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Medicina (Kaunas, Lithuania) Sep 2023Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease that affects both the upper and lower motor neurons in the nervous system, causing muscle...
Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease that affects both the upper and lower motor neurons in the nervous system, causing muscle weakness and severe disability. The progressive course of the disease reduces the functional capacity of the affected patients, limits daily activities, and leads to complete dependence on caregivers, ultimately resulting in a fatal outcome. Respiratory dysfunction mostly occurs later in the disease and is associated with a worse prognosis. Forty-six participants were included in our study, with 23 patients in the ALS group and 23 individuals in the control group. The ultrasound examination of the phrenic nerve (PN) was performed by two authors using a high-resolution "Philips EPIQ 7" ultrasound machine with a linear 4-18 MHz transducer. Our study revealed that the phrenic nerve is significantly smaller on both sides in ALS patients compared to the control group ( < 0.001). Only one significant study on PN ultrasound in ALS, conducted in Japan, also showed significant results ( < 0.00001). These small studies are particularly promising, as they suggest that ultrasound findings could serve as an additional diagnostic tool for ALS.
Topics: Humans; Amyotrophic Lateral Sclerosis; Phrenic Nerve; Neurodegenerative Diseases; Prognosis; Muscle Weakness
PubMed: 37893463
DOI: 10.3390/medicina59101745 -
World Neurosurgery May 2022Traumatic brachial plexus injuries are devastating lesions, and neurotization is an usually elected surgical therapy. The phrenic nerve has been harvested as a motor...
BACKGROUND
Traumatic brachial plexus injuries are devastating lesions, and neurotization is an usually elected surgical therapy. The phrenic nerve has been harvested as a motor fibers donor in brachial plexus neurotization, showing great results in terms of motor reinnervation. Unfortunately, these interventions lack solid evidence regarding long-term safety and possible late respiratory function sequelae, raising crescent concerns after the COVID-19 pandemic onset and possibly resulting in reduced propensity to use this technique. The study of the distal anatomy of the phrenic nerves may lead to a better understanding of their branching patterns, and thus the proposition of surgical approaches that better preserve patient respiratory function.
METHODS
Twenty-one phrenic nerves in 10 formalized cadavers were scrutinized. Prediaphragmatic branching patterns were inspected through analysis of the distance between the piercing site of the nerve at the diaphragm and the cardiac structures, number of divisions, and length from the point where the main trunk emits its branches to the diaphragm.
RESULTS
The main trunk of the right phrenic nerve reaches the diaphragm near the inferior vena cava and branches into 3 major divisions. The left phrenic nerve reaches the diaphragm in variable locations near the heart, branching into 2-5 main trunks. Moreover, we noticed a specimen presenting 2 ipsilateral parallel phrenic nerves.
CONCLUSIONS
The right phrenic nerve presented greater consistency concerning insertion site, terminal branching point distance to this muscle, and number of rami than the left phrenic nerve.
Topics: COVID-19; Diaphragm; Humans; Nerve Transfer; Pandemics; Phrenic Nerve
PubMed: 35077891
DOI: 10.1016/j.wneu.2022.01.061 -
Respiratory Physiology & Neurobiology Dec 2022HF-SCS is a novel technique of inspiratory muscle activation which results in coincident activation of the diaphragm and inspiratory intercostal muscles via spinal cord...
OBJECTIVE
HF-SCS is a novel technique of inspiratory muscle activation which results in coincident activation of the diaphragm and inspiratory intercostal muscles via spinal cord pathways and has the potential to provide respiratory support in ventilator dependent persons with spinal cord injury. The purpose of the present study was to examine the phrenic-to-intercostal reflex during HF-SCS.
METHODS
In 5 anesthetized and C2 spinalized dogs, electrical stimulation was applied via a stimulating electrode located on the ventral surface of the upper thoracic spinal cord at the T2 level. Fine wire recording electrodes were used to assess single motor unit (SMU) activity of the left and right external intercostal muscles (EI) in the 3rd interspace before and after sequential left and right phrenicotomy.
