To report a distinct syndrome within Anti-Ri spectrum. 

Anti-Ri paraneoplastic neurological syndrome (PNS) is classically associated with breast cancer but often present before a cancer diagnosis is established and is classically associated with opsoclonus-myoclonus (OMS), however variable presentations have been reported. Two previous reports described anti-Ri PNS that presented with a triad of ophthalmoplegia, jaw dystonia, and gait abnormalities.

The pertinent methods include neurological exam, autoimmune encephalitis panel, MRI, CT, cancer biomarkers, and lymph node biopsy.

We report a case of a 75-year-old female who presented with ophthalmoplegia (horizontal > vertical), diplopia, jaw dystonia, gait abnormalities, and ataxia. Cerebrospinal fluid (CSF) Ri-2 was 1:64 (Ref < 1:2) and serum Ri-2 was 1:960 (Ref < 1:240). Brain magnetic resonance imaging (MRI) demonstrated a white matter lesion, non-enhancing, in the dorsal aspect of the pons, around the periaqueductal gray (PAG). Despite radiographic resolution after treatment with methylprednisolone, there was no clinical improvement. The patient was also treated with plasmapheresis, prednisone, baclofen, and carbidopa-levodopa with no clinical improvement. The patient developed acute respiratory failure which required elevation of care to the neurocritical care unit (NCCU) and artificial ventilation. CA-125, the marker most associated with ovarian cancer, was mildly elevated at 48.3 (Ref < 35). Computed tomography (CT) showed a solitary enlarged para-aortic lymph node measuring 2.0 x 2.2 x 2.1 cm. A biopsy of this lymph node was attempted but was unsuccessful. The patient expired before a cancer diagnosis could be established.

Our case highlights the symptoms shared with nine previous reports which suggests that this pentad of clinical symptoms may represent a distinct syndrome within the anti-Ri PNS spectrum that differs from the classic OMS symptoms. Furthermore, this report demonstrates how radiographic resolution does not necessarily translate to clinical improvement and highlights the importance of respiratory management in patients with anti-Ri PNS.