Molecular Basis of Neuromuscular Disease

Longing: the lived experience of spirituality in adolescents with Duchenne muscular dystrophy

Although much has been written regarding ill adolescents, research has not described their spiritual response. The purpose of this descriptive phenomenological study was to describe the lived experiences of spirituality in adolescents with Duchenne muscular dystrophy using van Manen's phenomenological method. Findings from nine teens showed that the essential theme of spirituality was "longing," the strong desire for something unattainable. Consistent with Reed's (1992) paradigm for understanding spirituality, participants mediated their longing through "Connecting with others, self, and beyond self." These findings support the need for nursing to assess spirituality in teens and determine developmentally appropriate interventions to ameliorate longing.

Chronic pain in persons with myotonic dystrophy and facioscapulohumeral dystrophy

OBJECTIVE

To determine the nature and scope of pain in working-aged adults with myotonic muscular dystrophy (MMD) and facioscapulohumeral muscular dystrophy (FSHD).

DESIGN

Retrospective, cross-sectional survey.

SETTING

Community-based survey.

PARTICIPANTS

Convenience sample of subjects with MMD and FSHD.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Overall intensity and duration of pain, pain inference, pain sites, pain treatments, and relief provided by pain treatments.

RESULTS

More subjects with FSHD (82%) than with MMD (64%) reported pain. The most frequently reported pain sites for both diagnostic groups were lower back (66% MMD, 74% FSHD) and legs (60% MMD, 72% FSHD). Significant differences in pain intensity were found between the diagnostic groups in the hands, legs, knees, ankles, and feet, with patients with MMD reporting greater pain intensity at these sites than patients with FSHD. Age was related to the onset of pain (participants reporting pain were younger than those not reporting pain in the FSHD sample), but pain severity was not significantly associated with age in those reporting pain. Respondents with both diagnoses that reported mobility limitations and used assistive devices (eg, wheelchair, cane) reported more pain severity than those with mobility limitations who did not use assistive devices, who, in turn, reported more pain severity than respondents who reported no mobility limitations at all. The treatments that were reported to provide the greatest pain relief were not necessarily those that were the most frequently tried or still used.

CONCLUSIONS

The findings indicate that pain is a more common problem in persons with FSHD than in persons with MMD, although it is common in both populations. In addition, these pain problems are chronic, underscoring the need to identify and provide effective pain treatments for patients with these neuromuscular diseases.

Age-Related Dystrophin-Glycoprotein Complex Structure and Function in the Rat Extensor Digitorum Longus and Soleus Muscle

This study tested the hypothesis that age-related changes in the dystrophin-glycoprotein complex (DGC) may precede age-associated alterations in muscle morphology and function. Compared to those in adult (6 month) rats, extensor digitorum longus (EDL) and soleus muscle mass was decreased in old (30 month) and very old (36 month) Fischer 344/NNiaHSD x Brown Norway/BiNia rats. The amount of dystrophin, beta-dystroglycan, and alpha-sarcoglycan increased with aging in the EDL and decreased with aging in the soleus. alpha-Dystroglycan levels were increased with aging in both muscles and displayed evidence of altered glycosylation. Immunostaining for the presence of antibody infiltration and dystrophin following increased muscle stretch suggested that the aging in the soleus was characterized by diminished membrane integrity. Together, these data suggest that aging is associated with alterations in EDL and soleus DGC protein content and localization. These results may implicate the DGC as playing a role in age-associated skeletal muscle remodeling.

Electrodiagnostic evaluation of hereditary motor and sensory neuropathies

Electrodiagnosis can classify hereditary motor and sensory neuropathies (HMSN) into two basic types: primarily demyelinating with secondary axonal loss and primarily axonal. For the most part, the various forms of HMSN show uniform symmetric nerve conduction slowing, in contrast to acquired neuropathies, which may be multifocal with nonuniform conduction velocity slowing and temporal dispersion. Nevertheless, there are exceptions. This article reviews the available literature and describes the electrodiagnostic approach to HMSN, detailing potential sources of error that can lead to misinterpretation of data.

Hand strength and fatigue in patients with hereditary motor and sensory neuropathy (types I and II)

OBJECTIVES

To compare maximal isometric hand strength and fatigue between subjects with hereditary motor and sensory neuropathy (HMSN) and healthy controls and to test the reproducibility of handgrip strength (peak force of handgrip [PFgrip]) and fatigue.

DESIGN

PFgrip and the decline in PFgrip during 3 sets of 15 contractions were compared.

