From the Guidelines
Lambert-Eaton myasthenic syndrome (LEMS) is primarily characterized by craniocaudally progressive proximal muscle weakness, particularly at the hip girdle, which is the most common symptom of this condition. The symptoms of LEMS can be broken down into several key areas, including:
- Proximal muscle weakness, which occurs predominantly at the hip girdle 1
- Autonomic symptoms, such as dry mouth, constipation, impotence, and reduced sweating
- Diminished or absent deep tendon reflexes, which may temporarily return after brief exercise
- Less common ocular and bulbar muscle symptoms, including ptosis and diplopia, which occur in about 25% of cases
- Rare respiratory muscle involvement
The underlying mechanism of LEMS involves autoantibodies targeting voltage-gated calcium channels (VGCCs) at the neuromuscular junction, reducing acetylcholine release and causing the characteristic muscle weakness 1. The diagnosis of LEMS is generally made by clinical characteristics, electromyography, and anti-VGCC antibodies, and treatment options, such as IVIg, are available 1. It is essential to note that LEMS is frequently associated with small cell lung cancer, and any patient diagnosed with LEMS should undergo thorough cancer screening.
From the FDA Drug Label
The QMG is a 13-item physician-rated categorical scale assessing muscle weakness Each item is assessed on a 4-point scale, where a score of 0 represents no weakness, and a score of 3 represents severe weakness (total score 0-39). Higher scores represent greater impairment.
The symptoms of Lambert-Eaton myasthenic syndrome (LEMS) include muscle weakness.
- The Quantitative Myasthenia Gravis (QMG) score is used to assess the severity of muscle weakness, with higher scores indicating greater impairment. 2
From the Research
Symptoms of Lambert-Eaton Myasthenic Syndrome (LEMS)
The symptoms of LEMS include:
- Proximal muscle weakness, which predominates in hip and shoulder muscles, but may also affect ocular and oropharyngeal muscles to a lesser extent 3, 4, 5, 6, 7
- Depressed tendon reflexes, with reduced or absent muscle stretch reflexes 3, 4, 5, 6, 7
- Autonomic dysfunction, which may manifest as dry mouth, xerostomia, or other autonomic symptoms 3, 4, 5, 6
- Fluctuating proximal limb muscle weakness, which can be relieved with supportive therapy or treatment 4, 6
- Cerebellar ataxia, defined as a negative Romberg's test and at least one other positive ataxia test, was observed in some patients 7
- Reduced reflex tone and limited functioning, which can be sustained or improved with treatment 7
Associated Conditions
LEMS is often associated with: