Anti-Ri Paraneoplastic Neurological Syndrome Presenting with Ocular Flutter in a Patient with Breast Cancer.

Ocular flutter is an uncommon ophthalmic finding that may indicate paraneoplastic phenomena, and it is clinically characterized by intermittent bursts of conjugate, horizontal saccades without an intersaccadic interval. Ocular flutter must be differentiated from opsoclonus, which, although also characteristic of certain paraneoplastic syndromes, is instead defined by multidirectional saccades on both the horizontal and vertical planes. This report describes a very rare presentation of anti-Ri syndrome in a patient with an undiagnosed breast cancer, presenting with ocular flutter, dizziness, blurred vision, photophobia, and vomiting. Comprehensive evaluations, including contrast-enhanced brain Magnetic Resonance Imaging (MRI), brain Computed Tomography (CT) scan, ophthalmological assessment, viral serology, complete blood count and thyroid, renal coagulation, hepatic function assessments, vitamin D and B12 levels, were all normal. Upon excluding other potential etiologies for the neurological symptoms, a paraneoplastic origin was considered. Serological tests confirmed the presence of anti-Ri onconeural antibodies, and a whole-body CT scan identified nodules in the right breast. Despite surgical excision of the primary tumor and subsequent medical therapy, there was no improvement in the neurological symptoms. Follow-up evaluations at 2 months, 6 months, 1 year and 2 years revealed persistent vestibular and neurological symptoms, with serum tests remaining positive for anti-Ri antibodies and no clinical or radiological evidence of neoplastic recurrence.