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Clinical Neurophysiology : Official... Feb 2018In studies of phrenic nerve (PN) conduction in amyotrophic lateral sclerosis (ALS) both motor response amplitude and latency have been reported as abnormal. However,...
OBJECTIVE
In studies of phrenic nerve (PN) conduction in amyotrophic lateral sclerosis (ALS) both motor response amplitude and latency have been reported as abnormal. However, correlation with diaphragm motor unit loss, and with diaphragmatic function has not been fully evaluated.
METHODS
We studied 83 patients with ALS, and 21 patients referred with clinically suspected phrenic nerve lesions whose studies were normal. PN responses elicited by percutaneous electrical stimulation in the neck were recorded using superficial electrodes placed at the surface markings of the diaphragm on the chest wall, and a concentric needle electrode inserted into the diaphragmatic costal fibres. Electromyography of diaphragm was performed to analyse motor unit morphology and recruitment.
RESULTS
The 21 controls and 83 ALS patients were matched for age. In controls, the only significant correlation between surface and needle recording was for negative-peak amplitude (p = 0.03). In ALS patients, amplitudes and negative-peak area were highly correlated (p < 0.001), as were PN motor latencies (p = 0.002). Forced vital capacity (FVC) was highly correlated with both amplitude (p < 0.001) and PN latency (p < 0.02), whichever electrode was used. PN amplitude recording with needle electrode was consistent with EMG findings in the diaphragm.
CONCLUSION
In ALS, PN motor amplitude/area and latency measurements recorded by surface electrodes are highly correlated with needle EMG findings in the diaphragm. CMAP amplitude/area measurements showed high correlation with FVC.
SIGNIFICANCE
In ALS, amplitude/area of the motor PN response, recorded by surface or needle electrodes, correlates with dysfunction of the diaphragm.
Topics: Action Potentials; Adult; Aged; Amyotrophic Lateral Sclerosis; Diaphragm; Electric Stimulation; Electromyography; Female; Humans; Male; Middle Aged; Neural Conduction; Phrenic Nerve; Retrospective Studies; Young Adult
PubMed: 29288990
DOI: 10.1016/j.clinph.2017.11.019 -
Respiratory Physiology & Neurobiology Apr 2023We hypothesized that activation of phrenic afferents induces diaphragm motor plasticity. In anesthetized and spontaneously breathing rats we delivered 40 Hz, low...
We hypothesized that activation of phrenic afferents induces diaphragm motor plasticity. In anesthetized and spontaneously breathing rats we delivered 40 Hz, low threshold (twitch and 1.5X twitch threshold), inspiratory-triggered stimulation to the left hemidiaphragm for 30 min to activate ipsilateral phrenic afferents. Diaphragm amplitude ipsilateral and contralateral to stimulation were increased for 60 min following both currents compared to time controls not receiving stimulation. Diaphragm stimulation was repeated in laminectomy controls or following a unilateral C3-C6 dorsal rhizotomy to eliminate phrenic afferent volleys. Laminectomy controls expressed neuromuscular plasticity post-stimulation. In contrast, ipsilateral and contralateral diaphragm amplitude following dorsal rhizotomy was lower than laminectomy controls and no different than time controls, suggesting diaphragm motor plasticity was not induced post-rhizotomy. Our results indicate that diaphragm stimulation induces a novel form of plasticity in the phrenic motor system which requires phrenic afferent activation. Respiratory motor plasticity elicited by diaphragm stimulation may have value as a therapeutic strategy to improve diaphragm output in neuromuscular conditions.
Topics: Rats; Animals; Diaphragm; Thorax; Respiration; Phrenic Nerve; Electric Stimulation
PubMed: 36642318
DOI: 10.1016/j.resp.2023.104014 -
The Journal of Hand Surgery Sep 2023Nerve transfer is the gold standard to restore shoulder abduction in acute brachial plexus injuries. The aim of this study was to compare the phrenic nerve (Ph) to the...
PURPOSE
Nerve transfer is the gold standard to restore shoulder abduction in acute brachial plexus injuries. The aim of this study was to compare the phrenic nerve (Ph) to the spinal accessory nerve (XI) as the donor nerve for this purpose.
