Faculty Bibliography

OBJECTIVES/OBJECTIVE:To provide a level-adjusted correction to the current standard relating anatomical cochlear place to characteristic frequency (CF) in humans, and to re-evaluate anatomical frequency mismatch in cochlear implant (CI recipients considering this correction. It is proposed that a level-adjusted place-frequency function may represent a more relevant tonotopic benchmark for CIs in comparison to the current standard. DESIGN/METHODS:The present analytical study compiled data from 15 previous animal studies that reported isointensity responses from cochlear structures at different stimulation levels. Extracted outcome measures were CFs and centroid-based best frequencies at 70 dB SPL input from 47 specimens spanning a broad range of cochlear locations. A simple relationship was used to transform these measures to human estimates of characteristic and best frequencies, and nonlinear regression was applied to these estimates to determine how the standard human place-frequency function should be adjusted to reflect best frequency rather than CF. The proposed level-adjusted correction was then compared with average place-frequency positions of commonly used CI devices when programmed with clinical settings. RESULTS:The present study showed that the best frequency at 70 dB SPL (BF70) tends to shift away from CF. The amount of shift was statistically significant (signed-rank test z = 5.143, p < 0.001), but the amount and direction of shift depended on cochlear location. At cochlear locations up to 600° from the base, BF70 shifted downward in frequency relative to CF by about 4 semitones on average. Beyond 600° from the base, BF70 shifted upward in frequency relative to CF by about 6 semitones on average. In terms of spread (90% prediction interval), the amount of shift between CF and BF70 varied from relatively no shift to nearly an octave of shift. With the new level-adjusted place-frequency function, the amount of anatomical frequency mismatch for devices programmed with standard-of-care settings is less extreme than originally thought and may be nonexistent for all but the most apical electrodes. CONCLUSIONS:The present study validates the current standard for relating cochlear place to CF, and introduces a level-adjusted correction for how best frequency shifts away from CF at moderately loud stimulation levels. This correction may represent a more relevant tonotopic reference for CIs. To the extent that it does, its implementation may potentially enhance perceptual accommodation and speech understanding in CI users, thereby improving CI outcomes and contributing to advancements in the programming and clinical management of CIs.

Current models of eye movement control propose that motor neurons responsible for moving the eyes contribute to all eye movements, regardless of context. A recent study in larval zebrafish has instead identified specialized neural circuits, including subtypes of motor neurons, for two different types of fast eye movement, one for exploration and the other for hunting.

OBJECTIVE:What we hear may influence postural control, particularly in people with vestibular hypofunction. Would hearing a moving subway destabilize people similarly to seeing the train move? We investigated how people with unilateral vestibular hypofunction and healthy controls incorporated broadband and real-recorded sounds with visual load for balance in an immersive contextual scene. DESIGN/METHODS:Participants stood on foam placed on a force-platform, wore the HTC Vive headset, and observed an immersive subway environment. Each 60-second condition repeated twice: static or dynamic visual with no sound or static white noise or real recorded subway station sounds [real] played from headphones. SETTING/METHODS:Human motion laboratory. PARTICIPANTS/METHODS:41 healthy controls (mean age 52 years, range 22-78) and 28 participants with unilateral peripheral vestibular hypofunction (mean age 61.5, 27-82). MAIN OUTCOME MEASURES/METHODS:We collected center-of-pressure (COP, anterior-posterior, medio-lateral) from the force-platform and head (anterior-posterior, medio-lateral, pitch, yaw, roll) from the headset and quantified root mean square velocity (cm/s or rad/s). RESULTS:Adjusting for age, the vestibular group showed significantly more sway than controls on: COP medio-lateral (no sound or real with static or dynamic visual); COP anterior-posterior (only on dynamic visuals in the presence of either sound); head medio-lateral and anterior-posterior (all conditions), head pitch and yaw (only on dynamic visuals in the presence of either sound). A significant increase in sway with sounds was observed for the vestibular group only on dynamic visuals COP anterior-posterior and head yaw (real) and head anterior-posterior and pitch (either sound). CONCLUSIONS:The addition of auditory stimuli, particularly contextually-accurate sounds, to a challenging, standing balance task in real-life simulation increased sway in people with vestibular hypofunction but not in healthy controls. TRIAL REGISTRATION/BACKGROUND:Clinical trial registrationThis study was registered on clinicaltrials.gov at the following link: https://clinicaltrials.gov/study/NCT04479761.

