Sumit K. Agrawal

Human Experience with Canal Plugging

Abstract: Canal occlusion/plugging is a very effective technique with a low risk to hearing. The series of posterior semicircular canal occlusions described in this review now becomes the largest in the literature to date. It continues to support this procedure as the treatment of choice for intractable benign paroxysmal positional vertigo (BPPV). All 44 operated ears were relieved of BPPV, with one patient having an atypical late recurrence. Of the 40 ears with normal preoperative hearing, one had a delayed (3‐month) sudden and permanent profound loss, while one other had a mild (20 dB) loss. Six patients had protracted courses of imbalance and motion sensitivity.

Transmastoid semicircular canal occlusion: A safe and highly effective treatment for benign paroxysmal positional vertigo and superior canal dehiscence

Transmastoid occlusion of the superior semicircular canal in superior semicircular canal dehiscence (SSCD) syndrome and the posterior semicircular canal in intractable benign paroxysmal positional vertigo (BPPV) will produce resolution of preoperative symptoms.

Interactive computer-based simulator for training in blade navigation and targeting in myringotomy

A virtual-reality simulator was developed for the training of Otolaryngology (Ear-Nose-Throat) surgical residents to perform myringotomy, a relatively common surgical procedure in which an incision is made in the eardrum mainly to treat middle-ear infections. The simulator presents the trainee with a three-dimensional (3D) virtual model of the ear that can be viewed through a mock surgical microscope consisting of a stereo visor mounted on a custom-designed stand. The trainee interacts with the virtual ear using a real myringotomy blade, the movements of which are tracked in real time using a stereo optical tracker. Interactions of the blade with virtual tissues are calculated and rendered on the visor using freely available physics and graphics software engines. Six experienced surgical residents and surgeons assessed the effectiveness of the simulator as a viable training tool by completing a questionnaire designed specifically for this study after using the simulator. Surgeons and residents were positively impressed by the simulator as a training tool and would recommend its use as part of training.

Endoscopic ligation of the patulous eustachian tube as treatment for autophony

Patulous eustachian tube remains a challenging management problem in otolaryngology. The autophony experienced by this patient population can be severe, and as yet no reliable surgical method exists to reduce or eliminate this annoying symptom. Our objective was to develop a novel endoscopic technique to assist these patients.

Virtual reality myringotomy simulation with real-time deformation: Development and validity testing†‡

Surgical simulation is becoming an increasingly common training tool in residency programs. The first objective was to implement real‐time soft‐tissue deformation and cutting into a virtual reality myringotomy simulator. The second objective was to test the various implemented incision algorithms to determine which most accurately represents the tympanic membrane during myringotomy.

Measuring the quasi-static Young’s modulus of the eardrum using an indentation technique

Accurate estimation of the quasi-static Youngs modulus of the eardrum is important for finite-element modeling. In this study, we adapted a tissue indentation technique and inverse finite-element analysis to estimate the Youngs modulus of the eardrum. A custom-built indentation apparatus was used to perform indentation testing on seven rat eardrums in situ after immobilizing the malleus. Testing was done in most cases on the posterior pars tensa. The unloaded shape of each eardrum was measured and used to construct finite-element models with subject-specific geometries to simulate the indentation experiment. The Youngs modulus of each specimen was then estimated by numerically optimizing the Youngs modulus of each model so that simulation results matched corresponding experimental data. Using an estimated value of 12 microm for the thickness of each model eardrum, the estimated average Youngs modulus for the pars tensa was found to be 21.7+/-1.2 MPa. The estimated average Youngs modulus is within the range reported in some of the literature. The estimation technique is sensitive to the thickness of the pars tensa used in the model but is not sensitive to relatively large variations in the stiffness of the pars flaccida and manubrium or to the pars tensa/pars flaccida separation conditions.