METHODS
A retrospective chart review was performed on 136 patients with acute brachial plexus injuries who received a nerve transfer of the shoulder with either the Ph (94 patients) or XI (42 patients). Each group was divided into 3 subgroups based on the recipient nerve. The maximum degree of shoulder abduction was recorded after 2 years of postoperative follow-up. A generalized estimating equation model was performed to examine the variables affecting shoulder abduction over time.
RESULTS
The maximum degrees of shoulder abduction achieved were 61.9° ± 38.7° in patients with Ph and 51.1° ± 37.3° in patients with XI. More than M3 shoulder abduction was achieved by 67% of patients with Ph versus 59% of patients with XI. The regression analysis showed that the age at the time of surgery correlated more with the functional outcome over time than the choice of donor nerve.
CONCLUSIONS
In multiple root brachial plexus injuries, the Ph exhibited similar outcomes to the XI for shoulder abduction. Our routine exploration of the supraclavicular plexus exposes the Ph conveniently for nerve transfer. The phrenic nerve should be considered as an alternative when the XI is not available or is reserved for secondary reconstruction.
TYPE OF STUDY/LEVEL OF EVIDENCE
Therapeutic IV.
Topics: Adult; Humans; Shoulder; Nerve Transfer; Phrenic Nerve; Brachial Plexus Neuropathies; Retrospective Studies; Brachial Plexus; Accessory Nerve; Range of Motion, Articular
PubMed: 35610117
DOI: 10.1016/j.jhsa.2022.03.004 -
Journal of Neurophysiology Sep 2021Plasticity is a hallmark of the respiratory neural control system. Phrenic long-term facilitation (pLTF) is one form of respiratory plasticity characterized by...
Plasticity is a hallmark of the respiratory neural control system. Phrenic long-term facilitation (pLTF) is one form of respiratory plasticity characterized by persistent increases in phrenic nerve activity following acute intermittent hypoxia (AIH). Although there is evidence that key steps in the cellular pathway giving rise to pLTF are localized within phrenic motor neurons (PMNs), the impact of AIH on the strength of breathing-related synaptic inputs to PMNs remains unclear. Furthermore, the functional impact of AIH is enhanced by repeated/daily exposure to AIH (dAIH). Here, we explored the effects of AIH versus 2 wk of dAIH preconditioning on spontaneous and evoked phrenic responses in anesthetized, paralyzed, and mechanically ventilated rats. Evoked phrenic potentials were elicited by respiratory cycle-triggered lateral funiculus stimulation at the C2 spinal level delivered before and 60 min post-AIH (or the equivalent in time controls). Charge-balanced biphasic pulses (100 μs/phase) of progressively increasing intensity (100-700 μA) were delivered during the inspiratory and expiratory phases of the respiratory cycle. Although robust pLTF (∼60% from baseline) was observed after a single exposure to moderate AIH (3 × 5 min; 5-min intervals), there was no effect on evoked phrenic responses, contrary to our initial hypothesis. However, in rats preconditioned with dAIH, baseline phrenic nerve activity and evoked responses were increased, suggesting that repeated exposure to AIH enhances functional synaptic strength when assessed using this technique. The impact of daily AIH preconditioning on synaptic inputs to PMNs raises interesting questions that require further exploration. Two weeks of daily acute intermittent hypoxia (dAIH) preconditioning enhanced stimulus-evoked phrenic responses to lateral funiculus stimulation (targeting respiratory bulbospinal projection to phrenic motor neurons). Furthermore, dAIH preconditioning enhanced baseline phrenic motor output responses to maximal chemoreflex activation in intact rats.
Topics: Animals; Evoked Potentials; Hypoxia; Male; Motor Neurons; Neuronal Plasticity; Phrenic Nerve; Rats; Rats, Sprague-Dawley
PubMed: 34260289
DOI: 10.1152/jn.00112.2021 -
Acta Neurochirurgica Mar 2021Exploration and grafting of the brachial plexus remains the gold standard for post-ganglionic brachial plexus injuries that present within an acceptable time frame from...
