What are the symptoms of Lambert-Eaton myasthenic syndrome (LEMS)?

Updated: May 23, 2019
  • Author: David E Stickler, MD; Chief Editor: Nicholas Lorenzo, MD, MHA, CPE  more...
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Symptoms of Lambert-Eaton myasthenic syndrome (LEMS) usually begin insidiously and progress slowly. Many patients have symptoms for months or years before the diagnosis is made. Weakness is the major symptom. Weak muscles may ache and are occasionally tender. Proximal muscles are more affected than distal muscles; lower extremity muscles are affected predominantly. Patients typically have difficulty rising from a chair, climbing stairs, and walking.

Increased temperatures from fever or the environment may worsen the weakness. Patients may experience transient worsening after hot baths and showers or during systemic illnesses.

The oropharyngeal and ocular muscles [4] are mildly affected in about one quarter of cases of LEMS, with symptoms that may include ptosis, diplopia, and dysarthria, but they are usually not affected to the same extent or severity as in myasthenia gravis (MG). Differentiation between the 2 diseases may be difficult.

A study examining the localization of the initial muscle weakness and at the time of maximum severity in MG and LEMS patients found that patients with MG had initial muscle weakness involving the extraocular muscles (59%) and bulbar muscles (29%). [5] Conversely, LEMS patients never presented initially with ocular weakness; 5% presented with bulbar weakness, and 95% presented with limb weakness. In fact, almost all LEMS patients with oculobulbar or proximal upper extremity weakness also have proximal lower extremity weakness.

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