Drafting a Surgical Procedure Using a Computational Anatomy Driven Approach for Precise, Robust, and Safe Vestibular Neuroprosthesis Placement-When One Size Does Not Fit All

OBJECTIVE: To design and evaluate a new vestibular implant and surgical procedure that should reach correct electrode placement in 95% of patients in silico. DESIGN: Computational anatomy driven implant and surgery design study. SETTING: Tertiary referral center. PARTICIPANTS: The population comprised 81 patients that had undergone a CT scan of the Mastoid region in the Maastricht University Medical Center. The population was subdivided in a vestibular implant eligible group (28) and a control group (53) without known vestibular loss. INTERVENTIONS: Canal lengths and relationships between landmarks were calculated for every patient. The relationships in group-anatomy were used to model a fenestration site on all three semicircular canals. Each patient's simulated individual distance from the fenestration site to the ampulla was calculated and compared with the populations average to determine if placement would be successful. MAIN OUTCOME MEASURES: Lengths of the semicircular canals, distances from fenestration site to ampulla (intralabyrinthine electrode length), and rate of successful electrode placement (robustness). RESULTS: The canal lengths for the lateral, posterior, and superior canal were respectively 12.1 mm ± 1.07, 18.8 mm ± 1.62, and 17.5 mm ± 1.23, the distances from electrode fenestration site to the ampulla were respectively 3.73 mm ± 0.53, 9.02 mm ± 0.90, and 5.31 mm ± 0.73 and electrode insertions were successful for each respective semicircular canal in 92.6%, 66.7%, and 86.4% of insertions in silico. The implant electrode was subsequently revised to include two more electrodes per lead, resulting in a robustness of 100%. CONCLUSIONS: The computational anatomy approach can be used to design and test surgical procedures. With small changes in electrode design, the proposed surgical procedure's target robustness was reached

Vestibular Implantation and the Feasibility of Fluoroscopy-Guided Electrode Insertion

Recent research has shown promising results for the development of a clinically feasible vestibular implant in the near future. However, correct electrode placement remains a challenge. It was shown that fluoroscopy was able to visualize the semicircular canal ampullae and electrodes, and guide electrode insertion in real time. Ninety-four percent of the 18 electrodes were implanted correctly (<1.5 mm distance to target). The median distances were 0.60 mm, 0.85 mm, and 0.65 mm for the superior, lateral, and posterior semicircular canal, respectively. These findings suggest that fluoroscopy can significantly improve electrode placement during vestibular implantation

Impact of cochlear implantation on the function of the three semicircular canals

Contains fulltext : 229881.pdf (Publisher’s version ) (Open Access)OBJECTIVE: To assess the effect of cochlear implantation on the function of the semicircular canals (SCC) and on experienced vestibular symptoms. Second, to determine the relation between vestibular test results. DESIGN: Retrospective cohort study assessing absolute and categorised results of caloric irrigation test, video Head Impulse Test (vHIT) and Dizziness Handicap Inventory (DHI) before and after cochlear implantation.Study sample: 192 patients, aged ≥7 years old, without preoperative areflexia. RESULTS: Mean maximum slow phase velocity decreased with 3.1°/s and 4.7°/s for warm and cold caloric irrigation respectively. About 37.4% of the patients deteriorated one or more categories on caloric testing. Complete caloric postoperative areflexia was found in 6.2%. Mean vHIT gain decreased with 0.06, 0.04 and 0.05 for anterior, lateral and posterior SCC, respectively. Seven patients (7.7%) acquired an abnormal gain value for the anterior SCC. Only mean score on DHI's physical subdomain rose significantly (1.4 points). Overall, 9.0% of the patients deteriorated one or two categories on DHI. Only few weak correlations were found between caloric test, vHIT and DHI shifts. CONCLUSIONS: Although mean objective and subjective-physical vestibular deteriorations were significant, its clinical impact seems limited. However, 9% of patients experience vestibular deterioration, thus, advocate assessment. Vestibular test results show no or merely weak mutual correlations

