Objective:

To report unusual presentation of Anti-Ri antibody associated encephalopathy mimicking neuromyelitis optica spectrum disorder (NMOSD), leading to diagnosis of breast cancer.

Background:

Anti-Ri is an anti-neuronal antibody targeting the NOVA antigen in the CNS. Anti-Ri-associated encephalitis presents variably, commonly as opsoclonus-myoclonus or axial/pancerebellar syndrome. It can mimic other neuro-demyelinating conditions like NMOSD. Treatment typically involves immunosuppression or addressing underlying malignancies.

Design/Methods:

Case Report

Results:

65-year old female presented to hospital with 10 days of daytime sleepiness, left eyelid drooping, double vision, right sided drooling, and left arm and leg weakness. Examination revealed left sided ptosis, horizontal gaze palsy (right > left), right lower motor neuron facial palsy, and 3/5 strength in left upper and lower extremities. Initial blood work was unremarkable. MRI Brain revealed prominent CSF sleeves along bilateral optic nerves suggestive of optic atrophy, T2 and FLAIR hyperintensities in subcortical and deep white matter of bilateral frontal and parietal regions, periaqueductal region, dorsal aspect of pons and medulla. Her presentation and MRI led to provisional diagnosis of NMOSD and she was started on high dose steroids without response. Serum anti-MOG and anti-NMO antibodies were negative. CSF studies showed increased total cell count (18 cells/mm3), normal glucose and protein. Anti-MOG, anti-NMO, neurotropic virus and autoimmune encephalitis panel were negative. Serum paraneoplastic panel resulted positive for Anti-Ri antibodies. PET CT revealed suspicious nodule in left breast without metastasis. She was treated with intravenous immunoglobulin therapy resulting in significant improvement. Ultrasound guided biopsy revealed infiltrating carcinoma requiring total mastectomy with lymphadenectomy. Later, she required chemotherapy for symptoms recurrence.

Conclusions:

Anti-Ri encephalitis is uncommon entity, which further directs investigation to underlying occult malignancy. It can have overlapping symptoms with NMOSD and poses a diagnostic dilemma, as in our case. A high index of suspicion for Anti-Ri encephalitis is required to prevent tumor spread and enable prompt treatment.