"Transcanal view" computed tomography reformat: Applications for transcanal endoscopic ear surgery.

PURPOSE: Transcanal endoscopic ear surgery (TEES) is an increasingly used surgical approach for otologic surgeries, but no en face preoperative imaging format currently exists. We aim to assess the utility of a transcanal high resolution computed tomography (HRCT) reformat suitable for TEES preoperative planning. MATERIALS AND METHODS: Preoperative HRCTs of patients with middle ear pathologies (cholesteatoma, otosclerosis, and glomus tympanicum) who underwent TEES were obtained. Axial image series were rotated and reformatted -90 or +90 degrees for left and right ear surgeries, respectively, where additional rotation along the left-right axis was performed to align the transcanal series with the plane of the external auditory canal. Quantitative measurements of middle ear structures were recorded. Consecutive transcanal reformatted sections were then reviewed to identify critical middle ear anatomy and pathology with corresponding TEES cases. RESULTS: The aforementioned methodology was used to create three transcanal view HRCTs. The mean left-right axis degree of rotation was 4.0 ± 2.2 degrees. In the cholesteatoma transcanal HRCT, areas of cholesteatoma involvement in middle ear compartments (e.g. epitympanum) and eroded ossicles were successfully identified in the corresponding case. In the otosclerosis transcanal HRCT, areas for potential otosclerotic involvement were visualized such as the round window as well as a low-hanging facial nerve. In the glomus tympanicum transcanal HRCT, the span of the glomus tympanicum was successfully visualized in addition to a high riding jugular bulb. CONCLUSION: A transcanal HRCT reformat may aid preoperative planning for middle ear pathologies. This novel reformat may help highlight patient-specific anatomy.

Methods for the calibration of bone conduction transducers at frequencies from 5 to 20 kHz.

Techniques for standardizing the output of bone conduction transducers over the 5-20 kHz range are presented. The techniques include definitions of the standard artificial mastoid (AM) impedance and force sensitivity in that high-frequency range using an impedance head coupled to a vibration source. The AM impedance is shown to vary with the contact area of the vibration source. The AM force sensitivity does not vary with the contact area but does exhibit sharp frequency dependences over the 14-20 kHz range. The sharp frequency dependence complicates the use of the AM force sensor as a stand-alone calibration device at these high frequencies. An alternative calibration scheme that uses an accelerometer interposed between the vibrator and the AM impedance is described. Comparisons of the two schemes demonstrate that the accelerometer method produces more consistent results. Comparisons of the force and acceleration output of one bone conduction vibrator at high frequencies suggest those outputs depend on the driven load. The loads used in the two calibration schemes are compared to what is known of the impedance of the skin-covered head.

Optimized Diagnostic Approach to Patients Suspected of Superior Semicircular Canal Dehiscence.

OBJECTIVES: Current methods of diagnosing superior semicircular canal dehiscence syndrome (SCDS) include a clinical exam, audiometric testing, temporal bone computer tomography (CT) imaging, and vestibular evoked myogenic potential (VEMP) testing. The main objective of this study was to develop an improved diagnostic approach to SCDS optimized for accuracy, efficiency, and safety that utilizes clinical presentation, audiometric testing, CT imaging, high-frequency cervical VEMP (cVEMP) testing, and patient treatment preference. A secondary aim was to investigate the cost associated with the current versus proposed diagnostic paradigms. DESIGN: All patients who underwent cVEMP testing since introduction of the 2 kHz cVEMP in our clinical protocol in July 2018 were screened. Patients suspected of SCDS based upon symptoms who also had available audiogram, CT scan, and 2 kHz cVEMP were included (58 ears). Patients were categorized as dehiscent, thin, or not dehiscent based on their CT scan. Symptom prevalence and cVEMP outcomes were analyzed and compared for all groups. The accuracy of the 2 kHz cVEMP was calculated using CT imaging as the standard. Using a combination of patient symptomatology, audiometric, CT and 2 kHz cVEMP data, as well as patient preference, a best clinical practice approach was developed. The cost associated with this approach was calculated and compared with cost of the current SCDS diagnostic workup using Medicare reimbursement rates. RESULTS: In the overall patient population suspected of SCDS based on clinical presentation, the sensitivity and specificity of 2 kHz cVEMP were 76% and 100%, respectively, while the positive and negative predictive values were 100% and 84.6%, assuming that the CT scan finding was correct. Autophony was the most common symptom in patients who had both superior semicircular canal dehiscence on CT imaging plus abnormal 2 kHz cVEMP (p < 0.001). Combining patient symptomatology, 2 kHz normalized peak to peak cVEMP amplitude, and patient treatment preference to determine, which patients should undergo CT scanning resulted in a potential cost reduction between 45% and 61%. CONCLUSION: In patients suspected of SCDS based on their clinical presentation, the combination of symptomatology, 2 kHz cVEMP data, and patient preference can be used to determine which patients should undergo CT scanning, resulting in a diagnostic cost reduction and reduced patient radiation exposure.

