Autoimmune encephalitis: Clinical diagnosis versus antibody confirmation

Context: Autoimmune encephalitis is a heterogeneous disorder which is being diagnosed with increasing frequency. The diagnosis of these disorders is based on the detection of autoantibodies and characteristic clinical profiles. Aims: We aimed to study the antibody profile in encephalitis patients with suspected autoimmune etiology presenting to a tertiary care center. Settings and Design: The subjects were selected by screening all patients with clinical profile suggesting autoimmune encephalitis admitted in the neuromedical intensive care unit (ICU) of a tertiary care center in South India. Materials and Methods: Patients who fulfilled modified Zuliani et al.'s, criteria for autoimmune encephalitis were identified during the period December 2009-June 2013. Blood samples from these subjects were screened for six neuronal antibodies. Statistical analysis used: Chi-square test was applied to compare the antibody positive and negative patients. Results: Out of 1,227 patients screened, 39 subjects (14 males: 25 females) were identified with a mean age of 15.95 years and 19 cases were assessed in the acute and 20 in the convalescent phase of the illness. Seizure (87.8 %) was the most common presenting symptom; status epilepticus occurred in 23 (60.5%) patients during the course of the illness. Fourteen (35.9%) patients were N-methyl-D-aspartate receptor (NMDAR) antibody-positive and all were negative for the other antibodies tested. Conclusions: One-third of patients presenting with acute noninfective encephalitis would be positive for NMDAR antibodies with the remaining two-thirds with clinically suspected autoimmune encephalitis being antibody-negative. There are few markers in the clinical and investigative profiles to distinguish antibody-positive and -negative patients.