View source for Lambert-Eaton myasthenic syndrome

==Background==
*Disease of the neuromuscular junction leading to primary presentation of weakness
*Caused by auto-antibodies against the voltage-gated calcium channels at the NMJ

===Epidemiology===
*Predominantly a disease associated with older men with history of cigarette smoking and lung cancer
**50% of patients have concurrent small-cell lung cancer 
*Syndrome can precede detection of malignancy by several years
*Paraneoplastic syndrome in 60-70% of cases

==Clinical Features==
*Often presents with alteration in gait or difficulty rising from a chair
*Fluctuating symmetric [[weakness]] and fatigue, especially of proximal leg muscles
*Improvement in strength with sustained or repeated exercise (in contrast to MG)
**Lambert sign: handshake strength increases over several seconds
*[[Myalgia]]s
*Muscle stiffness (especially in hip and shoulders)
*[[Paresthesia]]s
*Metallic taste
*Eye movements are unaffected
*Sensory examination normal
*Autonomic dysfunction (dry mouth, erectile dysfunction)
*Compared with myasthenia gravis, LEMS begins with lower extremities weakness and rarely begins with extraocular muscle weakness
*[[Respiratory failure]] can occur in late stages of the disease
*Paraneoplastic and autoimmune form of LEMS have similar signs and symptoms

==Differential Diagnosis==
{{Weakness DDX}}

==Evaluation==
*Diagnosis is generally a clinical diagnosis
*Confirmation testing for VGCC antibodies
*Neurophysiologic testing

==Management==
*Supportive (progression to respiratory or bulbar failure is rare)
*[[Acetylcholinesterase inhibitors]] (e.g. [[pyridostigmine]]) can improve symptoms
*Guanidine
*Aminopyridines: 2-10 mg/day
*[[IVIG]]
*[[Glucocorticoids]]
*[[Plasma exchange]]

==Disposition==
*Admission required when infectious complications occur or when severe disability requires inpatient immunotherapy
*Referral to rheumatology
*Any patients with risk factors for small cell lung cancer will need to be referred for evaluation of underlying malignancy

==See Also==
*[[Myasthenia Gravis]]

==References==
<references/>
[[Category:Neurology]]