Limitations of present models of blast-induced sound power conduction through the external and middle ear.

The use of models to predict the effect of blast-like impulses on hearing function is an ongoing topic of investigation relevant to hearing protection and hearing-loss prevention in the modern military. The first steps in the hearing process are the collection of sound power from the environment and its conduction through the external and middle ear into the inner ear. Present efforts to quantify the conduction of high-intensity sound power through the auditory periphery depend heavily on modeling. This paper reviews and elaborates on several existing models of the conduction of high-level sound from the environment into the inner ear and discusses the shortcomings of these models. A case is made that any attempt to more accurately define the workings of the middle ear during high-level sound stimulation needs to be based on additional data, some of which has been recently gathered.

3D-printed tracheoesophageal puncture and prosthesis placement simulator.

OBJECTIVES: A tracheoesophageal prosthesis (TEP) allows for speech after total laryngectomy. However, TEP placement is technically challenging, requiring a coordinated series of steps. Surgical simulators improve technical skills and reduce operative time. We hypothesize that a reusable 3-dimensional (3D)-printed TEP simulator will facilitate comprehension and rehearsal prior to actual procedures. METHODS: The simulator was designed using Fusion360 (Autodesk, San Rafael, CA). Components were 3D-printed in-house using an Ultimaker 2+ (Ultimaker, Netherlands). Squid simulated the common tracheoesophageal wall. A Blom-Singer TEP (InHealth Technologies, Carpinteria, CA) replicated placement. Subjects watched an instructional video and completed pre- and post-simulation surveys. RESULTS: The simulator comprised 3D-printed parts: the esophageal lumen and superficial stoma. Squid was placed between components. Ten trainees participated. Significant differences existed between junior and senior residents with surveys regarding anatomy knowledge(p<0.05), technical details(p<0.01), and equipment setup(p<0.01). Subjects agreed that simulation felt accurate, and rehearsal raised confidence in future procedures. CONCLUSIONS: A 3D-printed TEP simulator is feasible for surgical training. Simulation involving multiple steps may accelerate technical skills and improve education.

Transcanal endoscopic infracochlear vestibular neurectomy: A pilot cadaveric study.

PURPOSE: Effective operative approaches for the treatment of refractory vertigo in Meniere's disease are invasive. Vestibular neurectomy can preserve hearing and has been shown to be effective; however, current approaches require an extensive craniotomy. Transcanal endoscopic approaches to the internal auditory canal (IAC) with cochlear preservation have been recently described and may offer a minimally invasive approach to selectively sectioning the distal vestibular nerves while preserving residual hearing. MATERIALS AND METHODS: Three cadaveric human heads were imaged using high resolution computed tomography (CT). Anatomic analysis of preoperative CT scans showed adequate diameters (>3 mm) of the infracochlear surgical corridor for access to the IAC. A transcanal endoscopic approach was attempted to section the vestibular nerve. Post-operative CT scans were assessed to define the operative tract, determine cochlear preservation and assess cochlear and facial nerve preservation. RESULTS: Transcanal endoscopic approach was successfully performed (n = 3) using 3 mm-diameter, 14 cm-length 0°, 30°, and 45° endoscopes and microsurgical drills. In all cases the tympanomeatal flap and ossicular chain remained intact. Internal auditory canalotomy was performed using angled instruments and confirmed in real time via lateral skull base navigation. The vestibular nerves were readily identified and sectioned with preservation of the facial and cochlear nerves. Post-procedure CT showed no violation of the cochlea. CONCLUSION: A transcanal, infracochlear approach to the IAC may permit a minimally invasive approach to distal vestibular neurectomy in cadavers with appropriate anatomy.

