Results of singular neurectomy in the posterior ampullary recess

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.

Effectiveness of Canal Occlusion for Intractable Posterior Canal Benign Paroxysmal Positional Vertigo: A Systematic Review

Objectives

A last resort for therapy for intractable benign paroxysmal positional vertigo (BPPV) is mechanical occlusion of the posterior semicircular canal. The aim of this review was to assess the effect of posterior canal occlusion for intractable posterior canal BPPV on vertigo and to determine the risk of loss of auditory or vestibular function.

Data Sources

A systematic literature search according to the PRISMA statement was performed on PubMed, the Cochrane Library, Embase, Web of Science, and CINAHL. The last search was conducted in June 2018.

Review Methods

Cohort studies with original data and case reports describing >5 cases were included if they analyzed the effect of posterior semicircular canal obliteration in adults with intractable posterior BPPV on vertigo. Two authors screened titles and abstracts for eligibility. The first author screened full texts and analyzed the data.

Results

Eight retrospective studies met the eligibility criteria. The quality of all individual studies was rated fair. Canal occlusion was performed on 196 patients. All studies reported complete resolution of BPPV in all patients (100%). Among postoperatively tested patients, total loss of auditory function and vestibular function was reported in 2 of 190 (1%) and 9 of 68 (13%), respectively.

Conclusion

Posterior semicircular canal plugging resulted in 100% resolution of BPPV in patients with intractable BPPV in all studies. However, the strength of evidence was weak. Potential serious complications, such as deafness and loss of vestibular function, should be taken into account.

Benign paroxysmal positional vertigo

Objectives

Benign paroxysmal positional vertigo (BPPV) is the most common peripheral vestibular end‐organ disease. This article aims to summarize research findings and key discoveries of BPPV. The pathophysiology, diagnosis, nonsurgical, and surgical management are discussed.

Methods

A comprehensive review of the literature regarding BPPV up through June 2018 was performed.

Results

BPPV is typified by sudden, brief episodes of vertigo precipitated by specific head movements. While often self‐limited, BPPV can have a considerable impact on quality of life. The diagnosis can be established with a Dix‐Hallpike maneuver for the posterior and anterior canals, or supine roll test for the horizontal canal, and typically does not require additional ancillary testing. Understanding the pathophysiology of both canalithiasis and cupulolithiasis has allowed for the development of various repositioning techniques. Of these, the particle repositioning maneuver is an effective way to treat posterior canal BPPV, the most common variant. Options for operative intervention are available for intractable cases or patients with severe and frequent recurrences.

Conclusions

A diagnosis of BPPV can be made through clinical history along with diagnostic maneuvers. BPPV is generally amenable to in‐office repositioning techniques. For a small subset of patients with intractable BPPV, canal occlusion can be considered.

Level of Evidence

N/A

Recent surgical options for vestibular vertigo

Vertigo is not a well-defined disease but a symptom that can occur in heterogeneous entities diagnosed and treated mainly by otolaryngologists, neurologists, internal medicine, and primary care physicians. Most vertigo syndromes have a good prognosis and management is predominantly conservative, whereas the need for surgical therapy is rare, but for a subset of patients often the only remaining option. In this paper, we describe and discuss different surgical therapy options for hydropic inner ear diseases, Menière's disease, dehiscence syndromes, perilymph fistulas, and benign paroxysmal positional vertigo. At the end, we shortly introduce the most recent developments in regard to vestibular implants. Surgical therapy is still indicated for vestibular disease in selected patients nowadays when conservative options did not reduce symptoms and patients are still suffering. Success depends on the correct diagnosis and choosing among different procedures the ones going along with an adequate patient selection. With regard to the invasiveness and the possible risks due to surgery, in depth individual counseling is absolutely necessary. Ablative and destructive surgical procedures usually achieve a successful vertigo control, but are associated with a high risk for hearing loss. Therefore, residual hearing has to be included in the decision making process for surgical therapy.

Eye Movements in Response to Electric Stimulation of the Human Posterior Ampullary Nerve

Objectives:

The concept of a vestibular implant to restore balance, similar to that of a cochlear implant to restore hearing in deaf patients, has been investigated in animal models. It remains to be shown, however, that electric stimulation of the human end organ or its vestibular nerve branches is capable of eliciting a nystagmic eye movement response.

Methods:

Three subjects were given electric stimulation of their posterior ampullary nerve, which was surgically exposed under local anesthesia, by a procedure developed by Gacek. The stimulus was a multiphasic, charge-balanced train of electric pulses.

Results:

In all subjects, a pulse repetition rate of 200 pulses per second produced a robust vertical nystagmus without any apparent change in the slow component velocity of the preexisting horizontal nystagmus.

