LGI1 and encephalitis: However, the encephalitis group could be divided between those with otherwise seronegative LE and high GAD-Ab values (all but one > 10,000 IU/mL), and those with other encephalitis syndromes (e.g. LGI1-Ab or Rasmussen’s) whose GAD-Ab were all < 2000 IU/mL.