Contralateral motor rootlets and ipsilateral nerve transfers in brachial plexus reconstruction

Object. The goal of this study was to evaluate outcomes in patients with brachial plexus avulsion injuries who underwent contralateral motor rootlet and ipsilateral nerve transfers to reconstruct shoulder abduction/external rotation and elbow flexion.

Methods. Within 6 months after the injury, 24 patients with a mean age of 21 years underwent surgery in which the contralateral C-7 motor rootlet was transferred to the suprascapular nerve by using sural nerve grafts. The biceps motor branch or the musculocutaneous nerve was repaired either by an ulnar nerve fascicular transfer or by transfer of the 11th cranial nerve or the phrenic nerve. The mean recovery in abduction was 90° and 92° in external rotation. In cases of total palsy, only two patients recovered external rotation and in those cases mean external rotation was 70°. Elbow flexion was achieved in all cases. In cases of ulnar nerve transfer, the muscle scores were M5 in one patient, M4 in six patients, and M3+ in five patients. Elbow flexion repair involving the use of the 11th cranial nerve resulted in a score of M3+ in five patients and M4 in two patients. After surgery involving the phrenic nerve, two patients received a score of M3+ and two a score of M4. Results were clearly better in patients with partial lesions and in those who were shorter than 170 cm (p < 0.01). The length of the graft used in motor rootlet transfers affected only the recovery of external rotation. There was no permanent injury at the donor sites.

Conclusions. Motor rootlet transfer represents a reliable and potent neurotizer that allows the reconstruction of abduction and external rotation in partial injuries.

Laryngeal abductor muscle reinnervation in a pig model

OBJECTIVE

To develop a large animal model for studies of laryngeal abductor reinnervation.

MATERIAL AND METHODS

Six minipigs underwent unilateral anastomosis of the phrenic nerve-abductor branch of the recurrent laryngeal nerve (RLN). Polyhydroxybutyrate (PHB) conduits were used for repair. At each of 30, 60 and 120 days, 2 animals underwent video laryngeal endoscopy (VLE) and were then killed. VLE was also performed in the 120-day pair at 60 days. Nerve-conduit-nerve-muscle samples were fixed for light and immunofluorescence (pan-neurofilaments, S-100) microscopy. Laryngeal muscles were harvested (myosin heavy chain analysis).

RESULTS

VLE showed recovery of abductor function in 1 animal at 60 days and in 1 at 120 days. Haematoxylin-eosin staining demonstrated a complex inflammatory response. Eosinophil recruitment was observed. Stepwise regeneration and reorganization of the distal nerve between 30 and 120 days was observed with pan-NF staining. The mean minimum diameter in the reinnervated posterior crico-arytenoids tended to increase for up to 120 days.

CONCLUSIONS

Anastomosis of the phrenic nerve-abductor branch of the RLN with a PHB conduit in a pig can result in functional and histological recovery within 2-4 months and appears to at least sustain abductor muscle fibre morphology. Recovery occurs despite a complex inflammatory response, which may be an essential part of healing rather than inhibitory.

Surgical options for complete resectable lung cancer invading the phrenic nerve

We describe a 58-year-old male diagnosed with a tumour of the left lung, which on subsequent thoracotomy proved to be invading the phrenic nerve. The clinical and spirometric outcome of a lobectomy, which resulted in a postoperative ipsilateral hemidiaphragmatic paralysis, versus the alternative surgical option of a pneumonectomy is discussed.

[Changes of energy metabolism in canine respiratory muscles after phrenic nerve transection]

OBJECTIVE

To examine the changes in energy metabolism in the respiratory muscles of canines with unilateral phrenic nerve transection using high-performance liquid chromatography (HPLC).

METHODS

The left phrenic nerve of 8 canines was transected and the contents of adenine nucleotide in respiratory muscles were determined by HPLC before and 1 and 2 months after the operation.

RESULTS

In the intercostal muscles, ATP contents remained almost unchanged during the entire course of the observation, while ADP content was elevated 2 months after the operation as compared with that measured before and 1 month after the operation (P<0.05). One month postoperatively, the content of total adenylic acid (TAN) decreased to the lowest point, but the difference between the measurements was not statistically significant; also at 1 month after the operation, the content of adenylate energy charge (AEC) was the lowest, with statistically significant difference from the measurements before and 2 months after the operation (P<0.05). In the diaphragm, the contents of ATP, ADP, TAN and AEC 2 months postoperatively were 9.05+/-12.70, 2.99+/-2.57, 14.72+/-13.98, 0.57+/-0.29, significantly different from the levels at the other two time points (P<0.05).

CONCLUSION

After unilateral phrenic nerve transection in canines, the energy metabolism of the diaphragm declines significantly, whereas that of the intercostal muscle can be compensated to some extent.

Selective Transfer of the C7 Nerve Root: An Experimental Study

The authors present selective C7 nerve root transfer in a rat model. The musculocutaneous nerve was neurotized by various portions of ipsilateral C7. The latent period and maximum amplitude of evoked motor action potential of the biceps, number of regenerating myelinated nerve fibers, cross-sectional area and wet weight of the biceps, and twitch and tetanic tensions of the biceps were measured at four postoperative intervals. In the early postoperative period (1 and 2 months), nerve regeneration in neurotization with the posterior division or the anterior division of C7 was significantly better than that with the anterolateral fascicles of the anterior division or the phrenic nerve. As the postoperative interval prolonged, the parameters of nerve regeneration in the latter two groups approximated those in the former two groups. This indicated that there were enough regenerating nerve fibers in the anterolateral fascicles of the anterior division and a promising potential for nerve regeneration. The clinical significance of the results lies in the design of selective C7 transfer which, using the anterolateral fascicles of the anterior division, could preserve the function of the muscles innervated by the posterior division to the greatest extent, and provide sufficient donor outflow as well. It is therefore a new option for C7 transfer.

A fuzzy-classifier system to distinguish respiratory patterns evolving after diaphragm paralysis in the cat

We applied the fuzzy "k-nearest neighbor" (k-NN) classifier of the pattern recognition theory to fathom the abnormal way of breathing resulting from diaphragm paralysis and to distinguish the dominant component, tidal or frequency, of the breathing pattern on which ventilatory compensation relies in such a pathological state. We addressed this issue in the experimental model of diaphragm paralysis as a result of bilateral phrenicotomy in anesthetized, spontaneously breathing cats. Of several variables recorded, we selected two features, minute ventilation and arterial CO(2) tension, that were used for the k-NN analysis. The results demonstrate that the ability to maintain ventilation critically depended on the increase in frequency of breathing. Other breathing pattern strategies were ineffective. The k-NN evaluation with the two selected features discerned the prevailing pattern of breathing with sufficient probability. Such an evaluation may be a useful tool in predicting the development of compensatory strategies in disordered patterns of breathing.

Nerve transfers for severe brachial plexus injuries: a review

Nerve transfer procedures are increasingly performed for repair of severe brachial plexus injury (BPI), in which the proximal spinal nerve roots have been avulsed from the spinal cord. The procedure essentially involves the coaption of a proximal foreign nerve to the distal denervated nerve to reinnervate the latter by the donated axons. Cortical plasticity appears to play an important physiological role in the functional recovery of the reinnervated muscles. The author describes the general principles governing the successful use of nerve transfers. One major goal of this literature review is to provide a comprehensive survey on the numerous intra- and extraplexal nerves that have been used in transfer procedures to repair the brachial plexus. Thus, an emphasis on clinical outcomes is provided throughout. The second major goal is to discuss the role of candidate nerves for transfers in the surgical management of the common severe brachial plexus problems encountered clinically. It is hoped that this review will provide the treating surgeon with an updated list, indications, and expected outcomes involving nerve transfer operations for severe BPIs.

[Surgery for diaphragmatic palsy]

Diaphragmatic palsy leads to a permanent ascension of one or both hemi-diaphragms with highly variable functional impact. The underlying mechanisms can be divided into two main categories: neurological or muscular disorder leading to peripheral dysfunction; defective or non-transmitted central command causing central dysfunction. A complete morphological and functional work-up is required to determine the circumstances leading to diaphragmatic palsy and the uni- or bilateral nature of the paralysis. The entire phreno-diaphragmatic transmission chain from the cranium to the diaphragmatic muscle must be analyzed to search for a local cause. Function tests are used to examine central command and transmission, function of the phrenic nerve, and the capacity of the diaphragmatic muscle to generate sufficient pressure for efficacious ventilation. Once indirect causes of diaphragmatic ascension (independent of the phreno-diaphragmatic system) have been ruled out, surgery may be proposed for symptomatic, permanent and irreversible diaphragmatic paralysis. A tension procedure may be sufficient in the event of eventration with or without phrenic palsy. For well-selected patients with central paralysis due to supraspinal lesions with intact nerves and muscles, implantation of a phrenic pacemaker may be helpful to eliminate positive pressure mechanical ventilation and restore more physiological respiration.

Phrenic paresis and respiratory insufficiency associated with cervical spondylotic myelopathy

Cervical spondylotic myelopathy is a common disease caused by chronic segmental compression of the spinal cord. Despite the fact that the columns of the nuclei of the phrenic nerve are located between the 3rd and 5th cervical nerve segments, phrenic nerve paresis is not usually clinically significant. We present one case of cervical spondylotic myelopathy with bilateral phrenic paresis in whom magnetic resonance imaging and surgical findings confirmed intrinsic cord disease as being the cause of this syndrome. This case report suggests that one pathophysiology of clinical phrenic nerve paresis may be segmental damage to the anterior horns caused by cervical spondylosis.

Comparative experimental study on treatment outcome of nerve transfer, using selective C7 nerve root vs. phrenic nerve

The treatment outcome of nerve transfer using the C7 nerve root or phrenic nerve was compared in a rat experiment. One hundred and twenty SD rats were divided into two groups, one undergoing phrenic nerve transfer to the musculocutaneous nerve, and the other partial ipsilateral C7 (anteriolateral fascicles of the anterior division) to the musculocutaneous nerve. Neurotization outcomes of the two groups were evaluated by comparing the electrophysiologic, histologic, and myophysiologic changes of the biceps muscle. No significant differences were found between parameters from the phrenic nerve transfer group and those from the ipsilateral C7 nerve transfer group. This indicates that the treatment outcome of selective ipsilateral C7 transfer is comparable to that of phrenic nerve transfer. It is the surgery of choice in treating brachial plexus upper-trunk avulsion accompanied by phrenic nerve injury.

[An study on functioning remobilization of the paralyzed vocal cord by latero-terminal neurorrhaphy in rats]

OBJECTIVE

To investigate the effect and the clinic value of latero-terminal neurorrhaphy to treat vocal cord paralysis.

METHOD

Sixty SD rats were divided into three groups. In the experimental group, the right recurrent laryngeal nerve(RLN) was incised and anastomosed to the right phren nerve by means of latero-terminal neurorrhaphy. The internal nerve of the right RLN was incised and anastomosed to the right ansa cervicals nerve by end-to-end nerve anastomosis. In control group, the right RLN was incised and sutured to the right phren nerve by end-to-end nerve anastomosis. The internal nerve of the right RLN were incised and anastomosed to the right ansa cervicals nerve by end-to-end nerve anastomosis. In normal group rats, the nerves were only exposed. One to three months later, 10 rats from each group were examined for vocal cord movement and nerve regeneration by using fibrolaryngscope and nerve electromyography.

RESULT

One months after operation. This effect of latero-terminal neurorrhaphy had significant difference compared with the control group (P < 0.05). Three months after operation. This effect of latero-terminal neurorrhaphy had not significant difference compared with the control group (P > 0.05).

CONCLUSION

The latero-terminal neurorrhaphy has a similar treatment effect compared with end-to-end nerve anastomosis. This microsurgical technique provides a new method for treating vocal cord paralysis.

[Early microsurgical treatment of upper obstetrical brachial plexus injury]

OBJECTIVE

To search for the operation timing and methods for obstetrical brachial plexus injury (OBPI).

METHODS

Thirty-two children with upper OBPI were treated by microsurgical procedure from October 1997 to April 2001. The average age of patients was 10 months, ranged from 3 months to 24 months; of them, 19 were below 6 months while 13 were over 6 months. Surgical procedure included neurolysis(n = 12), coaptation after resection of the neuroma without function (n = 7), phrenic nerve transfer to anterior cord of upper trunk or musculocutaneous nerve (n = 7) and intercostal nerves transfer to musculocutaneous nerve(n = 6). The children underwent operation with microsurgical technique and 7/0 or 9/0 nylon was used for nerve suture.

