Anti-NMDAR encephalitis mimicking HaNDL syndrome

Background: Anti-NMDA receptor encephalitis typically manifests as severe multistage neuropsychiatric syndrome. However, milder or incomplete forms of the disorder have been recognised. Here, we report on a patient with anti-NMDA receptor encephalitis with a clinical phenotype mimicking the syndrome of headache with neurological deficits and cerebrospinal fluid (CSF) lymphocytosis (HaNDL). Case: A 67-year-old man presented with recurrent stereotyped episodes of hemianopia, aphasia and right hemiparesis accompanied by throbbing headaches as well as confusion and agitation. CSF analysis showed lymphocytic pleocytosis. Additional analysis revealed NMDA receptor IgG antibodies in the patient's CSF. Following immunotherapy, no further episodes occurred and NMDAR antibodies became undetectable. No NMDAR or other neuronal antibodies were detected in archived serum and CSF samples of 12 HaNDL patients fulfilling the current diagnostic criteria. Conclusions: While anti-NMDAR encephalitis can manifest with a HaNDL-like clinical picture, HaNDL syndrome itself does not appear to be mediated by anti-NMDAR antibodies.