Lambert-Eaton myasthenic syndrome: Difference between revisions

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==Background==
==Background==
*Autoantibodies against Ca channels of axon nerve terminals responsible for ACh release
*Disease of the neuromuscular junction leading to primary presentation of weakness
*Epidemiology
*Caused by auto-antibodies against the voltage-gated calcium channels at the NMJ
**Predominantly a disease a/w older men w/ history of cigarette smoking and lung cancer
 
***50% of pts have concurrent small-cell lung cancer  
===Epidemiology===
**Syndrome can precede detection of malignancy by several years
*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


==Clinical Features==
==Clinical Features==
*Fluctuating symmetric weakness and fatigue, esp of proximal leg muscles
*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)
*Improvement in strength with sustained or repeated exercise (in contrast to MG)
**Lambert sign: handshake strength increases over several seconds
**Lambert sign: handshake strength increases over several seconds
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*Paresthesias
*Paresthesias
*Metallic taste
*Metallic taste
*Autonomic symptoms (dry mouth, impotence)
*Eye movements are unaffected
*Eye movements are unaffected
*Sensory examination normal
*Sensory examination normal
*Symmetrical muscle weakness and fatiguability often beginning in lower extremities
*Autonomic dysfunction (dry mouth, erectile dysfunction)
*Compared with myastenia gravis, ELS 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==
==Differential Diagnosis==
{{Weakness DDX}}
{{Weakness DDX}}


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


==Treatment==
==Management==
*Supportive (progression to respiratory or bulbar failure is rare)
*Supportive (progression to respiratory or bulbar failure is rare)
*Acetylcholinesterase inhibitors (e.g. pyridostigmine) can improve symptoms
*[[Acetylcholinesterase inhibitors]] (e.g. [[pyridostigmine]]) can improve symptoms
*Guanidine
*Aminopyridines
*[[IVIG]]
*Glucocorticoids
*[[Plasma exchange]]


==Disposition==
==Disposition==
*Admission required when infectious complications occur or when severe disability requires inpatient immunotherapy
*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==
==See Also==
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==References==
==References==
 
<references/>
[[Category:Neuro]]
[[Category:Neurology]]

Revision as of 09:43, 18 July 2017

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

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
  • Myalgias
  • Muscle stiffness (especially in hip and shoulders)
  • Paresthesias
  • Metallic taste
  • Eye movements are unaffected
  • Sensory examination normal
  • Symmetrical muscle weakness and fatiguability often beginning in lower extremities
  • Autonomic dysfunction (dry mouth, erectile dysfunction)
  • Compared with myastenia gravis, ELS 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

Evaluation

  • Diagnosis is generally a clinical diagnosis
  • Confirmation testing for VGCC antibodies
  • Neurophysiologic testing

Management

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

References