Ketamine use in refractory status epilepticus associated with anti-NMDA receptor antibody encephalitis

Anti-N-methyl-D-aspartate receptor encephalitis (anti-NMDAr encephalitis) is an auto-immune disorder associated with the production of antibodies against NR1 and NR2 sub units of the NMDA receptor. Seizures in this population are reported in up to 50% of cases with status epilepticus being reported in 25% of cases, refractory status epilepticus in 13.8% of cases and super-refractory status epilepticus in 10.2% of cases. Treatment of refractory epileptic activity in this population is not uniform and heterogeneous.

We present three cases of super refractory status epilepticus in patients with anti-NMDAr encephalitis treated successfully with ketamine, a noncompetitive NMDA receptor antagonist. All patients had failed to improve clinically on multiple anti-convulsants and immunotherapy prior to initiation of ketamine therapy.

In all three cases, administration of a load followed by maintenance infusion (0.05 mg/kg/min infusion) of ketamine yielded clinical and/or electrographic seizure cessation in less than 48 h. Patients were treated for a heterogeneous duration although ultimately, epilepsy outcomes were favorable from a seizure freedom standpoint. Earlier treatments with ketamine were associated with better epilepsy outcomes in this case series.

Ketamine may be a useful adjunct treatment in super-refractory status epilepticus in patients with NMDAr encephalitis.