Recurrent Laryngeal Research Articles

Surgical treatment of laryngeal stenosis with semiconductor laser.

The article reflects the current trends in the treatment of diseases of the larynx, accompanied by stenosis and impaired fonatory function, such as laryngeal papillomatosis and double-sided paresis of the recurrent larynx nerve. Actuality of surgical treatment of bilateral paresis of the recurrent larynx nerve is due to the fact that a significant proportion of patients with this disease are persons of vocal professions and functional result of the operation determines the quality of life, professional suitability. Using semiconductor laser causes a good functional outcome in this pathology treatment. The aim of the study was to improve the effectiveness of treatment of patients with laryngeal papillomatosis and with bilateral paresis of the recurrent larynx nerve. All patients underwent surgery with using semiconductor laser "Lika - surgeon." Results of treatment made it possible to draw a conclusion that microlaryngoscopy with laser vaporization of papillomas can reduce frequency of relapses by 15.4% during the first year after surgery as compared to the control group. Using of semiconductor laser in patients with bilateral paresis of the larynx allows to more effectively restore compensated breathing through upper airways as compared with the control group. Application of laser in phonosurgery allow to save a good voice function in 76.9% of patients.

Analyses of functional and oncologic outcomes following supracricoid partial laryngectomy.

To review the functional and oncologic outcomes of patients who received supracricoid partial laryngectomy (SCPL) with cricohyoidoepiglottopexy (CHEP) or cricohyoidopexy (CHP) in our institution. A total of 208 patients who received SCPL with CHEP or CHP from our institution from 1995 to 2007 were involved. Among them, 190 cases were patients with squamous cell carcinoma of the larynx (T1-T4, N0-N2), 14 cases were patients with recurrent larynx cancer and 4 cases were patients with laryngeal stenosis. Forty-four patients also received unilateral neck dissection, and 41 patients received a bilateral neck dissection. All patients were assessed at functional outcome and complications of their treatment. Also, the oncologic outcomes, such as disease-specific survival, total survival, and local recurrence, were measured for patients with tumor. Decannulation was achieved in nearly all patients, with the average time to decannulation being 20 ± 11.52 days in CHEP patients and 28 ± 8.92 days in CHP patients (P < 0.05). The average nasogastric tubes were removed, days postoperation, was 18 ± 7.39 days in CHEP patients and 25 ± 13.87 days in CHP patients (P < 0.05). The 5-year local recurrence rate was 5.77%, the 5-year disease-specific survival was 82.7%, and the 5-year overall survival was 84.1%. The patients with CHEP had a better recovery than the patients with CHP. SCPL was a well-tolerated procedure with generally good functional outcomes for patients with advanced laryngeal cancer, also for some patients with laryngeal stenosis.

Management of invasive well‐differentiated thyroid cancer: An American head and neck society consensus statement: AHNS consensus statement

Invasive differentiated thyroid cancer (DTC) is relatively frequent, yet there is a paucity of specific guidelines devoted to its management. The Endocrine Committee of the American Head and Neck Society (AHNS) convened a panel to provide clinical consensus statements based on review of the literature, synthesized with the expert opinion of the group. An expert panel, selected from membership of the AHNS, constructed the manuscript and recommendations for management of DTC with invasion of recurrent laryngeal nerve, trachea, esophagus, larynx, and major vessels based on current best evidence. A Modified Delphi survey was then constructed by another expert panelist utilizing 9 anchor points, 1 = strongly disagree to 9 = strongly agree. Results of the survey were utilized to determine which statements achieved consensus, near-consensus, or non-consensus. After endorsement by the AHNS Endocrine Committee and Quality of Care Committee, it received final approval from the AHNS Council.

