Chronic respiratory insufficiency in Myotonic Dystrophies: management and implications for research

Location: Naarden, The Netherlands

Workshop organisers: Dr VA Sansone (Italy) and C Gagnon (Canada)

Myotonic Dystrophies are the most frequent muscular dystrophies of adulthood. Patients with myotonic dystrophy type 1 (DM1) die primarily from respiratory complications in mid-life and patients with the congenital form of DM 1 may require a stoma in the trachea at birth (invasive ventilation). Myotonic dystrophy type 2 (DM2) also affects multiple organs, but the degree and severity of respiratory involvement has not been investigated in detail. Although respiratory involvement is a major concern in the myotonic dystrophies,  respiratory care has been limited by the complex pathophysiology of respiratory involvement and by specific clinical characteristics of DM patients.

Patients progressively develop respiratory muscle and diaphragm weakness which affects their ability to ventilate efficiently, especially at night while lying in bed. This leads to low blood oxygen levels and high blood carbon dioxide levels, initially during the night and then even during the day. Patients slowly habituate to the abnormal blood gas levels. It is however not only the muscle component and obstructive sleep apnea which come into play, but there are several complex central nervous system (CNS) pathways which interfere with synchronous activity of respiratory and abdominal muscles. Especially during the night, which disrupts sleep patterns, thus worsening ventilation. Management is therefore challenging. The choice of the type of non-invasive ventilation (NIV), such as C-PAP, BiPaP or Auto-SV, needs to be tailored for each patient.  These complex underlying mechanisms of the disease are largely responsible for excessive daytime sleepiness and fatigue which are frequent in DMpatients.

The cognitive and behavioral features of these patients are such that there is lack of awareness of chronic respiratory insufficiency and patients seldom complain of symptoms of respiratory involvement. When cough assistance rehabilitation programs or non-invasive ventilation are prescribed, compliance is limited and respiratory management becomes very challenging.

This workshop provided a platform for experts in myotonic dystrophy and in respiratory care from across Europe, Canada and USA to share best practice. It allowed to start to work together on a common standardized pathway of respiratory care for these patients when first seen and during follow-up. The combination of experts in myotonic dystrophy and experts in ventilation also created a platform to adapt existing consensus care recommendations for cough assistance and domiciliary non-invasive ventilation in these patients. Specifically, it was very important to merge knowledge in respiratory care with that of the muscular and multisystem additional aspects of the disease, including the ability to manage the cognitive and behavioural characteristics of these patients.

The workshop heard from clinical experts on the issues of fatigue and excessive daytime sleepiness and on how specific CNS pathways may play a role in the development of chronic respiratory insufficiency, disturbed sleep and reduced awareness. The issue of the patients not reporting symptoms was discussed and there was general consensus that this is a major limitation to care and management.The relationship between cardiac and respiratory involvement was also addressed with specific focus on the arrhythmic risk in patients with or without ventilation. Each country representative provided indicative data on the frequency and severity of respiratory involvement and on the pathway of care and management in these patients. Similarities and differences were discussed. It was noted that the efficiency of the healthcare systems in different countries in providing respiratory care are dependent on existing structures and/or specific persons and existing pathways and the extent to which these enable coordination and interdisciplinarity. This indicated that respiratory assessments, management and the quality of care is highly variable and could sometimes be quite fragile. It was also noted that the use of cough-assistance devices and respiratory rehabilitation programs varied widely amongst the different countries. This session played an integral part in identifying gaps in existing care and helping to adapt existing recommendations and move towards a consensus statement for respiratory care, specific for myotonic dystrophies regarding recommendations for the diagnostic work-up, succession planning and monitoring. The workshop also heard  personal experience from an Italian patient and spouse and from a Dutch patient and spouse and from organisations representing patients – the Myotonic Dystrophy Support Group. This patient´s voice was essential to help in defining ways to overcome and manage the lack of awareness of symptoms, to better address the need for respiratory care and to improve compliance.

To summarize, the main points of discussion were:

• The importance of accessibility for patients with myotonic dystrophies to a neuromuscular centre with experience in non-invasive ventilation or referral by a neuromuscular or myotonic dystrophy healthcarer to a respiratory center with experience in non-invasive ventilation to allow co-ordination of care.
• The importance of dedicated healthcare pathways to define respiratory care during screening visits and during follow-up assessments were also discussed.
• It is critical to understand that patients with myotonic dystrophies require more time from the healthcarers during clinical assessments, administration of questionnaires, explanation of specific healthcare pathways and treatment options, and during training. In order to improve compliance to treatment
• Specifically, the workshop allowed to:
• Provide a basic screening respiratory protocol to assess patients at baseline (when first assessing respiratory function) including a symptoms check-list and a list of recommended respiratory laboratory tests for screening, applicable by myotonic dystrophy experts and non-experts. The symptoms check-list includes a list of questions with adequate wording for myotonic dystrophy patients to increase the patients’ understanding of symptoms.
• Discuss uncertainties and benefits and side-effects of NIV and lack of knowledge of its effects in the long-term given the lack of natural history studies in respiratory involvement in myotonic dystrophies. Consensus was reached on the need to launch NIV when specific criteria are present. The workshop allowed to adapt existing recommendations for launching of NIV (ACI Respiratory Network Domiciliary Non-Invasive Ventilation in Adult Patients : A Consensus Statement) making them specifically applicable to these patients.
• Address additional management issues including: peri-operative management, secretion management, weight control, physical exercise program and patient and carer education, training and acclimatization. Existing emergency care plan could be implemented in all countries to help improve management of these patients.

To determine future areas of research including natural history study to understand the course of the respiratory involvement and outcome measures validation.
Margaret Bowler from the Myotonic Dystrophy Support Group and the patients representatives will help in diffusing information and results obtained from the workshop discussions.

A full report is published in Neuromuscular Disorders (pdf)