A weak balance: the contribution of muscle weakness to postural instability and falls

Muscle strength is a potentially important factor contributing to postural control. In this article, we consider the influence of muscle weakness on postural instability and falling. We searched the literature for research evaluating muscle weakness as a risk factor for falls in community-dwelling elderly individuals, for evidence that strength training reduces falls, and for pathophysiological evidence from patients with neuromuscular disease that supports the link between muscle weakness and falls. In virtually all studies that included strength testing, muscle weakness was a consistent risk factor for falls in the elderly. Studies that evaluated the merits of muscle strength training often showed a reduction in fall rates, particularly when strength training was a component of a multifactorial intervention, although it was unclear whether strength training alone led to a fall reduction. Surprisingly few studies addressed the pathophysiological relationship between muscle strength and balance control. We conclude that muscle weakness is an important risk factor for falls that is potentially amenable to therapeutic intervention, and that future studies should further clarify the role of muscle weakness in balance control and the pathophysiology of falls.     

Clinical and molecular overlap between myopathies and inherited connective tissue diseases

This review presents an overview of myopathies and inherited connective tissue disorders that are caused by defects in or deficiencies of molecules within the extracellular matrix (ECM). We will cover the myopathies caused by defects in transmembrane protein complexes (dystroglycan, sarcoglycan, and integrins), laminin, and collagens (collagens VI, XIII, and XV). Clinical characteristics of several of these myopathies imply skin and joint features. We subsequently describe the inherited connective tissue disorders that are characterized by mild to moderate muscle involvement in addition to the dermal, vascular, or articular symptoms. These disorders are caused by defects of matrix-embedded ECM molecules that are also present within muscle (collagens I, III, V, IX, lysylhydroxylase, tenascin, fibrillin, fibulin, elastin, and perlecan). By focussing on the structure and function of these ECM molecules, we aim to point out the clinical and molecular overlap between the groups of disorders. We argue that clinicians and researchers dealing with myopathies and inherited connective tissue disorders should be aware of this overlap. Only a multi-disciplinary approach will allow full recognition of the wide variety of symptoms present in the spectrum of ECM defects, which has important implications for scientific research, diagnosis, and for the treatment of these disorders.     

A new phenotype of autosomal dominant nemaline myopathy.

We present a five-generation family with a novel phenotype of autosomal dominant nemaline myopathy not linked to the three genes known to be causative for nemaline myopathy (alpha-tropomyosin-3, nebulin, and alpha-actin). Although there was muscle weakness in the neck flexors and proximal muscles of the limbs, as found in other families, facial, ankle dorsiflexor and respiratory muscles were normal. The most remarkable clinical feature was a peculiar kind of slowness in movement not reported previously in nemaline myopathy.     

Development of a tool to guide referral of patients with neuromuscular disorders to allied health services. Part two

PURPOSE: The Perceived Limitations and Needs Questionnaire (PLAN-Q) was developed to guide referral for a one-off consultation by occupational therapy (OT), physical therapy (PT), and speech therapy (ST) consultation, to provide a tailor-made advice on allied health interventions. This article reports on the testing of validity and reliability of the PLAN-Q. METHODS: In the validation study, 208 patients with a broad spectrum of neuromuscular disorders completed the PLAN-Q, Medical Outcome Study short-form 36-item version (SF-36), and the Impact of Participation on Autonomy (IPA) questionnaires. A subsection of 51 patients, whose physical condition was stable, participated in the evaluation of the intra-rater reliability of the questionnaire. The theoretical construct was tested with factorial analysis, subscales were constructed and reliability and validity of the PLAN-Q subscales were assessed. RESULTS: Factorial analysis resulted in an 18-item self-report questionnaire. Items were grouped into four subscales ('physical capacity', 'transferring', 'oropharyngeal capacity', and 'hand-use'), each with two dimensions ('capacity' and 'need for help'). The internal consistency of all subscales was good (Cronbach's alpha: 0.77-0.94) as well as the intra-rater reliability of the subscales 'physical capacity' and 'transferring' in the 'capacity' dimension (Kappa: 0.70-0.75). The 'need' dimension showed poor intra-rater reliability suggesting that 'need for help' is a variable phenomenon that changes between two points of measurement. The construct validity of the subscales against the SF-36 and the IPA was satisfactory. CONCLUSION: The PLAN-Q is a valid self-report instrument that measures patients' perception of capacity and needs in domains relevant to referral for a one-off OT, PT, or ST consultation.     

Different distribution of the genetic subtypes of the Prader�CWilli syndrome in the elderly

The Prader–Willi syndrome (PWS) is a genetic disorder caused by the absent expression of the paternal copy of maternally imprinted genes in chromosome region 15q11–13. The frequencies of different subtypes in PWS are usually given in literature as 70% deletion, 25–30% maternal uniparental disomy (mUPD) and 3–5% others (imprinting centre (IC) defects and translocations). Little is known about factors that influence the frequency of genetic subtypes in PWS. The study sample comprised 102 adults with clinically and genetically confirmed PWS, contacted through the Dutch Prader–Willi Parent Association and through physicians specialized in treating persons with intellectual disabilities. Genetic testing showed 55 persons (54%) with a paternal deletion, 44 persons (43%) with an mUPD and 3 persons (3%) with a defect of the IC. The observed distribution in our study differed from that in literature (70% deletion, 30% mUPD), which was statistically significant (z-score: P<0.05). This was mainly caused by a higher proportion of mUPD in the advanced age groups. Differences in maternal age and BMI of persons with PWS could not explain the differences in distribution across the age groups. Our study population had a much broader age range, compared with other studies, because of a predominance of elderly people (40+ years) with PWS. In other studies, these elderly persons might have been undiagnosed and/or underreported because of a lack of genetic diagnosis. The results underline both the need for correct genetic diagnosis in all persons with PWS and adjustment of the guidelines for preventive management in adulthood.