First report of colonoscopic closure of a gastrocolocutaneous PEG migration with over-the-scope-clip-system

Percutaneous endoscopic gastrostomy (PEG) is a common practice for long-term nutrition of patients who are unable to take oral food. We report of an 85-year old man with a history of recurrent larynx carcinoma and hemicolectomy many years ago due to unknown reason. Laryngectomy was indicated. Preoperatively a PEG was inserted endoscopically after an abdominal ultrasonography without abnormal findings. Few months after PEG insertion, the patient was evaluated for diarrhea and insufficient feeding without signs of infection or peritonism. An upper endoscopy and computed tomography scan confirmed a buried bumper syndrome with migration of the PEG tube into the colon as a rare complication. He underwent successful colonoscopic removal of the internal bumper and closure of the colonic orifice of the fistula with the over-the-scope-clip system (OTSC). OTSC is an endoscopic device for treatment of bleeding, perforation, leak and fistula in the gastrointestinal tract. To the best of our knowledge, this is the first report of the use of OTSC for colonoscopic closure of a gastrocolocutaneous fistula due to a buried bumper syndrome with transcolonic PEG tube migration.

Anomalous Relationship of Coexisting Ipsilateral Recurrent and Nonrecurrent Inferior Laryngeal Nerves During Thyroid Surgery

One of the most important complications of thyroid surgery is inferior laryngeal nerve injury. Variations of inferior laryngeal nerve may increase the risk of iatrogenic injury. Coexistence of ipsilateral nonrecurrent laryngeal nerve and recurrent laryngeal nerve is a very rare variation, and sufficient data are not available on the anatomical and functional relationship of the 2 branches and probable clinical outcomes resulting from the injury of one of them. Herein, we present a case with coexistence of nonrecurrent laryngeal nerve and ipsilateral recurrent laryngeal nerve and discuss the clinical importance of this rare variation.

A Closer Look at Laryngeal Nerves during Thyroid Surgery: A Descriptive Study of 584 Nerves

Morbidity after thyroidectomy is related to injuries to the parathyroids, recurrent laryngeal (RLN) and external branch of superior laryngeal nerves (EBSLN). Mostly these are due to variations in the surgical anatomy. In this study we analyse the surgical anatomy of the laryngeal nerves in Indian patients undergoing thyroidectomy. Materials and Methods. Retrospective study (February 2008 to February 2010). Patients undergoing surgery for benign goitres, T1, T2 thyroid cancers without lymph node involvement were included. Data on EBSLN types, RLN course and its relation to the TZ & LOB were recorded. Results. 404 thyroid surgeries (180 total & 224 hemithyroidectomy) were performed. Data related to 584 EBSLN and RLN were included (324 right sided & 260 left sided). EBSLN patterns were Type 1 in 71.4%, Type IIA in 12.3%, and Type IIB in 7.36%. The nerve was not seen in 4.3% cases. RLN had one branch in 69.34%, two branches in 29.11% and three branches in 1.36%. 25% of the RLN was superficial to the inferior thyroid artery, 65% deep to it and 8.2% between the branches. TZ was Grade 1 in 65.2%, Grade II in 25.1% and Grade III in 9.5%. 31.16% of the RLN passes through the LOB. Conclusions. A thorough knowledge of the laryngeal nerves and anatomical variations is necessary for safe thyroid surgery.

Repeated assessment of larynx compound muscle action potentials using a self-sizing cuff electrode around the vagus nerve in experimental rats

Rationale Vagus nerve stimulation (VNS) is an adjunctive treatment for patients with refractory epilepsy. In more than 30% of the patients VNS has no therapeutic effect. The goal of this study was to find an objective parameter that can be used as an indicator of effective stimulation of the vagus nerve. Methods The electrophysiological response to VNS was recorded from the vagus nerve, recurrent laryngeal nerve and larynx muscles. Nerve lesions and muscle relaxing agent were used to find the source of the electrophysiological response. A cuff-electrode for chronic stimulation and recording was implanted for chronic recording of the VNS-induced electrophysiological response after implantation. Dose–response curves were determined daily during a follow-up period of 2 months. Results VNS induced an electrophysiological response around 3 ms after start of the stimulation. This response was identified as a larynx compound action potential (LCMAP) LCMAP could be recorded immediately after surgery in 11/21 rats, while in the other 10/21 rats, a recovery period with an average of 25 days was required. Once the LCAMP could be recorded, the latency and overall characteristics of the doses response curves of the LCMAP remained stable during the entire follow-up period. Conclusions In this study, we provide an objective electrophysiological parameter for vagus nerve activation. LCAMP may indicate recovery of the vagus nerve after implantation, which may help to determine when uptitration of VNS therapy can be initiated. LCAMP could be of value in future experiments for objectification of VNS in animal models for epilepsy.

