Characterization of the human diaphragm muscle with respect to the phrenic nerve motor points for diaphragmatic pacing

Diaphragm pacing from laparoscopically placed electrodes is an alternative to conventional phrenic pacers that use electrodes placed in direct contact with the nerve in the neck or chest. The challenge with the laparoscopic approach is determining where to implant the electrodes, as the phrenic nerves are not visible from the abdomen. The objective of this study was to locate the phrenic nerve "motor points" in the human diaphragm muscle from an abdominal perspective. Twenty-five cadavers were examined by excising the diaphragm muscle and assessing for the thickness of the muscle, the motor point area, and the accessibility of the motor point from the abdominal approach. The data indicate the average thickness of the muscle in the motor point region was 3.0 mm for the left and 2.9 mm for the right hemidiaphragm. The average motor point area was 73 mm2 for the left and 58.7 mm2 for the right hemidiaphragm. The motor points were accessible from an abdominal approach, but the motor point on the right hemidiaphragm was located on the central tendon in many cases (12 of 25). Thus, although the nerves branch prior to entry into the muscle on the right side, several well-placed electrodes could still activate the entire nerve. In this study, we have characterized the human diaphragm muscle in the motor point region and found that it is feasible to place laparoscopically intramuscular electrodes in the motor point region. This is the foundation for the laparoscopically placed diaphragm pacing device that has been utilized in a small series of patients.     

Conditioning of the diaphragm by phrenic nerve pacing in primary alveolar hypoventilation.

A patient with respiratory muscle weakness due to alveolar hypoventilation was treated with nocturnal bilateral phrenic nerve pacing for one year. Treatment was associated with a progressive increase in diaphragmatic strength and endurance.     

Eventration of the diaphragm due to phrenic nerve injury caused by intercostal drainage.

Acquired eventration of the diaphragm is caused by injury to the phrenic nerve with resultant paralysis and elevation of the entire diaphragm. In this reported case, damage to the phrenic nerve was caused by an intercostal drain. This has not been previously reported.     

Phrenic nerve stimulation for diaphragm pacing with a spinal cord stimulator: technical note

BACKGROUND: Diaphragm pacing with electrical stimulation of the phrenic nerve is an established treatment for central hypoventilation syndrome. The device, however, is not readily available, at least in Japan. We used the spinal cord stimulator for pain control for phrenic nerve stimulation. The purpose of this study is to evaluate the efficacy and feasibility of phrenic pacing with the compromise method. METHODS: We implanted a stimulator for spinal cord stimulation (Itrel 3 or X-trel, Medtronic, MN) in 4 patients with chronic hypoventilation because of brainstem dysfunction of various origins. The stimulation electrode was placed along the right phrenic nerve in the neck, and the device was implanted in the anterior chest. We used the cyclic mode, and set the parameters at 1 second ramp up, 2 seconds on, 3 seconds off. The pulse width and the frequency were set at 150 microsec and 21 Hz, respectively. The amplitude of the output was adjusted to obtain sufficient tidal volume and to maintain PaCO(2) at around 40 mm Hg. RESULTS: During the follow-up period from 6 to 19 months (mean 8.3 months), stable and sufficient ventilation were observed in all patients without complications. One patient with sleep apnea syndrome used the device only at night and became free from a respirator. Three patients who were completely respirator-dependent became ambulatory during the daytime. CONCLUSION: Though longer follow-up is necessary, diaphragm pacing by stimulation of the phrenic nerve with the spinal cord stimulator is feasible for a treatment of central hypoventilation syndrome.     

Minimally invasive trans-mediastinal endoscopic approach to insert phrenic stimulation electrodes in the human diaphragm: a preliminary description in cadavers

Objective: Diaphragm pacing by phrenic nerve (PN) stimulation is currently used for patients with central respiratory paralysis to be weaned from mechanical ventilation. Electrodes are inserted either through bilateral thoracotomy or through four ports laparoscopy. The aim of this experimental work is to demonstrate the feasibility of trans-mediastinal bilateral implantation of PN electrodes using a flexible gastroscope introduced through a cervical incision in human cadavers. Methods: Ten refrigerated and non-embalmed cadavers were used. The gastroscope was introduced through a cervical incision into the latero-tracheal space and then subsequently into both pleura by opening the mediastinal pleura. After identification of the PN, electrodes were introduced through an intercostal space to the desired diaphragmatic location using a long, pliable needle with the electrode loaded in its lumen. Results: Results are described for each hemi-diaphragm not for an anatomic subject. Mediastinal exploration and introduction of the video gastroscope into the pleural cavities proved easy in all subjects. Pleural adherences were present in five hemi-diaphragms. The central tendon of both hemi-diaphragms could be identified unambiguously in all the subjects. Identification of the entry point of the phrenic nerve into the diaphragm was straightforward in 10 hemi-diaphragms. In the remaining 10, this proved more difficult because of mediastinal fat or lung parenchyma. Introduction of the electrode-holding needles through the intercostal space and their insertion close to the phrenic nerve entry point was also easy. Withdrawal of the needle from the diaphragm and ‘capture’ of the hook were successful on the first attempt in 14 hemi-diaphragms, but failed in six others in whom a second attempt was necessary. Conclusion: Trans-mediastinal implantation of PN stimulation electrodes is possible using a flexible endoscope. This application of endoscopic surgery could allow a minimally invasive placement of PN electrodes in patients with central respiratory paralysis, for example, at the time of tracheostomy.     