SETTING

University hospital in The Netherlands.

PARTICIPANTS

Twenty subjects with HMSN and 20 age- and sex-matched healthy controls; 15 healthy subjects for the reproducibility part of the study.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

PFgrip and the decline in PFgrip were compared by using a digital handgrip dynamometer. Two-point and lateral pinch measurements of subjects with HMSN were standardized against reference values. Reproducibility measurements were performed on 15 healthy subjects on 2 separate occasions within a 1-week interval.

RESULTS

PFgrip was significantly lower in the HMSN subjects compared with controls (P<.05). Pinch measurements also showed a large variance from average normal performance. No significant difference was found in the decline in percentage of PFgrip. Reproducibility was excellent for PFgrip (intraclass correlation coefficient [ICC]=.98; 95% confidence interval [CI],.95-.99) but poor for fatigue (ICC=.62; 95% CI,.20-.85).

CONCLUSION

PFgrip and 2-point and lateral pinch in HMSN subjects were significantly reduced compared with healthy controls. Our findings indicated that the rate of decline of PFgrip during effort does not vary between groups.

CDNA microarray analysis of gene expression in fibroblasts of patients with X-linked Emery-Dreifuss muscular dystrophy

To clarify the molecular nature of the pathogenesis in X-linked Emery-Dreifuss muscular dystrophy (EDMD), we monitored the expression of 2400 genes in control and EDMD fibroblasts by using complementary DNA (cDNA) microarray techniques. A total of 60 genes whose expression was altered in EDMD fibroblasts when compared with control fibroblasts were identified. Twenty-eight genes whose expression was altered with the emerin deficiency were rescued by infection with a recombinant adenovirus expressing emerin. The altered expression in five genes, including the lamin A/C gene, was confirmed by reverse transcription-polymerase chain reaction. Our preliminary results suggest a correlation between disease similarity and gene expression. We conclude that the cDNA microarray is a very efficient tool to clarify genetic and pathological features of diseases.

Diagnosis of pediatric neuromuscular disorders in the era of DNA analysis

Extraordinary breakthroughs in the molecular pathogenesis of muscle and nerve disease have resulted in an evolving genetic classification of neuromuscular disorders and the development of new diagnostic methods. This remarkable progress has introduced new genetic tests and has changed the indications for use of certain invasive diagnostic procedures in the evaluation of children with presumed disorders of the motor unit. In this review, we present the current diagnostic approach to the more common neuromuscular diseases of infancy and childhood and define the diagnostic role of muscle biopsy and pediatric electromyography/nerve conduction studies in the era of genetic analysis.

Preserving function in Duchenne dystrophy with long-term pulse prednisone therapy

We report a case of a patient with Duchenne muscular dystrophy who was treated with intermittent pulse prednisone for severe asthma from age 3 to 17 yr and had remarkable preservation of skeletal muscle function. He had a maternal uncle with Duchenne muscular dystrophy who had the identical familial deletion mutation and died at age 19 of respiratory failure. Compared with his untreated uncle, our patient remains partially ambulatory at age 20. This case provides interesting, albeit anecdotal, evidence of considerable clinical benefit from pulse prednisone used on a much longer term basis than has been previously studied and promotes the need for further investigation on this type of therapy in Duchenne muscular dystrophy.

Contractile properties of single muscle fibers in myotonic dystrophy

Muscle fiber contractile dysfunction in myotonic dystrophy (MD) is poorly understood. We biopsied the tibialis anterior of two symptomatic and three asymptomatic subjects (aged 21-31 years) with the MD mutation. Biopsies were freeze dried. A total of 103 single muscle fibers were activated with Ca(++), allowing maximal force measurements and specific force (SF) estimates. The slack test was performed to calculate maximum unloaded shortening velocity (V(o)). The myosin heavy chain composition of each fiber was determined using sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Type I and IIA fibers of all subjects had reduced SF when compared with healthy control subjects (P < 0.001). In addition, the type I fibers of symptomatic subjects generated less SF than those of asymptomatic subjects (P < 0.001). Type I fibers from asymptomatic and symptomatic subjects did not differ in V(o), but V(o) was lower than in control subjects (P < 0.001). There was no significant difference in V(o) of type IIA fibers from symptomatic, asymptomatic, and control subjects. These results indicate that the MD mutation leads to a diminished force-generating capacity of the myofilaments in both symptomatic and asymptomatic individuals. The results further suggest that reduction in force-generating capacity at the cellular level develops prior to clinical weakness.