The clinical interest of the ary‐thyro‐cricoid fascicle

The aim of this work was to study the prevalence and form of the ary-thyro-cricoid (ATC) muscular fascicle, a variable muscular slip connecting the oblique and/or transverse arytenoid muscles with the thyroarytenoid (TA) and/or lateral cricoarytenoid (LCA) muscles resembling a sphincter encircling the glottis. Thirty larynges obtained from necropsies of individuals with no known laryngeal pathology were dissected. The ATC fascicle was observed in 96.7% of the larynges. It appeared bilaterally in 60% of subjects and unilaterally in 36.7%. The posterior attachment of the muscular slip was observed to be in common with either the transverse arytenoid (34%), or the oblique arytenoid (28%) or both muscles (38%). Its fibers terminated by intermingling with either those of the LCA muscle (10.6%), or the TA muscle (38.3%) or both (51.1%). These variable attachments mean that there are nine possible variants of this muscular fascicle. The ATC fascicle was supplied by branches originating bilaterally from the recurrent laryngeal (RLN) and internal laryngeal nerves. The existence of this ATC fascicle could explain the variable position (intermediate, paramedian or lateral) adopted by the vocal folds after lesion of the RLN. The bilateral disposition and innervation of the fascicle could also complicate the interpretation of electromyographic techniques used for testing laryngeal nerve function.

Characterization of fast oscillatory rhythms in multiple respiratory‐related motor outputs during eupnea in decerebrate adult rat in vivo

Respiratory motor discharges exhibit both slow and fast oscillatory rhythms. The slow rhythms correspond to inspiratory (I), expiratory (E), or phase‐spanning behaviors while the fast rhythms appear to be exclusive to motor outputs exhibiting inspiratory‐related discharges. To further evaluate these respiratory‐related rhythms, we examined basal phrenic (PHR), hypoglossal (XII), and recurrent laryngeal (RLN) nerve bursts recorded simultaneously from decerebrate (unanesthetized) paralyzed mechanically‐ventilated adult rats in vivo. PHR discharge served as an index of I activity, and burst duration (TI) and the duration between bursts (TE) were determined from PHR traces. XII activity exhibited pre‐I and I phase discharge and RLN activity exhibited pre‐I, I, and E phase discharge. In each respiratory‐related motor output, high frequency oscillations (HFO) were identified but they were restricted to the I phase of each burst (i.e., no significant HFO activity was seen during pre‐I or E phases). PHR and RLN HFO peaks were located between 100‐150 Hz, and XII activity exhibited several distinct peaks with a broadband power distribution. HFO onset occurred at ~50% TI for PHR activity and somewhat earlier for XII and RLN activities; RLN HFO activity spanned most of the TI period. These data suggest that fast oscillatory rhythms in respiratory‐related motor discharges underlie only the I phase. Supported by NS049310.

Phonatory Functions after ArytenoidAdduction and That When Combined with Ansa Cervicalisto Recurrent Laryngeal Nerve Anastomosisor Type I Thyroplasty

Dysphonia due to unilateral vocal fold immobility (UVFI) can have detrimental effects on quality of patients’ daily lives (QOL). Arytenoid adduction and type I thyroplasty are widely accepted treatment methods for UVFI. However, postoperative voice does not always reach ‘normal’ although dysphonia is improved to a certain degree. The reasons for this unsatisfactory result may be originated from subtle failures to locate the immobile vocal fold (IVF) at the median position and to augment the IVF with the same thickness and tension as that on the healthy side. We started to combine reinnervation procedure with arytenoid adduction to acquire ‘near-normal’ postoperative voice. Phonatory Functions after Arytenoid Adduction and That When Combined with Ansa Cervicalis to Recurrent Laryngeal Nerve Anastomosis or Type I Thyroplasty Eiji Yumoto, MD*, Tetsuji Sanuki, MD, Yutaka Toya, MD and Narihiro Kodama Department of Otolaryngology – Head and Neck Surgery, Graduate School of Medicine, Kumamoto University