RESULTS

Thirty cases were followed up for 21 months postoperatively; the excellent and good rate was 76.7% (23/30). The results of the children under 6 months were better than those over 6 months.

CONCLUSION

The microsurgical operation might be considered at the age of 3-6 month infants who had shown little or no improvement in elbow flexion. Neurolysis and nerve coaptation are superior to neurotization. The appropriate procedure should be selected according to the findings of exploration.

Reversed latissimus dorsi muscle flap for repair of recurrent congenital diaphragmatic hernia

BACKGROUND/PURPOSE

Neonates with large congenital diaphragmatic hernias (CDH) require prosthetic patch closure of the defect because of the paucity of native diaphragmatic tissue. As the child grows, patch separation can occur necessitating reoperation. Use of vascularized autologous tissue may decrease the incidence of reherniation as tissue incorporation and growth may be improved. The authors report our early experience using a local muscle advancement flap with microneural anastomosis for those children in whom reherniation develops after prosthetic patch placement.

METHODS

Seven patients with CDH (6 left and 1 right) whose synthetic diaphragmatic patch separated from the chest wall resulting in a clinically significant recurrent hernia were followed up with prospectively. After dissecting the ipsilateral latissimus dorsi off the chest wall and dividing the thoracodorsal neurovascular bundle (based on its lumbar blood supply), the synthetic patch was removed via an eighth intercostal incision. The muscle flap was placed into the hemithorax through the bed of the tenth rib and sutured in place over a Vicryl mesh scaffold. The thoracodorsal nerve was anastomosed to the phrenic nerve. Functional analysis of the flap was performed in 4 patients.

RESULTS

Age at placement of the muscle graft ranged from 2 months to 48 months (median, 24 months). There has been no evidence of reherniation after placement of the muscle graft. Long-term outcome and functional analysis of the flap was available in 4 patients (mean, 19 months). Two infants had fluoroscopic and sonographic evidence of nonparadoxical neodiaphragmatic motion. In one of these, electromyographic evidence of function was documented with a phrenic nerve conduction velocity of 22 meters per second. The third infant showed no evidence of neodiaphragmatic motion, and the fourth infant had paradoxical motion.

CONCLUSIONS

This is the first direct documentation of phrenic nerve function in an infant with CDH. An innervated reversed latissimus dorsi (RLD) flap reconstruction for recurrent CDH provides an alternative to prosthetic patch repair. This technique offers the advantages of autologous vascularized tissue with potential phrenic nerve innervation and physiologic neodiaphragmatic motion.

The crossed phrenic phenomenon: a model for plasticity in the respiratory pathways following spinal cord injury

Hemisection of the cervical spinal cord rostral to the level of the phrenic nucleus interrupts descending bulbospinal respiratory pathways, which results in a paralysis of the ipsilateral hemidiaphragm. In several mammalian species, functional recovery of the paretic hemidiaphragm can be achieved by transecting the contralateral phrenic nerve. The recovery of the paralyzed hemidiaphragm has been termed the "crossed phrenic phenomenon." The physiological basis for the crossed phrenic phenomenon is as follows: asphyxia induced by spinal hemisection and contralateral phrenicotomy increases central respiratory drive, which activates a latent crossed respiratory pathway. The uninjured, initially latent pathway mediates the hemidiaphragm recovery by descending into the spinal cord contralateral to the hemisection and then crossing the midline of the spinal cord before terminating on phrenic motoneurons ipsilateral and caudal to the hemisection. The purpose of this study is to review work conducted on the crossed phrenic phenomenon and to review closely related studies focusing particularly on the plasticity associated with the response. Because the review deals with recovery of respiratory muscles paralyzed by spinal cord injury, the clinical relevance of the reviewed studies is highlighted.

Intractable hiccup: an odd complication after laparoscopic fundoplication for gastroesophageal reflux disease

Intractable hiccup can be an unbearable circumstance and its treatment is often frustrating. More than 100 causes for hiccup have been described in the literature; the most common cause is gastroesophageal reflux disease (GERD). We report a case of a 31-year-old patient who suffered from intractable hiccup starting 3 weeks after laparoscopic Nissen fundoplication for GERD, a potential surgical complication that has not been described. After frustrating medical treatment, the patient underwent computed tomography and nerve stimulator-guided blockade of vagal and phrenic nerves on each side separately. Hiccup ceased only after blockade of the right phrenic nerve with 4 ml/h l% ropivacaine and relapsed soon after discontinuation. He underwent thoracoscopic right phrenicectomy, which rendered him symptom free for well over 2 months, at the time of this writing.

Diaphragm plication following phrenic nerve injury: a comparison of paediatric and adult patients

BACKGROUND

A study was undertaken to evaluate whether adults differ from children in the indications and outcome of diaphragmatic plication following phrenic nerve injury.

METHODS

A retrospective study was performed of 21 patients, 10 below the age of 5 and 11 older than 37 years. The indication for surgery for all the children was failure to wean from ventilatory support. The indications for surgery in the adult group were ventilator dependency (n=4) and symptomatic dyspnoea (n=7). All patients had at least one imaging study confirming diaphragmatic paralysis. The American Thoracic Society (ATS) dyspnoea scale, pulmonary function tests, and quantitative pulmonary perfusion scans were used as evaluation parameters. At surgery the diaphragm was centrally plicated.

RESULTS

One child died immediately after surgery due to irreversible heart failure and two children died within 2 months of surgery from ongoing complications of their original condition. These three patients were considered as selection failures. Seven children were weaned from ventilatory support within a median of 4 days (range 2-140). Only one of four ventilated adults was successfully weaned. Seven adults who underwent surgery for chronic symptoms had a marked subjective improvement of 2-3 levels in the ATS dyspnoea scale. Pulmonary function studies in the seven symptomatic adults showed a 40% improvement above baseline. Severely asymmetrical perfusion scans reverted to a normal pattern after plication.

CONCLUSIONS

Diaphragmatic plication offers a significant benefit to children with diaphragmatic paralysis and should be performed early to facilitate weaning from mechanical ventilation. While plication is of limited benefit in weaning ventilated adults, it results in significant subjective and objective lifetime improvement in non-ventilated symptomatic adults.

[Reinnervation of the posterior cricoarytenoid muscle by the phrenic nerve for bilateral vocal cord paralysis in humans]

OBJECTIVE

To reestablish the respiratory abduction of the paralyzed vocal cord through reinnervation of the posterior cricoarytenoid(PCA) muscle by the phrenic nerve in humans.

