Is paravertebral muscles edema a consequence of neurogenic changes in MuSK-positive myasthenia gravis?

Anti-MuSK myasthenia gravis (Anti-MuSK MG) is a chronic autoimmune disease caused by complement-independent dysfunction of the agrin-MuSK-Lrp4 complex, accompanied by the development of the pathological muscle fatigue and sometimes muscle atrophy. Fatty replacement of the tongue, mimic, masticatory and paravertebral muscles, revealed by muscle MRI and proton magnetic resonance spectroscopy (MRS), is considered to be a consequence of the myogenic process in anti-MuSK antibody MG in the patients with a plenty long course of the disease. However, in most experimental studies on animal models with anti-MuSK MG, complex presynaptic and postsynaptic changes are revealed, accompanied by the functional denervation of masticatory and paravertebral muscles predominantly. This study presents the MRI, nerve conduction studies (NCS), repetitive nerve stimulation (RNS) and electromyography (EMG) of neurogenic lesions of the axial muscles (m. Multifidus Th12, L3-L5; m. Erector spinae L4-L5) in two patients K. (51 years old), and P. (44 years old), both of whom were having weakness of the paravertebral muscles for 2-4 months due to anti-MuSK MG. The clinical manifestations, as well as the edematous changes in the paravertebral muscles, regressed after therapy. Thus, these clinical examples may confirm the presence of the neurogenic changes at an early stage of anti-MuSK myasthenia gravis and indicate importance of immediate initiation of therapy to avoid the development of muscle atrophy and fatty infiltration.

Magnetic resonance imaging pattern variability in dysferlinopathy.

The widespread use of magnetic resonance imaging (MRI) in the diagnosis of myopathies has made it possible to clarify the typical MRI pattern of dysferlinopathy. However, sufficient attention has not been given to the variability of MRI patterns in dysferlinopathy. MATERIALS AND METHODS: Twenty-five patients with the clinical manifestations of dysferlinopathy were examined. For all patients, creatine phosphokinase levels were measured and molecular genetics were examined. In two patients, immunohistochemical examinations of muscle biopsies were performed. MRI scanning was included T2 multi-slice multi-echo, T1 weighted, T2 weighted and Short Tau Inversion Recovery T2 weighted sequences. Quantitative and semi-quantitative evaluations of fatty replacement and swelling of the muscles were undertaken. RESULTS: Variability in the MRI patterns was lowest in the pelvis and leg muscles and highest in the thigh muscles. Three main types of MRI patterns were distinguished: posterior-dominant (80%), anterior-dominant (16%), and diffuse (4%). Among patients with the anterior-dominant pattern, the collagen-like variant (4%), proximal variant (4%) and pseudo-myositis (8%) were separately distinguished. CONCLUSIONS: Awareness of atypical MRI patterns in dysferlinopathy is important for increasing the efficiency of routine diagnostics and optimizing the search for causative gene mutations.