Rationale: We report this 1st case because perampanel may be effective against the seizures and abnormal behavior that occur in anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis.
Patient concerns: The patient was a healthy 26-year-old woman who suddenly developed seizures and exhibited abnormal behavior.
Diagnoses: NMDAR encephalitis was diagnosed based on positive NMDAR antibody on cerebrospinal fluid analysis.
Interventions: Treatment with anticonvulsants and sedatives was started immediately, along with steroid pulse therapy and plasmapheresis, but these measures did not adequately control the repeated seizures and abnormal behavior. However, with the addition of oral perampanel, an α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist, the seizures and abnormal behavior promptly disappeared.
Outcomes: The patient was transferred to the rehabilitation hospital and returned to her job.
Lessons: It appears that perampanel rapidly eliminated these clinical features by inhibiting inflow of abnormal glutamic acid and attenuating nerve hyperexcitability by acting as a selective and noncompetitive antagonist of AMPA receptors that had increased in the postsynaptic membrane due to anti-NMDAR encephalitis. To the best of our knowledge, there are no other reports showing that perampanel was effective against anti-NMDAR encephalitis. This case suggests that perampanel may be effective against the seizures and abnormal behavior that occur in anti-NMDAR encephalitis.