The adoption of large language models (LLMs) in healthcare demands a careful analysis of their potential to spread false medical knowledge. Because LLMs ingest massive volumes of data from the open Internet during training, they are potentially exposed to unverified medical knowledge that may include deliberately planted misinformation. Here, we perform a threat assessment that simulates a data-poisoning attack against The Pile, a popular dataset used for LLM development. We find that replacement of just 0.001% of training tokens with medical misinformation results in harmful models more likely to propagate medical errors. Furthermore, we discover that corrupted models match the performance of their corruption-free counterparts on open-source benchmarks routinely used to evaluate medical LLMs. Using biomedical knowledge graphs to screen medical LLM outputs, we propose a harm mitigation strategy that captures 91.9% of harmful content (F1 = 85.7%). Our algorithm provides a unique method to validate stochastically generated LLM outputs against hard-coded relationships in knowledge graphs. In view of current calls for improved data provenance and transparent LLM development, we hope to raise awareness of emergent risks from LLMs trained indiscriminately on web-scraped data, particularly in healthcare where misinformation can potentially compromise patient safety.

BACKGROUND:Human papillomavirus (HPV) negative oropharyngeal squamous cell carcinoma (OPSCC) is associated with worse survival when compared to HPV-positive OPSCC. Primary surgery is one option to intensify therapy in this high-risk group of patients. Unfortunately, the only randomized trial to explore this approach (RTOG 1221) failed to accrue and the role of primary surgery in the treatment of HPV-negative OPSCC remains unanswered. METHODS:A systematic review and meta-analysis were performed to examine the outcomes of surgery in the treatment of HPV-negative OPSCC. We used the PRISMA statement for reporting and queried Pubmed, Web of Science and the Cochrane databases for studies examining the use of primary surgery in the treatment of HPV-negative OPSCC. Excluded from analysis were reviews, commentaries, case series with fewer than 10 patients, and studies that included HPV-negative head and neck cancers of mixed sites. Our primary outcomes were 2-year and 5-year overall survival (OS) and disease-free survival (DFS). OS and DFS were pooled using meta-analysis of proportions. RESULTS: = undetermined; 2 studies). CONCLUSIONS:The two- and five-year OS for patients with HPV-negative OPSCC treated with any surgical approach and pathology-directed adjuvant therapy is 84% and 72%, respectively. The two- and five-year OS for HPV-negative OPCSCC treated with transoral surgery and pathology-directed adjuvant therapy is 87% and 82%, respectively.

Inhibitory interneurons are highly heterogeneous circuit elements often characterized by cell biological properties, but how these factors relate to specific roles underlying complex behavior remains poorly understood. Using chronic silicon probe recordings, we demonstrate that distinct interneuron groups perform different inhibitory roles within HVC, a song production circuit in the zebra finch forebrain. To link these functional subtypes to molecular identity, we performed two-photon targeted electrophysiological recordings of HVC interneurons followed by post hoc immunohistochemistry of subtype-specific markers. We find that parvalbumin-expressing interneurons are highly modulated by sensory input and likely mediate auditory gating, whereas a more heterogeneous set of somatostatin-expressing interneurons can strongly regulate activity based on arousal. Using this strategy, we uncover important cell-type-specific network functions in the context of an ethologically relevant motor skill.

Vertebrates stabilize gaze using a neural circuit that transforms sensed instability into compensatory counterrotation of the eyes. Sensory feedback tunes this vestibulo-ocular reflex throughout life. We studied the functional development of vestibulo-ocular reflex circuit components in the larval zebrafish, with and without sensation. Blind fish stabilize gaze normally, and neural responses to body tilts mature before behavior. In contrast, synapses between motor neurons and the eye muscles mature with a time course similar to behavioral maturation. Larvae without vestibular sensory experience, but with mature neuromuscular junctions, had a strong vestibulo-ocular reflex. Development of the neuromuscular junction, and not sensory experience, therefore determines the rate of maturation of an ancient behavior.

