Evaluation of Diffusional Characteristics and Microstructure in Unilateral Vocal Fold Paralysis Using Diffusion Tensor Imaging.

OBJECTIVE: To investigate the value of diffusion tensor imaging (DTI) in the evaluation of vocal fold tissue microstructure after recurrent laryngeal nerve (RLN) injury. METHODS: Six canines were divided into 2 groups: a unilateral vocal fold paralysis group (n = 4) and a control group (n = 2). The RLN was cut in the unilateral vocal fold paralysis group, and no intervention was applied in the control group. After 4 months, the canines' larynges were removed and placed in a small animal magnetic resonance imaging (MRI) system (9.4T BioSpec MRI; Bruker, Germany). After scanning, the vocal folds were isolated, sectioned, and stained. The slides were then analyzed for the cross-sectional area and muscle fiber density through feature extraction technology. Pearson correlation analysis was performed on the DTI scan and histological section extraction results. RESULTS: In the vocal fold muscle layer, the fractional anisotropy (FA) of the unilateral RLN injury group was higher than that of the control group, and the Tensor Trace was lower than that of the control group. This difference was statistically significant, P < .05. In the lamina propria, the FA of the unilateral RLN injury group was lower than that of the control group, P > .05, and the Tensor Trace was lower than that of the control group, P < .05. The muscle fiber cross-sectional area of the RLN injury group was significantly smaller than the control group with statistical significance, P < .05, and the density of muscle fibers was lower, P < .05. The correlation coefficient between FA and the cross-sectional area was -0.838, P = .002, and .726; P = .017 between Tensor Trace and the cross-sectional area. CONCLUSION: Diffusion tensor imaging is an effective method to assess the changes in the microstructure of atrophic vocal fold muscle tissue after RLN injury.

Intraoperative Neuromonitoring During Thyroid Surgery: The Effect of Surgical Positioning.

Intraoperative neuromonitoring during thyroid surgery has been used to successfully prevent permanent neurological injury by early identification of anatomical variants. Proper interpretation of neuromonitoring data requires knowledge of what factors might affect the data. In this study, we examined the effect of surgical positioning on the latency and amplitude of neural recordings made from the vocalis muscle during thyroid surgery. A retrospective review was performed of 145 patients who underwent thyroid surgery. Eighty-three had open cervical procedures, and 62 had robotic-assisted transaxillary procedures. Intraoperative neuromonitoring recordings were made by stimulation of the vagus and recurrent laryngeal nerves for both groups. Ultrasound measurements were made of a subset of the transaxillary patients immediately before and after arm positioning. Groups differed only on right-sided recordings. Patients with transaxillary surgeries had significantly shorter latencies evoked from the vagus nerve. We found that vagus nerve-evoked latencies were also correlated to ultrasound measurements of the nerves. Surgical positioning during thyroid surgery is a factor that may affect intraoperative neuromonitoring data and should be taken into account by the surgeon during interpretation.

Delayed Recurrent Laryngeal Nerve Palsy Following Anterior Cervical Discectomy and Fusion.

BACKGROUND: Vocal cord dysfunction resulting from recurrent laryngeal nerve palsy (RLNP) is a known complication following anterior cervical discectomy and fusion. RLNP occurs typically secondary to neurapraxia caused by intraoperative compression or traction on the nerve and less commonly from direct nerve injury intraoperatively in the setting of anterior cervical spine surgery. Patients with RLNP typically present with hoarseness immediately after surgery owing to unilateral vocal cord paralysis. In rare cases, there is late-onset, progressive development of RLNP that may potentially lead to permanent vocal cord paralysis or respiratory failure. CASE DESCRIPTION: A 75-year-old woman presented with myeloradiculopathy and chronic urinary incontinence. Imaging showed severe foraminal and central stenosis with T2 cord signal change. A C4-7 anterior cervical discectomy and fusion was successfully performed without immediate complications following surgery. The patient had a normal voice and was tolerating a regular diet well. On postoperative day 3, the patient developed new hoarseness and dysphagia. An otolaryngologist was consulted, and flexible nasolaryngoscopy showed left vocal cord paralysis consistent with left RLNP. The patient was treated with a course of steroids, and her hoarseness and dysphagia had resolved at the 6-month follow-up visit. CONCLUSIONS: To our knowledge, this is the first report of delayed RLNP in patients undergoing anterior cervical discectomy and fusion. This rare complication should be discussed during preoperative patient counseling. Previous literature indicates the underlying pathophysiology for delayed onset of RLNP may be small vessel ischemia, vasospasm, or viral resurgence that leads to recurrent laryngeal nerve dysfunction.

Diagnostic value of intraoperative ultrasonography in assessing thoracic recurrent laryngeal nerve lymph nodes in patients with esophageal cancer.

