Clinical Research Directory

Inclusion Criteria: * Age ≥ 18 years old * "Possible" sensory neuronopathy according to the criteria of Camdessanché et al. \[2\] with ONLS score ≥ 1 * Dominant picture of sensory ataxia (damage to the central nervous system and/or the neuromuscular junction is allowed, provided that it has a minor impact on the patient's disability) * Positive anti-Hu antibodies in blood and/or cerebrospinal fluid * Outpatient (modified Rankin Score (mRS) 2 or 3) * Onset of neurological symptoms less than 3 months ago * Free, informed, written and signed consent * Affiliation to a social security or beneficiary scheme (except AME) Exclusion Criteria: * Known hypersensitivity to one of the treatments under study, to their metabolites, or to one of the excipients * Absolute contraindications to IVIg: selective IgA deficiency, known thrombophilia, patients suffering from type I or II hyperprolinemia, hypersensitivity to human immunoglobulins * Absolute contraindications to cyclophosphamide: vaccination against yellow fever in the 3 months preceding inclusion, acute urinary infection, pre-existing hemorrhagic cystitis, urinary tract obstruction, acute bone marrow failure * Contraindication to methylprednisolone: live vaccines, or live attenuated vaccines within 3 months, infectious state or evolving virus (hepatitis, herpes, chickenpox, shingles) * More than two courses of IVIg administered within 3 months before recruitment * Other concomitant immunotherapy * Other cause of immunosuppression (acquired or congenital) * Treatment with checkpoint inhibitors in progress or completed less than 3 months previously * Woman or man without effective contraception * Pregnant or breastfeeding woman * History of psychiatric or general illnesses that may contraindicate treatment * Patients unable to complete the follow-up required by the study * Patients under guardianship or curatorship * Patient deprived of liberty by a judicial or administrative decision