BACKGROUND
Exploration and grafting of the brachial plexus remains the gold standard for post-ganglionic brachial plexus injuries that present within an acceptable time frame from injury. The most common nerves available for grafting include C5 and C6. During the surgical exposure of C5 and C6, the phrenic nerve is anatomically anterior to the cervical spinal nerves, making it vulnerable to injury while performing the dissection and nerve stump to graft coaptation. We describe a novel technique that protects the phrenic nerve from injury during supraclavicular brachial plexus exposure and grafting of C5 or upper trunk ruptures or neuromas in-continuity.
METHODS
A 4-step technique is illustrated: (1) The normal anatomic relationships of the phrenic nerve anterior to C5 is displayed in the face of the traumatic scarring. (2) The C5 spinal nerve stump is then transposed from its anatomic position posterior to the phrenic nerve to an anterior position. (3) The C5 stump is then moved medially for retrograde neurolysis of C5 from its phrenic nerve contribution. The graft coaptation to C5 is performed in this medial position, which minimizes retraction of the phrenic nerve. (4) The normal anatomic relationship of the phrenic nerve and the C5 nerve graft is restored.
RESULTS
We have been routinely relocating the C5 spinal nerve stump around the phrenic nerve for the past 10 years. We have experienced no adverse respiratory events.
CONCLUSION
This technique facilitates surgical exposure and prevents iatrogenic injury on the phrenic nerve during nerve reconstruction.
Topics: Brachial Plexus; Brachial Plexus Neuropathies; Humans; Iatrogenic Disease; Nerve Transfer; Neurosurgical Procedures; Peripheral Nerve Injuries; Phrenic Nerve; Plastic Surgery Procedures
PubMed: 33507373
DOI: 10.1007/s00701-021-04713-6 -
Journal of Cancer Research and... Dec 2022This study aimed to analyze the cases of phrenic nerve injury caused by the percutaneous microwave ablation of lung tumors conducted at our center and to explore the...
OBJECTIVE
This study aimed to analyze the cases of phrenic nerve injury caused by the percutaneous microwave ablation of lung tumors conducted at our center and to explore the risk factors.
MATERIALS AND METHODS
The data of 455 patients who underwent the percutaneous microwave ablation of lung tumors at the Department of Interventional Radiology, First Affiliated Hospital of Fujian Medical University from July 2017 to October 2021, were retrospectively analyzed. The cases of phrenic nerve injury after the percutaneous ablation were reported to analyze the risk factors involved, such as the shortest distance between tumor margin and phrenic nerve, tumor size, and ablation energy. The groups were divided based on the shortest distance between the tumor edge and the phrenic nerve into group 1, d ≤ l cm; group 2, 1 < d ≤2 cm; and group 3, d >2 cm. Lesions with a distance ≤2 cm were compared in terms of tumor size and ablation energy.
RESULTS
Among the 455 patients included in this study, 348 had primary lung cancer, and 107 had oligometastatic cancer. A total of 579 lesions were detected, with maximum diameter of 1.27 ± 0.55 cm, and the ablation energy was 9,000 (4,800-72,000) J. Six patients developed phrenic nerve injury, with an incidence of 1.32%. For these six patients, the shortest distance from the lesion edge to the phrenic nerve was 0.75 ± 0.48 cm, and the ablation energy was 10,500 (8,400-34,650) J. There were statistically significant differences in phrenic nerve injury among groups 1, 2, and 3 (P < 0.05). In patients with a distance (d) ≤ 2 cm, there were no significant differences in tumor diameter and energy between the phrenic nerve injury group and the non-injury group (P = 0.80; P = 0.41). In five out of six patients, the diaphragm level completely recovered to the pre-procedure state, and the recovery time of the phrenic nerve was 9.60 ± 5.60 months. Another one was re-examined 11 months after the procedure, and the level of the diaphragm on the affected side had partially recovered.
CONCLUSIONS
Phrenic nerve injury is a rare but not negligible complication of thermal ablation and is more likely to occur in lesions with a distance ≤2 cm from the phrenic nerve.
