Subcutaneous Ports for Chronic Nerve Cuff and Intramuscular Electrode Stimulation in Animal Models.

OBJECTIVE: Tracking recovery after nerve injury may require many intermittent assessments over long periods, preferably with non- or minimally invasive methods. We developed subcutaneous electrical connection ports (ECPs) for repeated connection to nerve cuff or intramuscular electrodes via transdermal needles and evaluated them during studies of laryngeal reinnervation. STUDY DESIGN: Animal experiment. SETTING: Laboratory. METHODS: ECPs were designed and 3-dimensionally printed for connection to bipolar electrodes with biocompatible polymers. Dual compartments filled with conductive silicone capped with nonconductive silicone were used to make the connections between electrode leads and transdermally inserted needles. Ten dogs (19-29 kg) were implanted with 22 ECPs. In 7 dogs, 11 electrodes were placed on recurrent laryngeal nerves proximal to transection and suture repair to track laryngeal reinnervation. In 6 dogs, 8 spinal accessory nerve cuff electrodes were used to stimulate neck muscle contraction. In 2 dogs, 3 electrodes were implanted in the thyroarytenoid muscle. Stimulation thresholds, electromyography, and videolaryngoscopic imaging were obtained in 156 tests over survival periods up to 32 months. Stimulation data provided information about ECP performance. RESULTS: ECPs added negligible resistance to electrodes (mean ± SD, 2.14 ± 0.9 Ω). Despite some electrode leads breaking distally, ECPs were reliable and well tolerated at implant sites and enabled periodic assessment of nerve and muscle function over the time course of laryngeal reinnervation. Histology showed ECP encapsulation as thin layers of connective tissue and minimal acute inflammation. CONCLUSION: Custom ECPs are easily fabricated and cause little tissue reaction over months to years of subcutaneous implantation, facilitating long-term physiologic studies.

Recurrent Laryngeal Nerve Stimulator.

Electrical stimulation of the recurrent laryngeal nerve is a safe and promising therapeutic approach with the potentiality to overcome the shortcomings of conventional surgical glottal enlargement. Although aberrant or synkinetic reinnervation is commonly considered an unfavorable condition, particularly for recovery of vocal fold movement, its presence is essential to ensure the effective clinical performance of laryngeal pacemakers. Thus, the effective selection of patients who can profit from laryngeal pacemakers implantation demands the implementation of new diagnostic tools based on tests capable of reliably detecting the presence of viable reinnervation on at least one vocal fold.

[The possibilities for the restoration of the laryngeal function: the current state-of-the-art]. / Vozmozhnosti vosstanovleniia funktsii gortani: sovremennyi podkhod.

The restoration of the functional competence of the larynx following bilateral laryngeal nerve damage and vocal fold paralysis is a serious challenge for the surgeon that has thus far no satisfactory solution. Physiological re-innervation that occurs naturally with time is non-selective and, in the majority of the cases, leads to synkinesis. Laryngeal pacing achieved with the application of the implantable microchips appears to be a promising approach. The animal experiments have demonstrated the possibility of successful restoration of all the functions of the larynx by means of laryngeal pacing but simultaneously revealed a number of technical issues that have to be addressed if the further progress in this field is to be achieved including the choice of the proper materials for implantation, solution of problems pertaining to the neuromuscular mapping during pacer implantation, etc.). The results of the first prospective clinical trial involving the human patients gave evidence suggesting that the laryngeal electrostimulation technology is both safe and efficient. Nevertheless, further investigations and modification of the method are needed before it can be recommended for the wider application in the routine clinical practice.

Feasibility and safety of nerve stimulator attachment to energy-based devices: A porcine model study.

BACKGROUND: Recently, several energy-based devices (EBDs) have been developed and applied in the context of thyroid surgery. EBDs can reduce operation time, blood loss, and postoperative pain. Compared to conventional electrocautery, EBDs operate at a relatively lower temperature and produce minimal lateral tissue damage. Yet, during device operation, the tip of the EBD is hot enough to cause thermal nerve damage, increasing the need for surgeons to be cautious about EBD application. To increase the safety of EBDs, we attached nerve stimulators to the tips of two EBDs and compared them to conventional monopolar nerve stimulation using a porcine model. METHODS: Three piglets (30-40 kg) underwent total thyroidectomy after orotracheal intubation with a nerve integrity monitor (NIM) electromyography (EMG) endotracheal tube. Nerve stimulators were attached to two EBDs (Harmonic Focus®+ and LigaSure™). After dissection and identification of six recurrent laryngeal nerves in the three piglets, both of the EBDs with attached nerve stimulators and a conventional monopolar nerve stimulator were applied near the nerve and EMG parameters were recorded using the NIM 3.0 system. The stimulus intensity was varied from 5 mA to 1 mA and the maximum distance and amplitude at which nerve detection was achieved were measured. RESULTS: There were no statistically significant differences between the maximum distance or mean amplitude obtained from nerve stimulators attached to EBDs and those obtained from the conventional nerve stimulator. Additionally, there were no adverse EMG events related to the use of nerve stimulators attached to EBDs. CONCLUSIONS: Attachment of a nerve stimulator to an EBD for nerve detection during thyroidectomy was as safe and effective as attachment of a conventional nerve stimulator. Use of a nerve stimulator attachment may reduce the likelihood of EBD-associated nerve damage during thyroid surgery.

