Bilateral isolated phrenic neuropathy causing painless bilateral diaphragmatic paralysis:

Isolated diaphragm weakness and the diagnostic value of phrenic nerve stimulation

Acute onset, atraumatic, bilateral diaphragm paralysis due to isolated bilateral phrenic neuropathy is uncommon. Respiratory physicians should be alert to this disorder because it is associated with considerable morbidity and diagnosis is often delayed. These case reports highlight important aspects of the presentation, investigations and management of this disorder.

Bilateral phrenic neuropathy responsive to intravenous immunoglobulin treatment

The aetiology of phrenic neuropathy is often unknown, but immune mechanisms may play a role. In a typical case of bilateral phrenic neuropathy with paradoxical breathing (video), an inflammatory pathogenesis was suggested by prolonged distal latency of phrenic nerve compound muscle action potentials in nerve conduction studies and a clear-cut albumin-cytologic dissociation. This encouraged us to treat the patient with a standard dose of intravenous immunoglobulin. After obtaining a strong improvement at spirometry, we repeated the second cycle of intravenous immunoglobulin and observed normalization of symptoms within few weeks and no relapse after 3 years. This case suggests that lumbar puncture should be performed in the acute phase of phrenic neuropathies to detect potential responders to immunomodulatory treatment.

Nosology of idiopathic phrenic neuropathies

Phrenic neuropathies (PN) are an important cause of dyspnoea, orthopnoea and hypercapnic respiratory failure. However, there is no agreement on the nosology of this disorder. The aim of this cohort study was to analyze the author's and published PN patients and compare them with other immune-mediated focal neuropathies to determine the most appropriate nomenclature and classification of the disorder. All patients with PN referred to the author from March 2004 to March 2013 were included. In addition, to identify previously published patients with PN, a PubMed search was done. The demographic and clinical characteristics of both series were then compared with the published series of neuralgic amyotrophy (NA) patients. Of 19 PN patients from the author's series, 11 % fulfilled the criteria for definite and 58 % for probable NA; while in 58 previous patients, the values were 16 and 48 %, respectively. PN and NA both have a male preponderance and a frequent history of preceding events, but PN occur in an older population and more often in diabetics, are less commonly associated with pain, and have a less complete recovery. Although demonstrating some similarities with NA, the high proportion of isolated (particularly bilateral) PN point to a probable immune-mediated attack against some phrenic nerve-specific antigen with occasional spill-over to neighboring nerves. As a consequence, idiopathic PN seems to be more appropriately regarded as a distinct entity within the spectrum of immune-mediated focal neuropathies rather than as a variant of NA.

Novel sonomicrometry of ex vivo diaphragm after phrenic nerve injury: Role of matrix metalloproteinases

Extracellular matrix (ECM) proteins and their proteolytic enzymes, matrix metalloproteinases (MMPs), implicate in neuromuscular junctions (NMJs) function during development. However, their pathophysiological mechanisms in the diaphragm remain obscure, because a well-characterized ex vivo experimental system has still been lacking. In the study, we aim to develop a novel ex vivo method of sonomicrometry and evaluate validity of the method with a mouse diaphragm twitch after phrenic nerve injury. In an ex vivo experiment using phrenic nerve-injured mice, diaphragm twitch during electrical pulse stimulation of phrenic nerve was transiently suppressed on day 1. Recombinant MMPs administered in recording solution exerted dose-responsive suppression on the diaphragm twitch in normal mice tissue. Furthermore, gelatinolytic and immunoblot experiments were performed to evaluate MMPs' involvement and NMJs' insults. After nerve injury, (1) in vivo levels of MMPs were transiently upregulated at day 1 and (2) expressions of ECM proteins, agrin (nicotinic acetylcholine receptor stabilizer) and laminin, were transiently reduced at day 1 in the diaphragm. These alterations were cancelled by preinjection of the MMP inhibitor. In conclusion, MMPs hamper NMJ synaptic function in association with the impairment of ECM milieu. Our novel experimental method using ex vivo sonomicrometry is necessary for examining the molecular pathophysiolgy for the dysfunction of NMJs in the diaphragm.

Brachial neuritis with bilateral diaphragmatic paralysis following herpes zoster: a case report

We present a case of supine respiratory failure due to a bilateral diaphragmatic paralysis associated with brachial neuritis secondary to thoracic herpes zoster. Fluoroscopy in both the standing and supine positions revealed bilateral diaphragmatic paralysis accentuated in the supine position. To our knowledge, this is the first case of thoracic herpes zoster associated with brachial neuritis and bilateral diaphragmatic paralysis.