Phrenic nerve stimulation: The Australian experience

Phrenic nerve stimulation is a technique whereby a nerve stimulator provides electrical stimulation of the phrenic nerve to cause diaphragmatic contraction. The most common indications for this procedure are central alveolar hypoventilation and high quadriplegia. This paper reviews the available data on the 19 patients treated with phrenic nerve stimulation in Australia to date. Of the 19 patients, 14 required pacing due to quadriplegia, one had congenital central hypoventilation syndrome and one had brainstem encephalitis. Information was unavailable for the remaining three patients. Currently, 11 of the pacers are known to be actively implanted, with the total pacing duration ranging from 1 to 21 years (mean 13 years). Eight of the 19 patients had revision surgeries. Four of these were to replace the original I-107 system (which had a 3–5-year life expectancy) with the current I-110 system, which is expected to perform electrically for the patient’s lifetime. Three patients had revisions due to mechanical failure. The remaining patients’ notes were incomplete. These data suggest that phrenic nerve stimulation can be used instead of mechanical ventilators for long-term ongoing respiratory support.     

Ultrasound in the management of iatrogenic spinal accessory nerve palsy at the posterior cervical triangle area

Introduction: The purpose of this study was to evaluate the application of ultrasound in the management of iatrogenic spinal accessory nerve palsy at the posterior cervical triangle area. Methods: In this retrospective study, we compared ultrasonographic results with intraoperative findings in patients with iatrogenic spinal accessory nerve palsy during the time period from 2014 to 2018 at our hospital. Results: Eleven patients were included. Ultrasound detected nerve transections in 9 patients and continuities in 2 patients. The ultrasonographic results were consistent with the intraoperative findings. Furthermore, ultrasound was able to accurately reveal lesion location in 8 of 9 patients with nerve transections. Discussion: Ultrasound provides direct images about nerve lesions contributing to the diagnosis of iatrogenic spinal accessory nerve palsy at the posterior cervical triangle area and also reveals lesion location, assisting in formulating suitable surgical plans preoperatively. We recommend that ultrasound be integrated into the preoperative evaluation. Muscle Nerve 59 :64–69, 2019     

Phrenic Nerve Stimulation for Diaphragm Pacing in a Quadriplegic Patient

Chronic hypoventilation due to injury to the brain stem respiratory center or high cervical cord (above the C3 level) can result in dependence to prolonged mechanical ventilation with tracheostomy, frequent nosocomial pneumonia, and prolonged hospitalization. Diaphragm pacing through electrical stimulation of the phrenic nerve is an established treatment for central hypoventilation syndrome. We performed chronic phrenic nerve stimulation for diaphragm pacing with the spinal cord stimulator for pain control in a quadriplegic patient with central apnea due to complete spinal cord injury at the level of C2 from cervical epidural hematoma. After diaphragmatic pacing, the patient who was completely dependent on the mechanical ventilator could ambulate up to three hours every day without aid of mechanical ventilation during the 12 months of follow-up. Diaphragm pacing through unilateral phrenic nerve stimulation with spinal cord stimulator was feasible in an apneic patient with complete quadriplegia who was completely dependent on mechanical ventilation. Diaphragm pacing with the spinal cord stimulator is feasible and effective for the treatment of the central hypoventilation syndrome.     

Accessory nerve palsy.

After apparently uncomplicated excision of benign lesions in the posterior cervical triangle, two patients had shoulder pain. In one, neck pain and trapezius weakness were not prominent until one month after surgery. Inability to elevate the arm above the horizontal without externally rotating it, and prominent scapular displacement on arm abduction, but not on forward pushing movements, highlighted the trapezius dysfunction and differentiated it from serratus anterior weakness. Spinal accessory nerve lesions should be considered when minor surgical procedures, lymphadenitis, minor trauma, or tumours involved the posterior triangle of the neck.     

Spinal cord localization and characterization of the neurons which give rise to the accessory phrenic nerve in the adult rat

This study describes the spinal cord location and morphology of the neurons which give rise to the accessory phrenic nerve in the rat. The results indicate that the cell bodies of the accessory phrenic nerve are a caudal extension of the phrenic nucleus. These cell bodies are located from cervical spinal cord levels C5 to upper C6 and comprise approximately 11% of the total phrenic motoneuron pool. The substantial phrenic contribution indicates the importance of the accessory phrenic nerve in both experimental and clinical manipulations of diaphragm innervation.     

