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Lambert-Eaton myasthenic syndrome
From WikEM
(Redirected from Lambert-Eaton Myasthenic Syndrome)
Contents
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
- Neuromuscular weakness
- UMN:
- Spinal cord disease:
- Infection (Epidural abscess)
- Infarction/ischemia
- Trauma (Spinal Cord Syndromes)
- Inflammation (Transverse Myelitis)
- Degenerative (Spinal muscular atrophy)
- Tumor
- Peripheral nerve disease:
- Guillain-Barre syndrome
- Toxins (Ciguatera)
- Tick paralysis
- DM neuropathy (non-emergent)
- NMJ disease:
- Myasthenia gravis crisis
- Botulism
- Organophosphate toxicity
- Lambert-Eaton myasthenic syndrome
- Muscle disease:
- Rhabdomyolysis
- Dermatomyositis
- Polymyositis
- Alcoholic myopathy
- Non-neuromuscular weakness
- Can't miss diagnoses:
- ACS
- Arrhythmia/Syncope
- severe infection/Sepsis
- Hypoglycemia
- Periodic paralysis (electrolyte disturbance, K, Mg, Ca)
- Respiratory failure
- Emergent Diagnoses:
- Symptomatic Anemia
- Severe dehydration
- Hypothyroidism
- Polypharmacy
- Malignancy
- Other causes of weakness and paralysis
- Acute intermittent porphyria (ascending weakness)
- Can't miss diagnoses:
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
- 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
