An evaluation of otolaryngology resources at United States medical schools.

OBJECTIVE: Otolaryngology (OTO) is a competitive specialty, and medical school factors outside an applicant's control, such as presence of OTO student resources and an affiliated OTO residency program, can impact the competitiveness of a student's application. This study sought to evaluate the extent of OTO resources United States (U.S.) allopathic medical schools provide to help their students be successful, and to evaluate for medical school factors which may bias toward inequitable distribution of student OTO resources. METHODS: A 48-question cross-sectional survey evaluating the extent of OTO resources was distributed by email to LCME accredited U.S. allopathic medical schools in 2020 and 2021. RESULTS: Schools with residency programs and where faculty were employed through an OTO or surgery department were more likely to have an Otolaryngology Interest Group (OIG), an Otolaryngology Medical Student Education Director (OMSED), and were more likely to provide opportunities for OTO research.

A Cross-Sectional Survey Study Evaluating United States Medical School Curricula in Otolaryngology.

OBJECTIVES: With an ever-expanding medical knowledge base and requirements for clinical training, medical schools struggle to incorporate subspecialty education, such as otolaryngology (OTO), into curricula. This study aims to assess the current state of OTO education, and evaluate factors contributing to the extent of OTO teaching in United States (U.S.) medical schools. METHODS: A 48-question survey evaluated the extent and practices of OTO teaching. The survey was distributed by email to all 155 LCME accredited U.S. allopathic medical schools in 2020 and 2021. RESULTS: Sixty-eight unique responses were received (43.9% of U.S. allopathic medical schools). 36.8% (n = 25) of schools reported having formal expectations of OTO knowledge in their core curriculum. Only 1 school (1.5%) had a required OTO rotation; the majority of schools offered an optional third or fourth year clerkship rotation (76.5% and 95.6%, respectively). Schools with residency programs and who employ their faculty through an OTO or surgery department were more likely to have otolaryngologists teach basic science lectures and the Head & Neck exam, offer an optional third year rotation, and have formal expectations of rotating students. CONCLUSIONS: Medical schools with residency programs and who employ their faculty through an OTO or surgery department have more robust OTO curricula. Despite the ubiquity of OTO presentations across specialties, incorporation of OTO knowledge in U.S. medical school curricula remains variable, and at times limited.

Development of a functional salivary gland tissue chip with potential for high-content drug screening.

Radiation therapy for head and neck cancers causes salivary gland dysfunction leading to permanent xerostomia. Limited progress in the discovery of new therapeutic strategies is attributed to the lack of in vitro models that mimic salivary gland function and allow high-throughput drug screening. We address this limitation by combining engineered extracellular matrices with microbubble (MB) array technology to develop functional tissue mimetics for mouse and human salivary glands. We demonstrate that mouse and human salivary tissues encapsulated within matrix metalloproteinase-degradable poly(ethylene glycol) hydrogels formed in MB arrays are viable, express key salivary gland markers, and exhibit polarized localization of functional proteins. The salivary gland mimetics (SGm) respond to calcium signaling agonists and secrete salivary proteins. SGm were then used to evaluate radiosensitivity and mitigation of radiation damage using a radioprotective compound. Altogether, SGm exhibit phenotypic and functional parameters of salivary glands, and provide an enabling technology for high-content/throughput drug testing.

Long-Term Maintenance of Acinar Cells in Human Submandibular Glands After Radiation Therapy.