Auditory Brainstem Implant Array Position Varies Widely Among Adult and Pediatric Patients and Is Associated With Perception.

OBJECTIVES: The auditory brainstem implant (ABI) provides sound awareness to patients who are ineligible for cochlear implantation. Auditory performance varies widely among similar ABI cohorts. We hypothesize that differences in electrode array position contribute to this variance. Herein, we classify ABI array position based on postoperative imaging and investigate the relationship between position and perception. DESIGN: Retrospective review of pediatric and adult ABI users with postoperative computed tomography. To standardize views across subjects, true axial reformatted series of scans were created using the McRae line. Using multiplanar reconstructions, basion and electrode array tip coordinates and array angles from vertical were measured. From a lateral view, array angles (V) were classified into types I to IV, and from posterior view, array angles (T) were classified into types A to D. Array position was further categorized by measuring distance vertical from basion (D1) and lateral from midline (D2). Differences between array classifications were compared with audiometric thresholds, number of active electrodes, and pitch ranking. RESULTS: Pediatric (n = 4, 2 with revisions) and adult (n = 7) ABI subjects were included in this study. Subjects had a wide variety of ABI array angles, but most were aimed superiorly and posteriorly (type II, n = 7) from lateral view and upright or medially tilted from posterior view (type A, n = 6). Mean pediatric distances were 8 to 42% smaller than adults for D1 and D2. In subjects with perceptual data, electrical thresholds and the number of active electrodes differed among classification types. CONCLUSIONS: In this first study to classify ABI electrode array orientation, array position varied widely. This variability may explain differences in auditory performance.

Quantitative imaging analysis of transcanal endoscopic Infracochlear approach to the internal auditory canal.

PURPOSE: A transcanal endoscopic infracochlear surgical approach to the internal auditory canal (IAC) in a human temporal bone model has previously been described. However, the proportion of patients with favorable anatomy for this novel surgical technique remains unknown. Herein, we perform a quantitative analysis of the transcanal endoscopic infracochlear corridor to the IAC based on computed tomography. MATERIALS AND METHODS: High resolution computed tomography scans of adult temporal bones were measured to determine the accessibility of the IAC when using an endoscopic transcanal, cochlear-sparing surgical corridor. RESULTS: This approach to the IAC was feasible in 92% (35 of 38) specimens based on a minimum distance of 3mm between the basilar turn of the cochlear and the great vessels (jugular bulb and carotid artery). CONCLUSIONS: Infracochlear access to the IAC is feasible in the majority of adult temporal bones and has implications for future hearing preservation drug delivery approaches to the IAC.

Temporal bone computed tomography findings associated with feasibility of endoscopic ear surgery.