BACKGROUD: The incidence of recurrent laryngeal nerve (RLN) injury has increased due to RLN lymph node dissection. The aim of this study was to evaluate the ability of intraoperative ultrasonography (IU) to detect RLN nodal metastases in esophageal cancer patients. METHODS: Sixty patients with esophageal cancer underwent IU, computed tomography (CT), and endoscopic ultrasonography (EUS) to assess for RLN nodal metastasis. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were compared. RESULTS: The sensitivities of IU, CT, and EUS in diagnosing right RLN nodal metastases were 71.4, 14.3, and 30.0%, respectively, and a significant difference among these three examinations was observed (χ2 = 10.077, P = .006). The specificities of IU, CT, and EUS for diagnosing right RLN nodal metastasis were 67.4, 97.8, and 95.0%, respectively, and a significant difference was observed (χ2 = 21.725, P < .001). No significant differences in either PPV or NPV were observed when diagnosing right RLN nodal metastases. For diagnosis of left RLN lymph nodal metastases, the sensitivities of IU, CT, and EUS were 91.7, 16.7, and 40.0% respectively. There was a significant difference among these diagnostic sensitivities (χ2 = 14.067, P = .001). The specificities of IU, CT, and EUS for diagnosis of left RLN nodal metastases were 79.2, 100, and 82.5%, respectively and a significant difference was observed (χ2 = 10.819, P = .004). No significant differences were observed in PPV or NPV for these examinations when diagnosing left RLN nodal metastases. CONCLUSION: Intraoperative ultrasonography showed superior sensitivity compared with preoperative CT or EUS in detecting RLN lymph node metastasis in patients with thoracic esophageal cancer.

Management of unilateral recurrent laryngeal nerve injury after thyroid surgery: A review.

BACKGROUND: Recurrent laryngeal nerve (RLN) damage because of thyroid and parathyroid surgery has been recognized for over a century. Injury rates have been slowly decreasing in this period while effective treatment strategies have been increasing. METHODS: Recent literature was evaluated on the topics of anatomy, pathophysiology, avoidance, and conservative and surgical treatment of RLN injury. Data for this literature review were identified by PubMed and references from relevant articles using the search terms "thyroid," "laryngeal nerve," and "injury." Only articles published in English between 1990 and 2015 were included. RESULTS: Advances in technique and equipment have made injury less likely. The evidence and role for neuromonitoring is discussed. Treatment strategies may include speech therapy, vocal cord augmentation using injection, laryngeal framework surgery techniques (including laryngoplasty and arytenoid adduction), and reinnervation. CONCLUSION: Injury rates in specialist centers are very low. Good to excellent results may be obtained in most cases.

Vocal fold motion outcome based on excellent prognosis with laryngeal electromyography.

OBJECTIVES/HYPOTHESIS: As laryngeal electromyography (LEMG) becomes more refined, accurate predictions of vocal fold motion recovery are possible. Focus has been on outcomes for patients with poor prognosis for vocal fold motion recovery. Limited information is available regarding the expected rate of purposeful vocal fold motion recovery when there is good to normal motor recruitment, no signs of denervation, and no signs of synkinetic activity with LEMG, termed excellent prognosis. The objective of this study is to determine the rate of vocal fold motion recovery with excellent prognosis findings on LEMG after acute recurrent laryngeal nerve injury. STUDY DESIGN: Retrospective review. METHODS: Patients undergoing a standardized LEMG protocol, consisting of qualitative (evaluation of motor recruitment, motor unit configuration, detection of fibrillations, presence of synkinesis) and quantitative (turns analysis) measurements were evaluated for purposeful vocal-fold motion recovery, calculated after at least 6 months since onset of injury. RESULTS: Twenty-three patients who underwent LEMG for acute vocal fold paralysis met the inclusion criteria of excellent prognosis. Eighteen patients (78.3%) recovered vocal fold motion, as determined by flexible laryngoscopy. CONCLUSION: Nearly 80% of patients determined to have excellent prognosis for vocal fold motion recovery experienced return of vocal fold motion. This information will help clinicians not only counsel their patients on expectations but will also help guide treatment. LEVEL OF EVIDENCE: 4. Laryngoscope, 126:2310-2314, 2016.

Effects of Functional Electrical Stimulation on Denervated Laryngeal Muscle in a Large Animal Model.

Bilateral vocal fold paralysis (BVCP) is a life-threatening condition that follows injury to the Recurrent Laryngeal nerve (RLn) and denervation of the intrinsic laryngeal musculature. Functional electrical stimulation (FES) enables restoration and control of a wide variety of motor functions impaired by lower motor neuron lesions. Here we evaluate the effects of FES on the sole arytenoid abductor, the posterior cricoarytenoid (PCA) muscle in a large animal model of RLn injury. Ten horses were instrumented with two quadripolar intramuscular electrodes in the left PCA muscle. Following a 12-week denervation period, the PCA was stimulated using a once-daily training session for 8 weeks in seven animals. Three animals were used as unstimulated controls. Denervation produced a significant increase in rheobase (P < 0.001). Electrical stimulation produced a 30% increase in fiber diameter in comparison with the unstimulated control group (33.9 ± 2.6 µm FES+, 23.6 ± 4.2 µm FES-, P = 0.04). A trend toward a decrease in the proportion of type 1 (slow) fibers and an increase in type 2a (fast) fibers was also observed. Despite these changes, improvement in PCA function at rest was not observed. These data suggest that electrical stimulation using a relatively conservative set of stimulation parameters can reverse the muscle fiber atrophy produced by complete denervation while avoiding a shift to a slow (type 1) fiber type.