PURPOSE: In a combined retrospective and prospective study, human salivary glands were investigated after radiation treatment for head and neck cancers. The aim was to assess acinar cell loss and morphologic changes after radiation therapy and to determine whether irradiated salivary glands have regenerative potential. METHODS AND MATERIALS: Irradiated human submandibular and parotid salivary glands were collected from 16 patients at a range of time intervals after completion of radiation therapy (RT). Control samples were collected from 14 patients who had not received radiation treatments. Tissue sections were analyzed using immunohistochemistry to stain for molecular markers. RESULTS: Human submandibular and parotid glands isolated less than 1 year after RT showed a near complete loss of acinar cells. However, acinar units expressing functional secretory markers were observed in all samples isolated at later intervals after RT. Significantly lower acinar cell numbers and increased fibrosis were found in glands treated with combined radiation and chemotherapy, in comparison to glands treated with RT alone. Irradiated samples showed increased staining for duct cell keratin markers, as well as many cells coexpressing acinar- and duct cell-specific markers, in comparison to nonirradiated control samples. CONCLUSIONS: After RT, acinar cell clusters are maintained in human submandibular glands for years. The surviving acinar cells retain proliferative potential, although significant regeneration does not occur. Persistent DNA damage, increased fibrosis, and altered cell identity suggest mechanisms that may impair regeneration.

Intrinsic mitotic activity supports the human salivary gland acinar cell population.

To develop treatments for salivary gland dysfunction, it is important to understand how human salivary glands are maintained under normal homeostasis. Previous data from our lab demonstrated that murine salivary acinar cells maintain the acinar cell population through self-duplication under conditions of homeostasis, as well as after injury. Early studies suggested that human acinar cells are mitotically active, but the identity of the resultant daughter cells was not clear. Using markers of cell cycle activity and mitosis, as well as an ex vivo 5-Ethynyl-2´-deoxyuridine assay, we show that human salivary gland acinar cells divide to generate daughter acinar cells. As in mouse, our data indicate that human salivary gland homeostasis is supported by the intrinsic mitotic capacity of acinar cells.

Salivary gland cell aggregates are derived from self-organization of acinar lineage cells.

OBJECTIVE: The objective of this study was to characterize the mechanism by which salivary gland cells (SGC) aggregate in vitro. DESIGN: Timelapse microscopy was utilized to analyze the process of salivary gland aggregate formation using both primary murine and human salivary gland cells. The role of cell density, proliferation, extracellular calcium, and secretory acinar cells in aggregate formation was investigated. Finally, the ability of cells isolated from irradiated glands to form aggregates was also evaluated. RESULTS: Salivary gland cell self-organization rather than proliferation was the predominant mechanism of aggregate formation in both primary mouse and human salivary gland cultures. Aggregation was found to require extracellular calcium while acinar lineage cells account for ∼80% of the total aggregate cell population. Finally, aggregation was not impaired by irradiation. CONCLUSIONS: The data reveal that aggregation occurs as a result of heterogeneous salivary gland cell self-organization rather than from stem cell proliferation and differentiation, contradicting previous dogma. These results suggest a re-evaluation of aggregate formation as a criterion defining salivary gland stem cells.

Retroductal Nanoparticle Injection to the Murine Submandibular Gland.

Two common goals of salivary gland therapeutics are prevention and cure of tissue dysfunction following either autoimmune or radiation injury. By locally delivering bioactive compounds to the salivary glands, greater tissue concentrations can be safely achieved versus systemic administration. Furthermore, off target tissue effects from extra-glandular accumulation of material can be dramatically reduced. In this regard, retroductal injection is a widely used method for investigating both salivary gland biology and pathophysiology. Retroductal administration of growth factors, primary cells, adenoviral vectors, and small molecule drugs has been shown to support gland function in the setting of injury. We have previously shown the efficacy of a retroductally injected nanoparticle-siRNA strategy to maintain gland function following irradiation. Here, a highly effective and reproducible method to administer nanomaterials to the murine submandibular gland through Wharton's duct is detailed (Figure 1). We describe accessing the oral cavity and outline the steps necessary to cannulate Wharton's duct, with further observations serving as quality checks throughout the procedure.

Murine Salivary Functional Assessment via Pilocarpine Stimulation Following Fractionated Radiation.

