To present a rare presentation of Lambert-Eaton: oculo-bulbar-onset

To demonstrate the importance of paraneoplastic antibody clinical correlation

Lambert-Eaton myasthenic syndrome (LEMS) is a paraneoplastic syndrome associated with small cell lung cancer due to P/Q-type voltage-gated calcium channel which manifests with proximal weakness with caudocranial spread, dysautonomia, and areflexia. The electrophysiologic findings include low compound muscle action potential, decrement on slow stimulation, and facilitation with exercise/fast stimulation. TRIM46 antibody presents with subacute progressive cerebellar ataxia while GAD-65 antibody presents with stiff-person syndrome, cerebellar ataxia, and limbic encephalitis.

A 66-year-old woman with an 80-pack-year smoking history presented with subacute ptosis, diplopia, facial palsy, dysarthria, dizziness, syncope, headache, and behavior and cognitive changes after 2 weeks of excessive alcohol consumption due to bereavement. MRI/MRA brain were normal. She was empirically treated for Wernicke encephalopathy without improvement. Due to persistent symptoms, she presented to our institution where her exam was significant for mild cognitive impairment, dysconjugate gaze, fatigable ptosis, proximal limb weakness, hyporeflexia, limb and truncal ataxia. Nerve conduction studies revealed low amplitude compound muscle action potentials of the left fibular, tibial, ulnar, and facial nerves. Repetitive nerve stimulation after a 10-second exercise showed 187% facilitation of the left fibular and 407% facilitation of the left facial nerves. Acetylcholine receptor-binding antibody was negative, however P/Q calcium (0.25; cutoff<0.02), serum TRIM46 (1:15360), CSF TRIM46 (1:256), serum GAD-65 (18.9; cutoff<0.02), and CSF GAD-65 (0.33; cutoff <0.02) were positive. CSF analysis revealed lymphocytic pleocytosis. Biopsy of an enlarged porta hepatis lymph node was positive for metastatic small cell lung carcinoma. She was started on 3,4-diaminopyridine, IV methylprednisolone, pyridostigmine, and chemotherapy with neurologic stability at 3-month follow-up.

Rarely, LEMS can initially present with oculo-bulbar symptoms despite usually being a late presentation. Repetitive nerve stimulation helps in differentiating the cause of oculo-bulbar symptoms from other paraneoplastic syndromes.