Conduction studies along the accessory nerve and follow-up of patients with trapezius palsy.

The accessory nerve was stimulated at the posterior triangle of the neck and responses were evoked simultaneously from the upper, middle and lower part of the trapezius muscle. Sixteen patients were investigated, 10 with trapezius palsy following surgical procedures at the posterior cervical triangle, three with a history suggestive of neuralgic amyotrophy and three of unknown origin. On the unaffected side the latency increases 0.16 ms per 10 mm increase in conduction distance corresponding to a conduction velocity of 63 m/s. Evidence is presented that the upper, middle and lower part of the trapezius muscle receive innervation from the accessory nerve. Follow-up of patients showed spontaneous nerve regeneration after complete axonal degeneration. These findings suggest that surgical intervention should be delayed to allow for spontaneous reinnervation. Clinical recovery was incomplete in cases of iatrogenic origin.     

Axillary nerve course and position in the fetal period: An anatomic dissection study for surgical practice

Objectives:

To examine the fetal axillary nerve to reveal and compare its morphometric features within the second and third trimester.

Methods:

This study was conducted at the Anatomy Department, School of Medicine, Mersin University, Mersin, Turkey. Thirty-five fetal shoulders were studied to provide anatomic data and to describe its position with regard to certain landmarks around the shoulder.

Results:

The shortest distance between the axillary nerve and the glenoid labrum was found 2.27 mm and 2.89 mm in the second and third trimester fetuses, respectively. The shortest distances between the anterior and posterior acromial tips and the axillary nerve were also measured and were used with arm length measurements to define the anterior and posterior indexes.

Conclusion:

The indexes show that the distance between the axillary nerve and the anterior/posterior acromial tips are approximately one-fourth of the arm length in both the second and third trimester fetuses. The data presented in this study will be of use to surgeons, particularly to pediatric and orthopedic surgeons who will undertake surgical procedures in the axilla and arm in the newborn or early childhood.There is detailed knowledge regarding the morphological features of the axillary nerve in adults, however, it in the fetal period we encountered no information. Brachial plexus injuries have been reported with a rate of 0.38-2.6 per thousand live births. Shenaq et al1 mentioned that the diagnosis, observation, and therapy are the initial approaches to these injuries, and should be initiated immediately. They also stated that early surgical intervention is essential to maximizing the long-term improvements in selected patients by helping to prevent residual growth deformities and underdevelopment of the affected limbs. The surgical treatment options include the reconstruction and neurotization.2 For the axillary nerve injuries, for example in case of C5-C6 avulsion, in which the upper roots have been avulsed from the spinal cord, and the clinical picture is that of a classic Erb palsy, they preferred to use neurotization technique. In this type of avulsion, the upper roots are not available as donors, and the C7-T1 roots are uninvolved. So, the suprascapular nerve is neurotized by the ipsilateral spinal accessory nerve, and the axillary nerve is neurotized by redundant branches to the triceps to ideally restore shoulder and elbow function. The thoracodorsal or the subscapular branches can also be neurotized to the axillary nerve to provide better shoulder function. Thus, anatomical details of the axillary nerve in fetal period become essential for such operations. We carried out this study to evaluate these parameters regarding the axillary nerve anatomy, which may be helpful to surgeons in certain conditions, such as end-to-side neurorrhaphy in brachial plexus reconstruction, neurotization, proximal humeral fracture repair, and shoulder dislocation treatment in the early childhood.     

