Acetazolamide as an effective treatment for pilomotor seizures in autoimmune encephalitis

Pilomotor seizures are strongly associated with autoimmune encephalitis (AE), particularly anti-LGI1 encephalitis. The carbonic anhydrase inhibitor acetazolamide may have special efficacy for treating AE-associated pilomotor seizures. Six patients with AE (five anti-LGI1, one seronegative) and temporal lobe pilomotor seizures (five with seizures inducible by hyperventilation) were treated with acetazolamide, administered in a cycling (2-days-ON, 4-days-OFF) regimen to offset tolerance. Seizures were assessed during epilepsy monitoring unit (EMU) recordings in four inpatients (one of whom also maintained an outpatient seizure diary chronicling 1203 seizures over 1079 days); two outpatients self-reported seizure frequencies. The extended diary revealed an inverse correlation between acetazolamide and proportion of seizures/day: 6%, 2% (days 1, 2 ON); 3%, 13%, 31%, 45% (days 1, 2, 3, 4 OFF). This patient later developed focal status epilepticus upon wean of antiseizure medications during a seropositive AE relapse that was remarkably aborted with acetazolamide monotherapy. The other three EMU patients averaged .56 seizures/day ON, and 3.81 seizures/day OFF (p = .004). The two outpatients reported seizure reductions from 3-5/day to 2/week, and 15-20/day to none, respectively, after initiation of cycling acetazolamide. Likely related to cerebral CO₂/pH sensitivity, acetazolamide can be unusually effective in controlling pilomotor seizures in AE, chronically or in acute settings.