Background and ObjectivesTo assess the clinical practice applicability of autoimmune encephalitis (AE) criteria (2016).MethodsMedical records of 538 adults diagnosed with AE or related autoimmune encephalopathy at Mayo Clinic (not including pure movement disorders) were reviewed and AE guideline criteria applied.ResultsOf 538 patients, 288 were male (52%). The median symptom onset age was 55 years (range, 11–97 years; 16 had onset as children). All had other non-AE diagnoses reasonably excluded. Of 538 patients, 361 (67%) met at least possible criteria, having all 3 of subacute onset; memory deficits, altered mental status or psychiatric symptoms, and ≥1 supportive feature (new focal objective CNS finding, N = 285; new-onset seizures, N = 283; supportive MRI findings, N = 251; or CSF pleocytosis, N = 160). Of 361 patients, AE subgroups were as follows: definite AE (N = 221, 61%, [87% AE-specific IgG positive]), probable seronegative AE (N = 18, 5%), Hashimoto encephalopathy (N = 20, 6%), or possible AE not otherwise categorizable (N = 102, 28%). The 221 patients with definite AE had limbic encephalitis (N = 127, 57%), anti–NMDA-R encephalitis (N = 32, 15%), ADEM (N = 8, 4%), or other AE-specific IgG defined (N = 54, 24%). The 3 most common definite AE-IgGs detected were as follows: LGI1 (76, 34%), NMDA-R (32, 16%), and high-titer GAD65 (23, 12%). The remaining 177 patients (33%) not meeting possible AE criteria had the following: seizures only (65, 12% of all 538 patients), brainstem encephalitis without supratentorial findings (55, 10%; none had Bickerstaff encephalitis), or other (57, 11%). Those 57 “others” lacked sufficient supportive clinical, radiologic, or CSF findings (N = 26), had insidious or initially episodic onset of otherwise typical disorders (N = 21), or had atypical syndromes without clearcut memory deficits, altered mental status, or psychiatric symptoms (N = 10). Fifteen of 57 were AE-specific IgG positive (26%). Among the remaining 42, evidence of other organ-specific autoimmunity (mostly thyroid) was encountered in 31 (74%, ≥1 coexisting autoimmune disease [21, 50%] or ≥1 non–AE-specific antibodies detected [23, 53%]), and all but 1 had an objective immunotherapy response (97%).DiscussionThe 2016 AE guidelines permit autoimmune causation assessment in subacute encephalopathy and are highly specific. Inclusion could be improved by incorporating AE-IgG–positive patients with isolated seizures or brainstem disorders. Some patients with atypical presentations but with findings supportive of autoimmunity may be immune therapy responsive.

A brainstem syndrome is recognizable in patients presenting with a combination of visual disturbances, incoordination, gait problems, speech and swallowing difficulties, and new-onset sleep symptomatology. Brainstem disorders of subacute onset (onset and progression with accumulation of disabling deficits in 6–12 weeks) are generally of autoimmune, infectious, inflammatory, or infiltrative neoplastic cause. An autoimmune or infectious brainstem disorder may be referred to as brainstem encephalitis or rhombencephalitis. We describe a patient with paraneoplastic autoimmune rhombencephalitis, in whom diagnostic clues included the following: diverse visual and sleep symptoms, trismus, and choking in the history; see-saw nystagmus, opsoclonus, dysarthria, jaw dystonia, and episodic laryngospasm on examination; subtle but longitudinal and nonenhancing T2 MRI abnormalities in the brainstem and upper cervical cord; and oligoclonal bands in the CSF. His movement disorder–specific neural IgG profile revealed ANNA-2 (anti-Ri) and KLHL-11-IgG. Both are biomarkers of paraneoplastic brainstem encephalitis. KLCHL-11-IgG has been reported to accompany germ cell tumors, which was found in a solitary metastasis to the left inguinal lymph node in our patient, along with an atrophic left testis. Multidisciplinary treatment (autoimmune neurology, sleep medicine, ophthalmology, and physiatry) led to significant clinical improvements. This case provides a framework for the evaluation of patients with subacute-onset brainstem syndromes and the investigation and management of those with paraneoplastic and other autoimmune diseases.