By Michael Rubin, MD
Professor of Clinical Neurology, Weill Cornell Medical College
Dr. Rubin reports no financial relationships relevant to this field of study.
SYNOPSIS: Isolated phrenic neuropathy is a rare syndrome, often associated with a surgical procedure and diabetes mellitus, and has no proven, effective therapy other than respiratory support.
SOURCE: Podnar S. Idiopathic phrenic neuropathies: A case series and review of the literature. Muscle Nerve 2015:52:986-992.
Diaphragm paralysis may be unilateral or bilateral, the former often asymptomatic, the latter associated with dyspnea that occurs within minutes of assuming the supine position. The clinical presentation includes paradoxical abdominal wall retraction rather than protrusion during inspiration, tachypnea, and rapid shallow breathing. Usually occurring in the context of severe generalized myopathy (inflammatory myositis), neuropathy (Guillain-Barre syndrome), junctionopathy (myasthenia), or neuronopathy (amyotrophic lateral sclerosis), it may occur in isolation as idiopathic phrenic neuropathy (PN). What are the diagnostic findings, therapeutic options, and clinical outcomes of these cases?
Between March 2004 and March 2013, patients with possible PN were recruited by the Division of Neurology, University Medical Center, Ljubljana, Slovenia, undergoing baseline and follow-up history, clinical examination, phrenic nerve conduction studies, diaphragm needle electromyography, respiratory function tests, and imaging studies comprising radiography, computerized tomography, or magnetic resonance imaging of the chest. Using PubMed, literature review of phrenic neuropathy was also performed. Statistical analysis was provided by the Z-test for two proportions, with P < 0.05 considered significant in all areas.
Over the 9-year study period, 10 unilateral and nine bilateral PN patients were identified, comprising 14 men and five women. Men predominated in both groups, and patients with bilateral PN were, on average, 10 years older than those with unilateral PN, presenting with more pronounced respiratory impairment, compared to only a single unilateral PN patient with orthopnea. Scapular winging was reported in a single patient in each group. Unilateral diaphragm elevation was noted in all but one unilateral case, and bilaterally in all but two bilateral cases, where it was reported only on the left. Surgery was the most commonly reported trigger, noted in 20% and 56%, respectively, with diabetes noted in 20%, overall. Hypertension was significantly associated with bilateral PN, while local pain, though more common in unilateral PN, did not reach statistical significance. Phrenic nerve conduction studies and diaphragm electromyography were abnormal in almost all patients. Partial recovery occurred in one unilateral and three bilateral PN patients, and only three unilateral PN patients had complete recovery. No bilateral PN achieved complete recovery. No therapeutic intervention, aside from ventilatory assistance, was offered. Review of the literature corroborated these findings, with the additional note that treatment with intravenous immunoglobulin, methylprednisolone, or valacyclovir was rarely undertaken and, thus, could not be confirmed to be of benefit.
COMMENTARY
In a separate paper, using the same personally accrued database, the author compared PN to published series of neuralgic amyotrophy, noting that of his personal cohort of 19 patients with PN, two (11%) fulfilled criteria for definite neuralgic amyotrophy and 11 (58%) for probable neuralgic amyotrophy.1 Among 58 prior patients, the values were 16% and 48%, respectively. Both PN and neuralgic amyotrophy have a history of precipitating events and male predominance, but the former occur more often in older patients and in diabetics, and are less associated with pain. Absent involvement beyond the diaphragm, PN appears to be immune mediated, with the target antigen possibly specific to the phrenic-nerve.
REFERENCE
- Podnar S. Nosology of idiopathic phrenic neuropathies. J Neurol 2015;262:558-562.
Isolated phrenic neuropathy is a rare syndrome, often associated with a surgical procedure and diabetes mellitus, and has no proven, effective therapy other than respiratory support.
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