METHODS

In six cases with bilateral recurrent laryngeal nerve paralysis, the phrenic nerve was anastomosed to the anterior branch of recurrent laryngeal nerve, while the adductor branch of recurrent laryngeal nerve was severed and its proximal end was implanted into the PCA muscle belly in one side, for the other side nerve-muscle pedicle technique was used. All cases had been subjected to preoperative and postoperative video laryngoscopy, stroboscopy, electromyography, voice recording and acoustic analysis.

RESULTS

Among the 6 patients, it is observed in five cases' phrenic nerve reinnervation side the inspiratory abducent motion evidently recovered, and the abducent range was from 3 to 5 mm, While only slight abductent motion or no motion could be recorded on the other side reinnervated with nerve-muscle pedicle technique, and the vocal cord excursion on this side was less than 1 mm in all cases. It is because the glottis is broad enough for the patients to have daily activities without short of breath, so all of them were decannulated postoperatively. The reinnervated PCA muscle by the phrenic nerve showed typical inspiratory high frequency discharge with 100-200 ms delay as compared with the other side, indicating the phrenic motoneuron pattern. No long-term diaphragmatic paralysis and lesion of respiratory function was found. All cases' voice was not weakened, and no aspiration occurred.

CONCLUSION

The phrenic reinnervation is feasible clinically for treating vocal cord paralysis, and it is found to be more effective for restoring inspiratory abducent function than the nerve-muscle pedicle technique.

[Applied anatomy for the reinnervation of posterior cricoarytenoid muscle by phrenic nerve for bilateral vocal cord paralysis]

OBJECTIVE

To study the anatomic basis for the anastomosis of phrenic nerve (PN) to the anterior branch of recurrent laryngeal nerve(RLN) for the treatment of the injured bilateral RLN.

METHODS

The origin and the nutritive arteries and the adjacent tissue construction of PNs in 46 cases were studied. The longest utilizable length of PNs and the distance from the root of PN to cricothyroid joint were measured. The sectional area and the number of myelinated fibers of PNs and the anterior branch of RLNs were measured by computer image processing system.

RESULTS

PNs coming from C4 comprised of 93.5%, 95.6% (44/46) of the nutritive arteries came from the ascending carotid artery and got into the cervical segment of PN from its root. The common trunk of PN was very deep, to the external of the common carotid artery and the vertebral vein, and deep to the internal jugular vein and thoracic duct (left), and in the superficies of the subclavian artery and in the deep of the subclavian vein when it was crossing the thoracic entrance. The distance from the root of PN to the level of the subclavian vein and to cricothyroid joint were (7.2 +/- 1.6) cm and (5.5 +/- 1.4) cm, respectively. The former was at least 1.5 cm longer than the latter. The average number of myelinated fibers and the sectional area of the PNs were 2.41 times and 2.15 times as many as those of the anterior branch of RLNs, respectively. The single-fasciculated PNs comprised of about 75.0% (18/24)).

CONCLUSION

Clinically, it may be safe and available for cutting PN off at the level of the subclavian vein. The length of PN is enough for the anastomosis of PN to the anterior branch of RLN.

Mobilization of the phrenic nerve in the thoracic cavity by video-assisted thoracic surgery. Techniques and initial experience

BACKGROUND

The use of video-assisted thoracic surgery (VATS) techniques to mobilize the phrenic nerve in the thoracic cavity for neurotization after brachial plexus injury was studied.

METHODS

From August 1999 to January 2000, 10 men and 1 woman with brachial plexus injury (left side in 5 and right side in 6) joined the study group. Their ages ranged from 20 to 38 years (average, 28 years). Supine after general anesthesia, all the patients had double-lumen trachea cannulas to guarantee complete lung collapse on the operative side. Three port incisions were made to allow introduction of the following: a 10-mm Stryker endoscope through the sixth intercostal space 2 cm medial to the anterior axillary line, one instrument for manipulation in the anterior axillary line of the third intercostal space, and another in the second intercostal space about 2 cm lateral to the parasternal line. The nerve was mobilized with two common long Mixter clamps and some endoscopic instruments by blunt and sharp dissection.

RESULTS

All patients were managed successfully without severe complications. The mean additional length of phrenic nerves by this technique was 16 cm.

CONCLUSIONS

Mobilization of the phrenic nerve by VATS is a safe and minimally invasive method for elongating the nerve for neurotization after brachial plexus injury.

Potential fascial dome made by the upper leaf of the phreno-esophageal membrane

We describe the configuration and size of the artificial fascial dome created in 57 cadavers. This dome protrudes into the thoracic cavity from the esophageal hiatus. This dome was a potential space realized by finger dissection (i.e., a specific but common surgical procedure during surgery of the upper part of the stomach). The vagus nerves penetrated the top of the dome and ran down along the esophagus. The height of the ventral wall of the dome ranged from 10-60 mm, while the dorsal wall was 10-40 mm longer than the ventral one since the dorsal wall attached to the lower, dorsal limb of the esophageal hiatus. Accordingly, the dorsal wall separated the "thoracic" aorta from the "abdominal" esophagus. We considered that the upper leaf of the phreno-esophageal membrane forms the fascial dome, although the lower leaf of the membrane was not identified in this study. According to the results, we proposed a schematic representation of the phreno-esophageal membrane.

Effects of phrenicotomy and exercise on hypoxia-induced changes in phrenic motor output

To investigate models of plasticity in respiratory motor output, we determined the effects of chronic unilateral phrenicotomy and/or exercise on time-dependent responses to episodic hypoxia in the contralateral phrenic nerve. Anesthetized (urethane), ventilated, and vagotomized rats were presented with three, 5-min episodes of isocapnic hypoxia (11% O(2)), separated by 5 min of hyperoxia (50% O(2)). Integrated phrenic (and hypoglossal) nerve discharge were recorded before and during each hypoxic episode, for the first 5 min after the first hypoxic episode, and at 30 and 60 min after the final episode. Of 36 rats, one-half were sedentary while the other one-half had free access to a running wheel; each of these groups was split into three subgroups: 1) unoperated, 2) chronic left phrenicotomy (27-37 days), and 3) sham operated. Neither unilateral phrenicotomy nor running wheel activity influenced the short-term hypoxic phrenic response (during hypoxia) or long-term facilitation (posthypoxia). Posthypoxia frequency decline was exaggerated in phrenicotomized-sedentary rats relative to unoperated-sedentary rats (change in burst frequency = -23+/-4 vs. -11 +/-5 bursts/min, respectively; 5 min posthypoxia; P<0.05), an effect that was eliminated by spontaneous exercise. The results indicate that neither voluntary running nor unilateral phrenicotomy has major effects on time-dependent hypoxic phrenic responses, with the exception of an unexpected effect of phrenicotomy on posthypoxia frequency decline in sedentary rats.