The human sperm head: a key for successful fertilization

In order to examine the predictive value of determining the sperm head shape, the acrosomal size, the presence of acrosomal vacuoles, and the challenged acrosome reaction (AR) on the outcome of a standard in vitro fertilization (IVF) program, a prospective study was conducted that included 75 couples undergoing IVF treatment. An assessment of sperm morphology was performed using the Hobson Sperm Tracker (Hobson Tracker Limited, Sheffield, United Kingdom). The assessment of the AR was performed before and after adding pooled undiluted human follicular fluid (FF). The outcome measure was an IVF rate of inseminated oocytes. A positive correlation was found between the fertilization rate (FR%) and the proportion of the sperm with a normal (oval) head shape (P <.001), the sperm exhibiting acrosomal vacuoles (P <.003), the sperm with a normal acrosomal size (40%-70% of total head area, P <.025), and the sperm undergoing AR after adding FF (P <.001). Multiple logistic regression analysis revealed that by incorporating the above 4 parameters, the sensitivity of prediction of IVF FR% values was 79%, and the specificity was 93%, with a positive predictive value of 96%. This study shows that the multiparametric assessment of the sperm head is useful in predicting the FR% values of a standard IVF treatment. The automated analysis used in this study is shown to maintain a level of precision and accuracy acceptable for application in a routine semen analysis situation.     

Ulnar nerve motor conduction to the first dorsal interosseous muscle

The ulnar motor study to the abductor digiti minimi (ADM) is commonly performed, but does not test the terminal deep palmar branch of the ulnar nerve. Although damage to the ulnar nerve most often occurs at the elbow, the damage may occur elsewhere along the course of the nerve, including damage to the deep palmar branch. Ulnar conduction studies of the deep branch have been performed with recording from the first dorsal interosseous (FDI) muscle. These studies have used differing methodologies and were mostly limited by small sample size. The aim of this study was to develop a normative database for ulnar nerve conduction to the FDI. A new method of recording from the FDI was developed for this study. It utilizes recording with the active electrode over the dorsal first web space, with the reference electrode placed at the fifth metacarpophalangeal joint. This technique reliably yields negative takeoff measurements. An additional comparison was made between ulnar motor latency with recording at the ADM and with recording at the FDI. For this study, 199 subjects with no risk factors for neuropathy were tested. The latency, amplitude, area, and duration were recorded. The upper limit of normal (ULN) was defined as the 97th percentile of observed values. The lower limit of normal (LLN) was defined as the 3rd percentile of observed values. For the FDI, mean latency was 3.8 +/- 0.5 ms, with a ULN of 4.7 ms for males, 4.4 ms for females, and 4.6 ms for all subjects. Mean amplitude was 15.8 +/- 4.9 mV, with a LLN of 5.1 for all subjects. Side-to-side differences in latency to the FDI, from dominant to nondominant hands, was -0.1 +/- 0.4 ms, with a ULN of 0.8 ms. For the amplitude, up to a 52% decrease from side to side was normal. For the same-limb comparison of the FDI and ADM, the mean latency difference was 0.6 +/- 0.4 ms, with a ULN increase of 1.3 ms for latency to the ADM versus the FDI.     

Response of the diaphragm muscle to electrical stimulation of the phrenic nerve. A histochemical and ultrastructural study

The histological, histochemical, and ultrastructural features of canine diaphragms subjected to pacing by high-frequency electrical stimulation (27 to 33 Hz) of the phrenic nerve are compared with unstimulated diaphragms and with diaphragms subjected to pacing by low-frequency stimulation (11 to 13 Hz). The high-frequency group showed a reduced tidal volume (fatigue) after long-term stimulation, and myopathic changes which included enlarged internal and sarcolemmal nuclei, ring fibers, moth-eaten fibers with irregular histochemical staining, core/targetoid fibers, and smearing and aggregation of Z-band material with electron microscopy. The low-frequency group did not develop a significant degree of fatigue or pathological changes, and showed histochemical evidence of transformation to fast-twitch (type II) fibers. Possible pathogenic mechanisms and their similarity to those in certain human neuromuscular diseases are discussed. The application of the findings resulting from high- and low-frequency stimulation to long-term diaphragm pacing in humans with chronic ventilatory insufficiency is also discussed.     

