Ptosis in myasthenia gravis: extended fatigue and recovery bedside test.

Fluctuating double vision and ptosis are the hallmarks of extraocular muscle weakness in myasthenia gravis (MG). On sustained upward gaze, ptosis usually increases temporarily. The first description of using this fatigue sign has been attributed to the Scottish neurologist John Simpson. Cogan added his lidtwitch sign to the diagnostic bedside armamentarium.1 For many years, we have applied a fatiguerecovery test at the bedside, whereby the strength of the previously fatigued levator palpebrae muscle is improved shortly after voluntary maximal contraction of the antagonistic orbicularis oculi muscles, leading to a temporary improvement of lid opening. This extended fatigue maneuver provides an additional hint to the typical myasthenic weakness, in particular in the absence of double vision. Furthermore, we often observed that Cogan’s lid-twitch sign may only be elicited when provoking recovery. This shortlived lid twitch is supposed to reflect the temporary recovery of phasic more than tonic motor units in the levator palpebrae muscles. Recovery of ptosis after 3 minutes of lid closure has been mentioned earlier by the late Dutch neurologist Hans Oosterhuis.2 However, the recovery test presented here requires only 10 to 30 seconds of maximal voluntary eye closure. In the differential diagnosis of pure ocular MG, the test proves particularly helpful in differentiating MG from other common disorders causing ptosis, e.g., Horner syndrome without miosis, mild forms of progressive external ophthalmoplegia, or habitual ptosis of the elderly where fatigue on upward gaze and recovery after lid closure is less pronounced or absent (figure).