BackgroundAnti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is a clinically heterogeneous disorder characterized by epileptic seizures, psychosis, dyskinesia, consciousness impairments, and autonomic instability. Symptoms are always various. Sometimes it presents in milder or incomplete forms. We report 4 cases of anti-NMDAR encephalitis with incomplete forms, 3 cases of which were accompanied by neuromyelitis optica spectrum disorder or neurosyphilis respectively.Case presentationA 33-year-old man presented with dysarthria, movement disorder and occasional seizures. He had 6 relapses in 28 years. When suffered from upper respiratory tract syndrome, he developed behavioral and consciousness impairment. Cranial MRI was normal. Viral PCR studies and oncologic work-up were negative. Anti-NMDAR antibody was detected in CSF and serum.A 21-year-old female manifested dizziness and diplopia ten months and six months before, respectively. Both responded to steroid therapy and improved completely. This time she presented with progressive left limb and facial anesthesia, walking and holding unsteadily. Spinal cord MRI follow-up showed abnormality of medulla oblongata and cervical cord(C1). Anti-AQP4 and anti-NMDAR were positive in CSF. Steroid-pulse therapy ameliorated her symptoms.A 37-year-old male experienced worsening vision. He was confirmed neurosyphilis since the CSF tests for syphilis were positive. Protein was elevated and the oligoclonal IgG bands(OB) and anti-NMDAR was positive in CSF. Anti-aquaporin 4(AQP4) antibodies and NMO-IgG were negative. Cranial MRI showed high FLAIR signal on frontal lobe and low T2 signal adjacent to the right cornu posterious ventriculi lateralis. Treatment for neurosyphlis was commenced with gradual improvement.A 39-year-old male, developed serious behavioral and psychiatric symptoms. Examination showed abnormal pupils and unsteady gait. He was confirmed neurosyphilis according to the CSF tests for syphilis. Anti-NMDAR was positive in CSF and serum. Cranial MRI showed lateral ventricles and the third ventricle enlargement and signal abnormality involving bilateral temporal lobe, corona radiate and centrum semiovale. PenicillinG, pulsed methylprednisolone and intravenous immunoglobulin was administered. He was stable.ConclusionAnti-NMDAR encephalitis can present in atypical types. When relapsing, it may present with partial aspects or with isolated symptoms of the full-blown syndrome. Anti-NMDAR encephalitis may be related to neuromyelitis optica spectrum disorder or neurosyphilis.

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A retrospective study was performed to compare the differences in clinical and laboratory features of asymptomatic neurosyphilis (ANS) and symptomatic neurosyphilis (SNS). A total of 264 HIV-negative inpatients with neurosyphilis were enrolled from Beijing Ditan Hospital and Beijing Tiantan Hospital between January 2014 and May 2018, including 110 SNS and 154 ANS. The SNS group had more patients in males, older median age and without antisyphilis treatment than ANS group (P<0.001, P<0.001, and P<0.001, respectively). The laboratory findings showed that the SNS group had higher pretreatment serum rapid plasma regain (RPR) titer, current serum RPR titer, cerebrospinal fluid (CSF) white blood cell (WBC) counts, CSF protein concentrations, and higher positive CSF RPR rate than those in the ANS group (P=0.011, P<0.001, P<0.001, P<0.001, and P<0.001, respectively). The multivariate logistic regression analysis revealed that male (OR=2.833, P=0.009), age≥45 years (OR=3.611, P=0.001), without antisyphilis treatment (OR=0.247, P<0.001), higher current serum RPR titer (OR=1.373, P=0.022), positive CSF RPR (OR=4.616, P<0.001), and higher CSF protein concentration (OR=1.017, P=0.026) were independent risk predictors for SNS. Therefore, clinical and laboratory features between SNS and ANS are quietly different. Male gender, age≥45 years, and lack of antisyphilis treatment are risk factors for SNS. The elevated level of serum RPR titer, CSF protein concentration, and CSF RPR titer may indicate the development of neurosyphilis and the aggravation of neurological symptoms.