PDR interstitial brachytherapy in recurrent larynx cancer

PDR interstitial brachytherapy in recurrent larynx cancer

P077 Swallowing Outcomes Following Supracricoid Partial Laryngectomy in the Setting of Adjuvant Therapy

Objective: To evaluate swallowing recovery following supracricoid partial laryngectomy. Design: Retrospective review. Setting: Major comprehensive cancer center. Patients: Twenty-seven patients treated with supracricoid partial laryngectomy for primary or recurrent larynx cancer. Intervention: Functional swallowing strategies, maneuvers, and therapies based on objective modified barium swallow (MBS) study results. Main Outcome Measures: Hospital recovery (length of stay, decannulation rates, complications), swallowing outcomes (physiology, symptoms), and nutritional results (time to oral intake, tube dependency, final diet). Results: Supracricoid partial laryngectomy included 1 arytenoid cartilage in 8 of 27 patients. The mean (SD) length of hospitalization was 8 days (9.23 days [median, 6 days; range, 3-53 days]) with a mean (SD) number of weeks to decannulation of 5 (8.23 weeks [median, 1 week; range, 1-30 weeks]). One patient required permanent tracheostomy. The most common complications were pneumonia and subcutaneous emphysema (7 [26%] of 27 complications). Pneumonia occurred more often in patients who had received radiation therapy (P=.02). Twenty-two patients had MBS studies. Initially, all patients aspirated thin liquids and 55% (12 of 22) aspirated pureed consistencies owing to neoglottic incompetency. Diet modifications alone did not alleviate aspiration; 64% (14 of 22) of patients needed to use swallowing strategies. The supraglottic swallow maneuver was most effective in reducing or eliminating aspiration. Eighty-one percent (22 of 27) of patients returned to complete oral intake with mean (SD) time to feeding tube removal of 10 weeks (8.33 weeks [median, 6 weeks; range, 1-29 weeks]); 7 of these patients used swallowing strategies. Nineteen percent of patients (5 of 27) remained partially (4 of 27) or fully (1 of 27) tube dependent. Arytenoid resection did not significantly affect hospital course or swallowing outcomes. Conclusion: Supracricoid partial laryngectomy initially produces severe swallowing dysfunction but most patients return to oral intake following targeted dysphagia intervention.

Dermatitis Artefacta in a Patient with Recurrent Larynx Cancer: A Rare Self-inflicted Dermatosis

Dermatitis Artefacta in a Patient with Recurrent Larynx Cancer: A Rare Self-inflicted Dermatosis

Intrathoracic blood supply of the left vagus and recurrent laryngeal nerves

The arteries and veins of the left vagus (VN) and left recurrent laryngeal (RLN) nerves from the thoracic inlet to the subaortic region are described following vascular casting with red colored latex in 6 adult fresh non-embalmed cadavers. In all specimens the anterior bronchoesophageal artery supplied at least one vessel to the VN and RLN in the subaortic region. For the RLN other arterial sources were arteries arising from the aortic arch in 1 specimen, the subclavian artery in 3 specimens, the first intercostal artery in 1 specimen, and the inferior thyroid artery in all specimens. For the VN other arterial sources were arteries arising from the aortic arch in 2 specimens and the inferior thyroid artery in 1 specimen. For both the VN and RLN the veins were located under the pleura and directed towards the internal thoracic vein anteriorly and the thoracic intercostal veins posteriorly. In conclusion, the inferior thyroid artery at the thoracic inlet for the RLN and the anterior bronchoesophageal artery are the more consistent vessels supplying the VN and RLN. Vascular damage occurring during mediastinal lymph node excision to the VN and RLN, especially in the subaortic region, may explain postoperative vocal fold paralysis.

Population and unit synchrony of fast rhythms in expiratory recurrent laryngeal discharges.

