Cerebellar Degeneration Causing Saccadic Dysmetria and Ocular Flutter: A Seronegative Paraneoplastic Syndrome (P4-5.015)

Abstract

<h3>Objective:</h3> To report a challenging case of a woman who developed eye movement abnormalities, progressive truncal, and gait ataxia due to a paraneoplastic syndrome. <h3>Background:</h3> Progressive cerebellar degeneration is a well-known paraneoplastic syndrome. However, it can be challenging to define phenotypically and diagnose in the absence of relevant antibodies. Response to treatment is often poor. <h3>Design/Methods:</h3> Case Report. <h3>Results:</h3> A 68-year-old woman presented with several months of moderately progressive truncal, gait ataxia, followed by development of saccadic hypermetria and ocular flutter. Her metastatic small cell lung cancer was in remission, and she no longer showed bilateral cerebellar metastases on brain MRI, following treatment with chemotherapy, durvalumab, and whole brain radiation. CSF analysis revealed lymphocytic pleocytosis (8/μL), normal protein, normal glucose, and 4 oligoclonal bands. Paraneoplastic antibodies from serum and CSF were negative. She was diagnosed with a probable paraneoplastic syndrome, based on a PNS-Care score of 7. She was treated with high dose intravenous methylprednisolone and plasmapheresis, with resolution of eye movement abnormalities, and improvement of ataxia. <h3>Conclusions:</h3> Subacute development of saccadic dysmetria and ocular flutter in this case helped define a new onset cerebellar syndrome in a patient with possible residual cerebellar dysfunction from prior cerebellar metastatic disease. Saccadic hypermetria is typically caused by dysfunction of the fastigial oculomotor region (FOR). In our case, ocular flutter might have been caused by indirect instability of the brainstem network due to impairment of the FOR projections to the omnipause neurons (OPN) in the pontine saccadic burst generator area. Even in the absence of relevant antibodies and in the setting of confounders such as prior cerebellar metastases, use of checkpoint inhibitors, clinical presentation and CSF findings should raise concern for a paraneoplastic disorder. Cerebellar paraneoplastic syndromes may respond to Immunotherapy with methylprednisolone and plasmapheresis. <b>Disclosure:</b> Dr. Zampino has nothing to disclose. Dr. Figgie has nothing to disclose. Dr. Shaikh has received personal compensation in the range of $10,000-$49,999 for serving on a Speakers Bureau for Acorda. Dr. Serra has received personal compensation in the range of $10,000-$49,999 for serving on a Speakers Bureau for Biogen Idec. Dr. Serra has received personal compensation in the range of $5,000-$9,999 for serving on a Speakers Bureau for Bristol Myers Squibb.