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Difference in distribution of muscle weakness between myasthenia gravis and the Lambert–Eaton myasthenic syndrome
  1. P W Wirtz1,
  2. M Sotodeh1,
  3. M Nijnuis1,
  4. P A van Doorn2,
  5. B G M van Engelen3,
  6. R Q Hintzen2,
  7. P L M de Kort4,
  8. J B Kuks5,
  9. A Twijnstra6,
  10. M de Visser7,
  11. L H Visser8,
  12. J H Wokke9,
  13. A R Wintzen1,
  14. J J Verschuuren1
  1. 1Department of Neurology, Leiden University Medical Centre, Leiden, Netherlands
  2. 2Department of Neurology, Erasmus Medical Centre, Rotterdam, Netherlands
  3. 3Department of Neurology, University Medical Centre Nijmegen, Nijmegen, Netherlands
  4. 4Department of Neurology, Tweesteden Hospital, Tilburg, Netherlands
  5. 5Department of Neurology, University Hospital Groningen, Groningen, Netherlands
  6. 6Department of Neurology, University Hospital Maastricht, Maastricht, Netherlands
  7. 7Department of Neurology, Academic Medical Centre, Amsterdam, Netherlands
  8. 8Department of Neurology, St Elisabeth Hospital, Tilburg, Netherlands
  9. 9Department of Neurology, University Medical Centre Utrecht, Utrecht, Netherlands
  1. Correspondence to:
 Dr P W Wirtz, Department of Neurology, J3R-166, Leiden University Medical Centre, PO Box 9600, 2300 RC Leiden, Netherlands;


Background: Myasthenia gravis and the Lambert–Eaton myasthenic syndrome (LEMS) may have a similar distribution of muscle weakness. Deciding on a diagnosis of myasthenia gravis or LEMS on clinical grounds may therefore be difficult.

Objective: To compare the localisation of initial muscle weakness and the distribution of weakness at the time of maximum severity in patients with myasthenia gravis and LEMS.

Subjects: 101 patients with myasthenia gravis and 38 patients with LEMS.

Results: In myasthenia gravis, initial weakness involved extraocular muscles in 59%, bulbar muscles in 29%, and limb muscles in 12% of the patients. In LEMS no patient had ocular weakness, 5% had bulbar weakness, and 95% had weakness of the limbs as the first symptom (p < 0.001). At the point of maximum severity, weakness in myasthenia gravis was purely ocular in 25%, oculobulbar in 5%, restricted to the limbs in 2%, and present in both oculobulbar muscles and limbs in 68%. At this point, none of the LEMS patients had weakness restricted to extraocular or bulbar muscles (p = 0.002). The legs were affected in all LEMS patients, whereas in 12 patients with generalised myasthenia gravis limb weakness was restricted to the arms (p = 0.024).

Conclusions: In a patient suspected to have a myasthenic syndrome whose first symptom is ocular weakness, LEMS is virtually excluded. Limb weakness confined to the arms is only found in generalised myasthenia gravis and not in LEMS. Muscle weakness in myasthenia gravis tends to develop in a craniocaudal direction, and in the opposite direction in LEMS.

  • myasthenia gravis; Lambert
  • Eaton myasthenic syndrome; muscular weakness

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  • Competing interests: none declared