDArE and neuroleptic malignant syndrome (NMS) can overlap.…”

N‐Methyl‐D‐Aspartate Receptor Antibodies in Autoimmune Encephalopathy Alter Oligodendrocyte Function

“…The high frequency of normal findings using standard MRI sequences was also indicated in a systematic review of the literature that included 1,167 patients, showing that 62% had normal MRI. Moreover, among the 38% of patients with abnormal findings, the subcortical white matter was as frequently involved as the gray matter . In contrast, when a cohort of 24 patients was examined using MRI DTI sequences, all patients had widespread changes in white matter integrity that correlated with disease severity.…”

Current Progress on Assessing the Prognosis for Anti-N-Methyl-D-Aspartate Receptor (NMDAR) Encephalitis

“…The incidence of abnormal MRI findings in cases of anti-NMDAR varies from 11% to 83% [18,46]. Indeed, a systematic review of 56 clinical studies showed that less than 50% of patients had abnormal MRI findings [47], with most abnormalities coming from T2-weighted scans as well as a high FLAIR signal. Abnormal findings are most commonly found in the temporal lobe, in addition to the cerebral cortex and subcortical white matter regions.…”

“…Compared with lower-sensitivity MRI, FDG-PET is extremely sensitive for detecting the most severe stages of anti-NMDAR encephalitis [47,51]. Typically, anti-NMDAR encephalitis is characterized by hyperfrontal and temporal lobe metabolism and a decrease in parietal and occipital lobe metabolism.…”