Motor excitability in myopathy.

OBJECTIVE: To explore whether patients with myopathy present changes in motoneuronal excitability. METHODS: Patients with well-defined myopathies were studied with single and paired pulse transcranial magnetic stimulations and electrical nerve stimulations to explore neuronal motor excitability. Motor-evoked potentials were recorded from the clinically unaffected first dorsal interosseous muscle (n=10) and the paretic deltoid muscle (n=8). RESULTS: Compared to an age-matched healthy control group, myopathic patients showed a reduction of intracortical inhibition, enhancements of alpha-motoneuron excitability and increased amplitudes of motor-evoked potentials during target muscle contraction. These alterations were present in clinically affected and clinically unaffected muscles. CONCLUSION: In myopathy, nervous system excitability may be altered, presenting as a motor disinhibition on cortical and subcortical levels.     

Outcome and effect of pregnancy in myotonic dystrophy type 2

The authors reviewed the obstetric histories of 42 women of 37 families with myotonic dystrophy type 2 (DM2). Nine women (21%) had the first symptoms during pregnancy and worsening in subsequent pregnancies. Of 96 pregnancies, 13% ended as early and 4% as late miscarriages. Preterm labor occurred in 50% of pregnancies resulting in 27% preterm deliveries in women with overt DM2 in pregnancy. There was no evidence of a congenital DM2.     

Perceived pain and temporomandibular disorders in neuromuscular diseases

Little is known about pain associated with temporomandibular disorders (TMD) in neuromuscular diseases. Inpatients (N = 134) with neuromuscular disorder diagnoses were given questionnaires to estimate pain localization and intensity. Research Diagnostic Criteria for Temporomandibular Disorders and the Temporomandibular Index (TMI) were utilized to assess TMD. Pain was reported by 116 patients (86%). Legs (52%) and arms (33%) were the most common locations for pain localization, but the highest Pearson correlations (TMI vs. perceived pain) appeared for pain located in the trunk and arms (0.861, P < 0.01). No correlation between TMI and diagnosis group existed except for “acquired myopathy” and “miscellaneous neuromuscular diseases.” These results suggest that the degree of TMD does not correlate with pain according to disease, although common mechanisms might be responsible for pain development in specific body regions connected with TMD. Most important, higher levels of TMD are associated with higher levels of perceived pain. Muscle Nerve, 2009     

High frequency of co-segregating CLCN1 mutations among myotonic dystrophy type 2 patients from Finland and Germany

Based on previous reports the frequency of co-segregating recessive chloride channel (CLCN1) mutations in families with myotonic dystrophy type 2 (DM2) was suspected to be increased. We have studied the frequency of CLCN1 mutations in two separate patient and control cohorts from Germany and Finland, and for comparison in a German myotonic dystrophy type 1 (DM1) patient cohort. The frequency of heterozygous recessive chloride channel (CLCN1) mutations is disproportionally higher (5 %) in currently diagnosed DM2 patients compared to 1.6 % in the control population (p = 0.037), while the frequency in DM1 patients was the same as in the controls. Because the two genes segregate independently, the prevalence of CLCN1 mutations in the total DM2 patient population is, by definition, the same as in the control population. Our findings are, however, not based on the total DM2 population but on the currently diagnosed DM2 patients and indicate a selection bias in molecular diagnostic referrals. DM2 patients with co-segregating CLCN1 mutation have an increased likelihood to be referred for molecular diagnostic testing compared to DM2 patients without co-segregating CLCN1 mutation.     

Inflammatorische Myopathien

Inflammatory myopathies cover infectious, focal and immunogenic myopathies. This review focuses on the clinical features, diagnostic techniques, pathogenesis and therapy of immunogenic myopathies. Besides myositis associated with other autoimmune disorders, dermatomyositis is the most common immunogenic myopathy. The independent diagnosis of polymyositis has come under debate, since within this group of patients some are now diagnosed as having either hereditary muscular dystrophy with inflammatory signs or inclusion body myositis (IBM). Even more strikingly, patients diagnosed with sporadic IBM may now be diagnosed with either a form of hereditary IBM or with a form belonging to the group of protein aggregate myopathies or myofibrillar myopathies. This re-classification reflects the well-known and clinically evident therapeutic dilemma in many of these patients. Thus the indication for muscle biopsy or rebiopsy requires new consideration and attention.     

Metabolische Myopathien – ein Überblick

Metabolic disorders of energy production characterise the group of rare, mainly autosomal recessively inherited metabolic muscular diseases which are often associated with multi-systemic symptoms. In this report, an update on the clinics, pathophysiology, pathomorphology and current treatment options of metabolic myopathies will be given. Beyond classic phenotypes of these disorders, one should be aware of oligosymptomatic patients who can be easily missed. The relevant gene mutations and the pathophysiology and pathomorphology they cause are now known for almost all these metabolic diseases. Establishing the correct diagnosis has become even more important since highly specific therapy options are now available for at least some of these inherited disorders, e.g. enzyme replacement therapy in Pompe disease.