PURPOSE: There are no formal radiologic criteria to stratify patients for transcanal (TEES) or transmastoid endoscopic ear surgery for resection of cholesteatoma. We aim to determine 1) whether standard preoperative computed tomography (CT) findings are associated with the need for conversion to a transmastoid approach and 2) the amount of time added for conversion from TEES to transmastoid techniques. MATERIALS AND METHODS: Retrospective chart review of consecutive pediatric and adult cases of TEES for primary cholesteatoma from 2013 through 2015 (n=52). TEES cases were defined as endoscope-only procedures that did not require a transmastoid approach (n=33). Conversion cases were defined as procedures that began as TEES however, required conversion to a transmastoid approach due to the inability to complete cholesteatoma removal (n=19). Preoperative CT findings and total operating room (OR) times of TEES and conversion cases were compared. RESULTS: Preoperative CT scan characteristics that were associated with conversion included tegmen erosion (p=0.026), malleus erosion (p<0.001), incus erosion (p=0.009), mastoid opacification (p=0.009), soft tissue opacification extending into the aditus ad antrum (p=0.009) and into antrum (p=0.006). Total OR time for TEES cases was significantly shorter than conversion cases (median 143min versus 217min, p<0.001). CONCLUSIONS: Preoperative CT findings, notably extension of soft tissue in the aditus ad antrum, antrum and mastoid, are associated with need for conversion to transmastoid technique to achieve removal of cholesteatoma. Endoscope-only cases were significantly faster than cases that required conversion to a transmastoid approach.

Placement of a 16-French voice prosthesis at the time of secondary tracheoesophageal voice restoration.

PURPOSE: Tracheoesophageal voice restoration (TEVR) has traditionally been described with fistula tract creation, catheter placement, and prosthesis placement. Prosthesis placement at the time of tracheoesophageal puncture (TEP) utilizing 20-French prostheses has been previously described. Smaller initial prostheses may allow fluent speech with reduced long-term complications, such as widening of the fistula and peri-prosthesis leakage. This study evaluates the safety and efficacy of the 16-French prostheses placement at the time of secondary TEP. METHODS: All cases of 16-French tracheoesophageal voice prosthesis (TEVP) placement at the time of secondary TEP were reviewed from 1/2011 through 12/2013 at a large academic medical center. Perioperative complications attributable to device placement were recorded, including inability to place prosthesis, intraoperative complications, post-operative infection, prosthesis dislodgement, prosthesis leakage, and inability to obtain voice. RESULTS: Twenty-one patients received placement of a 16-French TEVP at the time of secondary TEP. All prostheses were placed without intraoperative complications. The proportion of patients who had minor complications within the first postoperative month was 23.8%, including leakage through the prosthesis (3 of 21), granulation tissue near the prosthesis (1 of 21), retained sheath (1 of 21) and prosthesis displacement (1 of 21). Leakage and displacement were addressed with change and replacement, respectively. Fluent voicing was achieved in 85.7% patients, with a median time to voicing of 18.5days. CONCLUSIONS: Placement of 16-French TEVPs is effective and safe, with an acceptable rate of minor complications attributable to the prosthesis. Therefore, a smaller prosthesis may be primarily placed at the time of secondary TEP and is our preference.

Endoscopic transcanal removal of symptomatic external auditory canal exostoses.

Exostoses are bony outgrowths of the external auditory canal (EAC) that can lead to cerumen entrapment, recurrent infections, and conductive hearing loss. When surgical removal is indicated, a drill or osteotome may be used via a post-auricular, endaural, or transcanal approach. Studies suggest that exostoses removed by transcanal osteotome result in decreased morbidity when compared to open, drilled approaches; however, inadvertent injury to the facial nerve or inner ear is a theoretical concern given the restrictive geometry of the EAC and challenges of visualizing the tip of the chisel through the microscope. The endoscope provides superior visualization of the external auditory canal and tympanic membrane compared to the microscope. We sought to demonstrate the efficacy and safety of endoscopic exostosis surgery with an osteotome. We find that the endoscope provides improved wide angled views without blind spots. There were no intraoperative complications. Endoscopic canaloplasty for exostoses may be readily applied.

Subspecialty emergency room as alternative model for otolaryngologic care: implications for emergency health care delivery.

