Influencing electroclinical features and prognostic factors in patients with anti-NMDAR encephalitis: a cohort follow-up study in Chinese patients

The clinical manifestations of patients with anti-N-methyl-d-aspartate receptor (anti-NMDAR) encephalitis in East China and factors associated with prognosis were analyzed. A retrospective study of 106 patients (58 females; 48 males) with anti-NMDAR encephalitis in East China was carried out from June 2015 to February 2019. Clinical features and factors influencing outcomes were reviewed. Behavioral changes were observed in 74.5% (79/106) of patients, and comprised the initial symptoms in 61.3% (65/106). Seizures were observed in 67% (71/106) of patients, and served as initial symptoms in 31.1% (33/106). A total of 54.9% (39/71) of seizures were focal seizures. More clinical symptoms were observed in female patients than in male patients (P = 0.000). Similarly, background activity (BA) with high cerebrospinal fluid (CSF) antibody titers at the peak stage was more severe in female patients than in male patients (P = 0.000). The Binary logistic regression and receiver operating characteristic (ROC) curve analyses revealed the factors associated with poor outcomes included consciousness disturbance (OR 4.907, 95% CI 1.653–14.562, P = 0.004; area: 65.4%, sensitivity: 44.2%, specificity: 86.5%, P = 0.014), EEG BA (OR 3.743, 95% CI 1.766–7.932, P = 0.001; area: 76.6%, sensitivity: 73%, specificity: 75%, P = 0.000), number of symptoms (OR 2.911, 95% CI 1.811–4.679, P = 0.000; area: 77.1%, sensitivity: 59.5%, specificity: 78.6%, P = 0.000) and CSF antibody titer (OR 31.778, 95% CI 8.891–113.57, P = 0.000; area: 83.9%, sensitivity: 89.2%, specificity: 78.6%, P = 0.000). EEG BA and number of symptoms were associated with CSF antibody titers. Consciousness disturbances, EEG BA, number of symptoms and CSF antibody titers served as predictors of poor outcomes.

Statistics. The Statistical Package for Social Sciences was used to performed statistical analyses (IBM Corporation, Armonk, NY, USA). The Mann-Whitney U test was performed to compare EEG categorical variables at the peak stage between patients with low and high CSF antibody titers and between female and male patients. The independent-samples t test was adopted to compare symptoms between patients with low and high CSF antibody titers, and between female and male patients, as well as to compare CSF white cell and protein levels between patients with abnormal T2/fluid-attenuated inversion recovery (FLAIR) image and patients with normal T2/FLAIR image. The binary logistic regression analysis and receiver operating characteristic (ROC) curve were used to analyze the association between age, sex, consciousness disturbance, CSF antibody titers, EEG BA during peak stage, number of symptoms, imaging results, relapse, intensive care unit (ICU) admissions, followup period and prognosis in patients with anti-NMDAR encephalitis. P < 0.05 indicated statistical significance. All methods in this study were carried out in accordance with relevant guidelines and regulations.
Clinical characteristics. High CSF antibody titers were observed in 60 patients with anti-NMDAR encephalitis and low CSF antibody titers in 37 patients. The twice positive anti-NMDAR IgG in serum were observed in the remaining 9 patients with unsuccessful lumber puncture. The forty female patients with anti-NMDAR encephalitis were performed the gynecological sonography, pelvic MRI or CT. Ovarian teratomas were observed in 6 female patients, and 1 patient manifested pituitary microadenoma. Eight patients experienced relapse. Eleven patients were admitted the ICU.
Behavioral changes were observed in 74.5% (79/106) of the patients. Behavioral changes comprised the initial symptoms in 61.3% (65/106). Seizures were observed in 67% (71/106) of the patients, and 54.9% (39/71) of seizures were focal seizures. Seizures served as initial symptoms in 31.1% (33/106) of the patients. Constant chewing was noted in 10 female patients with high CSF antibody titers during the peak clinical state. The patients with high CSF antibody titers experienced more clinical symptoms than those with low CSF antibody titers (female mean: 4.06 ± 0.98 vs 1.88 ± 0.86, respectively, P = 0.000; male mean: 2.29 ± 1.0 vs 1.50 ± 0.79, P = 0.006). Similarly, more clinical symptoms were observed in the female patients than in the male patients (mean: 4.06 ± 0.98 vs 2.29 ± 1.0, P = 0.000) (Fig. 1B Fig. 3). One hundred and fourteen EEG or VEEG recordings were obtained from 92 patients. EEG BA was significantly aggravated at 12 days ( Fig. 4 A,C,E,G). A total of 107 EEGs and CSF antibody titers were collected from 85 patients. 91 EEGs and CSF antibody titers during 12 to 60 days from 76 patients were obtained. 76 first EEGs during from 12 to 60 days (median 19.5 days) from 76 patients were analyzed. SDPS was observed in 15 anti-NMDAR encephalitis patients, moderate DPS in 32 patients, mild DPS in 25 patients, and normal activity in 4 patients, separately (Table 1, Fig. 4B,D,F,H). The BA during the peak stage in female patients with high CSF antibody titers was more severe than that in female patients with low CSF antibody titers ( Fig. 4B vs C; Mann-Whitney U test, P = 0.000). BA in those with high CSF antibody titers at the peak stage was more severe in female patients than in male patients ( Fig. 4B vs F; Mann-Whitney U test, P = 0.000) ( Table 1, Fig. 4).
Factor-related prognosis. A total of 103 (97.2%) patients were treated with first-line immunotherapy, 3 (2.8%) with second-line immunotherapy, and 1 with tumor removal and immunotherapy.