Restoration of shoulder abduction in brachial plexus injury with phrenic nerve transfer

BACKGROUND

Shoulder abduction is one of the most essential functions in reconstruction of the brachial plexus following injury. In the literature there are few reports on phrenic nerve transfer, especially in relation to restoration of shoulder function. The purpose of the present study was to evaluate the clinical effectiveness and safety of phrenic nerve transfer.

METHODS

A study was made of 10 cases of phrenic nerve transfer to the suprascapular nerve.

RESULTS

The average shoulder abduction was 41 degrees (range: 20-60 degrees). The average degree of shoulder abduction in patients with C5 or C6 root avulsions was slightly more than that in the patients with total root avulsions. There was no clinically significant respiratory insufficiency in any patient.

CONCLUSIONS

Phrenic nerve transfer to the suprascapular nerve is an effective, reliable and safe method of shoulder abduction restoration in brachial plexus injury.

The intercostal to phrenic nerve transfer: an effective means of reanimating the diaphragm in patients with high cervical spine injury

Nerve transfers have been well described for the treatment of congenital and traumatic injuries in the brachial plexus and extremities. This series is the first to describe nerve transfers to reanimate the diaphragm in patients confined to long-term positive pressure ventilation because of high cervical spine injury. Patients who have sustained injury to the spinal cord at the C3 to C5 level suffer axonal loss in the phrenic nerve. They can neither propagate a nerve stimulus nor respond to implanted diaphragmatic pacing devices (electrophrenic respiration). Ten nerve transfers were performed in six patients who met these conditions. The procedures used end-to-end anastomoses from the fourth intercostal to the phrenic nerve approximately 5 cm above the diaphragm. A phrenic nerve pacemaker was implanted as part of the procedure and was placed distal to the anastomosis. Each week, the pacemaker was activated to test for diaphragmatic response. Once diaphragm movement was documented, diaphragmatic pacing was instituted. Eight of the 10 transfers have had more than 3 months to allow for axonal regeneration. Of these, all eight achieved successful diaphragmatic pacing (100 percent). The average interval from surgery to diaphragm response to electrical stimulation was 9 months. All patients were able to tolerate diaphragmatic pacing as an alternative to positive pressure ventilation, as judged by end tidal CO2 values, tidal volumes, and patient comfort. Intercostal to phrenic nerve transfer with diaphragmatic pacing is a viable means of liberating patients with high cervical spine injury from long-term mechanical ventilation.

[Hiccup]

Hiccup is defined as involuntary contractions of the diaphragm and the auxiliary respiratory muscles, mostly in irregular series, followed by glottic closure, thereby producing a typical "hiccupping" inspiration. This is a physiologic phenomenon, which already exists in utero. Hiccup is believed to be a gastrointestinal reflex; however, function and the reflex arch are hypothetical. Acute hiccup is distinguished from pathological, chronic hiccup, defined by a duration executing 48 h, or recurrent episodes. Among approximately 100 causes for hiccup, the most common are located in the gastrointestinal tract, with gastro-esophageal reflux as the most important. While the respiratory effect is generally negligible, alkalosis may ensue in tracheotomized patients due to hyperventilation. A stepwise management plan for patients with hiccup is presented. If simple physical maneuvers and causal therapy fail, or causal therapy is impossible, the treatment of choice is medical, with baclofen. Interruption of the reflex arch may be causal therapy or be considered as a last resort.

Determinants of rib motion in flail chest

We have previously developed a canine model of isolated flail chest to assess the effects of this condition on the mechanics of breathing, and these studies have led to the conclusion that the respiratory displacement of the fractured ribs is primarily determined by the fall in pleural pressure (Delta Ppl) and the action of the parasternal intercostal muscles. The present studies were designed to test the validity of this conclusion. A flail was induced in six supine anesthetized animals by fracturing both dorsally and ventrally the second to fifth ribs on the right side of the chest, after which the phrenic nerve roots were bilaterally sectioned in the neck. Sectioning the phrenic nerves caused a 34% decrease in Delta Ppl, associated with a 39% increase in parasternal intercostal inspiratory EMG activity (p < 0.05), and resulted in a marked reduction in the inspiratory inward displacement of the ribs. In three animals, the inward rib displacement was even reversed into a small outward displacement. When the airway was then occluded at end-expiration to increase Delta Ppl during the subsequent inspiration, all animals again showed a clear-cut inward rib displacement. These observations therefore confirm that in dogs with flail chest, the inspiratory displacement of the fractured ribs is set by the balance between the force related to pleural pressure and that generated by the parasternal intercostals. These observations also point to the critical importance of the pattern of inspiratory muscle activation in determining the magnitude of rib cage paradox in such patients.

Reinnervation aspects of laryngeal transplantation

Although restoration of laryngeal function after laryngeal transplantation depends on appropriate reinnervation, non-selective reinnervation procedures result in synkinesis and poor function restoration. This study was performed to test the feasibility of selective reinnervation procedures to restore laryngeal function. Three surgical reinnervation procedures were studied each in a group of ten cats: in group 1 a non-selective procedure in which the recurrent laryngeal nerve (RLN) was cut and reanastomosed; in group 2 selective abductor reinnervation was performed with the phrenic nerve; in group 3 selective abductor reinnervation with the phrenic nerve (PN) was combined with selective adductor reinnervation with the ansa cervicalis. Ten weeks after surgical reinnervation abductor and reflex adductor functions were evaluated with videolaryngoscopy and electromyography. Findings demonstrated that non-selective reinnervation not only gave poor abduction during inspiration but even resulted in paradoxical movement during reflex adduction. Selective abductor reinnervation resulted in good abductor function. Selective adductor reinnervation with the ansa cervicalis brought about muscle tonus in the animals studied but no restoration of reflex adduction. Enhanced activity during respiratory distress gave only slight compromise to the abductor function. In all, selective laryngeal reinnervation with the PN and ansa cervicalis produced good restoration of respiratory laryngeal function. However, deglutition following laryngeal motor and sensory reinnervation with protection of the respiratory tract is probably not sufficient, as in the present group of animals no reflex glottic closure was achieved. More research is required.

