Background

Normal swallowing function is divided into oral, pharyngeal, and oesophageal phases. The anatomy and physiology of the oral cavity facilitates an oral preparatory phase of swallowing, in which food and liquid are pushed towards the pharynx by the tongue. During pharyngeal and oesophageal phases of swallowing, food and liquid are moved from the pharynx to the stomach via the oesophagus. Our understanding of swallowing function in health and disease has informed our understanding of how muscle weakness can disrupt swallowing in people with muscle disease. As a common complication of long-term, progressive muscle disease, there is a clear need to evaluate the current interventions for managing swallowing difficulties (dysphagia). This is an update of a review first published in 2004.

Objectives

To assess the effects of interventions for dysphagia in people with long-term, progressive muscle disease.

Search methods

On 11 January 2016, we searched the Cochrane Neuromuscular Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, AMED, LILACS, and CINAHL. We checked references in the identified trials for additional randomised and quasi-randomised controlled trials. We also searched ClinicalTrials.gov and the World Health Organization International Clinical Trials Registry Platform on 12 January 2016 for ongoing or completed but unpublished clinical trials.

Selection criteria

We included randomised and quasi-randomised controlled trials that assessed the effect of interventions for managing dysphagia in adults and children with long-term, progressive muscle disease, compared to other interventions, placebo, no intervention, or standard care. Quasi-randomised controlled trials are trials that used a quasi-random method of allocation, such as date of birth, alternation, or case record number. Review authors previously excluded trials involving people with muscle conditions of a known inflammatory or toxic aetiology. In this review update, we decided to include trials of people with sporadic inclusion body myositis (IBM) on the basis that it presents as a long-term, progressive muscle disease with uncertain degenerative and inflammatory aetiology and is typically refractory to treatment.

Data collection and analysis

We applied standard Cochrane methodological procedures.

Main results

There were no randomised controlled trials (RCTs) that reported results in terms of the review's primary outcome of interest, weight gain or maintenance. However, we identified one RCT that assessed the effect of intravenous immunoglobulin on swallowing function in people with IBM. The trial authors did not specify the number of study participants who had dysphagia. There was also incomplete reporting of findings from videofluoroscopic investigations, which was one of the review's secondary outcome measures. The study did report reductions in the time taken to swallow, as measured using ultrasound. No serious adverse events occurred during the study, although data for the follow-up period were lacking. It was also unclear whether the non-serious adverse events reported occurred in the treatment group or the placebo group. We assessed this study as having a high risk of bias and uncertain confidence intervals for the review outcomes, which limited the overall quality of the evidence. Using GRADE criteria, we downgraded the quality of the evidence from this RCT to 'low' for efficacy in treating dysphagia, due to limitations in study design and implementation, and indirectness in terms of the population and outcome measures. Similarly, we assessed the quality of the evidence for adverse events as 'low'. From our search for RCTs, we identified two other non-randomised studies, which reported the effects of long-term intravenous immunoglobulin therapy in adults with IBM and lip-strengthening exercises in children with myotonic dystrophy type 1. Headaches affected two participants treated with long-term intravenous immunoglobulin therapy, who received a tailored dose reduction; there were no adverse events associated with lip-strengthening exercises. Both non-randomised studies identified improved outcomes for some participants following the intervention, but neither study specified the number of participants with dysphagia or demonstrated any group-level treatment effect for swallowing function using the outcomes prespecified in this review.

Authors' conclusions

There is insufficient and low-quality RCT evidence to determine the effect of interventions for dysphagia in long-term, progressive muscle disease. Clinically relevant effects of intravenous immunoglobulin for dysphagia in inclusion body myositis can neither be confirmed or excluded using the evidence presented in this review. Standardised, validated, and reliable outcome measures are needed to assess dysphagia and any possible treatment effect. Clinically meaningful outcomes for dysphagia may require a shift in focus from measures of impairment to disability associated with oral feeding difficulties.

Purpose

To report novel genotypes and expand the phenotype spectrum of SSBP1-disease and explore potential disease mechanism.

Methods

Five families with previously unsolved optic atrophy and retinal dystrophy underwent whole genome sequencing as part of the National Institute for Health Research BioResource Rare-Diseases and the UK's 100,000 Genomes Project. In silico analysis and protein modelling was performed on the identified variants. Deep phenotyping including retinal imaging and International Society for Clinical Electrophysiology of Vision standard visual electrophysiology was performed.

Results

Seven individuals from five unrelated families with bilateral optic atrophy and/or retinal dystrophy with extraocular signs and symptoms in some are described. In total, 6 SSBP1 variants were identified including the previously unreported variants: c.151A>G, p.(Lys51Glu), c.335G>A p.(Gly112Glu), and c.380G>A, p.(Arg127Gln). One individual was found to carry biallelic variants (c.380G>A p.(Arg127Gln); c.394A>G p.(Ile132Val)) associated with likely autosomal recessive SSBP1-disease. In silico analysis predicted all variants to be pathogenic and Three-dimensional protein modelling suggested possible disease mechanisms via decreased single-stranded DNA binding affinity or impaired higher structure formation.

Conclusions

SSBP1 is essential for mitochondrial DNA replication and maintenance, with defects leading to a spectrum of disease that includes optic atrophy and/or retinal dystrophy, occurring with or without extraocular features. This study provides evidence of intrafamilial variability and confirms the existence of an autosomal recessive inheritance in SSBP1-disease consequent upon a previously unreported genotype.