In a decerebrate, vagotomized, gallamine-paralyzed cat that had a prominent bilaterally coherent fast rhythm (50 Hz) in expiratory (E) recurrent laryngeal (RL) nerve discharges, recordings were taken of the firing of nine RL E fibers. This rhythm (called E high-frequency oscillation or EHFO) was seen as a sharp peak in all unit autospectra, all unit-nerve coherence spectra (value range 0.39-0. 91), and all unit-unit coherence spectra (value range 0.27-0.85). In addition, 8/9 units had a sharp autospectral peak in a lower frequency range (19-35 Hz) called E medium-frequency oscillation (EMFO), but there was no coherence at this frequency between signal pairs (unit-unit, unit-nerve, nerve-nerve). The MFOs are specific for each unit and are considered to arise from asynchronous inputs and membrane properties. The HFOs are considered to arise from widespread network interactions that produce a common (correlated) rhythm in virtually all neurons of the RL E network. These phenomena suggest the use of the RL E network as a model system for analyzing rhythmic neural interactions.

Synchronized fast rhythms in inspiratory and expiratory nerve discharges during fictive vocalization.

In precollicular decerebrate and paralyzed cats, respiratory nerve activities were recorded during fictive vocalization (FV), which consisted of a distinctive pattern of 1) decreased inspiratory (I) and expiratory (E) phase durations, 2) marked increase of phrenic activity and moderate changes of recurrent laryngeal (RL) and superior laryngeal (SL) I activities, and 3) massive recruitment of laryngeal and abdominal (ABD; lumbar) E activities. FV was produced by electrical stimulation (100 Hz) in the midbrain periaqueductal gray (PAG) or its putative descending pathways in the ventrolateral pons (VLP). Spectral and correlation analyses revealed three types of effect on fast rhythms during FV. 1) I activities: the coherent high-frequency oscillations in I (I-HFO, 60-90 Hz) present in phrenic and RL discharges during the control state did not change qualitatively, but there was an increase of power and a moderate increase (4-10 Hz) of frequency. Sometimes a distinct relatively weak stimulus-locked rhythm appeared. 2) RL and SL activities during E: in recruited discharges, a prominent intrinsic rhythm (coherent E-HFOs at 50-70 Hz) appeared; sometimes a distinct relatively strong stimulus-locked rhythm appeared. 3) ABD activities during E: this recruited activity had no intrinsic rhythm but had an evoked oscillation locked to the stimulus frequency. Thus FV is characterized by 1) appearance of prominent coherent intrinsic rhythms in RL and SL E discharges, which presumably arise as a result of excitation and increased interactions in laryngeal networks; 2) modification of intrinsic rhythmic interactions in inspiratory networks; and 3) evoked rhythms in augmenting-E neuron networks without occurrence of intrinsic rhythms.

Anatomy and Physiology of the Upper Esophageal Sphincter

The upper esophageal sphincter (UES) is composed of the cricopharyngeus (CP), thyropharyngeus (TP; inferior pharyngeal constrictor [IPC] in humans), and cranial cervical esophagus. All 3 muscles may at times function to maintain tone in the UES, but only the CP contracts and relaxes in all physiologic states consistent with the UES. The CP is a striated muscle composed of variable-sized small (25–35 μm) muscle fibers that are primarily type I (slow twitch), highly oxidative, and contain abundant (40%) endomysial elastic connective tissue. The fibers may attach to the connective tissue framework, forming a muscular net. In humans and rats, but not other animals, the CP has no median raphe. The optimum length of the CP for development of active tension is about 1.7 times resting length; therefore, in some respects the CP acts more like cardiac than striated muscle. A passive tone in the CP is present and increases through all degrees of stretch. The high compliance of the CP allows it to be opened by distraction of other muscles (e.g., geniohyoideus) or increased intraluminal pressure. The CP is innervated by branches of the vagus nerves: pharyngoesophageal (PE), superior laryngeal (SLN), and recurrent laryngeal (RLN); glossopharyngeal (GPN); and cervical sympathetics. Only the PE and SLN provide motor fibers to the CP. The GLN may be sensory; the sympathetics may innervate the mucosa, blood vessels, and glands; but no functional innervation by the RLN has been identified. Parasympathetic ganglia and various peptides (galanin, cGRP, VIP, neuropeptide Y, substance P, tyrosine hydroxylase) have been found in the CP, but their role in control of the CP is unknown. The motoneurons of the CP are found in the nucleus ambiguus, and the innervation is ipsilateral for animal species in which the CP has a median raphe. These motoneurons are topographically organized with other pharyngeal and laryngeal muscles and the striated muscle esophagus. Pharyngeal motoneurons often have a respiratory rhythm, but not a spontaneous background discharge. Therefore, the CP motoneurons may not generate CP tone. Various reflexes control the tone of the CP. Distension of the esophagus causes contraction of the CP and UES, which is mediated by a vago-vagal reflex. Pressure on the pharyngeal mucosa contracts the CP and UES and is mediated by a glossopharyngo-vagal reflex. Inflation of the lungs causes contraction of the CP and UES, which is mediated by a vago-vagal reflex. The pharyngo-UES and pulmonary-UES reflexes may generate the respiratory rhythm often observed on UES pressure or electromyographic activity. The UES or CP also contracts with arousal or with changes in posture. All of these reflexes and responses and the passive elastic properties of the CP may contribute to the generation of tone in the CP and UES.