Topics: Humans; Catheter Ablation; Phrenic Nerve; Retrospective Studies; Microwaves; Lung Neoplasms; Treatment Outcome
PubMed: 36647962
DOI: 10.4103/jcrt.jcrt_1254_22 -
Journal of Neurophysiology Jul 2019In aging Fischer 344 rats, phrenic motor neuron loss, neuromuscular junction abnormalities, and diaphragm muscle (DIAm) sarcopenia are present by 24 mo of age, with...
In aging Fischer 344 rats, phrenic motor neuron loss, neuromuscular junction abnormalities, and diaphragm muscle (DIAm) sarcopenia are present by 24 mo of age, with larger fast-twitch fatigue-intermediate (type FInt) and fast-twitch fatigable (type FF) motor units particularly vulnerable. We hypothesize that in old rats, DIAm neuromuscular transmission deficits are specific to type FInt and/or FF units. In phrenic nerve/DIAm preparations from rats at 6 and 24 mo of age, the phrenic nerve was supramaximally stimulated at 10, 40, or 75 Hz. Every 15 s, the DIAm was directly stimulated, and the difference in forces evoked by nerve and muscle stimulation was used to estimate neuromuscular transmission failure. Neuromuscular transmission failure in the DIAm was observed at each stimulation frequency. In the initial stimulus trains, the forces evoked by phrenic nerve stimulation at 40 and 75 Hz were significantly less than those evoked by direct muscle stimulation, and this difference was markedly greater in 24-mo-old rats. During repetitive nerve stimulation, neuromuscular transmission failure at 40 and 75 Hz worsened to a greater extent in 24-mo-old rats compared with younger animals. Because type IIx and/or IIb DIAm fibers (type FInt and/or FF motor units) display greater susceptibility to neuromuscular transmission failure at higher frequencies of stimulation, these data suggest that the age-related loss of larger phrenic motor neurons impacts nerve conduction to muscle at higher frequencies and may contribute to DIAm sarcopenia in old rats. Diaphragm muscle (DIAm) sarcopenia, phrenic motor neuron loss, and perturbations of neuromuscular junctions (NMJs) are well described in aged rodents and selectively affect FInt and FF motor units. Less attention has been paid to the motor unit-specific aspects of nerve-muscle conduction. In old rats, increased neuromuscular transmission failure occurred at stimulation frequencies where FInt and FF motor units exhibit conduction failures, along with decreased apposition of pre- and postsynaptic domains of DIAm NMJs of these units.
Topics: Aging; Animals; Diaphragm; Female; Male; Motor Neurons; Muscle Fatigue; Muscle Fibers, Fast-Twitch; Neuromuscular Junction; Phrenic Nerve; Rats; Rats, Inbred F344; Synaptic Potentials
PubMed: 31042426
DOI: 10.1152/jn.00061.2019 -
Annals of Plastic Surgery Feb 2021In brachial plexus injuries, useful recovery of arm function has been documented in most patients after phrenic nerve transfer after variable follow-up durations, but...
INTRODUCTION
In brachial plexus injuries, useful recovery of arm function has been documented in most patients after phrenic nerve transfer after variable follow-up durations, but there is not much information about long-term functional outcomes. In addition, there is still some concern that respiratory complications might become manifest with aging. The aim of this study was to report the outcome of phrenic nerve transfer after a minimum follow-up of 5 years.
PATIENTS AND METHODS
Twenty-six patients were reviewed and evaluated clinically. Age at surgery averaged 25.2 years and follow-up averaged 9.15 years.
RESULTS
Shoulder abduction and external rotation achieved by transfer of phrenic to axillary nerve (or posterior division of upper trunk), combined with spinal accessory to suprascapular nerve transfer, were better than that achieved by transfer of phrenic to suprascapular nerve, combined with grafting the posterior division of upper trunk from C5, 52.3 and 45.5 degrees versus 47.5 and 39.4 degrees, respectively. There was no difference in abduction when the phrenic nerve was transferred directly to the posterior division of upper trunk or to the axillary nerve using nerve graft. Elbow flexion (≥M3 MRC) was achieved in 5 (83.3%) of 6 cases. Elbow extension M4 MRC or greater was achieved in 4 (66.6%) of 6 cases. All patients, including those who exceeded the age of 45 years and those who had concomitant intercostal nerve transfer, continued to have no respiratory symptoms.
