SOX1 antibody-related paraneoplastic neurological syndromes: clinical correlates and assessment of laboratory diagnostic techniques.

OBJECTIVE: To describe the clinical associations of SOX1 antibodies (SOX1-Abs), determine the accuracy of various detection techniques, and propose laboratory criteria to identify definite paraneoplastic neurological syndromes (PNS) associated with SOX1-Abs. METHODS: Single-center, retrospective study of patients referred to the French Reference Center between 2009 and 2019 for confirmation of SOX1-Ab positivity, without concurrent neural antibodies. Patients were classified according to the updated diagnostic PNS criteria; biological samples were systematically retested with three distinct techniques (line blot, cell-based assay, indirect immunofluorescence). RESULTS: Among 77 patients with isolated SOX1-Ab positivity, 23 (29.9%) fulfilled the criteria for definite PNS; all of them had lung cancer (mostly small-cell) and presented mainly with Lambert-Eaton myasthenic syndrome (10/23) and rapidly progressive cerebellar ataxia (6/23). SOX1-Ab positivity varied depending on the laboratory methods which were used, and a single technique was not sufficient to draw conclusions about the PNS diagnosis. The combination of an antigen-specific test (line blot and/or cell-based assay) and immunofluorescence showed the highest accuracy (81.5%, 95% CI 70.0-90.1) in identifying definite PNS. Moreover, when the PNS-Care score was recalculated assigning three points at the laboratory-level only to patients with positive "antigenic-specific test + immunofluorescence" and 0 points to the remaining cases, a higher certainty for definite and non-PNS was achieved (from 41/77, 53.2%, to 60/77, 77.9%; p < 0.001). CONCLUSION: SOX1-Abs should be considered high-risk antibodies only when detected with a positive antigenic-specific test and immunofluorescence. Other laboratory results and clinical associations different from Lambert-Eaton myasthenic syndrome and rapidly progressive cerebellar ataxia should be carefully reassessed to rule out false positivity and alternative diagnoses.

Refractory anti-NMDAR encephalitis successfully treated with bortezomib and associated movements disorders controlled with tramadol: a case report with literature review.

Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is a potentially fatal autoimmune disease, characterized by autoantibody-mediated neurotransmission impairment in multiple brain locations. The course of this condition often comprises altered mental status, autonomic dysfunctions, refractory seizures and hyperkinetic movement disorders. Available disease-modifying therapies include corticosteroids, i.v. immunoglobulins, plasma exchange, rituximab and cyclophosphamide. In a subgroup of patients not responding to B-cell depletion, bortezomib, a proteasome inhibitor, has shown promising evidence of efficacy. The time course of recovery from acute phase may be very slow (weeks/months), and only few data are available in literature about the concurrent management of encephalitis-associated movement disorders. We report a case of severe anti-NMDAR encephalitis in a 29-year-old woman, not responsive to first- and second-line treatments, with persistent involuntary motor manifestations. Starting three months after symptom onset, four cycles of bortezomib have been administered; subsequently we observed a progressive improvement of neurological status. Meanwhile, motor manifestations were controlled after the administration of tramadol, a non-competitive NMDA receptor antagonist.

Diagnosing autoimmune encephalitis in a real-world single-centre setting.

BACKGROUND: Early recognition and treatment of autoimmune encephalitis (AE) are crucial for patients, but diagnosis is often difficult and time-consuming. For this purpose, a syndrome-based diagnostic approach was published by Graus et al. (Lancet Neurol 15:391-404, 2016), but very little is known in the literature about its application in clinical practice. AIM: Our aims are to test the feasibility of such approach in a real-world single-centre setting and to analyse the most relevant factors in criteria fulfilment. METHODS: We retrospectively applied these criteria to our cohort of patients discharged from our hospital with diagnosis of autoimmune encephalitis (n = 33, 58% antibody-positive). RESULTS: All the subjects fulfilled criteria for possible AE (pAE), with EEG and MRI playing a central role in diagnosis, while CSF was useful mainly to rule out other conditions. Three patients respected criteria for probable anti-NMDA-R encephalitis (pNMDA). Definite anti-NMDAR encephalitis was diagnosed in 4 patients with detection of the autoantibody but, surprisingly, none of these subjects had fulfilled criteria for pNMDA. 18 patients were diagnosed with definite limbic AE (15 patients were antibody-positive, three antibody-negative). Need for MRI bilateral involvement in antibody-negative limbic AE limited diagnosis. One patient fulfilled criteria for probable antibody-negative AE, while ten patients remained classified as pAE. CONCLUSION: From our retrospective analysis, some suggestions for a better definition of the criteria may emerge. Larger studies on prospective cohorts may be more helpful to explore possible important issues.