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Advanced Neurology The diagnosis and treatment of anti-LGI1 autoimmune encephalitis

disease . The pathogenic mechanism of hyponatremia These symptoms can reflect the severity of the disease and
[50]
is likely associated with the syndrome of inappropriate the effectiveness of treatment to a certain extent.
antidiuretic hormone secretion caused by the simultaneous
expression of LGI1 by the hypothalamus and the kidney . 4. Supplementary examination
[51]
Sometimes, severe hyponatremia can be seen as a precursor 4.1. Cerebrospinal fluid examination
to anti-LGI1 AE. The serum sodium concentration of
patients with refractory hyponatremia who have been Cerebrospinal fluid examinations of patients with anti-
receiving continuous intravenous and oral sodium LGI1 AE are often non-inflammatory and without any
supplementation can no longer be maintained at the normal apparent specificity. Lumbar puncture pressure can be
level. As a result, they need to take concentrated sodium for normal or slightly increased, and the white blood cell
a long time and recheck their serum sodium concentration count in cerebrospinal fluid can also be normal or slightly
[1,51,57]
regularly after being discharged from the hospital. increased, especially lymphocytes . Cerebrospinal
fluid routine biochemical examinations are usually
3.4. Hyperkinetic movements (HMs) normal. However, few patients may show slightly increased
cerebrospinal fluid protein and glucose , with positive
[58]
In contrast to the extensive discussion on FBDS, HMs oligoclonal bands .
[59]
have been overlooked in the past. HMs are characterized
as a group of jerk-like or twisting movements . This type 4.2. Brain magnetic resonance imaging (MRI)
[43]
of manifestation has only been described in a few case Brain MRI is the first choice for an early diagnosis of anti-
reports [43,52-54] . HMs may occur when the patient is asleep or LGI1 AE. In most patients, brain MRI shows unilateral
awake, and they do not interrupt the patient’s autonomous or bilateral medial temporal lobes (amygdala and
movements. As a result, only a small number of patients hippocampus) with long T1 and long T2 signals in the acute
would notice such symptoms and inform the doctor at phase, and slightly higher signals can be seen on diffusion-
the time of admission. According to Liu et al. , HMs are weighted imaging (DWI) sequence. T2-fluid-attenuated
[43]
very common in anti-LGI1 AE and can be promoted by inversion recovery (FLAIR) hyperintensity can be seen on
sleep. Therefore, it is inferred that HMs are the result of both plain and enhanced MRI . Amygdaloid hypertrophy,
[58]
the imbalance of the motor cortex, basal ganglia, thalamus, which is sensitive to FLAIR sequence, can be found in
and substantia nigra/red nucleus. HMs may also be the some patients. Abnormal signals in basal ganglia can also
potential cause of sleep disorders. be observed in the brain MRIs of some patients. However,

3.5. Psychiatric disorders the brain MRIs of some patients may be normal. Significant
reductions in brain connectivity involving inferior frontal
Results from the previous studies have shown that the gyrus, anterior and posterior cingulate gyri, several regions
incidence of psychiatric symptoms in patients with of the default mode network (DMN), and higher visual
anti-LGI1 AE is significant. The main manifestations networks have been demonstrated in patients with anti-
are personality and behavioral disorders, irritability, LGI1 AE using resting-state functional MRI (fMRI) .
[3]
anxiety, impulsive behavior, hallucinations, delusions, Irani et al. have shown that the hippocampal volume
[38]
and coma [50,51] . In a South Korean study by Jang et al. , of patients was significantly smaller than that of matched
[55]
62.5% of patients with anti-LGI1 AE developed psychiatric normal controls during the follow-up period after recovery,
symptoms that were associated with mood, with depressed although the brain MRIs revealed no abnormal signals in
mood being the most common symptom, while others their hippocampus in the acute phase, thus suggesting that
such as irritability, self-injurious behavior, and emotional anti-LGI1 AE may be caused by brain atrophy.
instability were also observed. These mood-related
18
symptoms may mislead patients and their clinicians into 4.3. F-fluorodeoxyglucose position emission
18
considering the illness as a psychiatric disorder, such as tomography ( F-FDG PET)
geriatric depression, early behavioral and psychological According to current research, F-FDG-PET is considered
18
symptoms of dementia (BPSD), or epilepsy-related to be more sensitive than MRI in the diagnosis of anti-
psychosis. As a result, a considerable number of patients LGI1 AE [42,60] . Parietal and frontal cortex hypometabolism
may visit the psychiatric department first, thus precluding and medial temporal lobe (MTL), basal ganglia (BG), and
the early diagnosis of anti-LGI1 AE. Among the various occipital lobe hypermetabolism can be detected by F-FDG
18
sleep disorders, insomnia is the most common. Insomnia PET in patients with anti-LGI1 AE . The hypometabolism
[42]
is characterized by difficulty in falling asleep or lack of sleep may be a result of functional impairment propagated along
caused by frequent waking. These symptoms are mainly cortical and subcortical networks, arising from the sites
related to hippocampal and amygdala impairment . of primary abnormalities in MTL and BG . Occipital
[56]
[3]
Volume 1 Issue 3 (2022) 4 https://doi.org/10.36922/an.v1i3.237