Clinical features of paraneoplastic neurologic syndromes with anti-Ri antibodies: PRISMA systematic review.

BACKGROUND AND OBJECTIVES: Paraneoplastic neurological syndromes (PNSs) are a group of neurological disorders linked to malignancies. Their clinical trajectory, differential diagnoses, immune-mediated mechanisms, and outcomes remain inadequately understood. The review aims to improve our understanding of the main syndrome and its clinical progression by systematic review of studies involving patients with anti-Ri-antibody-associated paraneoplastic neurological syndrome (Ri-PNS). METHODS: The protocol adhered to the PRISMA guidelines and is registered with PROSPERO (ID: CRD420251152531). RESULTS: Eighty-five cases with comprehensive clinical data were identified, with a median age of 61.0 ± 11.8 years, and the majority were female (78.6%). At the disease onset, ataxia was the most prevalent neurological symptom (70.6%). Ataxia rarely manifested as a state of isolation, and was frequently accompanied by other symptoms: tremor, dysarthria, spasticity, and dystonia. Twenty-six patients (30.6%) developed opsoclonus, and 22.4% developed myoclonus. The median interval from the onset of PNS to cancer diagnosis was 1.5 months (IQR, 0-7.0 months). Breast cancer was frequently observed in female patients (65.2%), whereas lung cancer was more common in male patients (38.9%). Of the patients with cancer, fifty-eight received oncological treatment. In addition, 62/85 patients (72.9%) underwent immunotherapy. CONCLUSIONS: Ri-PNS is a multisystem neurological syndrome with significant involvement of the cerebellum and brainstem. The syndrome is frequently associated with tumors, and its appearance often signals the presence of a concurrent or occult tumor. Anti-tumor therapy and immunotherapy remain the two major management approaches in treatment. Considering that early intervention has the potential to enhance neurological function and improve the prognosis in patients with Ri-PNS, it could be given particular attention in clinical practice.