Discussion
Our study focused on clinical features and factors related to prognosis in patients with anti-NMDAR encephalitis. The male patients were older than the female patients (P = 0.000) ( Table 1). There was no sex difference in this sample, which is similar to a previous report on adult-onset anti-NMDAR encephalitis in Korea 17 . The prevalence of teratomas in females over 18 years old was 56%, but only 31% in females under 18 years old, and only 9% in females under 14 years old 3 . There were only 15% female patients with ovarian teratoma in this study. In addition to age and sex, the presence of an ovarian teratoma is also dependent on ethnicity 3 . Behavioral changes and seizures were the major symptoms. Behavioral changes comprised the initial symptoms in 61.3% (65/106) of the patients with anti-NMDAR encephalitis in this study. Seizures were observed as the onset symptoms in 31.3% (33/106) of the patients. Moreover, 54.9% (39/71) of the seizures were focal (Table 1). Behavioral changes and seizures served as initial symptoms in most patients, which aligned with previous findings 18,19 . In an observational cohort study, 87% of patients exhibited 4 or more categories of symptoms by the end of the first month 20  www.nature.com/scientificreports/ were observed in patients with high CSF antibody titers than in those with low CSF antibody titers (Table 1, Fig. 1), which aligned with our previous findings 9 . The BA during the peak-stage was worse in the female patients with high CSF antibody titers than in those with low CSF antibody titers (P = 0.000) ( Table 1, Fig. 4). The number of clinical symptoms were greater in the female patients with high CSF antibody titers than in male patients with high CSF antibody titers (mean: 3.97 ± 0.17 vs 2.33 ± 0.20, respectively, P = 0.000) ( Table 1, Fig. 1). Meanwhile, the peak stage BA was worse in the female patients with high CSF antibody titers than in the male patients with high CSF antibody titers (P = 0.000) ( Table 1, Fig. 4). The constant chewing was observed in the female patients with high CSF antibody titers during the peak stage, which may be a useful marker of the peak period of the disease. During the constant chewing, no epileptiform discharges (EDs) were observed in the EEG recordings, and antiepileptic drugs (AEDs) were ineffective 9 .
In a large unselected cohort of adults, a normal posterior rhythm in the first EEG recording at a median of 19 days from disease onset predicted a favorable clinical outcome, while a severely abnormal EEG was associated with a poor outcome 22 . Ordinal logistic regression showed that the presence of a normal posterior rhythm was associated with lower mRS at final follow-up 22 . Binary logistic regression analysis and ROC curve analysis showed that EEG BA during the peak clinical state (median: 19.5 days) was associated with poor outcomes in this study. The number of symptoms and CSF antibody were also predictors of poor outcomes (Table 2, Fig. 5). A greater number of clinical symptoms were noted in patients with high CSF antibody titers than in those with low CSF antibody titers (Table 1, Fig. 1). The main epitope targeted by the antibodies is in the extracellular N-terminal domain of the NR1 subunit. Patients' antibodies decreased the numbers of cell-surface NMDA receptors and NMDA-receptor clusters in postsynaptic dendrites, an effect that could be reversed by antibody removal. The www.nature.com/scientificreports/ severity of anti-NMDAR encephalitis was associated with antibody titers 5 . Furthermore, consciousness disturbance was a factor associated with nonfavorable outcomes in this study ( Table 2, Fig. 5), which was similar to a previous study 23 . In previous studies, the predictors of good outcomes were early treatment and lack of ICU admission 4 . In our study, 11 patients were admitted to the ICU. ICU stay was not a predictor of poor outcomes. Many patients are not admitted to the ICU due to the shortage of ICU beds. All patients admitted to the ICU had poor outcomes (mRS ≥ 2). Relapses were defined as the new onset of symptoms, or worsening of symptoms after at least 2 months of improvement or stabilization. Although relapses were not a predictor of poor outcomes in our study, all patients with relapse had poor outcomes (mRS ≥ 2). The follow-up period may have been short in our study. Titulaer et al. followed their anti-NMDAR encephalitis patients for a median duration of 24 months and 7.8% of patients in that study experienced one or more clinical relapses 4 .

Conclusion
EEG BA and the number of symptoms were associated with CSF antibody titers. CSF white cell and protein levels in patients with abnormal T2/FLAIR were higher than in patients with normal T2/FLAIR. Consciousness disturbance, EEG BA, number of symptoms and CSF antibody titers served as predictors of poor outcomes.    www.nature.com/scientificreports/