Synonyms:
LEMS a.k.a. Myasthenic syndrome
Diagnosis:
The diagnosis is made by a combination of clinical features, autoantibodies and electrophysiology
Clinical features:
- Proximal weakness (shoulder and pelvic) and neck muscle weakness
- Improve with exercise, sometimes this is not clinically detectable
- Reduced or absent reflexes
- Cholinergic autonomic failure (dry mouth, constipation, impotence, decreased sweating, blurred vision)
Findings on investigations:
RNST Repetitive nerve stimulation test:
- at 3 Hz: decremental response
- at 20-50 Hz: potentiation of response i.e. facilitation
- Post exercise: potentiation of response i.e. facilitation
- Anti P/Q VGCC antibodies (Voltage gated Ca++ channel antibodies)
Investigations to consider:
Extensive to rule out cancer
Treatment:
Treat or remove tumor
Consider:
- Immunosuppresion:
- Prednisolone
- Azathioprine
- Ciclosporin
- Immunomodulation:
- IVIg or Plasmaphoresis
- Cholinergic drugs:
- 3,4-diamiopyridine
- 4-aminopyridine
- Guanidine hydrochloride side effects: renal failure, bone marrow suppression
- Antiacetylcholinesterase
Avoid:
- Drugs that block the neuromuscular junction
- Ca++ channel blockers