Adult-onset ocular flutter–opsoclonus spectrum across diverse neurological disorders: a video-oculographic case series

BACKGROUND: Ocular flutter and opsoclonus are rare ocular motor disorders most often associated with paraneoplastic or autoimmune conditions, although their full aetiological spectrum in adults remains incompletely defined. Because the distinction between ocular flutter and opsoclonus may be challenging using routine video-oculographic tracings alone, the broader term flutter-opsoclonus spectrum is used in this study. METHODS: We conducted a retrospective case series of adult patients evaluated between September 2024 and February 2026 at a tertiary neurology centre, in whom high-frequency saccadic oscillations consistent with the flutter-opsoclonus spectrum were documented using video-oculographic recordings alongside comprehensive neurological assessment. RESULTS: Five patients with distinct underlying disorders were identified, comprising autoimmune, neurodegenerative, prion-related, and demyelinating aetiologies. These included anti-glutamic acid decarboxylase stiff-person spectrum disorder, relapsing anti-NMDA receptor encephalitis with dual antibody positivity, multisystem atrophy of the cerebellar subtype, sporadic Creutzfeldt-Jakob disease, and advanced progressive multiple sclerosis. Flutter-opsoclonus spectrum abnormalities frequently co-occurred with additional ocular motor findings, including saccadic intrusions, various forms of nystagmus, and deficits of smooth pursuit and saccades. CONCLUSIONS: This series expands the recognised aetiological spectrum of adult-onset flutter-opsoclonus spectrum abnormalities and highlights their diagnostic value as clinical signs of potentially serious neurological disease. Objective eye-movement recording facilitates detection and should be considered in patients presenting with unexplained cerebellar syndromes, encephalopathies, or complex movement disorders.