Myasthenia Gravis, Ocular
Conditions
Keywords
Ocular Vestibular Evoked Myogenic Potentials
Brief summary
Myasthenia gravis is an autoimmune disorder of neuromuscular transmission, characterized by fluctuating muscle weakness and fatigability. In isolated ocular myasthenia, when only the extraocular muscles are involved, most common ancillary tests, such as acetylcholine receptor autoantibodies and repetitive nerve stimulation, are often negative. A simple, quick and non-invasive test for ocular myasthenia based on ocular vestibular evoked myogenic potentials (oVEMP) was recently developed. The main goal of the study is to validate repetitive oVEMP stimulation in a blinded diagnostic accuracy study in order to facilitate early and accurate diagnosis of ocular myasthenia.
Interventions
DIAGNOSTIC_TESTOcular vestibular evoced myogenic potentials
The oVEMP technique is an accepted standard for testing otolith function in vestibular patients. It represents a quick, simple and non-invasive technique utilizing repetitive stimulation of the otolith organs with bone-conducted vibration to elicit an extraocular muscle response. Repetitive oVEMP stimulation leads to a characteristic decrement in patients with myasthenia, which can be quantified with surface electromyography from the inferior oblique muscle underneath the eye.
Sponsors
University of Zurich
Study design
Allocation
NA
Intervention model
SINGLE_GROUP
Primary purpose
DIAGNOSTIC
Masking description
Blinded diagnostic accuracy study (index test vs. reference standard).
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
No
Inclusion criteria
* Informed Consent as documented by signature * Patients with diplopia and/or ptosis suspicious for myasthenia gravis.
Exclusion criteria
* Vestibular disorders * Significant systemic myasthenia symptoms (respiration or swallowing difficulties) unable to undergo oVEMP testing. * Patients with significant cardiac or respiratory disease will be excluded from the Tensilon test as part of the reference standard. * Women who are pregnant or breast feeding.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Decrement (as quantified in %) of repetitive 20 Hz ocular vestibular-evoked myogenic potentials (oVEMP) | The primary outcome measure (index test oVEMP) will be assessed at baseline, in conjunction with reference standard/standard clinical workup (including blood analysis, neurological exam, edrophonium test, electromyography, single-fiber electromyography). | oVEMP have been established as a standard clinical test of otolith function. Based on this technique, repetitive oVEMP stimulation, as a novel method for detecting ocular myasthenia gravis, was recently developed. Using this method, a response decrement in extraocular muscles can be quantified. The method is based on the conventional oVEMP montage with surface electrodes placed below the eyes. In order to elicit a response decrement, trains of ten bone-conducted vibration bursts at repetition rates of 20Hz will be applied with a hand-held 'minishaker' to the forehead. The oVEMP in response to these repetitive vibration stimuli will be measured in sustained upgaze from both inferior oblique muscles via surface electrodes. The magnitude of the decrement will be calculated as the difference between the amplitude of the second stimulus repetition and the mean amplitude of the fifth to ninth stimulus repetition. For further Information see: Valko et al. 2016 PMID:26791146 |
Countries
Switzerland
Outcome results
None listed