Muscle strength and fatigue in newly diagnosed patients with myasthenia gravis

INTRODUCTION: Dynamometry is increasingly used as an objective measurement of muscle strength in neurological diseases. No study has applied dynamometry in untreated newly diagnosed patients with myasthenia gravis (MG). METHODS: Isometric muscle strength at the shoulder, knee, and ankle was determined in 21 MG patients before and after initial anti-myasthenic treatment. Isometric strength was compared with MG evaluation scales. RESULTS: Muscle strength was reduced for knee extensors and shoulder abductors but normal for ankle extensors. Isometric muscle strength did not correlate significantly with manual muscle testing (MG Composite). Dynamometry revealed improved muscle strength of up to 50% (median 17%; range -1.8-49.8) despite no change in the MG Composite score. CONCLUSIONS: Dynamometry appears to be a more sensitive method of identifying changes in limb strength than MG evaluation scales. This supports the use of dynamometry in MG patients, especially for evaluation of the effect of anti-myasthenic treatment. Muscle Nerve 54: 709-714, 2016.