Unusual adverse reaction in a patient sensitized with Photosan 3

Serious side effects of photodynamic therapy (PDT) are rare (A.L. Abramson, M.J. Shikowitz, M.J. Shikowitz, V.M. Mullooly, Clinical effects of photodynamic therapy on recurrent laryngeal papillomas, Arch. Otolaryngology Head Neck Surg., 118 (1992) 25–29; A.L. Abramson, M.J. Shikowitz, Clinical exacerbation of systemic lupus erythematosus after photodynamic therapy of laryngotracheal papillomatosis, Laser Surg. Med., 13 (1993) 677–679). The most frequent side effects of PDT are hypersensitive skin reactions, local edema, nausea, a metallic taste and liver-toxicity (J. Feyh, E. Kastenbauer, Treatment of laryngeal papillomatosis with photodynamic laser therapy, Laryngorhinootologie, 71 (1992) 190–192; J. Feyh, R. Gutmann, A. Leunig, Die Photodynamische Therapie im Bereich der Hals-, Nasen-, Ohrenheilkunde Laryngorhinootologie, 72(6) (1993) 273–278; M.S. Kavuru, A.C. Mekta, Treatment of recurrent respiratory papillomatosis, N. Engl. J. Med., 326 (1992) 204–205; B.L. Wenigg, D.M. Kurtzmann, Photodynamic therapy in the treatment of squamous cell carcinomas of the head and neck, Arch. Otolaryngol Head Neck Surg., 116 (1990) 1267–1270). In this case a patient (aged 57 years) suffering from a recurrent larynx papillomatosis was treated with PDT. He was sensitized with Photosan 3 (DHE) 2.5 mg kg −1 body weight, 24 h to photoradiation. As a light source, an argon dye lase, operating at a wavelength of 630 nm was used, coupled with a cylindrical light applicator. After treatment the patient was admitted to an intensive care unit for 24 h. 3 h after photoradiation, general urticarial wheals arose, as well as techycardia and a decrease in blood pressure followed by all the signs of serious anaphylaxis. 1.5 h after treatment with adrenaline and cortisone and stabilization of the cardiac and circulatory situation no more skin lesions were visible.

High-frequency oscillations in membrane potentials of medullary inspiratory and expiratory neurons (including laryngeal motoneurons).

