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A novel diagnostic method for myasthenia gravis
Author(s) -
Kocak Goknur Selen,
Tütüncü Melih,
Adatepe Nurten Uzun,
Yerlikaya Bengi Dolek,
Kara Eyup,
Atas Ahmet,
Yener Murat,
Oren Meryem Merve
Publication year - 2021
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.27353
Subject(s) - myasthenia gravis , eye movement , medicine , audiology , extraocular muscles , ophthalmology , physical medicine and rehabilitation
Abstract Introduction/Aims Videonystagmography (VNG) which directly records eye movements using infrared video goggles with mini‐cameras, is used to measure nystagmus. Our aim is to explore whether VNG can be used to detect a decrement in the extraocular muscle (EOM) activity of patients with myasthenia gravis (MG). Methods Thirty‐four patients with MG, including 13 with ocular‐predominant and 21 with generalized MG, and 23 healthy controls participated. Using VNG we recorded the velocity of the eye movements of the patients as they followed a moving target. We then calculated the gain by dividing the eye movement velocity (degrees/second) by the target velocity (degrees/second). Results In MG subjects, the mean initial gain (maximum gain) was 1.23 ± 0.31 (range: 0.63–2.15) for the right eye and 1.22 ± 0.37 (range; 0.60–2.28) for the left eye. The mean minimum gain was 0.11 ± 0.12 (0.01–0.58) for the right and 0.14 ± 0.5 (0.02–0.55) for the left. Due to fatigue, the movement gain was reduced by 91.7% in the right eye and 88.2% in the left eye. After reaching minimum velocity, gain remained at a minimum for a mean of 1.08 ± 0.52 (0.3–2.4) s for the right and 1.49 ± 0.85 (0.4–3.6) s for the left, before the velocity increased again. There was no fatigue‐induced decrement in healthy subjects. Discussion Our study documents a decrement in EOM activity recorded by VNG in patients with MG which begins to improve within 1–2 s after reaching minimum velocity, analogous to traditional low‐frequency repetitive nerve stimulation testing and its U‐shaped pattern. Thus, VNG may be a promising diagnostic test for MG.