Conclusions:

We have been able to replicate in humans a finding somewhat similar to that of Suzuki and Cohen in monkeys for electric stimulation of the posterior semicircular canal. The similarity is an eye movement with a large, predominant vertical component. The difference is that we saw no horizontal response component, and were not able to measure a torsional response, because we used 2-dimensional video methods. In addition, we found a robust nystagmus with slow component velocities that are large enough to compensate for vertical head movements. This is an essential step in demonstrating the feasibility of a vestibular prosthesis using electric stimulation.

Surgical Therapy in Intractable Benign Paroxysmal Positional Vertigo

OBJECTIVES: Benign paroxysmal positional vertigo (BPPV) is the most frequent vestibular disorder. Although it is easily cured with canal repositioning maneuvers for the majority of patients, it can be disabling in rare cases. For these patients, surgical solutions may be proposed. The aim of this article is to review the techniques used, the reported cases in the literature, and to discuss their indication in intractable BPPV.

STUDY DESIGN: Literature review.

MATERIALS AND METHODS: All the articles from 1972 to 2005 that discussed a specific surgical therapy in BPPV were reviewed. Many of them reported cases of operated patients and described original techniques. Some others are anatomic studies that discussed the two techniques used: singular neurectomy and posterior semicircular canal occlusion.

RESULTS: Singular neurectomy (posterior ampullary nerve transsection) and posterior semicircular canal occlusion are the 2 specific techniques used in intractable BPPV surgery. The numbers of operated cases are 342 and 97, respectively. These small numbers indicate that the procedures are difficult and risk compromising hearing and that a very small population of patients require surgical treatment of BPPV. The operated cases have been decreasing since the early 1990s because of improved management in BPPV. This article summarizes the techniques and their results and proposes a currently recommended practice of surgical therapy in BPPV as well as new insights into intractable BPPVs’ physiopathology.

[Treatment of benign paroxysmal positional vertigo]

Benign paroxysmal positional vertigo (BPPV) is the most common peripheral vestibular disorder. BPPV is easily diagnosed by positioning tests and effectively treated by repositioning maneuvers. The authors focus on the treatment of BPPV, when different canals are affected, including canalo- and cupulolithiasias. Complications of BPPV and surgery of cases, resistant to conservative treatment, are also discussed.

Vestibular Implants: 8 Years of Experience with Electrical Stimulation of the Vestibular Nerve in 11 Patients with Bilateral Vestibular Loss

BACKGROUND

The concept of the vestibular implant is primarily to artificially restore the vestibular function in patients with a bilateral vestibular loss (BVL) by providing the central nervous system with motion information using electrical stimulation of the vestibular nerve. Our group initiated human trials about 10 years ago.

METHODS

Between 2007 and 2013, 11 patients with a BVL received a vestibular implant prototype providing electrodes to stimulate the ampullary branches of the vestibular nerve. Eye movements were recorded and analyzed to assess the effects of the electrical stimulation. Perception induced by electrical stimulation was documented.

RESULTS

Smooth, controlled eye movements were obtained in all patients showing that electrical stimulation successfully activated the vestibulo-ocular pathway. However, both the electrical dynamic range and the amplitude of the eye movements were variable from patient to patient. The axis of the response was consistent with the stimulated nerve branch in 17 out of the 24 tested electrodes. Furthermore, in at least 1 case, the elicited eye movements showed characteristics similar to those of compensatory eye movements observed during natural activities such as walking. Finally, diverse percepts were reported upon electrical stimulation (i.e., rotatory sensations, sound, tickling or pressure) with intensity increasing as the stimulation current increased.

CONCLUSIONS

These results demonstrate that electrical stimulation is a safe and effective means to activate the vestibular system, even in a heterogeneous patient population with very different etiologies and disease durations. Successful tuning of this information could turn this vestibular implant prototype into a successful artificial balance organ.

Histopathologic Changes of the Inner ear in Rhesus Monkeys After Intratympanic Gentamicin Injection and Vestibular Prosthesis Electrode Array Implantation

