In this chapter we have selected relevant questions that over the years many colleagues have asked us at conferences or in consultations. Some answers are straightforward, but others are difficult because they reflect grey areas in our knowledge of autoimmune encephalitis that require further research. The chapter includes 90 questions covering 14 general topics: definitions and general concepts, diagnostic issues, pathogenesis and mechanisms of disease, limbic encephalitis, anti-NMDA receptor encephalitis, autoimmune cerebellar/brainstem encephalitis, autoimmunity against the inhibitory synapses, neurological syndromes and glial antibodies, autoimmune and inflammatory encephalopathies as a complication of cancer treatment, autoimmunity and psychiatric manifestations, seizures and autoimmunity, autoimmunity and sleep, abnormal movements in neurological autoimmune disorders, and CNS syndromes at the frontier of autoimmune encephalitis. The answers are short, and we strongly recommend readers go to the suggested sections in the book and read the related references, where more comprehensive answers can be found.

This chapter focuses on the syndromes that are associated with antibodies that target proteins of the inhibitory synapses. Two antibodies are directed against intracellular presynaptic proteins, including glutamic acid decarboxylase (GAD), a key enzyme in the synthesis of GABA, and amphiphysin, which is involved in the presynaptic reuptake of neurotransmitters. Both antibodies are associated with stiff-person syndrome (SPS), which results in rigidity in proximal muscles of legs, abdomen, and lower back, impaired gait, muscles spasms, exaggerated startle responses to acoustic or tactile stimuli, and anxiety and task-specific phobias. Three antibodies are directed against cell surface receptors, including GABAaR and GABAbR, and the glycine receptor (GlyR). Encephalitis with prominent seizures is the common presentation of patients with antibodies against GABAaR or GABAbR, whereas antibodies against GlyR associate with an SPS variant named progressive encephalomyelitis with rigidity and myoclonus (PERM). In addition, this chapter includes the antibodies against dipeptidyl-peptidase-like protein 6 (DPPX), an auxiliary subunit of the Kv4.2 potassium channels that is not restricted to inhibitory synapses, but patients with this disorder frequently show CNS hyperexcitability and sometimes clinical features similar to PERM.