PURPOSE: A dedicated otolaryngology emergency room (ER) represents a specialized surgical evaluation and treatment setting that may be an alternative triage pathway for acute otolaryngologic complaints. We aim to characterize practice patterns in this setting and to provide insight into the epidemiology of all-comer, urgent otolaryngologic complaints in the United States. METHODS AND METHODS: Electronic medical records were reviewed for all patients who registered for otolaryngologic care and received a diagnosis in the Massachusetts Eye and Ear Infirmary ER between January 2011 and September 2013. Descriptive analysis was performed to characterize utilization and diagnostic patterns. Predictors of inpatient admission were identified using multivariable regression. Geocoding analysis was performed to characterize catchment area. RESULTS: A total of 12,234 patient visits were evaluated with a mean age of 44.7. Auditory and vestibular problems constituted the most frequent diagnoses (50.0%). The majority of patients were discharged home (92.3%). Forty-three percent of patients underwent a procedure in the ER; the most common procedure was diagnostic nasolaryngoscopy (52%). Predictors of inpatient admission were post-operative complaint (odds ratio [OR] 7.3, P<0.0001), arrival overnight (OR 3.3, P<0.0001), and laryngeal complaint (OR 2.4, P<0.0001). Patients traveled farther for evaluation of hearing loss (11 miles) and less for common diagnoses including impacted cerumen (7.1 miles) (P<0.0001). CONCLUSION: In this report, we investigate practice patterns of a dedicated otolaryngology emergency room to explore an alternative to standard acute otolaryngologic health care delivery mechanisms. We identify key predictors of inpatient admission. This study has implications for emergency health care delivery models.

Ossicular joint histopathology in cases of age-related hearing loss.

Objectives: Age-related hearing loss (presbycusis) is a prevalent condition traditionally attributed to inner ear dysfunction. Little is known about age-related changes in the ossicular joints or their contribution to presbycusis. Herein, we performed an otopathologic evaluation of the ossicular joints in cases of presbycusis without a clear sensorineural explanation. Methods: Histopathologic analysis of the incudomallear (IM) and incudostapedial (IS) joints was performed in specimens from the National Temporal Bone Registry with audiometrically confirmed presbycusis but without histologically observed sensorineural, strial, or mixed features; deemed cases of "indeterminate" presbycusis. Specimens identified as "indeterminate" presbycusis (IP, n = 18) were compared to specimens with histologically confirmed sensorineural presbycusis (n = 16) and strial presbycusis (n = 11). Presbycutic specimens were also compared to age-matched controls (n = 9) and young controls (n = 14). Results: The synovial space at the center of the IM joint was wider in the IP group (194 ± 36.8 µm) compared to age-matched controls (138 ± 36.5 µm), young controls (149 ± 32.2 µm), and ears with sensorineural presbycusis (148 ± 52.7 µm) (p < .05). The synovial space within the IS joint was wider in the IP group (105 ± 33.0 µm) when compared to age-matched controls (57.9 ± 13.1 µm) and ears with sensorineural presbycusis (62.3 ± 31.2 µm) (p < .05). Conclusion: IP ears have wider IM and IS joints when compared to ears with sensorineural presbycusis and age-matched controls. Findings point to a potential middle ear source of high frequency conductive hearing loss in a subset of presbycutic ears. Level of Evidence: Retrospective study.

The human middle ear in motion: 3D visualization and quantification using dynamic synchrotron-based X-ray imaging.

The characterization of the vibrations of the middle ear ossicles during sound transmission is a focal point in clinical research. However, the small size of the structures, their micrometer-scale movement, and the deep-seated position of the middle ear within the temporal bone make these types of measurements extremely challenging. In this work, dynamic synchrotron-based X-ray phase-contrast microtomography is used on acoustically stimulated intact human ears, allowing for the three-dimensional visualization of entire human eardrums and ossicular chains in motion. A post-gating algorithm is used to temporally resolve the fast micromotions at 128 Hz, coupled with a high-throughput pipeline to process the large tomographic datasets. Seven ex-vivo fresh-frozen human temporal bones in healthy conditions are studied, and the rigid body motions of the ossicles are quantitatively delineated. Clinically relevant regions of the ossicular chain are tracked in 3D, and the amplitudes of their displacement are computed for two acoustic stimuli.

Primary Sarcoidosis of the Temporal Bone a Clinical Pathologic Correlation.

