We report a 37 year-old previously healthy woman who presented with confusion, agitation, lethargy, and abnormal movements within days of initiating antibiotic treatment for a urinary tract infection. Neurological exam revealed non-rhythmic jerky movements of face and upper extremities, ataxia, and abnormal dancing eye movements, all of which were consistent with OMS. Brain MRI revealed a few small discrete FLAIR signal hyperintense foci and subtle left greater than right small regions of abnormal cortical FLAIR signal without enhancement seen within the inferior aspects of the frontal lobes. CSF analysis showed mildly elevated WBC with normal RBC, protein and glucose levels. Viral and bacterial meningoencephalitis PCR testing was negative. Paraneoplastic and autoimmune encephalitis panel from CSF and serum showed a higher than normal titer of antibodies against the ganglionic (alpha-3) acetylcholine receptor. Two PET scan studies with 5 months interval revealed mild hypermetabolism in the neck area especially in the tonsils, thyroid and few cervical lymph nodes, but repeated CT scans of the neck with and without contrast revealed no evidence of neoplastic lesion in the area. The patient showed significant improvement in her symptoms after receiving four courses of IVIG treatment and prolonged oral steroid therapy. This patient is a rare case of idiopathic opsoclonus-myoclonus syndrome in a young adult with mildly elevated serum antibody titer against the alpha-3 cholinergic ganglionic receptor.