What are the physical findings in 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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Strength is usually reduced in proximal muscles of the legs and arms, producing a waddling gait and difficulty elevating the arms. The degree of weakness is usually mild, compared with that reported by the patient. Sensory examination is normal unless a coincident peripheral neuropathy is present, which is not uncommon in patients with underlying cancer.

Some degree of eyelid ptosis or diplopia, usually mild, is found in 25% of patients. Occasionally, difficulty chewing, dysphagia, or dysarthria is present. Most patients have a dry mouth, eyes, or skin. Constipation, urinary retention, pupillary constriction, sweating, postural hypotension, or respiratory muscle weakness may be present. Clinical manifestations of underlying malignancy (eg, cachexia) may be present. Fasciculations, common in diseases of the anterior horn cell, such as amyotrophic lateral sclerosis (ALS), are absent.

In some patients, strength may improve after exercise and then weaken as activity is sustained. This phenomenon is demonstrable in approximately half of all patients with LEMS. It can also occur in the proximal muscles of patients with MG; however, repeated testing of many separate muscle groups may differentiate the 2 diseases.

Reflexes usually are reduced or absent in LEMS. They can frequently be provoked or increased by having the patient actively contract the muscle group in question for 10 seconds prior to reflex testing or by repeatedly tapping the muscles. An increase in reflex activity after contraction is a hallmark of LEMS.

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