Laser Doppler Vibrometry measurements of human cadaveric tympanic membrane vibration

ObjectiveTo determine the feasibility of measuring tympanic membrane (TM) vibrations at multiple locations on the TM to differentiate normal eardrums from those with associated ossicular pathologies.DesignCadaveric human temporal bone study.SettingBasic science laboratory.MethodsA mastoidectomy and facial recess approach was performed on four cadaveric temporal bones to obtain access to the ossicles without disrupting the TM. Ossicles were palpated to ensure normal mobility and an intact ossicular chain. Laser Doppler Vibrometry (LDV) measurements were then taken on all four TMs. LDV measurements were repeated on each TM following stapes footplate fixation, incudo-stapedial joint dislocation, and malleus head fixation.Main outcome measuresLDV measurements of TM vibration at the umbo, the lateral process of the malleus, and in each of the four quadrants of the TM.ResultsThe best signal-to-noise ratios were found between 2 and 4 kHz, at the umbo, the anterior superior quadrant, the anterior inferior quadrant, and the posterior inferior quadrant. Since our goal was to assess the ossicular chain, we selected the TM locations closest to the ossicular chain (the umbo and lateral process of the malleus) for further analysis. Differences could be seen between normals and the simulated ossicular pathologies, but values were not statistically significant.ConclusionsLDV measurements are technically challenging and require optimization to obtain consistent measurements. This study demonstrates the potential of LDV to differentiate ossicular pathologies behind an intact tympanic membrane. Future studies will further characterize the clinical role of this diagnostic modality.

Recent advances in viral inner ear disorders.

Purpose of reviewTo highlight the recent advances in the understanding of the diagnosis and management of viral inner ear disorders. Congenital sensorineural hearing loss (cSNHL), sudden sensorineural hearing loss (SSNHL), Ménières disease, and vestibular neuritis/viral labyrinthitis are discussed. Recent findingsCytomegalovirus infection during pregnancy is an under-recognized cause of hearing loss and central nervous system disease amongst the general population. Prevention of maternal infection and treatment of affected newborns with ganciclovir are promising interventions. Recent evidence in SSNHL patients has resulted in recommendations against viral serology or the use of antivirals. There appears to be an increased risk of SSNHL in patients with comorbid hypertension and diabetes. The viral hypothesis of Ménières disease remains unproven. In patients with an acute episode of vestibular neuritis, there is presently not sufficient evidence to support the routine use of corticosteroids or antiviral medications. SummarycSNHL remains the most clearly defined of the viral inner ear disorders. The evidence for viral involvement in SSNHL, Ménières disease, and vestibular neuritis is indirect and equivocal. This review highlights the recent advancements in the diagnosis and management of these disorders.

Melanotic neuroectodermal tumour of infancy

Melanotic neuroectodermal tumour of infancy is an extremely rare neoplasm arising in newborns and young children, typically involving the face or cranium. A case arising from the maxilla, requiring extensive resection with a near-total maxillectomy, is presented. A thorough review of the literature on this unusual tumour is provided, with emphasis on prognostic factors and appropriate treatment.

Estimation of the quasi-static Young's modulus of the eardrum using a pressurization technique

The quasi-static Youngs modulus of the eardrums pars tensa is an important modeling parameter in computer simulations. Recent developments in indentation testing and inverse modeling allow estimation of this parameter with the eardrum in situ. These approaches are challenging because of the curved shape of the pars tensa which requires special care during experimentation to keep the indenter perpendicular to the local surface at the point of contact. Moreover, they involve complicated contact modeling. An alternative computer-based method is presented here in which pressurization is used instead of indentation. The Youngs modulus of a thin-shell model of the eardrum with subject-specific geometry is numerically optimized such that simulated pressurized shapes match measured counterparts. The technique was evaluated on six healthy rat eardrums, resulting in a Youngs modulus estimate of 22.8±1.5MPa. This is comparable to values estimated using indentation testing. The new pressurization-based approach is simpler to use than the indentation-based method for the two reasons noted above.