A Multidimensional Profile of Dysphagia in Myotonic Dystrophy Type 1 (DM1)

Background Myotonic Dystrophy Type 1 (DM1) is the most prevalent neuromuscular condition presenting in adulthood.

Dysphagia is the primary cause of acute respiratory failure and pneumonia in people living with DM1, accounting for >40% of deaths (Mathieu et al., 1999). Other consequences include malnutrition, dehydration, and sudden death from choking. There are no evidence-based tools to support the assessment and treatment of dysphagia in DM1.

This raises concern about delays in diagnosis, inadequacies of treatment programmes and variably in care provision which inflict significant cost to the individual and healthcare system.

The unique and complex profile of DM1 necessitates careful consideration before tools validated in other populations are integrated into clinical practice under a 'one size fits all' approach.

This research will acquire new data about the profile of dysphagia in DM1 to inform novel recommendations for assessment and treatment.

Aim To define the profile of dysphagia in DM1 across the domains of structure, function, patient experience and wellbeing.

Methods A multi-phase cross-sectional cohort study of patients living with DM1 will be conducted to address the aims of this research: Phase 1 will investigate the size and structure of muscles involved in swallowing both in those with DM1 (n=84) and age and gender-matched controls (n=21).

An ultrasound imaging protocol will be used to measure muscle size (indicative of atrophy) and echogenicity (indicative of fat infiltration) of pre-determined muscle groups. Linear regression will be used to compare measurements between patients and controls.

Phase 2 will explore how muscle size and structure are associated with swallowing biomechanics (function) and symptoms (experience).

Patients with DM1 (n=90) will undergo a battery of swallowing assessments, including videofluoroscopy (VFSS), assessments of muscle strength and speed, plus a symptom questionnaire.

Logistic regression will be used to investigate the relationship between swallowing muscles size and structure and swallowing biomechanics, using VFSS as the reference standard. Descriptive analysis will be used to investigate the relationship with swallowing speed, strength and symptoms.

Phase 3 will explore how swallowing biomechanics are associated with symptoms, patient and caregiver wellbeing, and motor and respiratory function.

Patients with DM1 (n=90) will undergo additional assessments of their physical and respiratory function, plus wellbeing questionnaires. Primary caregivers (n=45) will also complete wellbeing questionnaires.

Logistic regression will be used to investigate the relationship between swallowing biomechanics and patient and caregiver psychosocial wellbeing.

Descriptive analyses will be used to investigate the relationship of swallowing biomechanics to motor and respiratory function, and symptoms to patient well-being.

Impact The key deliverable from this research will be a set of recommendations for the assessment and treatment of dysphagia in DM1 which are ready to implement into clinical practice.

These recommendations will improve the health, social, and quality of life dysphagia outcomes for patients with DM1 by providing a knowledge base for targeted assessment and treatment. The anticipated timeframe for implementation of these recommendations within tertiary centres is within 5-years. It will enable targeted treatment-focused research to commence, with potential for clinical impact within 10-years.