Bilateral diaphragmatic weakness: a late complication of radiotherapy. Commentary
Authors: J. Moxham
Journal: Thorax (1997)

The case report by Brander and colleagues diaphragm weakness due to one of the many causes listed by Brander and colleagues remain of severe diaphragm weakness due to phrenic nerve damage from radiotherapy given many undiagnosed despite diaphragm dysfunction contributing to symptoms of breathlessness and years earlier is of considerable interest. 1It provides yet another cause of diaphragm dys-disability?This question can only be answered if we are prepared, when clinically appropriate, function to add to an already long list.The authors comment that the potential causes of to make specific measurements of respiratory muscle strength.diaphragm weakness include motor neurone disease, poliomyelitis, myasthenia, muscular Brander and co-workers treated their patient with nocturnal non-invasive ventilation with dystrophies, polyneuropathy, neuralgic amyotrophy, malignant invasion of the phrenic good control of symptoms; for patients with severe orthopnoea the achievement of com-nerves, chest wall trauma, cardiothoracic surgery, connective tissue diseases, amyloid, and fortable sleep is most welcome.Such symptomatic control is a good indication for non-thyroid disease.There are other causes that could be added to this list and it is therefore invasive ventilation.A second indication would be established chronic ventilatory failure.This an important clinical point that diaphragm weakness is unusual, but it is not rare.Any did not occur in the case presented because the respiratory muscle weakness was largely respiratory physician with a busy clinical practice can expect to see patients with diaphragm confined to the diaphragm. 4 In patients with more widespread and severe respiratory muscle weakness, of varying severity, on an infrequent but regular basis.An important issue therefore weakness, ventilatory failure first develops at night (hence the importance of sleep studies) is how diaphragm weakness is diagnosed and how its severity is accurately assessed.and often occurs rather suddenly when the degree of weakness becomes sufficiently pro-When diaphragm weakness is severe the diagnosis -in a qualitative sense -is not a problem, found.Thus, patients may have a reduction of 30%, 40%, 50%, 60%, or even 70% in and the key features, as in this case presentation, are orthopnoea, paradoxical ab-respiratory muscle strength without developing ventilatory failure unless, in addition, there is dominal movement, and a fall in vital capacity when supine.However, these are late symptoms increased ventilatory load.At a relatively sharp cut off point, when inspiratory muscle strength and signs that only occur when diaphragm strength is reduced to approximately 25% of is approximately 25-30% of normal, ventilatory failure then becomes quite common.Clearly, normal. 2 From the history of the patient described in this case report it is clear that dia-if an accurate diagnosis of respiratory muscle weakness at an earlier stage has not been made, phragm weakness was slowly progressing over several years.Eventually the diagnosis became the clinician will often be caught unawares by a patient who presents with established ventil-obvious, but presumably for a prolonged period of time the cause of increasing breathlessness atory failure.Not only are such patients at considerable risk of death, but the difficult was not appreciated.Until a secure diagnosis of diaphragm weakness is made, breathlessness question of whether to institute ventilatory support has to be addressed as a matter of urgency is likely to be attributed to other factors such as cardiac disease or pulmonary fibrosis, both whereas all concerned, including the patient, would much prefer to take decisions on this easily possible in patients treated for malignant disease with radiotherapy and chemotherapy.issue in a more thoughtful and proactive way.As always, when we have made appropriate As an everyday part of clinical practice, respiratory physicians assess breathless patients measurements and know exactly what the situation is, it becomes much easier to practise and conclude that the symptom is due to airways obstruction, obesity, pulmonary oedema, high quality clinical medicine.The report by Rigg and colleagues 5 is again etc, often in combination because we carefully set about the task of assessing the contribution one of considerable interest, demonstrating that right phrenic nerve damage may be a far of each of the components.Similarly, we can Department of accurately assess diaphragm strength 3 and from rare event in patients being treated for Thoracic Medicine, therefore the contribution of diaphragm weak-malignant disease with repeated courses of King's College School of Medicine ness to breathlessness, but in practice we sel-cytotoxic drugs delivered through a right Hickand Dentistry, dom do so.Most patients with mild through to man line.Thus, we now have yet another well Bessemer Road, moderately severe weakness are undiagnosed.documented cause of diaphragm dysfunction London SE5 9PJ, UK