RESULTS
Mean control peak firing frequency of the right EI and left EI was 11.4 ± 0.3 Hz and 10.6 ± 0.3 Hz respectively. Following unilateral right phrenic nerve section, mean SMU peak firing frequency of right EI (ipsilateral to the section) was significantly greater when compared to control (15.9 ± 0.5 Hz vs 11.4 ± 0.3 Hz; p = 0.01). Mean SMU peak firing frequency of the contralateral left EI remained unchanged (10.2 ± 0.3 Hz vs 10.6 ± 0.3 Hz, p = 0.40). Subsequent, section of the left phrenic nerve resulted in significantly higher mean SMU peak firing frequency of the left EI (16.2 ± 0.5 Hz vs 10.2 ± 0.3 Hz) when compared to before section p = 0.01). Contralateral, right EI peak firing frequency was not different if compared to before left phrenic nerve section (16.9 ± 0.4 Hz vs. 15.9 ± 0.5 Hz; p = 0.14).
CONCLUSION
This study demonstrates that during HF-SCS: 1) unilateral diaphragmatic afferents reflexly inhibit motor activity to the ipsilateral EI muscles, 2) the neural circuitry mediating the phrenic-to-intercostal reflex is preserved at a spinal level and does not require supraspinal input and 3) unilateral compensatory increases were observed in EI muscle activation following ipsilateral diaphragm paralysis.
Topics: Animals; Diaphragm; Dogs; Electric Stimulation; Intercostal Muscles; Phrenic Nerve; Reflex; Spinal Cord; Spinal Cord Injuries; Spinal Cord Stimulation
PubMed: 36064141
DOI: 10.1016/j.resp.2022.103962 -
Practical Radiation Oncology 2023Incremental use of high-dose radiation therapy (RT) with SABR in thoracic tumors has led to identification of many unusual toxicities (chest wall pain, rib fractures,...
Incremental use of high-dose radiation therapy (RT) with SABR in thoracic tumors has led to identification of many unusual toxicities (chest wall pain, rib fractures, vascular perforation, brachial plexopathy) and consequently additional organs at risk (OARs; chest wall, ribs, bronchial wall, carotid artery, brachial plexus). Phrenic nerve is another structure that may be affected at any point during its long course from origin until end, although symptomatic toxicities have been reported rarely in the setting of reirradiation, large-volume irradiation such as mantle field, or SABR. We undertook a prospective study to describe the delineation of phrenic nerve course on RT planning computed tomography scan as an OAR. An anonymized RT planning computed tomography scan of neck and thorax (1.5-mm slice thickness, intravenous contrast) was used for the study. Radiology textbooks and publications were reviewed, and the course was delineated with the help of 2 radiologists and 6 radiation oncologists well versed with thoracic radiologic anatomy. A step-by-step description in the form of a pictorial essay is given. The adjacent structures including cervical vertebrae, cervical and mediastinal vessels, lungs, heart, and so on were identified, and the course of phrenic nerve on either side is described in relation to these structures. Delineation of the phrenic nerve as an OAR is challenging but feasible. We recommend routine delineation of the phrenic nerve as an OAR during thoracic RT. Although specific dose constraints are not known yet, unnecessary dose to the same during RT planning should be minimized.
Topics: Humans; Phrenic Nerve; Prospective Studies; Lung Neoplasms; Lung; Thorax
PubMed: 35977668
DOI: 10.1016/j.prro.2022.08.002 -
Journal of Clinical Neuroscience :... Jul 2022Patients with central apnoea may use electro ventilation, provided their phrenic nerves and diaphragm muscles are normal. A tendency towards better survival has been...
Patients with central apnoea may use electro ventilation, provided their phrenic nerves and diaphragm muscles are normal. A tendency towards better survival has been found, and both an improved quality of life and facilitated nursing have been claimed with electro ventilation compared to mechanical ventilation. The high investment for the device may form a hurdle for fund providers like our hospital administration board. We, therefore, from our first patient onwards, collected clinically meaningful data in a special register of all patients using electro ventilation and their controls on mechanical ventilation. Since 1988 172 patients left our institution dependent on a respiratory device. Of these, all 48 patients with preserved phrenic nerves chose phrenic nerve stimulation. A patient on mechanical ventilation who agreed to participate was chosen as a control (n = 44). All patients were seen at least once a year. 90 patients suffered high tetraplegia, and 2 suffered central apnoea for other reasons. There is a tendency towards better survival, and there is a lower frequency of decubital ulcers (0.02) and respiratory tract infections (p0.000) with electro than with mechanical ventilation. The frequency of respiratory infections turned out to be a better measure of the quality of respiratory care than survival. The resulting decrease in the need for airway nursing, and the reduced incidence of respiratory infections repaid the high investment in electro ventilation within one year in our setting. Informed patients prefer electro to mechanical ventilation; fund providers might also agree with this preference.
