Abstract
Objectives Lambert-Eaton myasthenic syndrome (LEMS) is a rare, often paraneoplastic, presynaptic neuromuscular junctionopathy that typically presents with proximal weakness. We present a case with prominent ocular manifestations, to highlight this important yet atypical presentation.
Methods Case report.
Results A 66-year-old female was transferred to our service for investigation of a mediastinal mass, in the setting of 3-months of progressive ptosis and diplopia, later accompanied by proximal weakness. She had a background of a fifty pack-year smoking history.
Examination revealed bilateral ptosis which improved with sustained upgaze, mixed horizontal/vertical diplopia, non-fatigable 4+/5 power in the proximal limbs, and reduced lower limb reflexes which improved with repetition.
Nerve conduction studies revealed reduced compound muscle action potential (CMAP) amplitudes, with peroneal and ulnar CMAP amplitudes increasing >100% following 10 seconds exercise, and abductor digiti minimi CMAP amplitudes incrementing >100% with high-frequency repetitive nerve stimulation. Voltage-gated calcium channel antibodies were positive (462 pM) (normal <30 pM). Neuraxial imaging was normal. PET-CT scan and biopsy of the mediastinal mass revealed extensive stage small cell lung cancer.
With a diagnosis of paraneoplastic LEMS confirmed, she was commenced on amifampridine 10 mg twice-daily and had remarkable improvement within one week, back to baseline.
Conclusions Ocular symptoms in LEMS is uncommon, present in approximately one-quarter of patients in the largest case series.1 A predominantly ocular presentation, as in our case, is considered rare. As our case highlights, the presence of paradoxical lid elevation after sustained upgaze may be a particularly useful clinical sign in diagnosing these patients.
Reference
Young J, Leavitt J. Lambert-Eaton Myasthenic Syndrome. J Neuroophthalmol. 2016;36(1):20–2.