Objective: This report describes a case of sarcoidosis that presented as a lytic bone lesion in the squamous part of the temporal bone. Patients: A 64-year-old woman presented with right-sided aural fullness, pulsatile tinnitus, and intermittent otalgia. Interventions: CT and MRI were performed without contrast and suggested an osseodestructive, lytic bone lesion. An excisional biopsy was performed, showing granulomatous infiltration suggestive of osseous sarcoidosis. Main Outcome Measures: Removal of mass and resolution of symptoms. Results: Initial findings from patient imaging suggested a lytic bone lesion. An excisional biopsy was required for diagnosis and was performed with little patient morbidity. Biopsy findings showed granulomatous infiltration suggestive of osseous sarcoidosis. Osseous involvement of sarcoidosis is a rare manifestation and typically occurs secondary to other disease manifestations. After the removal of the mass and a short unrelated course of steroids, the patient's symptoms resolved. Conclusions: Sarcoidosis should be added to the differential diagnosis of lytic bone lesions in the temporal bone.

Characterization and Clinical Use of Bone Conduction Transducers at Extended High Frequencies.

Measurement of bone conduction (BC) hearing thresholds at extended high frequencies (EHF; above 8 kHz) is of clinical interest but is technically complicated by limitations in standard BC transducer output, a lack of calibration standards and sparse clinical data from human subjects. A recently described calibration scheme using an artificial mastoid and interposed accelerometer is applied in this study to characterize and compare acceleration and computed force outputs over the 4-20 kHz range of two standard BC transducers: the RadioEar® B71 and B81, as well as two non-standard, commercially available BC transducers: the Tascam® HP-F200 and the Aftershokz® AS400. Measures of linear output growth, harmonic distortion and acoustic radiation are assessed and compared across devices. A maximum linear input voltage is established for each BC transducer using measurements of linear output growth and total harmonic distortion. At maximum linear input level, the Tascam shows superior force output by 25 to 40 dB above 8 kHz and the widest dynamic EHF range. Acoustic radiation per output force was lowest for the Tascam, whereas the AS400 behaved more like an air conduction earphone than a force generator. In a cohort of 15 normal hearing volunteers, BC thresholds, measured with the Tascam and reported in dB re 1 rms µN, were consistent with historical measures of EHF BC thresholds in similar subjects using an alternative BC transducer.

Human otopathology in scleroderma.

Objective: Scleroderma is a complex chronic progressive immune-mediated disease that causes fibrosis of the skin and internal organs, and vasculopathy.Ear involvement has been poorly studied in patients with scleroderma. Vasculitic and autoimmune mechanisms are considered as possible etiologies on hearing impairment, however, this etiology still unclear.Herein, we reviewed three cases of scleroderma from a temporal bone repository. Methods: The national temporal bone database was reviewed for cases with scleroderma. Clinical case review and correlative otopathologic analysis. Middle and inner ear otopathologic analysis was performed following hematoxylin and eosin staining under light microscopy. Findings were compared to three age-matched controls. Results: Two patients (three cases) with a history of serologically confirmed scleroderma were identified. Both individuals reported tinnitus and demonstrated bilateral moderate to severe down-sloping sensorineural hearing loss on audiometry. Histologically, the incudomallear joint space was diminished and ossicles appeared demineralized. A loss of hyaline cartilage, and obliteration of the incudomallear and incudostapedial joint synovial spaces was observed. Decreased caliber and intimal hyperplasia of arteries adjacent to ossicles was also identified. Mild diffuse atrophy of stria vascularis in the middle and apical turns of cochlea were found. Hair cell populations were normal. Total spiral ganglion neurons were lower in cases of scleroderma (range 29%-51%) compared to age-matched controls. Conclusion: Fibrosis, inflammation, and vascular changes were observed in the middle and inner ear in patients with scleroderma. Findings have implications for understanding hearing and vestibular dysfunction in this patient population. Level of evidence: Retrospective study.

Evaluating the accuracy of speech to text applications for cochlear implant candidates during COVID-19.

