Page 48 - AN-1-3

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

hypermetabolism, on the other hand, may be a compensatory encephalopathy (such as Wernicke’s encephalopathy,
mechanism during the acute/early phase of the illness. In the hepatic encephalopathy, and pulmonary encephalopathy),
acute phase of the disease, FDG uptake shows a significant Hashimoto’s encephalopathy , central nervous system
[68]
increase, followed by a gradual decrease, which eventually neoplasms (such as cerebral gliomatosis, primary central
returns to normal after treatment [46,61] . Therefore, F-FDG nervous system lymphoma, and metastatic cancer),
18
PET can be used as a tool to measure disease activity and hereditary diseases (such as mitochondrial encephalopathy,
evaluate patients’ responses to treatment. methylmalonic acidemia, and adrenoleukodystrophy), and
neurodegenerative diseases (such as Creutzfeldt-Jakob
4.4. Electroencephalogram (EEG) disease, Lewy body dementia, multiple system atrophy,
The proportion of abnormal EEG during FBDS attacks is and hereditary cerebellar degeneration).
only 21% to 30%. During the interictal period of FBDS, mild
diffuse slow wave or bilateral frontotemporal slow wave 6. Treatment and prognosis
can be seen, or the EEG may also be completely normal . Early identification, diagnosis, and rapid initiation of
[37]
Navarro et al. have found that FBDS originates from the immunotherapy are all very important to improve the
primary motor cortex (M1) . Before muscle contraction, prognosis of patients with anti-LGI1 AE [31,38] . However,
[35]
EEG shows focal, contralateral, and frontal slow waves. The the median time from onset to diagnosis of patients with
previous studies have demonstrated the superiority of long- anti-LGI1 AE in China is about 2 months , indicating that
[69]
lasting EEG monitoring over short-lasting routine EEG many patients would have had missed the best opportunity
in revealing subclinical and recurrent seizures [62,63] , which for diagnosis and treatment.
enables clinicians to adjust the treatment plan in time.
First-line immunotherapy, including glucocorticoids,
4.5. Antibody detection intravenous immunoglobulin (IVIg), and plasma
Anti-LGI1 antibodies in serum and/or cerebrospinal fluid exchange, is the preferred treatment. The previous studies
are positive. It is worth noting that the detection of LGI1 have shown that immunotherapy is particularly effective
antibodies in the serum seems to be more sensitive than in achieving control of FBDS and other seizures. Patients
that in cerebrospinal fluid compared to other types of who receive glucocorticoids (intravenous, oral, or both)
autoimmune encephalitis [20,32,54] . Therefore, it is important tend to have better short-term prognosis than those
to detect both types of samples when anti-LGI1 AE is receiving IVIg alone. This may be due to the fact that LGI1
clinically suspected . According to Zhong et al. , the antibodies mainly belong to the IgG4 subclass, which
[64]
[27]
concentration of LGI1 antibody in the cerebrospinal fluid cannot activate complements; thus, steroids have a stronger
is related to the probability of recurrence of anti-LGI1 immunosuppressive effect on these antibodies, while
AE, in which the higher the concentration, the greater the IVIg has a lower efficacy in these diseases [70,71] . The side
probability of recurrence. effects of glucocorticoid therapy are common, especially
those affecting the musculoskeletal system (myopathy,
4.6. Tumor markers tendon rupture, and osteoporosis). Other rare but serious

According to the previous studies, the incidence of complications include acute respiratory distress syndrome
[31]
tumors in anti-LGI1 AE patients was found to be 0% to (ARDS), septicemia, and pulmonary embolism (PE) .
[72]
13% , which was comparatively less than other types Zhang et al. have demonstrated that plasmapheresis
[43]
of autoimmune encephalitis [65,66] . In addition, the serum can promptly relieve the symptoms of patients without
tumor markers of anti-LGI1 AE patients are often negative. fatal adverse events. However, it is more suitable for the
Due to the lack of specific recommendations for tumor emergency treatment of critically ill patients so as to
screening in anti-LGI1 AE, the tumor screening methods achieve faster remission in view of its high treatment cost
for paraneoplastic syndromes (PNS) can be referenced: and less trauma.
[67]
a second screening shall be repeated after 3–6 months, Second-line therapeutic agents include rituximab and
followed by regular screening every 6 months for 4 years. IV cyclophosphamide . They are mainly used for patients
[1]
Patients with concurrent neoplasia may seek chemotherapy, with poor effect of first-line immunotherapy (Figure 2) ,
[73]
radiotherapy, and/or surgery after AE is controlled. which account for 10% to 15% of all anti-LGI1 AE patients.
Rituximab can be used when the patient’s condition has
5. Differential diagnosis not significantly improved or is aggravated after 2 weeks
Anti-LGI1 AE needs to be differentiated from central of treatment with more than two kinds of first-line
nervous system infection (such as herpes simplex immunotherapies. Cyclophosphamide may be used when
virus meningitis), metabolic encephalopathy, toxic rituximab is not available or contraindicated. Rituximab is

Volume 1 Issue 3 (2022) 5 https://doi.org/10.36922/an.v1i3.237