Respiratory weakness in neuralgic amyotrophy: report of two cases with phrenic nerve involvement

An isolated affection of the phrenic nerve is a rare feature in patients with neuralgic amyotrophy. We report 1 case each of bilateral and unilateral phrenic neuropathy. The first patient presented a sudden onset of severe respiratory failure without pain. The second patient developed intense pain in the neck and in the right shoulder followed by dyspnea on mild effort and orthopnea. Chest X-rays showed elevation of the diaphragm. Needle electromyography revealed denervation restricted to the diaphragm. The phrenic nerve conduction was within the normal range. The diagnosis of neuralgic amyotrophy may be particularly difficult when the palsy of the phrenic nerve appears without brachial plexus involvement or the typical shoulder pain of acute onset. In our patients, electrophysiological evaluation combined with radiographic studies, ventilatory parameters and biochemical analyses were helpful in establishing the diagnosis.