OBJECTIVES: Universal mask wearing due to COVID-19 has introduced barriers to clear communication. In hearing impaired individuals this can impact informed surgical consent. For cochlear implant candidates, who do not rely on sign language, real-time transcription with a stenographer (CART) is the gold-standard in assistive technologies. If CART is not available, speech to text (STT) applications have been advertised as solutions, but their transcription accuracy with or without an N95 mask is not well-established. Herein, we sought to investigate the transcription accuracy of three STT solutions for iPhone and compare their performance to the CART service at our institution. METHODS: Three native English speakers and three non-native English speakers read two passages (a cochlear implant consent and the non-medical 'Rainbow passage') with and without an N95 mask. Error rates from the comparison of the transcript (from either the STT app or CART) with the original passage were calculated. RESULTS: The CART service had the lowest error rate of all testing conditions (4.79-7.14%). Ava 24/7 (15.0 ± 9.49%) and the iPhone dictation (15.6 ± 6.65%) had significantly lower average error rates than the Live Transcribe (37.7 ± 20.3%) (P < 0.0001) application. Neither the presence of an N95 nor the type of passage had a statistically significant impact on the error rate. CONCLUSION: CART should be used to augment communication with patients who are hard of hearing. If CART is not available, a STT application such as Ava 24/7 or the native iPhone dictation application may be considered, even in the context of medical terminology.

Measurements of ear-canal geometry from high-resolution CT scans of human adult ears.

Description of the ear canal's geometry is essential for describing peripheral sound flow, yet physical measurements of the canal's geometry are lacking and recent measurements suggest that older-adult-canal areas are systematically larger than previously assumed. Methods to measure ear-canal geometry from multi-planar reconstructions of high-resolution CT images were developed and applied to 66 ears from 47 subjects, ages 18-90 years. The canal's termination, central axis, entrance, and first bend were identified based on objective definitions, and the canal's cross-sectional area was measured along its canal's central axis in 1-2 mm increments. In general, left and right ears from a given subject were far more similar than measurements across subjects, where areas varied by factors of 2-3 at many locations. The canal areas varied systematically with age cohort at the first-bend location, where canal-based measurement probes likely sit; young adults (18-30 years) had an average area of 44mm2 whereas older adults (61-90 years) had a significantly larger average area of 69mm2. Across all subjects ages 18-90, measured means ± standard deviations included: canals termination area at the tympanic annulus 56±8mm2; area at the canal's first bend 53±18mm2; area at the canal's entrance 97±24mm2; and canal length 31.4±3.1mm2.

Design of medical tympanostomy conduits with selective fluid transport properties.

Implantable tubes, shunts, and other medical conduits are crucial for treating a wide range of conditions from ears and eyes to brain and liver but often impose serious risks of device infection, obstruction, migration, unreliable function, and tissue damage. Efforts to alleviate these complications remain at an impasse because of fundamentally conflicting design requirements: Millimeter-scale size is required to minimize invasiveness but exacerbates occlusion and malfunction. Here, we present a rational design strategy that reconciles these trade-offs in an implantable tube that is even smaller than the current standard of care. Using tympanostomy tubes (ear tubes) as an exemplary case, we developed an iterative screening algorithm and show how unique curved lumen geometries of the liquid-infused conduit can be designed to co-optimize drug delivery, effusion drainage, water resistance, and biocontamination/ingrowth prevention in a single subcapillary-length-scale device. Through extensive in vitro studies, we demonstrate that the engineered tubes enabled selective uni- and bidirectional fluid transport; nearly eliminated adhesion and growth of common pathogenic bacteria, blood, and cells; and prevented tissue ingrowth. The engineered tubes also enabled complete eardrum healing and hearing preservation and exhibited more efficient and rapid antibiotic delivery to the middle ear in healthy chinchillas compared with current tympanostomy tubes, without resulting in ototoxicity at up to 24 weeks. The design principle and optimization algorithm presented here may enable tubes to be customized for a wide range of patient needs.