Atraumatic Insertion of a Cochlear Implant Pre-Curved Electrode Array by a Robot-Automated Alignment with the Coiling Direction of the Scala Tympani

<b><i>Introduction:</i></b> Electrode array translocation is an unpredictable event with all types of arrays, even using a teleoperated robot in a clinical scenario. We aimed to compare the intracochlear trauma produced by the HiFocus™ Mid-Scala (MS) electrode array (Advanced Bionics, Valencia, CA, USA) using a teleoperated robot, with an automated robot connected to a navigation system to align the pre-curved tip of the electrode array with the coiling direction of the scala tympani (ST). <b><i>Methods:</i></b> Fifteen freshly frozen temporal bones were implanted with the MS array using the RobOtol® (Collin, Bagneux, France). In the first group (<i>n</i> = 10), the robot was teleoperated to insert the electrode array into the basal turn of the ST under stereomicroscopic vision, and then the array was driven by a slow-speed hydraulic insertion technique with an estimated placement of the pre-curved electrode tip. In the second group (<i>n</i> = 5), 3 points were obtained from the preoperative cone-beam computed tomography: the 2 first defining the ST insertion axis of the basal turn and a third one at the center of the ST at 270°. They provided the information to the automated system (RobOtol® connected with a navigation system) to automatically align the electrode array with the ST insertion axis and to aim the pre-curved tip toward the subsequent coiling of the ST. After this, the electrode array was manually advanced. Finally, the cochleae were obtained and fixed in a crystal resin, and the position of each electrode was determined by a micro-grinding technique. <b><i>Results:</i></b> In all cases, the electrode array was fully inserted into the cochlea and the depth of insertion was similar using both techniques. With the teleoperated robotic technique, translocations of the array were observed in 7/10 insertions (70%), but neither trauma nor array translocation occurred with automated robotic insertion. <b><i>Conclusion:</i></b> We have successfully tested an automated insertion system (robot + navigation) that could accurately align a pre-curved electrode array to the axis of the basal turn of the ST and its subsequent coiling, which reduced intracochlear insertion trauma and translocation.

Radiological measurement of cochlear dimensions in cochlear hypoplasia and its effect on cochlear implant selection

Objective To determine the effect of cochlear dimensions on cochlear implant selection in cochlear hypoplasia patients. Methods Temporal bone computed tomography images of 36 patients diagnosed with cochlear hypoplasia between 2010 and 2016 were retrospectively reviewed and compared with those of 40 controls without sensorineural hearing loss. Results Basal turn length and mid-modiolar height were significantly lower in the cochlear hypoplasia patients with subtypes I, II and III than in the control group (p < 0.001). Mid-scalar length was significantly shorter in subtype I–III patients as compared with the control group (p < 0.001). In addition, cochlear canal length (measured along the lateral wall) was significantly shorter in subtype I–IV patients than in the control group (subtypes I–III, p < 0.001; subtype IV, p = 0.002) Conclusion Cochlear hypoplasia should be considered if basal turn length is less than 7.5 mm and mid-modiolar height is less than 3.42 mm. The cochlear implant should be selected according to cochlear hypoplasia subgroup. It is critically important to differentiate subtype II from incomplete partition type I and subtype III from a normal cochlea, to ensure the most appropriate implant electrode selection so as to optimise cochlear implantation outcomes.

A novel cochlear measurement that predicts inner-ear malformation

The A-value used in cochlear duct length (CDL) estimation does not take malformed cochleae into consideration. The objective was to determine the A-value reported in the literature, to assess the accuracy of the A-value measurement and to evaluate a novel cochlear measurement in distinguishing malformed cochlea. High resolution Computer Tomography images in the oblique coronal plane/cochlear view of 74 human temporal bones were analyzed. The A-value and novel C-value measurement were evaluated as predictors of inner ear malformation type. The proximity of the facial nerve to the basal turn was evaluated subjectively. 26 publications report on the A-value; but they do not distinguish normal vs. malformed cochleae. The A-values of the normal cochleae compared to the cochleae with cochlear hypoplasia, incomplete partition (IP) type I, -type II, and -type III were significantly different. The A-value does not predict the C-value. The C-values of the normal cochleae compared to the cochleae with IP type I and IP type III were significantly different. The proximity of the facial nerve to the basal turn did not relate to the type of malformation. The A-value is different in normal vs. malformed cochleae. The novel C-value could be used to predict malformed anatomy, although it does not distinguish all malformation types.