Cervical dorsal rhizotomy enhances serotonergic innervation of phrenic motoneurons and serotonin-dependent long-term facilitation of respiratory motor output in rats

We tested the hypothesis that spinal plasticity elicited by chronic bilateral cervical dorsal rhizotomy (C3-C5; CDR) has functional implications for respiratory motor control. Surgery was performed on rats (CDR or sham-operated) 26 d before phrenic motoneurons were retrogradely labeled with cholera toxin. Rats were killed 2 d later, and their spinal cords were harvested and processed to reveal the cholera toxin-labeled phrenic motoneurons and serotonin-immunoreactive terminals. The number of serotonin-immunoreactive terminals within 5 micrometer of labeled phrenic motoneuron soma and primary dendrites increased 2.1-fold after CDR versus sham-operation. Time-dependent phrenic motor responses to hypoxia were compared among CDR, sham-operated, and control rats. Anesthetized, paralyzed, vagotomized, and artificially ventilated rats were exposed to three, 5 min episodes of isocapnic hypoxia (FiO2 = 0.11), separated by 5 min hyperoxic intervals (FiO2 = 0.5). One hour after hypoxia, a long-lasting, serotonin-dependent enhancement of phrenic motor output (long-term facilitation) was observed in both sham and control rats. After CDR, long-term facilitation was 108 and 163% greater than control and sham responses, respectively. Pretreatment of CDR rats with a 5-HT2 receptor antagonist (ketanserin tartrate, 2 mg/kg, i.v.) before episodic hypoxia prevented long-term facilitation and revealed a modest (-28 +/- 13%; p < 0.05) long-lasting depression of phrenic motor output. The results indicate that CDR: (1) increases serotonergic innervation of the phrenic motor nucleus; and (2) augments serotonin-dependent long-term facilitation of phrenic motor output. These results further suggest a form of plasticity based on changes in the capacity for neuromodulation.

Mediastinal lipoblastoma involving the left innominate vein and the left phrenic nerve

Lipoblastoma, a rare tumor of childhood, was first described by Vellois and associates in 1958. The extremities are the most common location for this tumor. Mediastinal lipoblastoma is exceedingly rare, with only four cases reported in the English-language literature. The authors report a case of mediastinal lipoblastoma in a 6-year-old girl, which, in contrast to previously reported cases, presented late in childhood and included sacrifice of the left innominate vein and phrenic nerve for successful resection.

[Study on contractile properties of the posterior cricoarytenoid muscle after delayed reinnervation]

To study date on the contractile properties of posterior cricoarytenoid muscle after delayed reinnervation of different reinnervated methods. Twenty four dogs were reinnervated at 0,4,5,6,10 and 12 month interval following recurrent laryngeal nerve via the phrenic nerve anastomosed to the recurrent laryngeal nerve after cutting the adductor branch and ansa cervicalis-sternothyroid muscle pedicle implanted into the posterior cricoarytenoid muscle. After 6 months, a series of contractions were recorded from each side in twenty living dogs. The results showed that contractile force of reinnervated muscle decreased gradually with the time of denervation, but contractile force of muscle was no significantly difference between reinnervated side of nerve anastomosed group in 4 months after denervated and normal side, and it was significantly difference between nerve anastomosed group and nerve-muscle pedicle implanted group at some time of delayed reinnervation. The contractile time of reinnervated side of two operated groups was similar to that of normal side. The conclusion demonstrated that the contractile properties can indicate exactly reinnervated degree of muscle, and the earlier reinnervation was performed, the better curative effect was.

Post cardiac surgery phrenic nerve palsy: value of plication and potential for recovery

OBJECTIVES

Evaluation of an aggressive policy for the treatment of phrenic nerve palsy (PNP), following cardiac operations, with emphasis on early diaphragmatic plication. Attention was given to the incidence and predisposing factors for PNP and the potential for recovery following plication.

METHODS

From 1 June 1991 to 1 January 1996 we prospectively screened patients for PNP following cardiac surgery. The diagnosis was suspected if difficulty was experienced in weaning the child from the ventilator. If abnormal elevation of the hemidiaphragm was present diaphragmatic plication was performed. Echocardiography was used to assess subsequent return of diaphragmatic function.

RESULTS

Seventeen children (nine boys, eight girls), out of 867 (1.9%) children younger than 16 years of age, undergoing cardiac operations were found to have PNP. The mean age was 66 days (range 1-17 months) with 16 patients below 1 year out of a total of 285 patients (incidence 5.6%) and one patient 17 months old. The incidence following open procedures was 11/190, following closed procedures 2/95 and following reoperation 4/83. PNP was diagnosed from 2 to 44 days (mean 14 days) following surgery. It was present on the right side in seven cases, the left in nine and was bilateral in one patient. Two patients were extubated at the time of diagnosis, one patient could be extubated shortly thereafter. Fourteen children underwent diaphragmatic plication, at a median 5 days post diagnosis. Extubation was possible 1-60 days (mean 4 days) after plication. Mean follow-up was 19 +/- 5 months. Subsequent recovery of diaphragmatic movement was documented in seven (41%) children. Time to recovery following plication was 16 months, without plication 38 months.

CONCLUSION

Prospective screening for PNP revealed an incidence in children younger than 1 year of 6%. Early plication substantially reduces the duration of ventilation, with its associated reduced morbidity and ICU stay.

Functional magnetic stimulation of the respiratory muscles in dogs

This study assessed the ability of functional magnetic stimulation (FMS) to activate the respiratory muscles in dogs. With the animal supine, FMS of the phrenic nerves using a high-speed magnetic stimulator was performed by placing a round magnetic coil (MC) at the carotid triangle. Following hyperventilation-induced apnea, changes in volume (deltaV) and airway pressure (deltaP) against an occluded airway were determined. FMS of the phrenic nerves produced substantial inspired function (deltaV = 373 +/- 20.5 mL and deltaP = -20 +/- 2.0 cm H2O). After bilateral phrenectomies, maximal inspired deltaV (219 +/- 12.2 mL) and deltaP (-10 +/- 1.0 cm H2O) were produced when the MC was placed near the C6-C7 spinous processes, while maximal expired deltaV (-199 +/- 22.5 mL) and deltaP (11 +/- 2.3 cm H2O) were produced following stimulation near the T9-T10 spinous processes. We conclude: (1) FMS of either the phrenic or upper intercostal nerves results in inspired volume production; (2) FMS of the lower intercostal nerves generates expired volume production; and (3) FMS of the respiratory muscles may be a useful noninvasive tool for artificial ventilation and assisted cough in patients with spinal cord injuries or other neurological disorders.