Bilateral vestibular deficiency (BVD) due to gentamicin ototoxicity can significantly impact quality of life and result in large socioeconomic burdens. Restoring sensation of head rotation using an implantable multichannel vestibular prosthesis (MVP) is a promising treatment approach that has been tested in animals and humans. However, uncertainty remains regarding the histopathologic effects of gentamicin ototoxicity alone or in combination with electrode implantation. Understanding these histological changes is important because selective MVP-driven stimulation of semicircular canals (SCCs) depends on persistence of primary afferent innervation in each SCC crista despite both the primary cause of BVD (e.g., ototoxic injury) and surgical trauma associated with MVP implantation. Retraction of primary afferents out of the cristae and back toward Scarpa's ganglion would render spatially selective stimulation difficult to achieve and could limit utility of an MVP that relies on electrodes implanted in the lumen of each ampulla. We investigated histopathologic changes of the inner ear associated with intratympanic gentamicin (ITG) injection and/or MVP electrode array implantation in 11 temporal bones from six rhesus macaque monkeys. Hematoxylin and eosin-stained 10-μm temporal bone sections were examined under light microscopy for four treatment groups: normal (three ears), ITG-only (two ears), MVP-only (two ears), and ITG + MVP (four ears). We estimated vestibular hair cell (HC) surface densities for each sensory neuroepithelium and compared findings across end organs and treatment groups. In ITG-only, MVP-only, and ITG + MVP ears, we observed decreased but persistent ampullary nerve fibers of SCC cristae despite ITG treatment and/or MVP electrode implantation. ITG-only and ITG + MVP ears exhibited neuroepithelial thinning and loss of type I HCs in the cristae but little effect on the maculae. MVP-only and ITG + MVP ears exhibited no signs of trauma to the cochlea or otolith end organs except in a single case of saccular injury due to over-insertion of the posterior SCC electrode. While implanted electrodes reached to within 50-760 μm of the target cristae and were usually ensheathed in a thin fibrotic capsule, dense fibrotic reaction and osteoneogenesis were each observed in only one of six electrode tracts examined. Consistent with physiologic studies that have demonstrated directionally appropriate vestibulo-ocular reflex responses to MVP electrical stimulation years after implantation in these animals, histologic findings in the present study indicate that although intralabyrinthine MVP implantation causes some inner ear trauma, it can be accomplished without destroying the distal afferent fibers an MVP is designed to excite.

Evidence-based practice: management of vertigo

The article focuses on the evidence basis for the management of benign paroxysmal positional vertigo, the most common diagnosis of vertigo in both primary care and subspecialty settings. An overview is presented, along with evidence-based clinical assessment, diagnosis, and management. Summaries of differential diagnosis of vertigo and outcomes are presented.

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

OBJECTIVES/HYPOTHESIS

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.

STUDY DESIGN

Retrospective review, quality assurance.

METHODS

Sixteen patients with SSCD and 61 patients (65 ears) with intractable BPPV who underwent canal occlusion were reviewed. All patients underwent occlusion of the affected semicircular canal through a transmastoid approach.

RESULTS

Preoperative symptoms (vestibular, 13 patients; pulsatile tinnitus, 2 patients; or hyperacusis, 1 patient) were greatly improved or completely resolved in 15 of the 16 SSCD patients who underwent transmastoid occlusion of the superior canal. Hearing was preserved in 14 patients and improved in two patients. Vestibular symptoms were resolved in all intractable BPPV patients who underwent transmastoid occlusion of the posterior canal. One patient had a late recurrence of atypical BPPV. Almost all BPPV patients with normal preoperative hearing have an initial transient postoperative hearing loss, which when tested for is usually a mild to moderate mixed loss. Delayed sensorineural hearing loss was noted in three patients; one loss was profound whereas two were mild.

CONCLUSIONS

The transmastoid approach to canal plugging is successful in the treatment of symptoms in both SSCD and intractable BPPV, and is a familiar approach for the otologist. This is a viable alternative to the middle fossa approach for SSCD, thereby avoiding a craniotomy. Transmastoid is the definitive approach for posterior canal occlusion.

The modified ampullar approach for vestibular implant surgery: feasibility and its first application in a human with a long-term vestibular loss

Objective: To assess, for the first time in a human with a long-term vestibular loss, a modified approach to the ampullae and the feasibility of evoking a VOR by ampullar stimulation. Materials and methods: Peroperative stimulation of the ampullae, using the ampullar approach, was performed under full anesthesia during cochlear implantation in a 21-year-old female patient, who had experienced bilateral vestibular areflexia and sensorineural hearing loss for almost 20 years. Results: The modified ampullar approach was performed successfully with as minimally invasive surgery as possible. Ampullar stimulation evoked eye movements containing vectors congruent with the stimulated canal. As expected, the preliminary electrophysiological data were influenced by the general anesthesia, which resulted in current spread and reduced maximum amplitudes of eye movement. Nevertheless, they confirm the feasibility of ampullar stimulation. Conclusion: The modified ampullar approach provides safe access to the ampullae using as minimally invasive surgery as possible. For the first time in a human with long-term bilateral vestibular areflexia, it is shown that the VOR can be evoked by ampullar stimulation, even when there has been no vestibular function for almost 20 years. This approach should be considered in vestibular surgery, as it provides safe access to one of the most favorable stimulus locations for development of a vestibular implant.

The vestibular implant: quo vadis?