Measurement of the Intracochlear Hypothermia Distribution Utilizing Tympanic Cavity Hypothermic Rinsing Technique in a Cochlea Hypothermia Model

Introduction: Cochlea implants can cause severe trauma leading to intracochlear apoptosis, fibrosis, and eventually to loss of residual hearing. Mild hypothermia has been shown to reduce toxic or mechanical noxious effects, which can result in inflammation and subsequent hearing loss. This paper evaluates the usability of standard surgical otologic rinsing as cooling medium during cochlea implantation as a potential hearing preservation technique.Material and Methods: Three human temporal bones were prepared following standard mastoidectomy and posterior tympanotomy. Applying a retrocochlear approach leaving the mastoidectomy side intact, temperature probes were placed into the basal turn (n = 4), the middle turn (n = 2), the helicotrema, and the modiolus. Temperature probe positions were visualized by microcomputed tomography (μCT) imaging and manually segmented using Amira® 7.6. Through the posterior tympanotomy, the tympanic cavity was rinsed at 37°C in the control group, at room temperature (in the range between 22 and 24°C), and at iced water conditions. Temperature changes were measured in the preheated temporal bone. In each temperature model, rinsing was done for 20 min at the pre-specified temperatures measured in 0.5-s intervals. At least five repetitions were performed. Data were statistically analyzed using pairwise t-tests with Bonferroni correction.Results: Steady-state conditions achieved in all three different temperature ranges were compared in periods between 150 and 300 s. Temperature in the inner ear started dropping within the initial 150 s. Temperature probes placed at basal turn, the helicotrema, and middle turn detected statistically significant fall in temperature levels following body temperature rinses. Irrigation at iced conditions lead to the most significant temperature drops. The curves during all measurements remained stable with 37°C rinses.Conclusion: Therapeutic hypothermia is achieved with standard surgical irrigation fluid, and temperature gradients are seen along the cochlea. Rinsing of 120 s duration results in a therapeutic local hypothermia throughout the cochlea. This otoprotective procedure can be easily realized in clinical practice.

Otopathologic Analysis of Patterns of Postmeningitis Labyrinthitis Ossificans

Objective Labyrinthitis ossificans (LO) may occur following meningitis and, in cases where cochlear implantation is indicated, complicate electrode insertion. LO is critical to identify for successful cochlear implantation, and histopathology is more sensitive than imaging for identification of LO. Herein we utilize otopathologic techniques to study the timing and location of intracochlear tissue formation following meningitic labyrinthitis (ML). Study Design Retrospective review. Setting Academic institution. Methods Temporal bone specimens with a history of bacterial ML were histologically evaluated. The location and extent of intracochlear tissue formation within the scala tympani (ST) and scala vestibuli (SV) were graded, and spiral ganglion neurons were counted. Results Fifty-one temporal bones were identified: 32 with no intracochlear tissue formation, 9 with fibrosis alone, and 10 with LO. Fibrosis was identified as early as 1.5 weeks after ML, while ossification was found only in specimens that survived multiple years after ML. All LO cases showed ossification of the ST at the round window membrane (RWM) with continuous extension throughout the basal turn. Extent of SV ossification correlated with that in the ST but showed frequent isolated distal involvement of the cochlea. Spiral ganglion neuron counts were lower than those in age-matched controls. Conclusion In this human temporal bone study, we found that postmeningitic LO results in ossification at the RWM with continuous extension into the ST of the basal turn and variable involvement of the SV. Identification of a patent basal turn beyond RWM ossification of the ST should permit full electrode insertion. Level of Evidence Retrospective review.

Shape of the Cochlear Basal Turn: An Indicator for an Optimal Electrode-to-Modiolus Proximity With Precurved Electrode Type

Objective: The objective of this study was to determine the shape of cochlear basal turn through basic cochlear parameters measurement. The secondary aim was to overlay an image of the precurved electrode array on top of the three-dimensional (3D) image of the cochlea to determine which shape of the cochlear basal turn gives optimal electrode-to-modiolus proximity. Materials and Methods: Computed tomography (CT) preoperative image-data sets of 117 ears were made available for the measurements of cochlear parameters retrospectively. Three-dimensional slicer was used in the visualization and measurement of cochlear parameters from both 3D and 2D (2-dimensional) images of the inner ear. Cochlear parameters including basal turn diameter ( A), width of the basal turn ( B), and cochlear height (H) were measured from the appropriate planes. B/ A ratio was made to investigate which ratios correspond to round and elliptical shape of the cochlear basal turn. Results: The cochlear size as measured by A value ranged between 7.4 mm and 10 mm. The B value and the cochlear height ( H) showed a weak positive linear relation with A value. The ratio between the B and A values anything above or below 0.75 could be an indicator for a more round- or elliptical shaped cochlear basal turn, respectively. One sized/shaped commercially available precurved electrode array would not offer a tight electrode-to-modiolus in the cochlea that has an elliptical shaped basal turn as identified by the B/A ratio of <0.75. Conclusion: Accurate measurement of cochlear parameters adds value to the overall understanding of the cochlear geometry before a cochlear implantation procedure. The shape of cochlear basal turn could have clinical implications when comes to electrode-to-modiolus proximity.