Phrenic nerve conduction studies in spinal cord injury: Applications for diaphragmatic pacing

The diaphragm pacing system (DPS) is a minimally invasive alternative to mechanical ventilation in patients with quadriplegia due to cervical myelopathy primarily caused by high cervical spinal cord injury. We evaluated 36 patients, 29 of whom had traumatic spinal cord injury, two who had a history of remote meningitis and demyelinating disease, and five who had cervical myelopathies of unknown etiology. Phrenic nerve conduction studies were performed with simultaneous fluoroscopic observation of diaphragm excursion to assess diaphragm viability. In the preoperative evaluation, diaphragm compound muscle action potentials (CMAPs) were recorded only when the diaphragm moved on fluoroscopy with ipsilateral stimulation. Twenty‐six patients who were determined to have a viable diaphragm underwent DPS. Following DPS the primary outcome was the time (hours per day) that patients were able to pace and stay off the ventilator. Of 26 implanted patients, 96% (25 patients) were able to pace and tolerate being off the ventilator for more than 4 h per day. This study demonstrates that the presence of a diaphragm CMAP is associated with diaphragm movement observed by fluoroscopy in cervical myelopathy. In addition, DPS can help patients with cervical spinal cord injury to breathe unassisted by a ventilator. Muscle Nerve 38: 1546–1552, 2008     

Evaluation of nerve transfer options for treating total brachial plexus avulsion injury: a retrospective study of 73 participants

Despite recent great progress in diagnosis and microsurgical repair,the prognosis in total brachial plexus-avulsion injury remains unfavorable.Insufficient number of donors and unreasonable use of donor nerves might be key factors.To identify an optimal treatment strategy for this condition,we conducted a retrospective review.Seventy-three patients with total brachial plexus avulsion injury were followed up for an average of 7.3 years.Our analysis demonstrated no significant difference in elbow-flexion recovery between phrenic nerve-transfer(25cn(17order function was attempted through anterior accessory nerve(27 cases),posterior accessory nerve(10 cases),intercostal nerve(5 cases),or accessory+intercostal nerve transfer(31 cases).Accessory nerve+intercostal nerve transfer was the most effective method.A significantlyfor elbow flexion,accessory nerve+intercostal nerve transfer for shoulder function,intercostal nerves transfer for elbow extension,entire     

Diaphragmatic pacing by electrical stimulation of the phrenic nerve--a case report

A four-year-old boy had traffic accident and was transferred to our hospital with cardiorespiratory arrest, on March 24, 1986. After resuscitation, quadriplegia and apnea were sustained. Computed tomography (CT) scan on the day of admission only demonstrated subarachnoid hemorrhage and plain roentgenograms of the skull and cervical spine showed no abnormalities. He opened his eyes to verbal order one week later, but apnea and quadriplegia sustained. CT scan obtained on that day demonstrated no abnormalities but roentgenogram of the cervical spine showed atlanto-axial dislocation. On May 26, 1986, he was treated with densectomy through transoral approach. Furthermore, on June 19, he underwent laminectomy of the atlas, partial craniectomy of the occipital bone, and posterior fusion with iliac bone graft. However, apnea continued, and bilateral diaphragmatic pacemaker (Avery Laboratory Inc.) was planed: On Sept. 18, platinum and silicone rubber electrodes were surgically implanted on the both phrenic nerves at the cervical portion. Each electrode was connected by lead wire and connector to a radio-frequency receiver which was implanted in a subcutaneous abdominal pocket. An external transmitter supplied electrical power and information of the stimulation to the implanted receiver by radiofrequency across the skin. Pacing time was gradually prolonged and continuous pacing for four hours could be successfully gained by March, 1987. Pneumonia once occurred in the course of gradual prolongation of the pacing time. The ideal candidates for diaphragmatic pacing are patients with normal phrenic nerves, diaphragm, and lungs.(ABSTRACT TRUNCATED AT 250 WORDS)     

Localization of the spinal accessory motoneurons in the cervical cord in connection with the phrenic nucleus: an HRP study in cats

The localization of the spinal accessory motoneurons (SAMNs) that innervate the accessory respiratory muscles, the sternocleidomastoid (SCM) and trapezius (TP) muscles, was identified in the cat using the horseradish peroxidase (HRP) method. In the cases of HRP bathing of the transected spinal accessory nerve (SAN), HRP-labeled motoneurons were observed ipsilaterally from the C1 to the rostral C6 segments of the spinal cord. Labeled neurons were located principally in the medial and central regions of the dorsomedial cell column of the ventral horn in the C1 segment, in the lateral region of the ventrolateral cell column in the C2-C4 segments, between the ventrolateral and ventromedial cell columns in the C5 segment and in the lateral region of the ventromedial cell column in the C6 segment. In the cases of HRP injection into either SCM or TP muscles, labeled SCM motoneurons were found in the C1-C3 segments of the spinal cord and labeled TP motoneurons were chiefly localized more caudally within the spinal accessory nucleus. The present study revealed that, in the C5 and C6 segments, the SAMNs have a very similar topographic localization to the phrenic nucleus in the ventral horn. This finding implicated the functional linkage of the SAMNs with the phrenic motoneurons in particular types of respiration.     

