Scalar localisation of peri-modiolar electrodes and speech perception outcomes.

OBJECTIVE: To identify the intracochlear electrode position in cochlear implant recipients and determine the correlation to speech perception for two peri-modiolar electrode arrays. METHODS: Post-operative cone-beam computed tomography images of 92 adult recipients of the 'CI512' electrode and 18 adult recipients of the 'CI532' electrode were analysed. Phonemes scores were recorded pre-implantation, and at 3 and 12 months post-implantation. RESULTS: All CI532 electrodes were wholly within scala tympani. Of the 79 CI512 electrodes intended to be in scala tympani, 58 (73 per cent) were in scala tympani, 14 (17 per cent) were translocated and 7 (9 per cent) were wholly in scala vestibuli. Thirteen CI512 electrodes were deliberately inserted into scala vestibuli. Speech perception scores for post-lingual recipients were higher in the scala tympani group (69.1 per cent) compared with the scala vestibuli (54.2 per cent) and translocation (50 per cent) groups (p < 0.05). Electrode location outside of scala tympani independently resulted in a 10.5 per cent decrease in phoneme scores. CONCLUSION: Cone-beam computed tomography was valuable for demonstrating electrode position. The rate of scala tympani insertion was higher in CI532 than in CI512 electrodes. Scala vestibuli insertion and translocation were associated with poorer speech perception outcomes.

Co-registration of cone beam CT and preoperative MRI for improved accuracy of electrode localization following cochlear implantation.

OBJECTIVES: To investigate the clinical usefulness and practicality of co-registration of Cone Beam CT (CBCT) with preoperative Magnetic Resonance Imaging (MRI) for intracochlear localization of electrodes after cochlear implantation. METHODS: Images of 20 adult patients who underwent CBCT after implantation were co-registered with preoperative MRI scans. Time taken for co-registration was recorded. The images were analysed by clinicians of varying levels of expertise to determine electrode position and ease of interpretation. RESULTS: After a short learning curve, the average co-registration time was 10.78 minutes (StdDev 2.37). All clinicians found the co-registered images easier to interpret than CBCT alone. The mean concordance of CBCT vs. co-registered image analysis between consultant otologists was 60% (17-100%) and 86% (60-100%), respectively. The sensitivity and specificity for CBCT to identify Scala Vestibuli insertion or translocation was 100 and 75%, respectively. The negative predictive value was 100%. DISCUSSION: CBCT should be performed following adult cochlear implantation for audit and quality control of surgical technique. If SV insertion or translocation is suspected, co-registration with preoperative MRI should be performed to enable easier analysis. There will be a learning curve for this process in terms of both the co-registration and the interpretation of images by clinicians.

The fetal larynx and pharynx: structure and development on two- and three-dimensional ultrasound.

OBJECTIVES: To present a systematic approach for evaluating the fetal pharynx and larynx based on two- and three-dimensional ultrasound (2D-US and 3D-US) modalities, describing the sonographic appearance and function of the fetal upper respiratory tract and measuring the anatomical components of the pharynx and larynx. METHODS: Gravidae presenting from the late first trimester to mid-gestation for routine booked examinations with structurally normal singleton fetuses of confirmed gestational age were enrolled. Transabdominal 2D-US was performed for anatomical and functional evaluation of the pharynx and larynx. Color Doppler was used to show fluid motion in the target area. 3D-US (Voluson® E6 with RAB-4-8-D transducer) scans of the fetal neck were acquired during fetal quiescence and in the absence of movements of the pharynx and larynx. Multiplanar reconstruction (MPR) in post-processing allowed adjustment of the volume to obtain the coronal plane. After a learning period to understand the sonographic anatomy of the target area, we measured the pharynx width and height, the upper, middle and lower larynx width and the larynx height. Render mode was applied for spatial evaluation of the target area. We developed a new methodological approach for structured evaluation of the fetal pharynx and larynx based on five spatial planes: posterior and anterior coronal planes and high, mid and low axial planes. RESULTS: We examined 582 fetuses during the second trimester of pregnancy; target anatomy was imaged successfully in 218 patients at 11-24 gestational weeks. Acquisition added approximately 1 min to examination time. Rates of successful visualization and measurements increased significantly as pregnancy progressed, being 23% (46/194) at 11-13 weeks, 29% (69/240) at 14-16 weeks, 35% (18/51) at 17-19 weeks and 88% (85/97) at 20-24 weeks (P < 0.01). Pharynx components identified were: the sphenoid bone, pterygoid processes, constrictor muscles, piriform recesses and uvula. Larynx components identified were: the epiglottis, aryepiglottic folds, corniculate cartilages, arytenoid cartilages, cricoid cartilage, thyroid cartilage and vocal cords. MPR showed the biconcave shape of the uvula, which may explain the 'equals sign' observed on 2D-US. We observed the bilateral mode of movements of the constrictor muscles, aryepiglottic folds and vocal cords, and the bidirectional fluid jet flows through the larynx. Scatterplots of measured structures vs gestational age were created. Pharynx width ranged from 0.11 to 0.93 (mean ± SD, 0.48 ± 0.17) cm; pharynx height ranged from 0.23 to 2.01 (mean ± SD, 0.94 ± 0.34) cm; upper larynx width ranged from 0.04 to 0.37 (mean ± SD, 0.15 ± 0.07) cm; middle larynx width ranged from 0.08 to 0.77 (mean ± SD, 0.34 ± 0.16) cm; lower larynx width ranged from 0.05 to 0.64 (mean ± SD, 0.24 ± 0.11) cm; and larynx height ranged from 0.20 to 1.83 (mean ± SD, 0.71 ± 0.31) cm. All measurements were positively correlated with gestational age. CONCLUSIONS: The fetal larynx and pharynx can be evaluated thoroughly using 2D- and 3D-US modalities. Knowledge of normal anatomy, function and biometry may prove useful in the evaluation of anatomical or functional pathology involving the fetal upper respiratory tract. Recognition of anatomical anomalies may enhance fetal intervention such as balloon placement in cases of diaphragmatic hernia.