Oculomotor Abnormalities in Large Cerebellopontine Angle Tumors:A Case Series of Bruns' Nystagmus

Patients with large or giant large cerebellopontine angle lesions can present with a wide range of audiovestibular symptoms, including Bruns' nystagmus. This is a rare variant of bidirectional nystagmus, characterized by a combination of slow, large-amplitude nystagmus when looking to the side of the lesion and rapid small-amplitude nystagmus when looking to the contralateral side. This phenomenon arises due to a unique situation in which 2 different neural circuits, specifically the floccular pathways and peripheral vestibular pathways, are simultaneously involved. The presence of Bruns' nystagmus is a good indicator for large CPA lesions of at least 3 cm in diameter with compression and displacement of the cerebellum, comprising the flocculus, and/or the brainstem. A case series of 4 different cases illustrates that investigating the presence of such nystagmus could be incorporated into the common diagnostic work-up of CPA lesions, since it is of particular interest in localizing large CPA tumors requiring urgent imaging

The resilience of the inner ear: vestibular and audiometric impact of transmastoid semicircular canal plugging

Background: Certain cases of superior semicircular canal dehiscence or benign paroxysmal positional vertigo can be treated by plugging of the affected semicircular canal. However, the extent of the impact on vestibular function and hearing during postoperative follow-up is not known. Objective: To evaluate the evolution of vestibular function and hearing after plugging of a semicircular canal. Methods: Six patients underwent testing before and 1 week, 2 months, and 6 months after plugging of the superior or posterior semicircular canal. Testing included caloric irrigation test, video Head Impulse Test (vHIT), cervical and ocular Vestibular Evoked Myogenic Potentials (VEMPs) and audiometry. Results: Initially, ipsilateral caloric response decreased in all patients and vHIT vestibulo-ocular reflex (VOR) gain of each ipsilateral semicircular canal decreased in 4/6 patients. In 4/6 patients, postoperative caloric response recovered to > 60% of the preoperative value. In 5/6 patients, vHIT VOR gain was restored to > 85% of the preoperative value for both ipsilateral non-plugged semicircular canals. In the plugged semicircular canal, this gain decreased in 4/5 patients and recovered to > 50% of the preoperative value. Four patients preserved cervical and ocular VEMP responses. Bone conduction hearing deteriorated in 3/6 patients, but recovered within 6 months postoperatively, although one patient had a persistent loss of 15 dB at 8 kHz. Conclusion Plugging of a semicircular canal can affect both vestibular function and hearing. After initial deterioration, most patients show recovery during follow-up. However, a vestibular function loss or high-frequency hearing loss can persist. This stresses the importance of adequate counseling of patients considering plugging of a semicircular canal

The Next Challenges of Vestibular Implantation in Humans

Patients with bilateral vestibulopathy suffer from a variety of complaints, leading to a high individual and social burden. Available treatments aim to alleviate the impact of this loss and improve compensatory strategies. Early experiments with electrical stimulation of the vestibular nerve in combination with knowledge gained by cochlear implant research, have inspired the development of a vestibular neuroprosthesis that can provide the missing vestibular input. The feasibility of this concept was first demonstrated in animals and later in humans. Currently, several research groups around the world are investigating prototype vestibular implants, in the form of vestibular implants as well as combined cochlear and vestibular implants. The aim of this review is to convey the presentations and discussions from the identically named symposium that was held during the 2021 MidWinter Meeting of the Association for Research in Otolaryngology, with researchers involved in the development of vestibular implants targeting the ampullary nerves. Substantial advancements in the development have been made. Yet, research and development processes face several challenges to improve this neuroprosthesis. These include, but are not limited to, optimization of the electrical stimulation profile, refining the surgical implantation procedure, preserving residual labyrinthine functions including hearing, as well as gaining regulatory approval and establishing a clinical care infrastructure similar to what exists for cochlear implants. It is believed by the authors that overcoming these challenges will accelerate the development and increase the impact of a clinically applicable vestibular implant