Abstract Details

Fifty-seven percent were male (median symptom-onset age, 56 years; range, 11-97). AE criteria-requiring subacute memory deficits/altered mental status were met by 179 (60%). AE diagnostic categories were: possible (n=62, 34.6 %, all seronegative), definite (autoimmune limbic encephalitis [n=60, 33.5%], ADEM [n=1, 0.5%], anti-NMDA-R encephalitis [n=21, 12%], other [n=16, 9%]), Hashimoto encephalopathy (n=16, 9%), or probable AE (n=3, 2%, all seronegative). Of 98 definite AE cases, 54 (45%) fulfilled criteria without antibody testing, and 44 required positivity to meet criteria. AE-specific Abs detected among definite cases were: LGl1 (n=32), NMDA-R (n=20), GAD65 (n=9), CASPR2 (n=4), DPPX (n=4), Ma2 (n=3), GFAP (n=3), NIF (n=2), AMPA-R (n=2), MOG (n=2), NMDA/MOG (n=1), ANNA-1 (n=1); 15 were seronegative. Three probable cases were diagnosed by AE-supportive MRI (n=3) and inflammatory CSF (n=3). The 62 possible cases were diagnosed by ≥1 new CNS finding (n=16), new-onset seizures (n=25), CSF pleocytosis (n=22), or AE-supportive MRI (n=22). Of 121 patients (40%) not assessable by AE criteria (without subacute-onset of memory deficits/altered mental status), 42 had insidious or uncertain onset, and 79 had subacute onset of other symptoms (most commonly seizures, brainstem encephalitis or psychiatric). Sixty-two (51%) had ≥1 well-characterized antibody (LGl1 > GAD65 > NMDA-R > CASPR2 = GFAP = IgLON5 > KLHL11 > DPPX > MOG = GlyR/CRMP-5/ANNA-1/ANNA-2). Although the remaining 59 were seronegative, 35 (59.3%) were immunotherapy-responsive.