Intratumoral hemorrhage due to hemangioblastoma arising from a cervical nerve root--a case report.

We describe a case of a 70 year old man suffering from sudden weakness of the left foot. Preoperative neuroimaging examinations showed an oval mass 2 cm in maximal diameter with intratumoral hemorrhage at the seventh cervical vertebra. The mass was supplied by the right lateral thoracocervical artery and was drained to the anterior spinal vein. The intraoperative findings showed the hard reddish tumor was not attached to the pia and the posterior root of the fifth cervical nerve was totally encased by the tumor. A histopathological examination revealed that hemangioblastoma encasing the posterior nerve root totally, so that the tumor was thought to arise from it. Unusual presentation of the neuroimaging examinations is described.     

Subcortical somatosensory evoked potentials after median nerve and posterior tibial nerve stimulation in high cervical cord compression of achondroplasia

Children with achondroplasia may have high cervical myelopathy from stenosis of the cranio-cervical junction resulting in neurological disability and an increased rate of sudden death. To detect myelopathy we recorded somatosensory evoked potentials after median nerve (MN) and posterior tibial nerve (PTN) stimulation in 77 patients with achondroplasia aged 0.3–17.8 years (mean 2.7 years). In addition to the conventional technique of recording the cortical components and the central conduction time (CCT) we employed non-cephalic and mastoid reference electrodes to record the subcortical waveforms N13b and P13 (MN-SEP) as well as P30 (PTN-SEP), respectively, which are generated near the cranio-cervical junction. The findings were related to the MRI results. Thirty-four patients had abnormal MRI findings including spinal cord compression (n = 28) and/or myelomalacia (n = 24) at or below the cranio-cervical junction. The sensitivity of the MN-SEPs was 0.74 including all abnormal upper cervical cord MRI findings (specificity 0.98), and the sensitivity was 0.79 (specificity 0.92) for cervical cord compression, respectively. The sensitivity of the PTN-SEPs was 0.52 (specificity 0.93) for all abnormal MRI findings and 0.59 (specificity 0.92) for cervical cord compression. The subcortical SEPs N13b and P13 as well as P30 were more sensitive than the conventional recordings. The MN-SEPs, notably the subcortical tracings, are useful for the detection of cervical myelopathy in children with achondroplasia. The PTN-SEPs are less sensitive. However, the tibial nerve SEPs might contribute additional information from the lumbar or thoracic spinal cord, which was, however, not tested in this study.     

Intratumoral hemorrhage due to hemangioblastoma arising from a cervical nerve root—a case report

We describe a case of a 70 year old man suffering from sudden weakness of the left foot. Preoperative neuroimaging examinations showed an oval mass 2 cm in maximal diameter with intratumoral hemorrhage at the seventh cervical vertebra. The mass was supplied by the right lateral thoracocervical artery and was drained to the anterior spinal vein. The intraoperative findings showed the hard reddish tumor was not attached to the pia and the posterior root of the fifth cervical nerve was totally encased by the tumor. A histopathological examination revealed that hemangioblastoma encasing the posterior nerve root totally, so that the tumor was thought to arise from it. Unusual presentation of the neuroimaging examinations is described.     

Restoration of function in the paralyzed diaphragm

The possibility of restoring function to the partially denervated diaphragm by anastomosing the distal stump of the transected phrenic nerve to the proximal stump of the transected anterior branch of the homolateral vagus nerve was examined in two cats and two dogs. Structural and functional observations revealed restoration of continuity across the anastomosis site after survival times ranging from 6 to 9 months. Restoration of function does not imply re-establishment of spontaneous contraction but rather reconstitution of a nerve pathway which permits the propagation of an artificially induced impulse. The ultimate objective of this study is to enable restoration of diaphragmatic function to be made in patients suffering from quadriplegia due to midcervical (C3–C5) spinal cord damage even if it entails attachment of a type of pacemaker to the proximal component of the reconstituted nerve pathway.     

