AUTHOR=Yedavalli Vivek Srikar , Hamam Omar , Bahouth Mona , Urrutia Victor Cruz , Ahmed Amara , Lu Hanzhang , Jones Craig , Luna Licia Pacheco , Sair Haris Iqbal , Lanzman Bryan 

TITLE=Arterial Spin Labeling Imaging Characteristics of Anti-leucine-rich Glioma-Inactivated 1 Encephalitis: A Qualitative and Quantitative Analysis

JOURNAL=Frontiers in Neurology

VOLUME=Volume 13 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/neurology/articles/10.3389/fneur.2022.850029

DOI=10.3389/fneur.2022.850029

ISSN=1664-2295

ABSTRACT=Autoimmune encephalitis (AE) is a rare group of diseases that can present with stroke-like symptoms. Anti-leucine-rich glioma inactivated 1 (LGI1) encephalitis is an AE subtype that is infrequently associated with neoplasms and highly responsive to prompt immunotherapy treatment. Neuroimaging plays a critical role in evaluating stroke and stroke mimics such as AE. Arterial Spin Labeling (ASL)is an MRI perfusion modality that is increasingly used in everyday clinical practice for stroke and stroke mimic assessment as a noncontrast sequence. Our goal in this preliminary study is to demonstrate the added value of ASL in detecting LGI1 AE for prompt diagnosis and treatment.
In this retrospective single center study, we identified six seropositive LGI1 AE patients who underwent baseline MRI with single delay 3D pCASL (five male and one female; 28-76 years of age, mean age, 55.0 years old). Two neuroradiologists qualitatively interpreted the ASL images by visual inspection using a three-point scale (unchanged, increased, decreased) when compared to both the ipsilateral and contralateral unaffected temporal and non-temporal cortex. The primary measures on baseline ASL evaluation were a) presence or absence of ASL signal abnormality, b) if present, signal characterization based on the three-point scale, c) territorial or non-territorial vascular distribution, d) localization, and e) laterality.
Quantitative assessment was also performed on postprocessed pCASL cerebral blood flow (CBF) maps. 
All six patients demonstrated ASL hyperperfusion and FLAIR hyperintensity in the hippocampus in a non-territorial distribution (6/6, 100%). ASL hyperperfusion was found in the right hippocampus or amygdala in 5/6 (83%) of cases. Four of the six patients underwent follow up  where all four showed resolution of ASL hyperperfusion. All four patients were also diagnosed with mesial temporal sclerosis (MTS). 
Quantitative assessment demonstrated marked increased CBF values in the affected temporal cortex (mean, 111.2 mL/min/100 g) compared to the unaffected ipsilateral parietal cortex (mean, 49 mL/min/100 g), contralateral temporal cortex (mean, 58.2 mL/min/100 g), and contralateral parietal cortex (mean, 52.2 mL/min/100 g).
Quantitative and qualitative evaluation on ASL imaging findings may add value as a potential diagnostic and therapeutic imaging biomarker for LGI1 AE in conjunction with structural imaging and clinical presentation.