Significance of Neuronal Autoantibodies in Comparison to Infectious Etiologies among Patients Presenting with Encephalitis in a Region with a High Prevalence of Infections.

Background: Prevalence of antibody-mediated autoimmune encephalitis (AE) is reported to be comparable to infectious encephalitis in Western populations. We evaluated the frequency and significance of AE and neuronal autoantibodies in comparison to infectious etiologies among patients presenting with encephalitis in a South Asian population. Methods: Ninety-nine consecutive patients with a clinical diagnosis of encephalitis/meningoencephalitis admitted to two of the largest tertiary-care hospitals in Sri Lanka were studied. PCR and ELISA were used to screen viruses while Gram stain and culture were used to screen bacteria. Sera were tested for antibodies binding to primary embryonic rat hippocampal neuronal cultures and cell-based assays for antibodies to NMDAR, LGI1, CASPR2, Contactin2, AMPAR, GABAAR, GABABR, aquaporin-4 and MOG. Results: Patient ages ranged from 1 month to 73 years (mean = 24.91; SD = 21.33) with a male: female ratio of 1.75:1. A viral etiology was identified in 27.3% and bacterial meningoencephalitis was diagnosed in 17.1%. Sera of nine patients had antibodies binding to live primary neurons, but only five had specific antibodies to CASPR2 (n = 1), NMDAR (n = 2) or GABABR-antibodies (n = 2). Moreover, the patients with CASPR2 antibodies and NMDAR-antibodies were also positive for dengue antibodies. Only the two patients with NMDAR-antibodies had features and responses to immunotherapy consistent with AE. Conclusions: Identified infectious forms of meningoencephalitis (44.4%) greatly exceeded the occurrence of neuronal autoantibodies (9.1%) and AE (2%) in Sri Lanka, and this may be common in those regions where infections are prevalent.

Investigation of neuronal auto-antibodies in children diagnosed with epileptic encephalopathy of unknown cause.

AIM: Cryptogenic forms of epileptic encephalopathies (EE) with their well-known features of drug-resistance, mental deterioration and partial response to immunotherapies are ideal candidates for screening for neuronal autoantibodies (NAA). METHOD: Fifty consecutive pediatric patients with a diagnosis of EE of unknown cause were included. Nine NAAs were tested by ELISA, RIA or cell-based assays. Clinical features of seronegative and seropositive patients were compared. RESULTS: NAAs were found in 7/50 (14%) patients. They were N-methyl-d-aspartate receptor in two (4%), glycine receptor in two (4%), contactin-associated protein-like 2 in one (2%), glutamic acid decarboxylase in one (2%) and type A gamma aminobutyric acid receptor in one patient (2%). Furthermore, serum IgGs of two patients negative for well-characterized NAAs, showed strong reactivity with the uncharacterized membrane antigens of live hippocampal neurons. There were no significant differences between seropositive and seronegative patients by means of epilepsy duration, anti-epileptic drug resistance, EE type, types of seizures, seizure frequencies, EEG features or coexisting autoimmune diseases. Some seropositive patients gave good-moderate response to immunotherapy. DISCUSSION: Potential clues for the possible role of autoimmunity in seropositive patients with EE were atypical prognosis of the classical EE type, atypical progression and unusual neurological findings like dyskinesia.

Neuronal autoantibodies in mesial temporal lobe epilepsy with hippocampal sclerosis.

OBJECTIVE: Our aim was to investigate the prevalence of neuronal autoantibodies (NAbs) in a large consecutive series with mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS) and to elucidate the clinical and laboratory clues for detection of NAbs in this prototype of frequent, drug-resistant epilepsy syndrome. METHODS: Consecutive patients diagnosed with MTLE fulfilling the MRI criteria for HS were enrolled. The sera of patients and various control groups (80 subjects) were tested for eight NAbs after ethical approval and signed consents. Brain tissues obtained from surgical specimens were also investigated by immunohistochemical analysis for the presence of inflammatory infiltrates. The features of seropositive versus seronegative groups were compared and binary logistic regression analysis was performed to explore the differentiating variables. RESULTS: We found antibodies against antigens, contactin-associated protein-like 2 in 11 patients, uncharacterised voltage-gated potassium channel (VGKC)-complex antigens in four patients, glycine receptor (GLY-R) in 5 patients, N-methyl-d-aspartate receptor in 4 patients and γ-aminobutyric acid receptor A in 1 patient of 111 patients with MTLE-HS and none of the control subjects. The history of status epilepticus, diagnosis of psychosis and positron emission tomography or single-photon emission CT findings in temporal plus extratemporal regions were found significantly more frequently in the seropositive group. Binary logistic regression analysis disclosed that status epilepticus, psychosis and cognitive dysfunction were statistically significant variables to differentiate between the VGKC-complex subgroup versus seronegative group. CONCLUSIONS: This first systematic screening study of various NAbs showed 22.5% seropositivity belonging mostly to VGKC-complex antibodies in a large consecutive series of patients with MTLE-HS. Our results indicated a VGKC-complex autoimmunity-related subgroup in the syndrome of MTLE-HS.

Neuronal autoantibodies in epilepsy patients with peri-ictal autonomic findings.

Autonomic dysfunction has frequently been reported in autoimmune encephalitis associated with seizures and there is growing evidence that epilepsy patients may display neuronal autoantibodies (NAAb). The aim of this study was to investigate the frequency of NAAb in epilepsy patients with peri-ictal autonomic findings. Fifty-eight patients (37 women/21 men; average age of 34.2 ± 9.9 years and epilepsy duration of 19.1 ± 9.6 years) who had at least one video-EEG recorded focal or secondary generalized seizure with clear-cut documented peri-ictal autonomic findings, or consistently reported seizures with autonomic semiology, were included. NAAb were tested by RIA or cell based assays. NAAb were present in 17 of 58 (29.3%) patients. Among seropositive patients, antibodies were directed against N-methyl-D-aspartate receptor (NMDAR) in 5 (29%), contactin-associated protein-like 2 (CASPR2) in 5 (29%), uncharacterized voltage gated potassium channel (VGKC)-complex antigens in 3 (18%), glutamic acid decarboxylase (GAD) in 2 (12%), glycine receptor (GLYR) in one (6%) and type A gamma aminobutyric acid receptor (GABAAR) in one patient (6%). Peri-ictal gastrointestinal manifestations, piloerection, ictal fever, urinary urge, and cough occurred more commonly in the seropositive group. The prevalences of psychotic attacks and status epilepticus were significantly increased in the seropositive group. Seropositivity prevalence in our patient group with peri-ictal autonomic findings is higher than other previously reported epilepsy cohorts. In our study, ictal fever-VGKC-complex antibody and pilomotor seizure-GABAAR antibody associations were documented for the first time. Chronic epilepsy patients with peri-ictal autonomic semiology, history of status epilepticus and psychotic disorder may benefit from autoantibody screening.