Hyposalivation is commonly observed in the autoimmune reaction of Sjögren's syndrome or following radiation injury to the major salivary glands. In these cases, questions remain regarding disease pathogenesis and effective interventions. An optimized technique that allows functional assessment of the salivary glands is invaluable for investigating exocrine gland biology, dysfunction, and therapeutics. Here, we present a step by step approach to performing pilocarpine stimulated saliva secretion, including tracheostomy and the dissection of the three major murine salivary glands. We also detail the appropriate murine head and neck anatomy accessed during these techniques. This approach is scalable, allowing for multiple mice to be processed simultaneously, thus improving the efficiency of the work flow. We aim to improve the reproducibility of these methods, each of which has further applications within the field. In addition to saliva collection, we discuss metrics for quantifying and normalizing functional capacity of these tissues. Representative data are included from submandibular glands with depressed salivary gland function 2 weeks following fractionated radiation (4 doses of 6.85 Gy).

Convergence of linear acceleration and yaw rotation signals on non-eye movement neurons in the vestibular nucleus of macaques.

Roughly half of all vestibular nucleus neurons without eye movement sensitivity respond to both angular rotation and linear acceleration. Linear acceleration signals arise from otolith organs, and rotation signals arise from semicircular canals. In the vestibular nerve, these signals are carried by different afferents. Vestibular nucleus neurons represent the first point of convergence for these distinct sensory signals. This study systematically evaluated how rotational and translational signals interact in single neurons in the vestibular nuclei: multisensory integration at the first opportunity for convergence between these two independent vestibular sensory signals. Single-unit recordings were made from the vestibular nuclei of awake macaques during yaw rotation, translation in the horizontal plane, and combinations of rotation and translation at different frequencies. The overall response magnitude of the combined translation and rotation was generally less than the sum of the magnitudes in responses to the stimuli applied independently. However, we found that under conditions in which the peaks of the rotational and translational responses were coincident these signals were approximately additive. With presentation of rotation and translation at different frequencies, rotation was attenuated more than translation, regardless of which was at a higher frequency. These data suggest a nonlinear interaction between these two sensory modalities in the vestibular nuclei, in which coincident peak responses are proportionally stronger than other, off-peak interactions. These results are similar to those reported for other forms of multisensory integration, such as audio-visual integration in the superior colliculus. NEW & NOTEWORTHY This is the first study to systematically explore the interaction of rotational and translational signals in the vestibular nuclei through independent manipulation. The results of this study demonstrate nonlinear integration leading to maximum response amplitude when the timing and direction of peak rotational and translational responses are coincident.

Responses of non-eye-movement central vestibular neurons to sinusoidal yaw rotation in compensated macaques after unilateral semicircular canal plugging.

After vestibular labyrinth injury, behavioral measures of vestibular performance recover to variable degrees (vestibular compensation). Central neuronal responses after unilateral labyrinthectomy (UL), which eliminates both afferent resting activity and sensitivity to movement, have been well-studied. However, unilateral semicircular canal plugging (UCP), which attenuates angular-velocity detection while leaving afferent resting activity intact, has not been extensively studied. The current study reports response properties of yaw-sensitive non-eye-movement rhesus macaque vestibular neurons after compensation from UCP. The responses at a series of frequencies (0.1-2 Hz) and peak velocities (15-210°/s) were compared between neurons recorded before and at least 6 wk after UCP. The gain (sp/s/°/s) of central type I neurons (responding to ipsilateral yaw rotation) on the side of UCP was reduced relative to normal controls at 0.5 Hz, ±60°/s [0.48 ± 0.30 (SD) normal, 0.32 ± 0.15 ipsilesion; 0.44 ± 0.2 contralesion]. Type II neurons (responding to contralateral yaw rotation) after UCP have reduced gain (0.40 ± 0.27 normal, 0.35 ± 0.25 ipsilesion; 0.25 ± 0.18 contralesion). The difference between responses after UCP and after UL is primarily the distribution of type I and type II neurons in the vestibular nuclei (type I neurons comprise 66% in vestibular nuclei normally; 51% ipsilesion UCP; 59% contralesion UCP; 38% ipsilesion UL; 65% contralesion UL) and the magnitude of the responses of type II neurons ipsilateral to the lesion. These differences suggest that the need to compensate for unilateral loss of resting vestibular nerve activity after UL necessitates a different strategy for recovery of dynamic vestibular responses compared to after UCP.

