Autoimmune Encephalitis Misdiagnosis in Adults.

Importance: Autoimmune encephalitis misdiagnosis can lead to harm. Objective: To determine the diseases misdiagnosed as autoimmune encephalitis and potential reasons for misdiagnosis. Design, Setting, and Participants: This retrospective multicenter study took place from January 1, 2014, to December 31, 2020, at autoimmune encephalitis subspecialty outpatient clinics including Mayo Clinic (n = 44), University of Oxford (n = 18), University of Texas Southwestern (n = 18), University of California, San Francisco (n = 17), University of Washington in St Louis (n = 6), and University of Utah (n = 4). Inclusion criteria were adults (age ≥18 years) with a prior autoimmune encephalitis diagnosis at a participating center or other medical facility and a subsequent alternative diagnosis at a participating center. A total of 393 patients were referred with an autoimmune encephalitis diagnosis, and of those, 286 patients with true autoimmune encephalitis were excluded. Main Outcomes and Measures: Data were collected on clinical features, investigations, fulfillment of autoimmune encephalitis criteria, alternative diagnoses, potential contributors to misdiagnosis, and immunotherapy adverse reactions. Results: A total of 107 patients were misdiagnosed with autoimmune encephalitis, and 77 (72%) did not fulfill diagnostic criteria for autoimmune encephalitis. The median (IQR) age was 48 (35.5-60.5) years and 65 (61%) were female. Correct diagnoses included functional neurologic disorder (27 [25%]), neurodegenerative disease (22 [20.5%]), primary psychiatric disease (19 [18%]), cognitive deficits from comorbidities (11 [10%]), cerebral neoplasm (10 [9.5%]), and other (18 [17%]). Onset was acute/subacute in 56 (52%) or insidious (>3 months) in 51 (48%). Magnetic resonance imaging of the brain was suggestive of encephalitis in 19 of 104 patients (18%) and cerebrospinal fluid (CSF) pleocytosis occurred in 16 of 84 patients (19%). Thyroid peroxidase antibodies were elevated in 24 of 62 patients (39%). Positive neural autoantibodies were more frequent in serum than CSF (48 of 105 [46%] vs 7 of 91 [8%]) and included 1 or more of GAD65 (n = 14), voltage-gated potassium channel complex (LGI1 and CASPR2 negative) (n = 10), N-methyl-d-aspartate receptor by cell-based assay only (n = 10; 6 negative in CSF), and other (n = 18). Adverse reactions from immunotherapies occurred in 17 of 84 patients (20%). Potential contributors to misdiagnosis included overinterpretation of positive serum antibodies (53 [50%]), misinterpretation of functional/psychiatric, or nonspecific cognitive dysfunction as encephalopathy (41 [38%]). Conclusions and Relevance: When evaluating for autoimmune encephalitis, a broad differential diagnosis should be considered and misdiagnosis occurs in many settings including at specialized centers. In this study, red flags suggesting alternative diagnoses included an insidious onset, positive nonspecific serum antibody, and failure to fulfill autoimmune encephalitis diagnostic criteria. Autoimmune encephalitis misdiagnosis leads to morbidity from unnecessary immunotherapies and delayed treatment of the correct diagnosis.

Aquaporin-4 Autoantibody Detection by ELISA: A Retrospective Characterization of a Commonly Used Assay.

OBJECTIVE: Aquaporin-4 (AQP4) serum autoantibodies are detected by a variety of methods. The highest sensitivity is achieved with cell-based assays, but the enzyme-linked immunosorbent assay (ELISA) is still commonly utilized by clinicians worldwide. METHODS: We performed a retrospective review to identify all patients at the University of Utah who had AQP4 ELISA testing at ARUP Laboratories from 2010 to 2017. We then reviewed their diagnostic evaluation and final diagnosis based on the ELISA titer result. RESULTS: A total of 750 tests for the AQP4 ELISA were analyzed, and 47 unique patients with positive titers were identified. Less than half of these patients (49%) met the clinical criteria for neuromyelitis optica spectrum disorder (NMOSD). In cases of low positive titers (3.0-7.9 U/mL, n = 19), the most common final diagnosis was multiple sclerosis (52.6%). In the moderate positive cohort (8.0-79.9 U/mL, n = 14), only a little more than half the cohort (64.3%) had NMOSD. In cases with high positives (80-160 U/mL, n = 14), 100% of patients met clinical criteria for NMOSD. CONCLUSIONS: Our data illustrates diagnostic uncertainty associated with the AQP4 ELISA, an assay that is still commonly ordered by clinicians despite the availability of more sensitive and specific tests to detect AQP4 autoantibodies in patients suspected of having NMOSD. In particular, low positive titer AQP4 ELISA results are particularly nonspecific for the diagnosis of NMOSD. The importance of accessibility to both sensitive and specific AQP4 testing cannot be overemphasized in clinical practice.

Autoimmune Neurology: The Need for Comprehensive Care.

Autoimmune neurology is a rapidly developing specialty driven by an increasing recognition of autoimmunity as the cause for a broad set of neurologic disorders and ongoing discovery of new neural autoantibodies associated with recognizable clinical syndromes. The diversity of clinical presentations, unique pathophysiology, and the complexity of available treatments requires a dedicated multidisciplinary team to diagnose and manage patients. In this article, we focus on antibody-associated autoimmune encephalitis (AE) to illustrate broader themes applicable to the specialty. We discuss common diagnostic challenges including the utilization of clinical assessment tools along with the determination of the prognostic significance of certain autoantibodies, with a focus on implications for long-term management. A growing body of literature demonstrates the long-term cognitive, behavioral, and physical sequelae of AE. Dedicated resources are needed to effectively manage these patients. These resources may be best provided by experienced neurology clinics in partnership with other neurologic subspecialists, as well as psychiatrists, neuropsychologists, and physical medicine and rehabilitation providers.

Examining the ocular fundus in neurology.

PURPOSE OF REVIEW: The funduscopic examination can be a technically difficult, and often omitted, portion of the neurologic examination, despite its great potential to influence patient care. RECENT FINDINGS: Medical practitioners are often first taught to examine the ocular fundus using a direct ophthalmoscope, however, this skill requires frequent practice. Nonmydriatic tabletop and portable fundus photography and even smartphone-based photography offer alternative and practical means for approaching examination of the ocular fundus. These alternative tools have been shown to be practical in a variety of settings including ambulatory clinics and emergency departments. Decreased retinal microvascular density detected with fundus photography has been linked to accelerated rates of cognitive decline. Research has also found optic disc pallor and retinopathy detected via fundus photography to be more prevalent in patients with recent stroke or transient ischemic attack. SUMMARY: Alternative methods of funduscopic examination based on fundus photography have the potential to improve the ease of use, portability, and availability of funduscopy. Recognition of changes in retinal microvasculature has the potential to noninvasively identify patients at the highest risk for cognitive impairment and cerebrovascular disease. However, further research is needed to determine the specific utility of measurements of retinal microvascular changes in clinical care. Innovative funduscopy techniques offer neurologists new approaches to this essential facet of the neurological examination.