Topics: Electric Stimulation Therapy; Humans; Phrenic Nerve; Prospective Studies; Quality of Life; Respiration, Artificial; Respiratory Tract Infections; Sleep Apnea, Central
PubMed: 35512426
DOI: 10.1016/j.jocn.2022.04.037 -
Cirugia Espanola Feb 2019In surgical procedures of the supraclavicular and lateral cervical regions, as well as in cardiac and mediastinal surgeries, diaphragm function can be compromised by the...
In surgical procedures of the supraclavicular and lateral cervical regions, as well as in cardiac and mediastinal surgeries, diaphragm function can be compromised by the risk of injury to the phrenic nerve and/or the C4 root. There are few publications that treat the intraoperative stimulation of these nerve structures to evaluate their functionality and, to our knowledge, until now it has not been hypothesized about whether it is possible to reduce the injury rates, which reach 26% in some cardiac surgery studies. We describe the technique used for the neurophysiological monitoring of the phrenic nerve. Also, its usefulness and advantages over other techniques are discussed. We conclude that, with the increasing incorporation in recent years of intraoperative neurophysiological monitoring, its application to the phrenic nerve is possible in procedures with a risk of injury and, thus, the reduction of iatrogenic injury rates may be feasible.
Topics: Humans; Intraoperative Neurophysiological Monitoring; Phrenic Nerve
PubMed: 30580833
DOI: 10.1016/j.ciresp.2018.11.002 -
Journal of Neurophysiology Dec 2021Phrenic afferents project to brainstem areas responsible for cardiorespiratory control and the mid-cervical spinal cord containing the phrenic motor nucleus. Our purpose...
Phrenic afferents project to brainstem areas responsible for cardiorespiratory control and the mid-cervical spinal cord containing the phrenic motor nucleus. Our purpose was to quantify the impact of small- and large-diameter phrenic afferent activation on phrenic motor output. Anesthetized and ventilated rats received unilateral phrenic nerve stimulation while contralateral phrenic motor output and blood pressure were recorded. Twelve currents of 40-Hz inspiratory-triggered stimulation were delivered (20 s on, 5 min off) to establish current response curves. Stimulation pulse width was varied to preferentially activate large-diameter phrenic afferents (narrow pulse width) and recruit small-diameter fibers (wide pulse width). Contralateral phrenic amplitude was elevated immediately poststimulation at currents above 35 µA for wide and 70 µA for narrow pulse stimulation when compared with animals not receiving stimulation (time controls). Wide pulse width stimulation also increased phrenic burst frequency at currents ≥35 µA, caused a transient decrease in mean arterial blood pressure at currents ≥50 µA, and resulted in a small change in heart rate at 300 µA. Unilateral dorsal rhizotomy attenuated stimulation-induced cardiorespiratory responses indicating that phrenic afferent activation is required. Additional analyses compared phrenic motor amplitude with output before stimulation and showed that episodic activation of phrenic afferents with narrow pulse stimulation can induce short-term plasticity. We conclude that the activation of phrenic afferents ) enhances contralateral phrenic motor amplitude when large-diameter afferents are activated, and ) when small-diameter fibers are recruited, the amplitude response is associated with changes in burst frequency and cardiovascular parameters. Acute, inspiratory-triggered stimulation of phrenic afferents increases contralateral phrenic motor amplitude in adult rats. When small-diameter afferents are recruited, the amplitude response is accompanied by an increase in phrenic burst frequency, a transient decrease in mean arterial blood pressure, and a slight increase in heart rate. Repeated episodes of large-diameter phrenic afferent activation may also be capable of inducing short-term plasticity.
Topics: Afferent Pathways; Animals; Arterial Pressure; Blood Gas Analysis; Electrophysiological Phenomena; Female; Heart Rate; Hemodynamics; Inhalation; Male; Neuronal Plasticity; Neurons, Afferent; Phrenic Nerve; Rats; Rats, Sprague-Dawley
PubMed: 34788165
DOI: 10.1152/jn.00433.2021 -
Muscle & Nerve Nov 2020
Topics: Healthy Volunteers; Humans; Neural Conduction; Phrenic Nerve
PubMed: 32841402
DOI: 10.1002/mus.27050 -
Respiratory Care May 2023Mechanical ventilation is widely used in ICU patients as a lifesaving intervention. Diaphragmatic atrophy and thinning occur from lack of contractions of the diaphragm...
