Carbon dioxide laser fiber for laryngeal cancer surgery

OBJECTIVES: The carbon dioxide laser has evolved to be the premier dissecting instrument for hemostatic cutting during endolaryngeal cancer resection. However, dissection is limited to mirror-reflected line-of-sight delivery of the laser. A recently developed flexible, hollow photonic bandgap fiber (PBF) appears to offer advantages in endolaryngeal dissection. METHODS: The suitability of the PBF for human application was evaluated in a canine experiment in which human surgical procedures for microlaryngoscopic en bloc partial laryngectomy were simulated. The specimens that were resected endoscopically and the completion laryngectomy specimen were evaluated histologically. RESULTS: Observations from this experiment revealed that en bloc partial laryngectomy procedures were substantially easier to achieve as compared with prior experience in humans. This improvement resulted from three factors: 1) enhanced tangential dissection due to increased angulation of the laser energy, 2) enhanced procedural orientation due to proprioception of the tissues in contact mode, and 3) improved hemostasis. Histopathologic analysis of the resection margins revealed minimal thermal trauma. CONCLUSIONS: The PBF shows substantial promise for human application in endoscopic partial laryngectomy. It will likely enhance the ability of any surgeon to extend his or her indications for performing endoscopic laryngeal cancer resections regardless of philosophy (en bloc resection or piecemeal).     

Intracellularly labeled stapedius-motoneuron cell bodies in the cat are spatially organized according to their physiologic responses

This study examines whether the locations of stapedius-motoneuron cell bodies are correlated with their responses to sound. Single-unit recordings and injections of horseradish peroxidase were made in axons of stapedius motoneurons in the fascicles which run from the facial nerve to the stapedius muscle in the cat. Single units were characterized physiologically by their responses to ipsilateral, contralateral, and binaural sounds. Labeled cell bodies (N = 28) were found in all of the brainstem regions previously identified as containing stapedius motoneurons. Motoneurons characterized as having similar response properties had cell bodies in relatively circumscribed locations. Most (eight of 12) motoneurons excited by sound in either ear had cell bodies in a narrow band around the facial nucleus. Most (seven of eight) motoneurons excited by ipsilateral but not contralateral sound had cell bodies in the cleft between the superior olivary complex and the facial nucleus. All four motoneurons excited by contralateral but not ipsilateral sound had cell bodies located ventromedial to the facial nucleus. The three motoneurons excited only by binaural sound had cell bodies located dorsal to the superior olivary complex. (Two of these were also in the cleft between the superior olivary complex and the facial nucleus.) The cell body of the one motoneuron showing activity in the absence of sound stimulation was located dorsolateral to the facial nucleus. These results show that the cell bodies of stapedius motoneurons with similar electrophysiologic properties tend to have similar locations in the brainstem. The results are consistent with the idea that the stapedius-motoneuron pool is divided into subgroups that are spatially segregated in terms of their patterns of input from the two ears.     

A new instrument for intraoperative assessment of individual vocal folds

OBJECTIVES: Intraoperative assessment of vocal fold vibration during phonomicrosurgery performed under general anesthesia may enhance surgical decision-making. We therefore developed and bench-tested a new device we refer to as the aerodynamic vocal fold driver (AVFD). MATERIALS AND METHODS: The AVFD comprises a hand-held probe that uses airflow to drive individual vocal folds into phonatory-like vibration. This permits stroboscopic visualization of mucosal waves with simultaneous control of subglottal air pressure. In initial experiments to validate the technique, AVFD driven phonation and conventional whole-larynx phonation were compared using excised canine larynges (n = 14). RESULTS: Single vocal fold phonation using the AVFD and whole larynx phonation yielded similar, positive correlations between subglottal pressure and both amplitude and frequency of vibration. Experiments simulating vocal fold scar-related mucosal stiffening by subepithelial injection of fixative showed the expected elevation of phonation threshold pressures as measured with the AVFD. Likewise, unilateral tissue compression injury disrupted vocal fold vibration, and the AVFD was useful for quantifying improvement in the damaged vocal fold after repair with injection of cross-linked hyaluronic acid gel. CONCLUSIONS: These results show that this new instrument has the potential to provide novel and useful information for laryngeal experimentation and to improve phonosurgery.