1. In midcollicular decerebrate, unanesthetized, paralyzed cats ventilated with a cycle-triggered pump system, the properties of high-frequency oscillations (HFOs, 50-100 Hz) in membrane potentials (MPs) of medullary inspiratory (I) and expiratory (E) cells were studied. Simultaneous recordings were taken from bilateral phrenic and recurrent laryngeal (RL) nerves and from cells in the intermediate ventral respiratory group (intVRG, 0-1 mm rostral to the obex) or the caudal ventral respiratory group (cVRG, 2-4 mm caudal to the obex). 2. Spectral coherence analyses were used to detect the presence of HFOs during I in I and E cell MPs. Cross-correlation histograms (CCHs) between the cell and phrenic signals were used to ascertain cell-nerve HFO phase relations and to identify cells as RL motoneurons. Of the 103 cells that had significant HFOs (cell-phrenic coherences > or = 0.1), measurable HFO peak lags in the CCH were seen in 53 cells: 1) RL cells (9 I cells and 7 E cells); and 2) other types of cell (8 intVRG I cells, 18 intVRG E cells, and 11 cVRG E cells). These cells had high HFO correlations; the cell-phrenic coherence range was 0.35-0.94, with a mean HFO frequency of 58 Hz. 3. The cell-phrenic HFO lag (in ms) was measured in the CCH as the lag of the primary peak (peak located nearest to 0 lag). The phase lag was defined as (lag of primary peak in ms)/(HFO period in ms). The phase lags differed markedly between two subsets of cells: 1) RL I cells had HFO depolarization peaks that lagged the phrenic HFO peaks (average cell-phrenic phase lag = -0.18); and 2) the non-RL cells, regardless of location (intVRG or cVRG) and type (I or E), had HFO depolarization peaks leading (preceding) the phrenic HFO peaks (average cell-phrenic phase lag = 0.28). In addition, the cVRG E cells had significantly shorter cell-phrenic phase lags than the intVRG E cells (0.23 vs. 0.31, respectively). 4. These lags can be compared with the (I unit)-phrenic phase lags (average approximately 0.3) found in earlier extracellular studies. 1) There is a transmission delay of about one half HFO cycle from excitatory I cells to RL I cells. 2) Because a depolarization peak in the MP of an E cell corresponds to the start of a hyperpolarizing wave, the excitatory bulbospinal pathways from I cells have transmission times comparable with those of the inhibitory intramedullary pathways from I cells to E cells. 5. These results indicate that study of HFO phase relations can furnish useful information on functional connectivity of medullary respiratory neurons during the I phase.

Analysis of recurrent laryngeal inspiratory discharges in relation to fast rhythms.

1. Inspiratory (I) activities of recurrent laryngeal (RL) motoneurons and efferent nerves were studied by autospectral, interval, and coherence analyses, with emphasis on fast rhythms of two types: medium-frequency oscillations (MFO, usual range 20-50 Hz for nerve autospectral peaks) and high-frequency oscillations (HFO, usual range 50-100 Hz). 2. In decerebrate, paralyzed, and artificially ventilated cats, recordings were taken from 27 isolated single RL fibers (14 cats) and 8 identified RL motoneurons in the medulla (6 cats), together with recordings of phrenic (PHR) and RL whole-nerve activities. In another 50 cats, RL and PHR nerve discharges were recorded simultaneously. 3. The autospectra of RL units showed prominent MFO peaks with frequencies close to that of the RL nerve MFO spectral peak, indicating presence of this type of fast rhythm in the units' discharges. Spectral analysis of RL unit activity in different segments of the I phase showed that the frequency of a unit's MFO was very close to the peak (maintained) firing rate of the unit during the portion of I analyzed. Thus a motoneuron's MFO spectral peak reflected its rhythmic discharge arising from the cell's refractoriness (and possibly with the rate changing in the course of I). 4. The coherences of motoneurons' MFOs to nerve MFOs were very low or 0, indicating that correlations between unitary MFOs of the RL population were rare and/or weak. 5. In those cats (19/20) that had discernible PHR nerve HFO autospectral peaks, about half of the recorded RL motoneurons (16/34) had HFO. For these motoneurons, the unit-nerve HFO coherences were substantial, indicating widespread correlations between unitary HFOs. 6. In a fraction of cats, coherence peaks in the MFO frequency range were observed between bilateral RL nerves, and between RL and PHR nerves, at frequencies that were subharmonics of the HFO frequency. 7. In light of theoretical considerations on the generation of aggregate rhythms from superposition of unitary rhythms, these observations indicate that, similarly, to the case of PHR motoneurons and nerves. 1) RL nerve MFO arises from superposition of uncorrelated, or at most partially correlated, MFOs of RL units, representing the rhythmic discharges of the cells. It is manifested therefore as a spectral deflection with a maximum in the band of peak firing rates of the units. 2) RL nerve HFO arises from correlated, common-frequency HFOs in a subpopulation of RL units, caused by HFO inputs from antecedent medullary I neurons.(ABSTRACT TRUNCATED AT 400 WORDS)