Disease-Specific Survival with Spindle Cell Carcinoma of the Head and Neck.

OBJECTIVES: (1) Determine factors influencing survival in patients diagnosed with spindle cell carcinoma (SpCC), a rare variant of head and neck squamous cell carcinoma (SCC). (2) Compare survival of patients with SpCC to those with conventional SCC. STUDY DESIGN: Retrospective cohort study. SETTING: Surveillance, Epidemiology, and End Results 18 database (years 2004-2009). SUBJECTS AND METHODS: Among patients receiving treatment for a single primary in the oral cavity, oropharynx, hypopharynx, or larynx, 118 subjects with SpCC and 18,298 subjects with SCC were identified with complete data for the variables of age, sex, grade, tumor size, stage group, and TNM stage. Disease-specific survival curves were compared. Univariate and multivariate analyses were used to examine the effects of each factor on survival over all sites and within each of 3 sites. RESULTS: Univariate analysis of the combination of the 3 anatomic subsites showed survival with SpCC was worse than with conventional SCC (P < .001). Three-year disease-specific survival with SpCC was 49.5%, and 5-year disease-specific survival was 40.2%. Compared with conventional SCC, survival was worse for SpCC of the oral cavity (P < .001) and oropharynx (P < .001) but no different for the larynx and hypopharynx site (P = .15). Multivariate analysis identified age (P = .02), tumor size (P = .006), and M stage (P < .001) as the only variables significantly affecting survival with SpCC. All variables significantly affected survival with conventional SCC. CONCLUSIONS: Spindle cell carcinoma carries a worse prognosis than SCC. Larger tumor size, older age, and metastatic disease portend worse survival with SpCC of the head and neck.

Long-term deficits in motion detection thresholds and spike count variability after unilateral vestibular lesion.

The vestibular system operates in a push-pull fashion using signals from both labyrinths and an intricate bilateral organization. Unilateral vestibular lesions cause well-characterized motor deficits that are partially compensated over time and whose neural correlates have been traced in the mean response modulation of vestibular nuclei cells. Here we compare both response gains and neural detection thresholds of vestibular nuclei and semicircular canal afferent neurons in intact vs. unilateral-lesioned macaques using three-dimensional rotation and translation stimuli. We found increased stimulus-driven spike count variability and detection thresholds in semicircular canal afferents, although mean responses were unchanged, after contralateral labyrinth lesion. Analysis of trial-by-trial spike count correlations of a limited number of simultaneously recorded pairs of canal afferents suggests increased noise correlations after lesion. In addition, we also found persistent, chronic deficits in rotation detection thresholds of vestibular nuclei neurons, which were larger in the ipsilesional than the contralesional brain stem. These deficits, which persisted several months after lesion, were due to lower rotational response gains, whereas spike count variability was similar in intact and lesioned animals. In contrast to persistent deficits in rotation threshold, translation detection thresholds were not different from those in intact animals. These findings suggest that, after compensation, a single labyrinth is sufficient to recover motion sensitivity and normal thresholds for the otolith, but not the semicircular canal, system.

Responses of non-eye movement central vestibular neurons to sinusoidal horizontal translation in compensated macaques after unilateral labyrinthectomy.

After vestibular labyrinth injury, behavioral deficits partially recover through the process of vestibular compensation. The present study was performed to improve our understanding of the physiology of the macaque vestibular system in the compensated state (>7 wk) after unilateral labyrinthectomy (UL). Three groups of vestibular nucleus neurons were included: pre-UL control neurons, neurons ipsilateral to the lesion, and neurons contralateral to the lesion. The firing responses of neurons sensitive to linear acceleration in the horizontal plane were recorded during sinusoidal horizontal translation directed along six different orientations (30° apart) at 0.5 Hz and 0.2 g peak acceleration (196 cm/s(2)). This data defined the vector of best response for each neuron in the horizontal plane, along which sensitivity, symmetry, detection threshold, and variability of firing were determined. Additionally, the responses of the same cells to translation over a series of frequencies (0.25-5.0 Hz) either in the interaural or naso-occipital orientation were obtained to define the frequency response characteristics in each group. We found a decrease in sensitivity, increase in threshold, and alteration in orientation of best responses in the vestibular nuclei after UL. Additionally, the phase relationship of the best neural response to translational stimulation changed with UL. The symmetry of individual neuron responses in the excitatory and inhibitory directions was unchanged by UL. Bilateral central utricular neurons still demonstrated two-dimension tuning after UL, consistent with spatio-temporal convergence from a single vestibular end-organ. These neuronal data correlate with known behavioral deficits after unilateral vestibular compromise.