Functional restoration of the paralyzed diaphragm in high cervical quadriplegia via phrenic nerve neurotization utilizing the functional spinal accessory nerve

The authors report a case of functional improvement of the paralyzed diaphragm in high cervical quadriplegia via phrenic nerve neurotization using a functional spinal accessory nerve. Complete spinal cord injury at the C-2 level was diagnosed in a 44-year-old man. Left diaphragm activity was decreased, and the right diaphragm was completely paralyzed. When the level of metabolism or activity (for example, fever, sitting, or speech) slightly increased, dyspnea occurred. The patient underwent neurotization of the right phrenic nerve with the trapezius branch of the right spinal accessory nerve at 11 months postinjury. Four weeks after surgery, training of the synchronous activities of the trapezius muscle and inspiration was conducted. Six months after surgery, motion was observed in the previously paralyzed right diaphragm. The lung function evaluation indicated improvements in vital capacity and tidal volume. This patient was able to sit in a wheelchair and conduct outdoor activities without assisted ventilation 12 months after surgery.     

Final analysis of the pilot trial of diaphragm pacing in amyotrophic lateral sclerosis with long-term follow-up: diaphragm pacing positively affects diaphragm respiration

Background

Respiratory insufficiency is the major cause of mortality in patients with amyotrophic lateral sclerosis or Lou Gehrig’s disease. This is the final report of the diaphragm pacing (DP) pilot trial.

Methods

Patients underwent laparoscopic diaphragm electrode implantations and subsequent conditioning of diaphragms. Serial respiratory function tests were performed in the initial year and followed until death.

Results

Sixteen patients were implanted with no perioperative or unanticipated device-related adverse events. There were 452 implant-months of follow-up. DP allowed greater movement of the diaphragm under fluoroscopy, increased muscle thickness, and decreased the decline in forced vital capacity. Median survival from implant was 19.7 months with the cause of death respiratory in only 31%.

Conclusions

Long-term analysis of DP in amyotrophic lateral sclerosis showed no safety issues and can positively influence diaphragm physiology and survival. This formed the initial basis for subsequent US Food and Drug Administration approval.     

移植神经长度对膈神经移位肌皮神经疗效的影响

目的 探讨移植神经长度对膈神经移位肌皮神经治疗臂丛神经根性撕脱伤疗效的影响.方法 对2007年至2010年于我院行膈神经移位肌皮神经治疗臂丛损伤的患者进行临床随访,其中17例需要做神经移植.通过检测肱二头肌肌力与体重指数(BMI)评定手术疗效.结果 17例患者的总体有效率82.4％,移植神经长度以及BMI与屈肘功能恢复无明显相关性.结论 臂丛损伤患者尤其是全臂丛损伤患者中,膈神经移位肌皮神经的临床疗效不受移植神经长度以及BMI的影响.     

Interscalene block with a nerve stimulator: a deltoid motor response is a satisfactory endpoint for successful block

BACKGROUND AND OBJECTIVES: The interscalene brachial plexus block (ISB) is an effective and well-established anesthetic technique for shoulder surgery. Using nerve stimulation as an aid in block placement, a motor response (twitch) in the biceps or a more distal upper limb muscle has been recommended to indicate accurate needle placement. Our clinical experience, as well as anatomic reasoning, suggests that a deltoid twitch may be just as effective as one in the biceps for predicting successful block. This prospective clinical study was undertaken to compare a deltoid with a biceps twitch with respect to onset and success of motor block. METHODS: A total of 160 patients scheduled for shoulder surgery were studied prospectively. Interscalene blocks were performed using neurostimulation according to our standard technique. Twitches of the deltoid or biceps or both, whichever appeared first, were accepted and used as the endpoint for needle placement and injection of local anesthetic. Motor block success, i.e., patient inability to lift the arm against gravity, and minutes to motor block onset were recorded. RESULTS: There was 1 failed motor block in the deltoid group and none in the other groups (not a statistically significant difference). When the same local anesthetic was used, there were no statistically significant differences in onset times between the biceps, deltoid, or biceps/deltoid groups. CONCLUSIONS: A deltoid twitch is as effective as a biceps twitch in determining accurate needle placement for ISB and in predicting successful motor block. Acceptance of a deltoid twitch during ISB eliminates the need for further probing and may translate into better patient acceptance and in a smaller risk of needle-induced nerve damage.