NCMP-02. UTILITY OF ICE PACK TEST FOR EARLY RECOGNITION OF IMMUNE CHECKPOINT INHIBITOR MEDIATED OCULAR WEAKNESS

Abstract INTRODUCTION Immune checkpoint inhibitors (ICI) are associated with neurological immune-related adverse events (NiArE) such as myasthenia gravis (MG) and myositis. These conditions often present with overlapping symptoms, notably ptosis, dyspnea, and extremity weakness. Early recognition and treatment are warranted to prevent disease progression. OBJECTIVE To test the utility of simple bedside ice pack test (IPT) in early recognition and distinction of ICI-mediated MG and myositis ocular manifestations. METHODS We administered IPT in 14 patients who had received ICI in the past 6 months and presented with ptosis. Improvement in ptosis was considered positive IPT (non-fixed, fatigable ptosis) that is suggestive of Immune-mediated MG-predominant process. Work up included myasthenia antibodies, EMG, serum markers of muscle injury (creatine kinase, aldolase), myositis panel and muscle biopsy. Statistical analyses employed median for continuous and frequencies for categorical variables. RESULTS Positive IPT was found in 2 (14%) patients with positive myasthenia antibodies and neuromuscular junction dysfunction on EMG in one patient with repetitive nerve stimulation. These patients had mild elevation in creatine kinase (CK). Muscle biopsy did not reveal a myositic process. Twelve (86%) patients had negative IPT (fixed and non-fatigable ptosis) with significantly elevated CK (>4000), positive myositis panel and muscle biopsy consistent with myositic process. Six of these patients (42%) also had positive myasthenia antibodies. Concomitant myocarditis was observed in 5 (36%) patients. CONCLUSION Clinical overlap between myasthenia and myositis is observed in immune mediated toxicity that may be due to cross-reactivity of antibodies, however, IPT was able to distinguish MG vs myositis-predominant process, thus helping guide management.