The role of cervical afferent nerve fiber inhibition of the crossed phrenic phenomenon

High cervical spinal cord hemisection produces a permanent paralysis of the ipsilateral hemidiaphragm. In many species, function is restored to this paretic hemidiaphragm if the contralateral hemidiaphragm is paralyzed by transecting the phrenic nerve. This response is termed the “crossed phrenic phenomenon.” The present study determines the long-term effects on diaphragmatic function after anesthetization or crushing the contralateral phrenic nerve, or after cutting its dorsal roots in rats subjected to a high cervical spinal cord hemisection. Dorsal root transection was the only procedure which resulted in a partial functional recovery of the hemidiaphragm paralyzed by the spinal cord hemisection without a loss of function in the contralateral hemidiaphragm. The results suggest that afferent nerve fibers in the contralateral phrenic nerve may normally inhibit the functional expression of the crossed phrenic pathway, although the precise mechanism for this inhibition is not yet known.     

Stretch-induced spinal accessory nerve palsy

Left spinal accessory nerve palsy occurred in a young man when he quickly turned his head to the right while his shoulders were pulled down by heavy hand-held objects. Electrophysiologic studies demonstrated partial axonotmesis of the spinal accessory nerve branches innervating the sternocleidomastoid and upper and middle trapezius and complete axonotmesis of spinal accessory branches to the lower trapezius. There was a separate, although functionally minor, cervical plexus innervation of the lower trapezius.     

Heterotopic neurons in human spinal nerve roots: what is their clinical significance?

Summary The significance of heterotopic nerve cells in human spinal nerve roots was studied. Heterotopia was a consistent finding in 230 routine necropsy series (neuropathologically normal) and 16 spinal cord malformation cases, the incidence ranging between 2.1% and 10.9%. It was more frequently found in the cervical posterior roots than in the anterior roots or in other segmental levels. The heterotopia was not increased in dysraphic anomalies. Aberrant sensory nerve cells in the posterior roots and aberrant motor cells in the anterior roots were morphologically ascertained. The clinical significance of the sensory function of the heterotopia in the anterior roots is discussed and compared with previous experimental data.     

Unilateral winged scapula: Clinical and electrodiagnostic experience with 128 cases,with special attention to long thoracic nerve palsy

Introduction: In this study we report a large series of patients with unilateral winged scapula (WS), with special attention to long thoracic nerve (LTN) palsy. Methods: Clinical and electrodiagnostic data were collected from 128 patients over a 25‐year period. Results: Causes of unilateral WS were LTN palsy (n = 70), spinal accessory nerve (SAN) palsy (n = 39), both LTN and SAN palsy (n = 5), facioscapulohumeral dystrophy (FSH) (n = 5), orthopedic causes (n = 11), voluntary WS (n = 6), and no definite cause (n = 2). LTN palsy was related to neuralgic amyotrophy (NA) in 61 patients and involved the right side in 62 patients. Discussion: Clinical data allow for identifying 2 main clinical patterns for LTN and SAN palsy. Electrodiagnostic examination should consider bilateral nerve conduction studies of the LTN and SAN, and needle electromyography of their target muscles. LTN palsy is the most frequent cause of unilateral WS and is usually related to NA. Voluntary WS and FSH must be considered in young patients. Muscle Nerve 57 : 913–920, 2018     

Neuropathologic observations in congenital phrenic nerve palsy

A right phrenic nerve palsy with severe respiratory and feeding difficulties throughout the patient's 2 1/2 years of survival was found at autopsy to relate to grossly complete atrophy of the muscle of the right diaphragm. An oblique fibrotic scar transected the right phrenic nerve at the level of the brachial plexus. There was marked reduction of the number of anterior motor neurons in the right central portion of cervical segments 2, 3, and 4. The lesion in the phrenic nerve is what would be expected following stretching during delivery.