Objective: To describe a patient with papillary Non-Small Cell Lung Cancer (NSCLC) who developed acute and rapidly progressive myoclonus with prominent palatal involvement as a paraneoplastic neurologic manifestation.

Background: NSCLC accounts for 80% of all primary lung malignancy. Adenocarcinoma, a NSCLC subtype, has been linked to a variety of neurologic presentations including choreiform movement disorders. However, its papillary variant has only been associated with Evans syndrome, a paraneoplastic hematologic disease.

Methods: A 78 year old man with stage IIIB papillary NSCLC was admitted for nausea, vomiting, vertigo and progressive myoclonus one week prior to his first planned chemotherapy. He initially demonstrated diffuse high frequency, low amplitude tremulousness of the arms. These movements progressed to spontaneous and stimulus-induced, very frequent, high amplitude myoclonus involving all extremities with a right sided predominance. Myoclonus was worse proximally and his palate was prominently involved. MRI with contrast of brain and entire spinal cord was unremarkable. Metabolic and infectious lab workup was unrevealing. CSF studies including oligoclonal bands, IgG index, cytology, lymphocyte/leukemia markers, and paraneoplastic antibodies were normal. Serum showed a mildly elevated positive P/Q type Calcium channel blocker antibody (0.09nmol/L, reference value <0.02nmol/L).

Results: He underwent carboplatin and pemetrexed chemotherapy with dexamethasone, with two 3-day courses of 1g of methylprednisolone/day and treatment with levetiracetam at 1.5g BID. He was briefly intubated early in his course because myoclonus severity and prominent palatal involvement caused inability to protect his airway and aspiration. Brief runs of generalized periodic discharges on EEG (consistent with cortical excitability) improved along with myoclonus. By discharge, nausea, vertigo and myoclonus had resolved with only mild residual arm tremulousness.

Conclusions: This presentation of myoclonus with prominent palatal involvement and vertigo is the first report of a neurologic syndrome associated with papillary NSCLC. It is consistent with a paraneoplastic syndrome given a clear response to treatment for an underlying malignancy. Causation by P/Q type calcium channel antibodies is less clear as they are usually associated with Lambert-Eaton, cerebellar degeneration and less commonly with encephalomyeloneuropathy. Possibly, an unknown antibody not detected by the commercial assay was responsible.

References: 1. Bentea G, Sculier C et al. Autoimmune paraneoplastic syndromes associated to lung cancer: A systematic review of the literature: Part 3: Neurological paraneoplastic syndromes, involving the central nervous system. Lung Cancer. April 2007;106:83-92. 2. Yu H, Fu R et al. Paraneoplastic Evans syndrome in a patient with adenocarcinoma of the lung: A case report. Thorac Cancer. Jan 2017;8(1):57-60.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/a-case-of-paraneoplastic-myoclonus-attributed-to-non-small-cell-lung-cancer/