Whole body muscle MRI in Myasthenia gravis

Myasthenia gravis (MG) is a chronic auto-immune with antibodies targeting
proteins in the neuromuscular junction, causing muscle weakness. Early
treatment could prevent generalisation of muscle weakness in MG. Therefore,
there is a clinical need to understand the clinical and subclinical involvement
of muscles to better understand the pattern of muscle involvement and the
process of generalisation. Furthermore, MG is treated with immunosuppressant
drugs like corticosteroids. Unfortunately, long term steroid use carries a
considerable risk of side effects. A clinical need exists to better monitor the
treatment response and the potential benefit of intensifying treatment for
specific muscles.

It is previously shown that in a specific group of MG patients, with MuSK
antibodies, atrophy and fat replacement of the bulbar muscle can be observed.
We have previously shown that eye muscles show fat replacement in most MG
patients. The extent in which muscles throughout the body can be structurally
damaged by the disease is unknown. Therefore, we propose a study to map the
extend of atrophy, fat replacement and inflammation of the muscles.

The amount of MRI-detectable muscle damage in muscles of MG patients can be
used as a biomarker to quantify disease activity and disease progression. This
could provide valuable information for choosing the correct treatment modality
and avoiding overtreatment with immunosuppressive drugs at the risk of severe
side-effects.

Main objective:
1. To determine the feasibility of measuring fat replacement, atrophy and
inflammation using MRI in several muscle groups in Myasthenia gravis patients,
by determining scan quality and the difference in these parameters between MG
patients and healthy controls.

Secondary Objectives:
2. To determine if the MRI findings correlate with the clinical pattern of
muscle weakness as measured by the QMG muscle test and as reported by MG-ADL.
3. To determine the patient experience of the proposed MRI protocol.
4. To confirm the measures of fat replacement, atrophy and inflammation using
MRI in refractory MG patients with clinical signs of atrophy.
5. To determine the change in MRI findings of fat replacement, atrophy and
inflammation due to clinical treatment in refractory MG patients

This study in an observational study. Patients will undergo one MRI scan (~60
minutes). Hereafter, patients will be asked to fill in the MRI acceptability
questionnaire, the IPAQ-sf questionairre, the mg-AGL questionnaire and muscle
weakness/fatigability will be tested with a QMG (~30 minutes). The refractory
patients will be asked for a follow-up visit after a clinical treatment period.

This study has no invasive procedures. Subjects with contraindications for MRI
will be excluded. There are no known risks known associated with the use of
MRI. Participants have no personal benefit from participating in this study.
However, the results study may contribute to the understanding of the course of
the disease and predictability of therapeutic response in all MG patients.