Sensory convergence in the parieto-insular vestibular cortex.

Vestibular signals are pervasive throughout the central nervous system, including the cortex, where they likely play different roles than they do in the better studied brainstem. Little is known about the parieto-insular vestibular cortex (PIVC), an area of the cortex with prominent vestibular inputs. Neural activity was recorded in the PIVC of rhesus macaques during combinations of head, body, and visual target rotations. Activity of many PIVC neurons was correlated with the motion of the head in space (vestibular), the twist of the neck (proprioceptive), and the motion of a visual target, but was not associated with eye movement. PIVC neurons responded most commonly to more than one stimulus, and responses to combined movements could often be approximated by a combination of the individual sensitivities to head, neck, and target motion. The pattern of visual, vestibular, and somatic sensitivities on PIVC neurons displayed a continuous range, with some cells strongly responding to one or two of the stimulus modalities while other cells responded to any type of motion equivalently. The PIVC contains multisensory convergence of self-motion cues with external visual object motion information, such that neurons do not represent a specific transformation of any one sensory input. Instead, the PIVC neuron population may define the movement of head, body, and external visual objects in space and relative to one another. This comparison of self and external movement is consistent with insular cortex functions related to monitoring and explains many disparate findings of previous studies.

Reduced choice-related activity and correlated noise accompany perceptual deficits following unilateral vestibular lesion.

Signals from the bilateral vestibular labyrinths work in tandem to generate robust estimates of our motion and orientation in the world. The relative contributions of each labyrinth to behavior, as well as how the brain recovers after unilateral peripheral damage, have been characterized for motor reflexes, but never for perceptual functions. Here we measure perceptual deficits in a heading discrimination task following surgical ablation of the neurosensory epithelium in one labyrinth. We found large increases in heading discrimination thresholds and large perceptual biases at 1 wk postlesion. Repeated testing thereafter improved heading perception, but vestibular discrimination thresholds remained elevated 3 mo postlesion. Electrophysiological recordings from the contralateral vestibular and cerebellar nuclei revealed elevated neuronal discrimination thresholds, elevated neurometric-to-psychometric threshold ratios, and reduced trial-by-trial correlations with perceptual decisions ["choice probabilities" (CPs)]. The relationship between CP and neuronal threshold was shallower, but not significantly altered, suggesting that smaller CPs in lesioned animals could be largely attributable to greater neuronal thresholds. Simultaneous recordings from pairs of neurons revealed that correlated noise among neurons was also reduced following the lesion. Simulations of a simple pooling model, which takes into account the observed changes in tuning slope and correlated noise, qualitatively accounts for the elevated psychophysical thresholds and neurometric-to-psychometric ratios, as well as the decreased CPs. Thus, cross-labyrinthine interactions appear to play important roles in enhancing neuronal and perceptual sensitivity, strengthening interneuronal correlations, and facilitating correlations between neural activity and perceptual decisions.

Responses of central vestibular neurons to sinusoidal yaw rotation in compensated macaques after unilateral labyrinthectomy.