CONCLUSIONS
The long-term follow-up confirms the safety and effectiveness and of phrenic nerve transfer for functional restoration of shoulder and elbow functions in brachial plexus avulsion injuries.
Topics: Accessory Nerve; Brachial Plexus; Brachial Plexus Neuropathies; Humans; Middle Aged; Nerve Transfer; Phrenic Nerve; Range of Motion, Articular; Recovery of Function; Treatment Outcome
PubMed: 33346562
DOI: 10.1097/SAP.0000000000002611 -
World Neurosurgery Apr 2016Phrenic neurofibromas are a rare pathologic entity, with 9 cases described in the English literature. They may occur in conjunction with or independently of... (Review)
Review
BACKGROUND
Phrenic neurofibromas are a rare pathologic entity, with 9 cases described in the English literature. They may occur in conjunction with or independently of neurofibromatosis type 1. Phrenic neurofibromas pose distinct therapeutic challenges compared with the more common phrenic schwannoma. We describe here a 12-year-old boy with neurofibroma of the left phrenic nerve presenting as dextroposition of the heart after paralysis of the left hemidiaphragm allowed herniation of abdominal contents into the left hemithorax and displaced the heart.
METHOD
Surgical resection of the tumor followed by diaphragmatic plication was performed to assess its degree of malignancy, reduce abdominal herniation, and improve lung capacity.
RESULTS
The operation markedly improved his hemidiaphragmatic elevation.
CONCLUSIONS
The spectrum of management options ranges from conservative surveillance to open thoracic surgery. Functional preservation of the phrenic nerve is technically challenging, and although phrenic neurofibromas often present with absent function that cannot be recovered, surgical intervention can be fruitful in restoring lung capacity through diaphragmatic reconstruction.
Topics: Child; Humans; Male; Neurofibroma; Neurosurgical Procedures; Peripheral Nervous System Neoplasms; Phrenic Nerve; Rare Diseases; Respiratory Insufficiency; Treatment Outcome
PubMed: 26746336
DOI: 10.1016/j.wneu.2015.12.076 -
Child's Nervous System : ChNS :... Jun 2016Case reports, case series and case control studies have looked at the use of phrenic nerve stimulators in the setting of high spinal cord injuries and central... (Review)
Review
Evaluating the evidence: is phrenic nerve stimulation a safe and effective tool for decreasing ventilator dependence in patients with high cervical spinal cord injuries and central hypoventilation?
INTRODUCTION
Case reports, case series and case control studies have looked at the use of phrenic nerve stimulators in the setting of high spinal cord injuries and central hypoventilation syndromes dating back to the 1980s. We evaluated the evidence related to this topic by performing a systematic review of the published literature.
METHODS
Search terms "phrenic nerve stimulation," "phrenic nerve and spinal cord injury," and "phrenic nerve and central hypoventilation" were entered into standard search engines in a systematic fashion. Articles were reviewed by two study authors and graded independently for class of evidence according to published guidelines. The published evidence was reviewed, and the overall body of evidence was evaluated using the grading of recommendations, assesment, development and evaluations (GRADE) criteria Balshem et al. (J Clin Epidemiol 64:401-406, 2011).
RESULTS
Our initial search yielded 420 articles. There were no class I, II, or III studies. There were 18 relevant class IV articles. There were no discrepancies among article ratings (i.e., kappa = 1). A meta-analysis could not be performed due to the low quality of the available evidence. The overall quality of the body of evidence was evaluated using GRADE criteria and fell within the "very poor" category.
CONCLUSION
The quality of the published literature for phrenic nerve stimulation is poor. Our review of the literature suggests that phrenic nerve stimulation is a safe and effective option for decreasing ventilator dependence in high spinal cord injuries and central hypoventilation; however, we are left with critical questions that provide crucial directions for future studies.
Topics: Cervical Vertebrae; Databases, Bibliographic; Electric Stimulation Therapy; Humans; Hypoventilation; Phrenic Nerve; Spinal Cord Injuries
PubMed: 27083568
DOI: 10.1007/s00381-016-3086-2