Surgery for invasive primary mediastinal tumors

BACKGROUND

There have been few reports on results after extended radical resection for primary mediastinal tumors invading neighboring organs.

METHODS

A retrospective analysis of 89 patients who underwent total or subtotal resection of a primary mediastinal tumor with resection of at least part of an adjacent structure between 1979 and 1995 was performed. Clinical data were collected from the medical records.

RESULTS

There were 35 invasive thymomas, 12 thymic carcinomas, 17 germ cell tumors, 16 lymphomas, 3 neurogenic tumors, 3 thyroid carcinomas, 2 radiation-induced sarcomas, and 1 mediastinal mesothelioma. The tumor was located in the anterior mediastinum in 74% of patients. Residual masses after chemotherapy were excised in 14 patients with germ cell tumor and 8 with lymphoma. A median sternotomy was the most frequently used approach (79% of patients). Total resection was achieved in 79% and significantly improved survival (p < 0.01). Adjacent resected structures included 38 phrenic nerves, 21 superior venae cavae, 16 upper lobes, and 13 innominate veins, in 5 patients, a pneumonectomy was required. The complication rate was 17% and the mortality rate, 6%. With follow-up available for 86 patients, the overall 5-year survival rate was 69% for patients with thymoma, 42% for patients with thymic carcinoma, 48% for patients with germ cell tumor, and 83% for patients with lymphoma.

CONCLUSIONS

Malignant mediastinal tumors can be safely resected even if they have invaded other mediastinal structures. Complete resection is important to achieve satisfactory long-term survival. A median sternotomy is an excellent approach, and a preoperative diagnosis by biopsy is desirable. Residual masses after chemotherapy for lymphoma or germ cell tumor should be resected. Extensive resection without a preoperative diagnosis is not indicated.

Morphological plasticity induced in the phrenic nucleus following cervical cold block of descending respiratory drive

Morphological plasticity occurs in the phrenic nucleus within hours following an ipsilateral C2 spinal cord hemisection. The plasticity has been associated with the unmasking of a latent respiratory pathway (the crossed phrenic pathway) which allows recovery of the hemidiaphragm paralyzed by the hemisection during a reflex known as the crossed phrenic phenomenon. This study tests if the plasticity is induced by the generalized effects of spinal cord trauma or the more specific effect of interrupting the main descending respiratory drive to phrenic motoneurons. Electron microscopic quantitative morphometric analysis of the phrenic nucleus neuropil was carried out on four Sprague-Dawley rats (200-250 g) sacrificed 4 h following unilateral reversible cold block of the descending bulbospinal respiratory drive at the second cervical segment of the spinal cord (C2). The data from four sham-operated control animals were compared with those of the experimental group. The following morphological alterations were documented in cold block animals compared to controls: (1) a significant increase in the number of multiple synapses (i.e., terminals with synaptic active zones contacting two or more postsynaptic profiles in the same plane of section), (2) a significant increase in the number of dendrodendritic appositions, and (3) a significant increase in the length of symmetric and asymmetric synaptic active zones. The above changes are similar to the changes induced in the phrenic nucleus following C2 hemisection. We conclude therefore, that injury to the spinal cord is not a requirement for this type of morphological plasticity in the phrenic nucleus, but rather the induced changes are activity-dependent and are likely caused by the interruption of the descending bulbospinal respiratory drive to the phrenic nucleus.

Selective resection of the phrenic nerve roots in rabbits. Part I: Cartography of the residual innervation

Partial unilateral diaphragmatic paralysis remains poorly understood. This study evaluates the residual innervation of the diaphragm after selective resection of one or several roots of the right phrenic nerve in rabbits. Forty-seven animals were operated on according to five root resection modalities. Seven animals served as control. Eight weeks after surgery, the different regions of each hemidiaphragm were analyzed. Electromyographic activity was measured during quiet inspiration and the following histomorphometric parameters were studied: mean fiber area, fiber area dispersion, and ratio large diameter over small diameter. The results obtained from the two measurements were similar. When the accessory phrenic nerve was spared, the crural diaphragmatic region was preserved; denervation was encountered in anterior and lateral parts of the hemidiaphragm. When the highest root of the right phrenic nerve was resected, denervation denervation was limited to the sternal region. When resection of the two highest roots was performed, partial denervation was observed in each region, with residual innervation in the posterior hemidiaphragm. When resection of both the lowest roots was performed, denervation was maximal in the costal region; sternal region remained intact. No contralateral innervation was observed. We conclude that in rabbits: 1) resection of a single root of the phrenic nerve preserves consistent residual innervation. 2) somatotopy of the diaphragm innvervation follows an anteroposterior distribution.

The superimposed effects of chronic phrenicotomy and cervical spinal cord hemisection on synaptic cytoarchitecture in the rat phrenic nucleus

The present study was carried out to determine the effects of a combined peripheral phrenicotomy and rostral spinal cord hemisection on the synaptic architecture in the ipsilateral rat phrenic nucleus. Young adult female Sprague-Dawley rats were divided into a hemisection-alone and two hemisection-plus-phrenicotomy (HPP) groups. In all animals, DiI, a fluorescent carbocyanine dye was injected into the left hemidiaphragm to retrogradely label the ipsilateral phrenic motoneurons. In the HPP groups, left intrathoracic phrenicotomies were carried out at 2 and 4 weeks prior to sacrificing. Hemisection-alone animals were not subjected to phrenicotomy. In all animals, a left C2 spinal cord hemisection was performed 24 h prior to death. Quantitative morphometric analysis of the phrenic nucleus showed that the number of synapses contacting phrenic profiles is significantly less in the HPP (2 week) group as compared to the hemisection-alone group, but this number returns to a level not significantly different from the hemisection-alone value in the HPP (4 week) group. The results suggest that the transient change in the number of synapses might contribute to the differential expression of the crossed phrenic phenomenon documented in another group of animals subjected to the same surgical procedures. Furthermore, the different stages of glial reaction induced by phrenicotomy/spinal cord hemisection might underlie the change in synaptic number.

