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Year : 2020  |  Volume : 35  |  Issue : 3  |  Page : 260-261  

Anti-leucine-rich glioma-inactivated 1 limbic encephalitis with normal magnetic resonance imaging detected on fluordeoxygluose positron emission tomography/computed tomography

1 Department of Nuclear Medicine, MIOT International, Chennai, Tamil Nadu, India
2 Department of Neurology, MIOT International, Chennai, Tamil Nadu, India

Date of Submission02-Mar-2020
Date of Acceptance18-Mar-2020
Date of Web Publication01-Jul-2020

Correspondence Address:
Dr. Piyush Chandra
Department of Nuclear Medicine, MIOT International, Manapakkam, Chennai - 600 056, Tamil Nadu
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijnm.IJNM_41_20

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Leucine-rich glioma-inactivated 1 (LGI1) antibody encephalitis is an emerging autoimmune disorder with antibodies to the voltage-gated potassium channel complex. Here, we report clinico-imaging findings of a 77-year-old female presenting with acute-onset seizures, normal magnetic resonance imaging and with abnormal fluordeoxygluose positron-emission tomography-computed tomography and positive anti-LGI1 antibodies on immunofluroscence assay.

Keywords: Autoimmune, encephalitis, fluordeoxygluose positron-emission tomography, leucine-rich glioma-inactivated 1, limbic, magnetic resonance imaging, positron-emission tomography-computed tomography

How to cite this article:
Chandra P, Nath S, Sundaram CS. Anti-leucine-rich glioma-inactivated 1 limbic encephalitis with normal magnetic resonance imaging detected on fluordeoxygluose positron emission tomography/computed tomography. Indian J Nucl Med 2020;35:260-1

How to cite this URL:
Chandra P, Nath S, Sundaram CS. Anti-leucine-rich glioma-inactivated 1 limbic encephalitis with normal magnetic resonance imaging detected on fluordeoxygluose positron emission tomography/computed tomography. Indian J Nucl Med [serial online] 2020 [cited 2022 Aug 16];35:260-1. Available from:

Seventy-seven-year-old female, with a history of hypertension, presented to the emergency department with two episodes of generalized tonic-clonic seizures. Routine laboratory investigations only revealed low serum sodium (116 mEq/L, Normal 136–142 mEq/L) and raised C-reactive protein (CRP) (22 mg/L, Normal <10 mg/L). Cerebrospinal fluid (CSF) analysis was normal, and CSF microarray test was negative for any viral encephalitis. An electroencephalogram (EEG) was suggestive of low amplitude polyphasic delta slow waves in the left anterior temporal lobe region [Figure 1]. Brain magnetic resonance imaging (MRI) and magnetic resonance (MR)-angiography done on day 3 of admission was unremarkable. In view of this EEG picture and high CRP, fluordeoxygluose (FDG) positron-emission tomography-computed tomography (PET/CT) was ordered to evaluate for limbic encephalitis. FDG PET/CT done on day 4 showed intense FDG uptake in the entire left mesial temporal lobe (Cortex ID Z score + 30.27) [Figure 2]. Rest of the whole-body scan was unremarkable for any malignancy. Cell-based indirect immunofluorescence assay revealed positive leucine-rich glioma-inactivated 1 (LGI1)-antibody in the serum sample.
Figure 1: Electroencephalogram showing abnormal slow and low amplitude delta waves in the left anterior temporal region

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Figure 2: (a) Trans-axial T2-weighted fluid-attenuated inversion recovery magnetic resonance imaging sequence showing no significant signal abnormality. (b) Serial trans-axial fluordeoxygluose positron emission tomography images showing intense fluordeoxygluose uptake in the entire left mesial temporal lobe. (c) Fused positron-emission tomography-magnetic resonance trans-axial images showing intense activity in the left mesial temporal lobe

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Autoimmune encephalitis is subclassified on the type of antibodies identified on various assays. These include autoantibodies to intracellular antigens (Hu, Ma2, glutamic acid decarboxylase (GAD)), to synaptic receptors (N-methyl-D-aspartate, Gamma amino-butyric acid (GABA), amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, mGluR5, D2 receptor) or against ion channels (LGI1, CASPR2, dipeptidyl-peptidase-like protein 6) Most patients with autoimmune encephalitis have a delay in clinical diagnosis due to the lack of well-defined clinical syndrome or normal or nonspecific MR findings, especially early in the disease course.[1] Anti-LGI1 antibody-related encephalitis are rarely associated with tumors and tends to respond well to treatment with more favorable outcomes seen in those treated with combined steroid and immunotherapy than those with monotherapy.[2] Hyponatremia seen in about 60% of these patients is presumed to be a result of inappropriate anti-diuretic hormone secretion, which is probably related to the co-expression of LGI1 in hypothalamus/kidneys.[3] In the acute phase of the disease, it is not unusual to have a normal MRI and abnormal FDG PET is seen in about three-fourth of the patients.[3],[4] FDG PET/CT done in acute phase of this disease frequently shows hyper-metabolism in bilateral basal ganglia and/or bilateral mesial temporal lobes, with unilateral involvement of mesio-temporal lobe without basal ganglia involvement (seen in case reported above) appears to be relatively uncommon.[4],[5],[6],[7]

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.

   References Top

Graus F, Titulaer MJ, Balu R, Benseler S, Bien CG, Cellucci T, et al. A clinical approach to diagnosis of autoimmune encephalitis. Lancet Neurol 2016;15:391-404.  Back to cited text no. 1
Shin YW, Lee ST, Shin JW, Moon J, Lim JA, Byun JI, et al. VGKC-complex/LGI1-antibody encephalitis: Clinical manifestations and response to immunotherapy. J Neuroimmunol 2013;265:75-81.  Back to cited text no. 2
Bien CG, Elger CE. Limbic encephalitis: A cause of temporal lobe epilepsy with onset in adult life. Epilepsy Behav 2007;10:529-38.  Back to cited text no. 3
Shan W, Liu X, Wang Q. Teaching NEUROIMAGES: (18) F-FDG-PET/SPM analysis in 3 different stages from a patient with LGI-1 autoimmune encephalitis. Neurology 2019;93:e1917-8.  Back to cited text no. 4
Lv, R. J., Pan, J., Zhou, G., Wang, Q., Shao, X. Q., Zhao, X. B, et al. Semi-quantitative FDG-PET Analysis Increases the Sensitivity Compared With Visual Analysis in the Diagnosis of Autoimmune Encephalitis. Frontiers in neurology, 10, 576.  Back to cited text no. 5
Lyons J, Wong J, Vodopivec I, Singhal T. Unique FDG-PET findings in anti-LGI-1 encephalitis. Neurology 2018;90 15 Suppl: 5.402.  Back to cited text no. 6
Park S, Choi H, Cheon GJ, Wook Kang K, Lee DS. 18F-FDG PET/CT in anti-LGI1 encephalitis: Initial and follow-up findings. Clin Nucl Med 2015;40:156-8.  Back to cited text no. 7


  [Figure 1], [Figure 2]


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