OBJECTIVES/OBJECTIVE:Recent studies suggest that hearing loss is associated with balance dysfunction and an increased risk of falls. The purpose of this study was to investigate whether adults with unilateral hearing loss (UHL) have an underlying vestibular dysfunction and whether vestibular testing explains balance function and fall risk. STUDY DESIGN/METHODS:Cross-sectional. SETTING/METHODS:Urban otology practice and a human motion laboratory. PATIENTS/METHODS:We recruited 41 healthy controls (mean age, 52 years; range, 22-78 years) and 29 adults with stable UHL (mean age, 53 years; range, 18-80 years) who denied symptoms of dizziness (Dizziness Handicap Inventory average, 1.86; range, 0-14). UHL occurred an average of 4 years (range from sudden loss, 4 months to 27.5 years) prior to testing. INTERVENTIONS/METHODS:We conducted the caloric portion of the videonystagmography test, video head impulse test (vHIT), and a battery of balance tests: standing on foam with eyes closed, timed up and go test, four square step test, 10-meter walk, and a virtual reality (VR) assessment of postural control. MAIN OUTCOME MEASURES/METHODS:Hearing was quantified by four-frequency pure-tone average (PTA). Caloric weakness was defined as asymmetry greater than 25%. Participants self-reported falls over the past 12 months and history of vertigo. Performance on balance tests was quantified by time to completion or duration of hold. Performance on the VR assessment was quantified by root-mean-square velocity of head sway. RESULTS:Proportion of unilateral caloric weakness was significantly higher in the UHL group (25%) than the control group (12%). Five participants with UHL refused caloric testing. vHIT gains of lateral canals were normal in both groups. The majority of participants in the UHL group experienced vertigo at the onset of hearing loss (72%). There were five fallers in the UHL group (17%) and three in the control group (7%). Participants with caloric weakness or vertigo at onset did not differ from those without in age or in any of the balance tests. Participants with history of falls differed in head sway and duration of hold standing on foam with eyes closed. CONCLUSIONS:Individuals with UHL are more likely to have caloric weakness than healthy controls; however, these findings are not correlated with functional outcomes or history of falls. Postural control testing using virtual reality or standing on foam with eyes closed may help detect those at a risk for falls.

INTRODUCTION/BACKGROUND:Tracheostomy is a commonly performed procedure in Otolaryngology and can be performed in different settings. We evaluate patient characteristics and cost efficacy of tracheostomy at the bedside versus operating room (OR). MATERIALS AND METHODS/METHODS:Retrospective chart review was performed for adult intensive care unit (ICU) patients who underwent tracheostomy from 2020 to 2023. Data and cost of procedures were analyzed using descriptive statistics. RESULTS:One hundred and sixty-five patients were included. One hundred and thirty-four (81.2%) patients underwent bedside tracheostomy. Age, sex, and BMI were not significantly different. Average time from consult to procedure and operative time was significantly shorter (p = 0.03; 0.008). There were no differences in postoperative complications, 30-day mortality, ICU length of stay (LOS), or overall LOS. Tracheostomy at the bedside offered a 73.1% cost reduction compared with performed in the OR. CONCLUSION/CONCLUSIONS:Advantages of bedside tracheostomy include decreased operative time, time from consult to procedure, and cost reduction for the hospital system. We advocate for consideration of bedside tracheostomy when appropriate.

BACKGROUND:Aneurysmal bone cysts (ABCs) are slow-growing, expansile bone tumors most often observed in the long bones and lumbar and thoracic spine. Anterior column ABCs of the spine are rare, and few cases have described their surgical management, particularly for lesions with extension into the odontoid process and the bilateral C2 pedicles. In the present case, the authors describe a two-stage strategy for resection of a symptomatic 2.3 × 3.3 × 2.7-cm C2 ABC with cord compression in a 13-year-old patient. OBSERVATIONS/METHODS:Initial tumor debulking was completed via a transoral approach, and resection of the involved region spanning the odontoid process to the C2-3 disc space was continued until visualization of the posterior longitudinal ligament. After appropriate decompression was confirmed, the patient was repositioned prone for removal of the residual tumor among the bilateral C2 pedicles. Posterior instrumentation was placed from the occiput to C4, with an autologous rib graft to encourage fusion. The postoperative recovery was uneventful, and 2-month imaging demonstrated postsurgical changes, resolution of compression, and a stable position of the instrumentation and graft material. LESSONS/CONCLUSIONS:The transoral approach facilitates sufficient exposure for the resection of large odontoid ABCs, and posterior stabilization can reduce the risk of postsurgical cervical subluxation. https://thejns.org/doi/10.3171/CASE2485.