After vestibular labyrinth injury, behavioral measures of vestibular function partially recover through the process of vestibular compensation. The present study was performed to improve our understanding of the physiology of macaque vestibular nucleus neurons in the compensated state (>6 wk) after unilateral labyrinthectomy (UL). The responses of neurons to sinusoidal yaw rotation at a series of frequencies (0.1-2.0 Hz) and peak velocities (7.5-210°/s) were examined to determine how the behavior of these cells differed from those in animals with intact labyrinths. The sensitivity of neurons responding to ipsilateral rotation (type I) did not differ between the intact and injured sides after UL, although this sensitivity was lower bilaterally after lesion than before lesion. The sensitivity of neurons that increase firing with contralateral rotation (type II) was higher ipsilateral to the UL than before lesion or in the nucleus contralateral to the UL. UL did not increase asymmetry in the responses of individual type I or II neurons to ipsilateral vs. contralateral rotation, nor does it change the power law relationship between neuronal firing and level of stimulation. Increased sensitivities of contralesional type I neurons to the remaining vestibular nerve input and increased efficacy of inhibitory vestibular commissures projecting to the ipsilesional vestibular nucleus appear to be responsible for recovery of dynamic function of central vestibular neurons in compensated animals. The portion of type I neurons on the ipsilesional side is reduced in compensated animals, which likely accounts for the asymmetries in vestibular reflexes and perception that characterize vestibular function after UL.

Tests of linearity in the responses of eye-movement-sensitive vestibular neurons to sinusoidal yaw rotation.

The rotational vestibulo-ocular reflex in primates is linear and stabilizes gaze in space over a large range of head movements. Best evidence suggests that position-vestibular-pause (PVP) and eye-head velocity (EHV) neurons in the vestibular nuclei are the primary mediators of vestibulo-ocular reflexes for rotational head movements, yet the linearity of these neurons has not been extensively tested. The current study was undertaken to understand how varying magnitudes of yaw rotation are coded in these neurons. Sixty-six PVP and 41 EHV neurons in the rostral vestibular nuclei of 7 awake rhesus macaques were recorded over a range of frequencies (0.1 to 2 Hz) and peak velocities (7.5 to 210°/s at 0.5 Hz). The sensitivity (gain) of the neurons decreased with increasing peak velocity of rotation for all PVP neurons and EHV neurons sensitive to ipsilateral rotation (type I). The sensitivity of contralateral rotation-sensitive (type II) EHV neurons did not significantly decrease with increasing peak velocity. These data show that, like non-eye-movement-related vestibular nuclear neurons that are believed to mediate nonlinear vestibular functions, PVP neurons involved in the linear vestibulo-ocular reflex also behave in a nonlinear fashion. Similar to other sensory nuclei, the magnitude of the vestibular stimulus is not linearly coded by the responses of vestibular neurons; rather, amplitude compression extends the dynamic range of PVP and type I EHV vestibular neurons.

Convergence of vestibular and neck proprioceptive sensory signals in the cerebellar interpositus.

The cerebellar interpositus nucleus (IN) contributes to controlling voluntary limb movements. We hypothesized that the vestibular signals within the IN might be transformed into coordinates describing the body's movement, appropriate for controlling limb movement. We tested this hypothesis by recording from IN neurons in alert squirrel monkeys during vestibular and proprioceptive stimulation produced during (1) yaw head-on-trunk rotation about the C1-C2 axis while in an orthograde posture and (2) lateral side-to-side flexion about the C6-T3 axis while in a pronograde posture. Neurons (44/67) were sensitive to vestibular stimulation (23/44 to rotation and translation, 14/44 to rotation only, 7/44 to translation only). Most neurons responded during contralateral movement. Neurons (29/44) had proprioceptive responses; the majority (21/29) were activated during neck rotation and lateral flexion. In all 29 neurons with convergent vestibular and neck proprioceptive input those inputs functionally canceled each other during all combined sensory stimulation, whether in the orthograde or pronograde posture. These results suggest that two distinct populations of IN neurons exist, each of which has vestibular sensitivity. One population carries vestibular signals that describe the head's movement in space as is traditional for vestibular signals without proprioceptive signals. A second population of neurons demonstrated precise matching of vestibular and proprioceptive signals, even for complicated stimuli, which activated the semicircular canals and otolith organs and involved both rotation and flexion in the spine. Such neurons code body (not head) motion in space, which may be the appropriate platform for controlling limb movements.