Papillary thyroid carcinoma with exclusive involvement of a functioning recurrent laryngeal nerve may be treated with shaving technique.

OBJECTIVES: We sought to validate the feasibility of preserving a functioning recurrent laryngeal nerve (RLN) invaded by papillary thyroid carcinoma (PTC) using a shaving technique followed by high-dose radioactive iodine (RAI) therapy. METHODS: A retrospective review of 34 patients with locally invasive PTC who had exclusive tumor involvement of a functioning RLN was performed. All patients underwent total thyroidectomy and high-dose RAI therapy. A shaving technique was conducted with the goal of leaving the smallest amount of residual tumor as possible while attempting to preserve nerve function. Clinicopathologic factors and oncologic outcomes of the patients with resected RLN (group A, n = 14) and preserved RLN (group B, n = 20) were compared. RESULTS: The two groups showed no differences in clinicopathologic factors or follow-up period. Mean dose of radioiodine therapy was 245.0 ± 140.3 mCi (range 100-540 mCi). Permanent postoperative vocal cord paralysis after RLN shaving occurred in two patients of group B (10%). Only one patient (5%) in group B had local recurrence at the thyroid bed where the residual tumor was located. The overall recurrence rate was 35.7% (5/14) and 20.0% (4/20) in groups A and B, respectively showing no significant difference (p = 0.525). There were no cases of death due to PTC during the median follow-up of 75 months (range 36-159 months). CONCLUSIONS: Patients with locally invasive PTC with exclusive involvement of a functioning RLN may be treated by nerve shaving followed by treatment of the macroscopic residual tumor with high-dose RAI therapy.

Locally advanced thyroid cancer.

PURPOSE OF REVIEW: The purpose of this review is to summarize existing literature with respect to locally advanced thyroid cancer and define the intricacies of preoperative evaluation, surgical management of involved sites and postoperative treatment. RECENT FINDINGS: Locally invasive thyroid cancer is an uncommon disease process, which carries significant morbidity and mortality. Current treatment modalities include appropriate surgery, radioactive iodine treatment and external beam radiation therapy. Proper evaluation of the extent of disease, with complete gross tumor removal, is paramount in managing this difficult problem. Surgical treatment is still the mainstay for locally advanced thyroid cancer. SUMMARY: Little progress has been made in advancing the treatment of locally advanced thyroid cancer. Patient identification, evaluation and proper surgical management with adjuvant therapy, still remain the most effective course of treatment. Aggressive surgical treatment including removal of all gross tumor and still preserving vital structures along with adjuvant therapy is likely to offer the best results. There is a very high incidence of locoregional and distant failure in this group of patients. The understanding and recognition of histopathological variations, such as poorly differentiated thyroid cancer is also important. New molecular markers are needed to help identify and predict aggressive tumor behavior.

The effects of chronic electrical stimulation on laryngeal muscle reinnervation.

The present study examined the effects of functional neuromuscular stimulation (FNS) on reinnervation of the posterior cricoarytenoid (PCA) muscle. In 4 canines, the recurrent laryngeal nerve (RLN) was sectioned and anastomosed and a patch electrode array implanted for stimulation and recording at multiple PCA sites. Following implantation, FNS was applied to 2 canines for a period of 6 weeks. Two additional animals served as nonstimulated controls. In each animal, histomorphometric analysis of the RLN was used to assess the quality of nerve regeneration and the potential for muscle reconnection. The magnitude of reinnervation was monitored by electromyographic (EMG) potentials evoked by RLN stimulation. The appropriateness of reconnection was determined by the pattern of spontaneous EMG activity and recovery of vocal fold abduction. Results of this preliminary study indicated that FNS caused an overall repression of reinnervation. However, the repression preferentially inhibited reconnection by foreign nerve fibers, promoting selective reinnervation and preventing synkinesis.

Treatment of spastic dysphonia without nerve section.

Spastic dysphonia is a disorder characterized by strained, constricted phonation with excessively adducted vocal cords. Despite initial success with recurrent laryngeal nerve section, the search for other treatment continues. Our clinical study involved inserting a needle electrode percutaneously into the region of the recurrent laryngeal nerve in five patients with spastic dysphonia. Electrical stimulation resulted in dramatic improvement in three patients and minimal improvement in two. Our experimental study was designed to create an animal model for an implantable nerve stimulator to be used on a long-term basis. A Medtronic spinal cord stimulation system was implanted into a dog, and a cuff electrode was positioned around the recurrent laryngeal nerve. Vocal cord position could be altered by varying the stimulus frequency. Long-term stimulation of the recurrent laryngeal nerve was relatively safe and effective. Eventually, we plan to implant nerve stimulators into spastic dysphonia patients who respond well to percutaneous stimulation.

Electrophysiologic pacing of vocal cord abductors in bilateral recurrent laryngeal nerve paralysis.

We have reconfirmed our previous findings that controlled, reproducible, sustained, discrete vocal cord abduction can be achieved synchronously with respiration by electrophysiologic stimulation of the paralyzed posterior cricoarytenoid muscles. Moreover, we have demonstrated that this can be triggered synchronously by employing the normal physiologic chest wall movements that occur on respiration. To our knowledge, this represents the first report of functionally paced vocal fold abduction with respiration employing physiologic chest wall motions using an implantable device, and may represent an important step in the development of a physiologic approach to bilateral recurrent laryngeal nerve paralysis.