Improving clinical practice with an old friend from the neuroimmunology toolkit: acute corticosteroids in LGI1 antibody encephalitis.

Autoantibodies against leucine glioma inactivated 1 (LGI1) are well recognised in elderly men without tumours who present with frequent, focal seizures and a hippocampal-centric pattern of cognitive impairment.1 These patients often progress over more than 3 months and show little evidence of inflammation on routine CSF testing, defying diagnostic criteria for autoimmune encephalitis. Furthermore, as the LGI1-antibodies are of the ‘non-inflammatory’ IgG4 subclass, several first principles collectively question a rationale for immunotherapy administration in this cohort. Yet, this form of autoantibody-mediated central nervous system disease is clearly, and often exquisitely, sensitive to immunotherapies. We have witnessed patients whose seizure frequency plummets from 100/day to nil after just three doses of corticosteroids. Larger studies have confirmed time-dependent immunotherapy sensitivity. For example, cessation of faciobrachial dystonic seizures (the most characteristic semiology in these patients) was observed in 75/85 (88%) patients 90 days after immunotherapy administration: an effect most marked in those who received early immunotherapies.2 However, the question of which immunotherapies to administer remains unanswered. The …