Truncal Ataxia: An Overlooked Symptom in Patients with Lambert–Eaton Myasthenic Syndrome in the Early Stage

Background: The classic triad in LEMS is proximal muscle weakness, areflexia, and autonomic dysfunction. We have frequently observed truncal ataxia as the first complaint in LEMS patients. In this study, we aimed to show the presence of ataxia in 10 newly diagnosed LEMS patients in the past 3 years and what factors influence it. Methods: We present the clinical findings, voltage-gated calcium channels antibody positivity, and electrophysiologic findings of newly diagnosed LEMS patients who presented to our tertiary care center during the past 3 years. Results: Of the 10 LEMS patients examined, 60% (6) were males and 40% (4) were females. The first and most dysfunctional symptoms were gait disorder and loss of balance in seven of the patients. These patients had ataxia, a gait disturbance that was disproportionate to the proximal weakness. Although the patients had mild proximal weakness in the lower extremities, they had considerable difficulty walking. Proximal muscle weakness was present in six patients, speech disorders in three patients, dysphagia in three patients, dry mouth in three patients, ptosis in two patients, diplopia in two patients, and nystagmus in one patient. Conclusion: We believe that more caution is needed in patients with truncal ataxia when LEMS is suspected. This is because we have seen that the first complaints in 7 out of 10 LEMS patients were truncal ataxia, loss of balance, and gait disturbance.