Selective laryngeal reinnervation with separate phrenic and ansa cervicalis nerve transfers

OBJECTIVE

To perform selective reinnervation of the laryngeal abductor and adductor muscle groups after injury to the recurrent laryngeal nerve, recovering laryngeal function without impairment by synkinesis.

DESIGN

Ten cats underwent the surgical procedure. To reinnervate the posterior cricoarytenoid muscle (abductor), a phrenic nerve graft was anastomosed to the main trunk of the recurrent laryngeal nerve. The adductor branch was severed, and the proximal stump was buried in the posterior cricoarytenoid muscle. The sternohyoid branch of the ansa cervicalis was anastomosed to the distal stump to reinnervate the adductor muscle group. After a period of 10 weeks, the laryngeal function was evaluated with videolaryngoscopy and electromyography of the posterior circoarytenoid and vocalis muscles.

RESULTS

Of the 10 cats, 9 could be evaluated. Laryngeal abductor function was comparable with the unaffected side in the 9 cats. During respiratory distress conditions, a minor compromise of the maximal abduction was observed in 5 cats. Phonation was not tested, but spontaneous adduction during expiration was seen in all cats. Reflex closure on ipsilateral, supraglottic, tactile mucosal stimulation was seen in only 2 cats. In each cat, evidence of nerve regeneration and reinnervation of both muscle groups was established with electromyography, electrical stimulation, and histological examination.

CONCLUSIONS

Using this selective reinnervation procedure, good laryngeal function can be achieved in the cat model, which may be applicable in humans. By reinnervation of the vocalis muscle, muscle tonus is achieved, which is expected to improve voice quality. Using this procedure, however, no active reflex closure may be expected.

[Treatment of nerve root avulsion of brachial plexus by nerve transfer]

The results of nerve transposition for root avulsion of brachial plexas in 21 cases were reported. The methods of the nerve transposition were divided into four groups as followings: By transfer of phrenic nerve, accesory nerve, the motor branches of cervical plexus and intercostal nerves in cease; By transfer of phrenic nerve, accessory nerve and the motor branches of cervical plexus in 6 cases; By transfer of phrenic nerve and accessory nerve in 9 cases, and by transfer of phrenic nerve or the motor branches of cervical plexus or intercostal nerve in 5 cases. During operation, in 1 cases variation of the brachial plexus was found. Injury to the subclavian artery occurred in 4 cases and they were repaired, which is good for the blood circulation of the upper arm and nerve regeneration. Nineteen cases were followed up with good results. The overall excellent and good rate was 73.7%. It was considered that transposition of nerve should be a routine operation for the treatment of root avulsion of brachial plexus and the accompanied arterial injury should be repaired at the same time during operation, and the latter would be advantageous to enhance functional recovery of nerve.

The superimposed effects of chronic phrenicotomy and cervical spinal cord hemisection on glial cytoarchitecture in the rat phrenic nucleus

This study was conducted to determine the effects of chronic phrenicotomy on spinal hemisection-induced morphological plasticity occurring in the phrenic nucleus. Young adult rats were divided into a hemisection-alone and two hemisection-plus-phrenicotomy (HPP) groups. HPP animals received a left phrenicotomy two or four weeks prior to sacrificing; whereas hemisection-alone animals did not. All animals received a left C2 spinal hemisection 24 hours prior to death. Quantitative morphometric analysis of the phrenic nucleus showed significant reductions in phrenic dendritic size and the number of dendrodendritic appositions in HPP (two week) animals and in the length of dendrodendritic appositions in HPP (four week) animals. Significant increases in microglial area fraction in HPP (two week) animals and in astroglia area fraction in HPP (four week) animals were also detected. The results suggest that the alterations in the spinal hemisection-induced dendrodendritic apposition formation is most likely influenced by the different stages of the glial reactions induced by the chronic phrenicotomy/spinal hemisection.

Myoneural interactions affect diaphragm muscle adaptations to inactivity

We hypothesized that inactivity effects on diaphragm muscle contractile and morphometric properties are attenuated if phrenic motoneurons are also inactive. Three models of rat diaphragm inactivity were compared: 1) spinal isolation; 2) tetrodotoxin (TTX) nerve blockade; and 3) denervation (Dnv). Motoneuron and muscle fiber inactivities were matched only in spinal isolated animals. After 2 wk, maximum tetanic force decreased in all three groups compared with control group but to a greater extent in TTX and Dnv animals. Fatigue resistance improved, and maximum unloaded shortening velocity slowed only in TTX and Dnv groups. Type IIa fiber proportions decreased in all three groups, and type IIx fiber proportions increased in TTX and Dnv animals. Type I fiber cross-sectional area increased in all three groups but to a greater extent in TTX and Dnv animals. Type IIa fibers hypertrophied, whereas type IIx and IIb fibers atrophied only in TTX and Dnv groups. These results support the hypothesis that muscle adaptations to prolonged inactivity are attenuated when muscle fiber and motoneuron inactivities are matched.

Neurotization procedures for brachial plexus injuries

The author presents three methods for neurotization procedures. The methods were developed for different reconstructive purposes. Nerve transfer is often the only option to restore basic or total function.

Regional adaptations of rabbit diaphragm muscle fibers to unilateral denervation

We hypothesized that adaptations of the rabbit diaphragm (Dia) after unilateral denervation (DNV) result from removal of a neural influence rather than from passive stress. Length changes of midcostal and sternal Dia regions were measured before and after DNV by using sonomicrometry. Midcostal fibers passively lengthened after DNV, whereas sternal fibers shortened. In both regions, these length changes were associated with minimal stress, as estimated from passive force-length relationships. Morphological and contractile adaptions of midcostal and sternal Dia regions were examined after 1 and 4 wk of DNV. In both Dia regions, type I fibers progressively hypertrophied, whereas type IIb fibers atrophied. After DNV, changes in isometric contraction were similar in both Dia regions. Twitch contraction and half-relaxation times increased, force-frequency relationships shifted leftward, and maximum tetanic force decreased. We conclude that passive length changes and mechanical stress are not the main determinants of the morphological and contractile adaptations of the Dia after unilateral DNV but that these adaptations result from DNV itself.