Background: Paraneoplastic Neurological Syndromes (PNS) comprise a diverse group of disorders propagated by immune-mediated effects of malignant tumors on neural tissue. Methods: A single-center longitudinal study was performed including consecutive adult patients treated at a tertiary academic hospital between 2015 and 2023 and diagnosed with PNS. PNS were ascertained using the 2004 and the revised 2021 PNS-Care diagnostic criteria. Results: Thirteen patients who fulfilled the 2004 definite PNS criteria were included. PNS comprise diverse neurological syndromes, with neuromuscular junction disorders (54%) and limbic encephalitis (31%) being predominant. PNS-related antibodies were detected in 85% of cases, including anti-AChR (n = 4), anti-P/Q-VGCC (n = 3), anti-Hu (n = 3), anti-Yo (n = 1), anti-Ma (n = 1), anti-titin (n = 1), anti-IgLON5 (n = 1), and anti-GAD65 (n = 1). Thymoma (31%), small-cell lung cancer (23%), and papillary thyroid carcinoma (18%) were the most frequent tumors. Imaging abnormalities were evident in 33% of cases. Early immunotherapy within 4-weeks from symptom onset was associated with favorable outcomes. At a mean follow-up of 2 ± 1 years, two patients with anti-Hu and anti-Yo antibodies died (18%). Four and three patients fulfilled the 2021 PNS-Care diagnostic criteria for definite and probable PNS, respectively. Conclusions: This study highlights the clinical heterogeneity of PNS, emphasizing the need for early suspicion and prompt treatment initiation for optimal outcomes.

Aquaporins (AQPs; AQP0–AQP12) are water channels expressed in many and diverse cell types, participating in various functions of cells, tissues, and systems, including the central nervous system (CNS). AQP dysfunction and autoimmunity to AQPs are implicated in several diseases. The best-known example of autoimmunity against AQPs concerns the antibodies to AQP4 which are involved in the pathogenesis of neuromyelitis optica spectrum disorder (NMOSD), an autoimmune astrocytopathy, causing also CNS demyelination. The present review focuses on the discovery and the potential role of antibodies against AQP1 in the CNS, and their potential involvement in the pathophysiology of NMOSD. We describe (a) the several techniques developed for the detection of the AQP1-antibodies, with emphasis on methods that specifically identify antibodies targeting the extracellular domain of AQP1, i.e., those of potential pathogenic role, and (b) the available evidence supporting the pathogenic relevance of AQP1-antibodies in the NMOSD phenotype.

Background/Objectives: Paraneoplastic cerebellar degeneration (PCD) is an inflammatory autoimmune process caused by onconeural antibodies directed against cerebellar Purkinje cells. In most cases, prognosis is poor as disease progression leads to pancerebellar dysfunction and permanent neurological damage. Through this case report, we aim to highlight the clinical presentation, diagnostic process, and therapeutic implications associated with PCD secondary to SCLC. Methods: Herein, we present the case of a 57-year-old patient diagnosed with PCD who presented with progressive limb ataxia and impaired mobility. CT scans and EBUS (endobronchial ultrasound) bronchoscopy established the diagnosis of limited-stage small-cell lung cancer (SCLC) of the right lung with marked lymphadenopathy. Results: Anti-CV2/CRMP5 and anti-SOX1 autoantibodies were identified in the serum that confirmed the diagnosis of PCD related to SCLC. A total of six cycles of chemotherapy with carboplatin and etoposide resulted in rapid clinical improvement and complete response of the disease. The patient remains in remission six years after the initial diagnosis with no neurological deficits. Conclusions: The prognosis of PCD greatly depends on early detection and management of the underlying malignancy. Despite the poor prognosis, early diagnosis and prompt initiation of chemotherapy may offer a great survival benefit in these patients.