Myasthenia gravis (MG) is characterized by fluctuating weakness and fatigability of skeletal muscles. In most patients, extraocular and bulbar muscles are affected first, leading to diplopia,... Show moreMyasthenia gravis (MG) is characterized by fluctuating weakness and fatigability of skeletal muscles. In most patients, extraocular and bulbar muscles are affected first, leading to diplopia, ptosis, and weakness of facial muscles.(1)We recorded the faces of 38 healthy controls and 52 patients with MG while performing a standardized set of facial expressions. These images were averaged using Python version 3.8.0. This resulted in highly similar faces with no recognizable individual features. The only discernible differences are typical clinical hallmarks of the disease: ptosis and generalized facial weakness around the eyes and mouth resulting in less vivid facial expression (figure). Show less
Objective To validate the repetitive ocular vestibular evoked myogenic potentials (RoVEMP) test for diagnostic use in myasthenia gravis (MG) and to investigate its value in diagnostically... Show moreObjective To validate the repetitive ocular vestibular evoked myogenic potentials (RoVEMP) test for diagnostic use in myasthenia gravis (MG) and to investigate its value in diagnostically challenging subgroups. Methods The RoVEMP test was performed in 92 patients with MG, 22 healthy controls, 33 patients with a neuromuscular disease other than MG (neuromuscular controls), 4 patients with Lambert-Eaton myasthenic syndrome, and 2 patients with congenital myasthenic syndrome. Results Mean decrement was significantly higher in patients with MG (28.4% +/- 32.2) than in healthy controls (3.2% +/- 13.9; p < 0.001) or neuromuscular controls (3.8% +/- 26.9; p < 0.001). With neuromuscular controls as reference, a cutoff of >= 14.3% resulted in a sensitivity of 67% and a specificity of 82%. The sensitivity of the RoVEMP test was 80% in ocular MG and 63% in generalized MG. The RoVEMP test was positive in 6 of 7 patients with seronegative MG (SNMG) with isolated ocular weakness. Of 10 patients with SNMG with negative repetitive nerve stimulation (RNS) results, 73% had an abnormal RoVEMP test. The magnitude of decrement was correlated with the time since the last intake of pyridostigmine (B = 5.40; p = 0.019). Conclusions The RoVEMP test is a new neurophysiologic test that, in contrast to RNS and single-fiber EMG, is able to measure neuromuscular transmission of extraocular muscles, which are the most affected muscles in MG. Especially in diagnostically challenging patients with negative antibody tests, negative RNS results, and isolated ocular muscle weakness, the RoVEMP test has a clear added value in supporting the diagnosis of MG. Classification of evidence This study provides Class III evidence that RoVEMP distinguishes MG from other neuromuscular diseases. Show less
