Motor neuron disease presenting following prolonged diaphragm paralysis

Diaphragm paralysis may be the presenting feature of motor neuron disease (MND), but signs attributable to the disease are usually found at that time or within the following month.

We present two patients who developed shortness of breath due to isolated diaphragm paralysis, which was confirmed by transdiaphragmatic pressure measurements and cervical magnetic stimulation of the phrenic nerves.

A 65-year-old man developed hypercapnia and progressive muscle wasting 6 years after first symptoms of diaphragm paralysis. Dysarthria, common peroneal nerve palsy on the right and fasciculations of the tongue were found a year later and MND was diagnosed.

A 47-year-old-man first presented with hypercapnic respiratory failure (PaCO₂ 18 kPa) and was intubated and ventilated. He had a 2-year history of dyspnoea and isolated bilateral diaphragm paralysis was confirmed. Other symptoms of MND developed 9 months later.

These cases serve as a reminder that MND may be the underlying diagnosis of diaphragm paralysis and may occasionally take years to develop more typical features.