BACKGROUND
Mechanical ventilation is widely used in ICU patients as a lifesaving intervention. Diaphragmatic atrophy and thinning occur from lack of contractions of the diaphragm during mechanical ventilation. It may prolong weaning and increase the risk of respiratory complications. Noninvasive electromagnetic stimulation of the phrenic nerves may ameliorate the atrophy seen with ventilation. The objective of this study was to show that noninvasive repetitive electromagnetic stimulation is safe, feasible, and effective to stimulate the phrenic nerves in both awake individuals and anesthetized patients.
METHODS
A single-center study with 10 subjects overall, 5 awake volunteers and 5 anesthetized subjects. We used a prototype electromagnetic, noninvasive, simultaneous bilateral phrenic nerve stimulation device in both groups. In the awake volunteers, we assessed time-to-first capture of the phrenic nerves and safety measures, such as pain, discomfort, dental paresthesia, and skin irritation. In the anesthetized subjects, time-to-first capture as well as tidal volumes and airway pressures at 20%, 30%, and 40% stimulation intensity were assessed.
RESULTS
Diaphragmatic capture was achieved in all the subjects within a median (range) of 1 min (1 min to 9 min 21 s) for the awake subjects and 30 s (20 s to 1 min 15 s) for the anesthetized subjects. There were no adverse or severe adverse events in either group, nor any dental paresthesia, skin irritation, or subjective pain in the stimulated area. Tidal volumes increased in all the subjects in response to simultaneous bilateral phrenic nerve stimulation and increased gradually with increasing stimulation intensity. Airway pressures corresponded to spontaneous breathing of ∼2 cm HO.
CONCLUSIONS
Noninvasive phrenic nerve stimulation can be safely performed in awake and anesthetized individuals. It was feasible and effective in stimulating the diaphragm by induction of physiologic and scalable tidal volumes with minimum positive airway pressures.
Topics: Humans; Phrenic Nerve; Feasibility Studies; Paresthesia; Respiration, Artificial; Diaphragm; Pain
PubMed: 36878642
DOI: 10.4187/respcare.10568 -
Clinical Neurophysiology : Official... May 2020Phrenic nerve conduction study is a marker of hypoventilation in amyotrophic lateral sclerosis. We aimed to evaluate its intra-rater reliability in healthy subjects and...
OBJECTIVE
Phrenic nerve conduction study is a marker of hypoventilation in amyotrophic lateral sclerosis. We aimed to evaluate its intra-rater reliability in healthy subjects and in a cohort of Primary Lateral Sclerosis (PLS) patients.
METHODS
Eighteen healthy subjects and 16 PLS patients were included. All subjects underwent three phrenic nerve conduction evaluations (time interval: 1 week for healthy controls; 1 year for PLS patients). We analyzed intra-rater reliability for five parameters of the diaphragmatic motor response: latency; negative-peak duration, area and amplitude; peak-to-peak amplitude.
RESULTS
Healthy subjects showed excellent inter-test reliability for most parameters (coefficients of variation <10%). In PLS patients coefficients of variation resulted <10% for latency and peak-to-peak amplitude, <20% for remaining parameters. Inter-test reliability was excellent for latency and peak-to-peak amplitude [intra-class correlation coefficient (ICC) > 0.9] and good for negative-peak amplitude and area (ICC 0.75 ≥ 0.9); duration was not reliable (ICC = 0.383). Negative peak and peak-to-peak amplitude had the least random error (respectively ±0.136 mV and ± 0.177 mV). All parameters showed homoscedasticity (R2 < 0.1).
CONCLUSIONS
Intra-rater reliability is high for phrenic nerve study, especially for latency, peak-to-peak and negative-peak amplitude.
SIGNIFICANCE
Phrenic nerve conduction study is a reliable method to monitor respiratory function.
Topics: Adult; Electromyography; Female; Healthy Volunteers; Humans; Male; Middle Aged; Motor Neuron Disease; Neural Conduction; Phrenic Nerve; Reproducibility of Results
PubMed: 32193165
DOI: 10.1016/j.clinph.2020.02.010