Changes detected in swallowing function in Friedreich ataxia over 12 months
Introduction
Friedreich ataxia (FRDA) is an autosomal recessive neurodegenerative condition resulting from deficiency of frataxin. In 96% of affected individuals, it is caused by homozygosity for a GAA trinucleotide repeat expansion in intron 1 of FXN [1], with the size of the smaller allele (GAA1) inversely correlated with symptom onset and severity [2]. FRDA is the most common of the hereditary ataxias, affecting approximately 1 in 29,000 individuals in European populations [3]. Symptoms often present in the teenage years (but can appear earlier or later [4], [5]) and include progressive gait and limb ataxia, auditory [6] and optic neuropathy [7], cardiomyopathy, scoliosis, dysarthria [8] and dysphagia [9], [10]. These symptoms impose significant morbidity and negatively impact on quality of life (QOL) [9–11].
Dysphagia is present in almost all individuals with FRDA [9]. Delayed pharyngeal swallowing initiation is common, as are lingual dysfunction and reduced clearance of solid foods from the pharyngeal structures [9], [10], reflecting underlying motor and sensory impairment. Approximately one-third of individuals with FRDA aspirate barium on videofluoroscopy (VFSS) with fluids and/or solids, and many of those do so silently [9]. A relationship is known to exist between aspiration and penetration of the airway and oromotor function relating to coughing, swallowing, and saliva control (X2(1, N = 30) = 5.98, p = 0.01) [9]. Aspiration can occur at any stage of disease progression [9], necessitating the need for monitoring of swallowing function in affected individuals.
Dysphagia is known to present significant challenges for individuals with FRDA, including reduced ability to participate in social gatherings and overall QOL [9], [10]. Significant positive correlations have been reported between swallowing-related QOL and dysphagia (as determined via VFSS), disease severity and duration [9], suggesting swallowing function progressively declines in this population. The rate at which swallowing function changes is unknown. Longitudinal data on swallowing function in FRDA may provide valuable prognostic information on the clinical course of the disease and further inform our understanding of the underlying disease mechanisms in FRDA.
Here we describe the rate of dysphagia progression over one year using scales deemed best clinical practice. An understanding of the relationship between disease and dysphagia progression is important to guide management and intervention [12], [13], [14], given dysphagia treatment has been shown to be less effective in the later stages of other neurodegenerative diseases [12]. Longitudinal data on swallowing function in FRDA will also provide valuable information on the clinical course of the disease, enhancing our understanding of the progression of this area of morbidity.
Section snippets
Participants
Twenty-three of 59 individuals from a previous study [9] participated in swallowing assessment at two timepoints (timepoint 1; TP1, and timepoint 2; TP2). Participants were recruited through the Friedreich Ataxia Clinic in Melbourne, Australia, and all had a genetically confirmed diagnosis of FRDA (homozygous for FXN intron 1 GAA expansions) (Table 1). Participants were excluded if they presented with a neurological disorder other than FRDA, or a speech and/or swallowing impairment prior to the
Participant characteristics
Twenty-three of the original 59 (40%) participants completed the second assessment (Fig. 1). Seventeen participants repeated the Swal-QOL (mean age 37.48 years, standard deviation 13.71 years), 9 participated in repeat FDA-2 assessment, and 12 underwent VFSS (Table 1). Repeated assessments were completed as close to 12 months apart as possible which coincided with the participants’ yearly visit to the FRDA clinic. On average, Swal-QOL assessment was conducted 332.4 days apart (range 194–423
Discussion
Small but measurable changes in swallowing function were observed in individuals with FRDA over a one-year period. Changes in swallowing function were observed between timepoints on self-report measures of dysphagia symptoms, oromotor performance on respiration tasks and oral and pharyngeal clearance of solid textures of food as determined via VFSS. These changes were observed in the absence of significant change to disease severity. Whilst this study is small in scale, it is the largest study
Acknowledgments
The authors wish to thank the participants for their involvement in this study and the staff at the Friedreich Ataxia Clinic and Monash Health Diagnostic Imaging departments for assistance with subject recruitment and VFSS, respectively.
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