The Role of the Parotid-Mastoid Fascia in Identification of the Facial Nerve Trunk During Parotidectomy.

OBJECTIVE: We aim to describe the parotid fascia as a landmark that can help identify the immediately underlying facial nerve trunk. METHODS: Dissection of the parotid fascia and identification of the facial nerve trunk were carried out on 8 fresh cadaveric parotid glands. The attachments and arrangement of the parotid gland and its fascia were evaluated and histologically assessed, with special attention to the fascia overlying the facial nerve trunk. RESULTS: The parotid fascia envelops the posterior aspect of the parotid gland in an open-book fashion. Posteriorly, it connects to the anterior and medial aspect of the mastoid tip. Posterosuperiorly, it attaches to the inferior aspect of the tragal pointer. Directly medial to the fascia lies the facial nerve trunk. CONCLUSION: The parotid fascia, particularly the parotid-mastoid segment overlying the facial nerve trunk, can be utilized as an additional landmark of depth to help identify the facial nerve trunk during a parotidectomy in conjunction with other commonly used standard anatomic landmarks. The parotid fascia sling spans from the mastoid and tragal pointer to the parotid gland and can be easily palpated intraoperatively. Once the fascia is removed, the facial nerve trunk is identified.

Noise-induced Cochlear Synaptopathy with and Without Sensory Cell Loss.

Prior work has provided extensive documentation of threshold sensitivity and sensory hair cell losses after noise exposure. It is now clear, however, that cochlear synaptic loss precedes such losses, at least at low-moderate noise doses, silencing affected neurons. To address questions of whether, and how, cochlear synaptopathy and underlying mechanisms change as noise dose is varied, we assessed cochlear physiologic and histologic consequences of a range of exposures varied in duration from 15 min to 8 h and in level from 85 to 112 dB SPL. Exposures delivered to adult CBA/CaJ mice produced acute elevations in hair cell- and neural-based response thresholds ranging from trivial (∼5 dB) to large (∼50 dB), followed by varying degrees of recovery. Males appeared more noise vulnerable for some conditions of exposure. There was little to no inner hair cell (IHC) loss, but outer hair cell (OHC) loss could be substantial at highest frequencies for highest noise doses. Synapse loss was an early manifestation of noise injury and did not scale directly with either temporary or permanent threshold shift. With increasing noise dose, synapse loss grew to ∼50%, then declined for exposures yielding permanent hair cell injury/loss. All synaptopathic, but no non-synaptopathic exposures produced persistent neural response amplitude declines; those additionally yielding permanent OHC injury/loss also produced persistent reductions in OHC-based responses and exaggerated neural amplitude declines. Findings show that widespread cochlear synaptopathy can be present with and without noise-induced sensory cell loss and that differing patterns of cellular injury influence synaptopathic outcomes.

Eustachian Tube Balloon Dilation: Emerging Practice Patterns for a Novel Procedure.

OBJECTIVES: To review the role of eustachian tube balloon dilation (ETBD) in the setting of chronic Eustachian tube dysfunction (ETD) and ascertain how ETBD is currently being used in practice today. METHODS: An online survey included 20 questions designed by 3 investigators to examine how otolaryngologists utilize ETBD in the management of ETD. The survey was distributed to the members of the American Rhinologic Society (ARS), American Otological Society (AOS), and American Neurotology Society (ANS) in their respective annual electronic mailings in April and May of 2017. RESULTS: A total of 1105 and 633 surveys were sent to ARS and AOS/ANS members, respectively. Of those, 157 surveys were returned (126 from ARS and 31 from AOS/ANS). Of those returning the survey, 72 (50%) had not performed ETBD and were excluded from subsequent analysis. Forty-four (66%) respondents consider ETBD after failure of medical management; conversely, 18 (27%) and 26 (39%) consider ETBD after failure of 1 or more trial of myringotomy tube placement. Routine testing for ETBD includes audiogram with tympanometry 64 (96%) and preoperative computer tomography (CT) 38 (57%). Fifty-three (80%) practitioners only perform ETBD in adults 18 years and older. Thirty-four (53%) respondents describe ETBD as "great" or "good," while 27 (42%) were unsure, and only 3 (5%) did not like ETBD. CONCLUSIONS: Eustachian tube balloon dilation is a novel technique for the treatment of chronic ETD, and its role continues to evolve and develop. Current practice patterns demonstrate wide variability in the assessment of ETD, heterogeneity in the timing of ETBD, and controversy in preoperative CT screening.

Effect of applied force and blade speed on histopathology of bone during resection by sagittal saw.

A sagittal saw is commonly used for resection of bone during joint replacement surgery. During sawing, heat is generated that can lead to an increase in temperature at the resected surface. The aim of this study was to determine the effect of applied thrust force and blade speed on generating heat. The effect of these factors and their interactions on cutting temperature and bone health were investigated with a full factorial Design of Experiments approach for two levels of thrust force, 15 N and 30 N, and for two levels of blade oscillation rate, 12,000 and 18,000 cycles per minute (cpm). In addition, a preliminary study was conducted to eliminate blade wear as a confounding factor. A custom sawing fixture was used to crosscut samples of fresh bovine cortical bone while temperature in the bone was measured by thermocouple (n=40), followed by measurements of the depth of thermal necrosis by histopathological analysis (n=200). An analysis of variance was used to determine the significance of the factor effects on necrotic depth as evidenced by empty lacunae. Both thrust force and blade speed demonstrated a statistically significant effect on the depth of osteonecrosis (p<0.05), while the interaction of thrust force with blade speed was not significant (p=0.22). The minimum necrotic depth observed was 0.50mm, corresponding to a higher level of force and blade speed (30 N, 18,000 cpm). Under these conditions, a maximum temperature of 93°C was measured at 0.3mm from the kerf. With a decrease in both thrust force and blade speed (15N, 12,000 cpm), the temperature in the bone increased to 109°C, corresponding to a nearly 50% increase in depth of the necrotic zone to 0.74 mm. A predictive equation for necrotic depth in terms of thrust force and blade speed was determined through regression analysis and validated by experiment. The histology results imply that an increase in applied thrust force is more effective in reducing the depth of thermal damage to surrounding bone than an increase in blade speed.