Objective: To assess the progress of the development of the vestibular implant (VI) and its feasibility short-term. Data sources: A search was performed in Pubmed, Medline, and Embase. Key words used were “vestibular prosth*” and “VI.” The only search limit was language: English or Dutch. Additional sources were medical books, conference lectures and our personal experience with per-operative vestibular stimulation in patients selected for cochlear implantation. Study selection: All studies about the VI and related topics were included and evaluated by two reviewers. No study was excluded since every study investigated different aspects of the VI. Data extraction and synthesis: Data was extracted by the first author from selected reports, supplemented by additional information, medical books conference lectures. Since each study had its own point of interest with its own outcomes, it was not possible to compare data of different studies. Conclusion: To use a basic VI in humans seems feasible in the very near future. Investigations show that electric stimulation of the canal nerves induces a nystagmus which corresponds to the plane of the canal which is innervated by the stimulated nerve branch. The brain is able to adapt to a higher baseline stimulation, while still reacting on a dynamic component. The best response will be achieved by a combination of the optimal stimulus (stimulus profile, stimulus location, precompensation), complemented by central vestibular adaptation. The degree of response will probably vary between individuals, depending on pathology and their ability to adapt.

Self-treatment of benign paroxysmal positional vertigo with DizzyFix, a new dynamic visual device

Benign paroxysmal positional vertigo is one of the most common disorders of the vestibular system. It is characterized by episodes of recurrent vertigo triggered by head movements or position changes associated with nystagmus. There is scientific evidence that in the majority of cases this condition responds well to the particle repositioning maneuver (PRM) correctly performed by the physician. However, the PRM needs to be repeated in approximately 30% of the cases. Although the maneuver is simple, patients often find it difficult to perform correctly as self-treatment, with the result that it fails to bring about an improvement in the symptoms. DizzyFix (Clearwater Clinical Limited, Canada) is the name given to a new dynamic visual device designed to provide a visual representation of the PRM based on the canalith theory. The DizzyFiX consists of a specially curved acrylic tube containing a nontoxic viscous fluid and a bead, the purpose of which is to help the patient and the inexperienced physician to perform the PRM correctly. A randomized clinical trial has shown that it reliably enables the maneuver to be performed correctly, and a study investigating the effectiveness of patient self-treatment of benign paroxysmal positional vertigo with the device in comparison with standard office treatment revealed both techniques to be equally effective. The device has now been approved by the US FDA.

Effects of vestibular prosthesis electrode implantation and stimulation on hearing in rhesus monkeys

To investigate the effects of vestibular prosthesis electrode implantation and activation on hearing in rhesus monkeys, we measured auditory brainstem responses (ABR) and distortion product otoacoustic emissions (DPOAE) in four rhesus monkeys before and after unilateral implantation of vestibular prosthesis electrodes in each of 3 left semicircular canals (SCC). Each of the 3 left SCCs were implanted with electrodes via a transmastoid approach. Right ears, which served as controls, were not surgically manipulated. Hearing tests were conducted before implantation (BI) and then 4 weeks post-implantation both without electrical stimulation (NS) and with electrical stimulation (S). During the latter condition, prosthetic electrical stimuli encoding 3 dimensions of head angular velocity were delivered to the 3 ampullary branches of the left vestibular nerve via each of 3 electrode pairs of a multichannel vestibular prosthesis. Electrical stimuli comprised charge-balanced biphasic pulses at a baseline rate of 94 pulses/s, with pulse frequency modulated from 48 to 222 pulses/s by head angular velocity. ABR hearing thresholds to clicks and tone pips at 1, 2, and 4 kHz increased by 5-10 dB from BI to NS and increased another ∼5 dB from NS to S in implanted ears. No significant change was seen in right ears. DPOAE amplitudes decreased by 2-14 dB from BI to NS in implanted ears. There was a slight but insignificant decrease of DPOAE amplitude and a corresponding increase of DPOAE/Noise floor ratio between NS and S in implanted ears. Vestibular prosthesis electrode implantation and activation have small but measurable effects on hearing in rhesus monkeys. Coupled with the clinical observation that patients with cochlear implants only rarely exhibit signs of vestibular injury or spurious vestibular nerve stimulation, these results suggest that although implantation and activation of multichannel vestibular prosthesis electrodes in human will carry a risk of hearing loss, that loss is not likely to be severe.

Benign paroxysmal positional vertigo: a series of eight singular neurectomies

CONCLUSION

The singular neurectomy as described by Gacek in 1974 is an efficient procedure to control symptoms in case of intractable benign paroxysmal positional vertigo (BPPV), with an acceptable risk of postoperative sensorineural hearing loss (SNHL). We postulate that this complication may not be a direct consequence of the surgical procedure but rather may be consecutive to the reactivation of the biological phenomenon that caused the BPPV. We also observed in one patient that BPPV may exist although no nystagmus can be elicited by provocative manoeuvres.

OBJECTIVE

To report our experience of the surgery, and to analyse the rate and causes of complications.

PATIENTS AND METHODS

The eight patients operated in the department between August 1997 and April 2006 were evaluated in June 2006. One had been operated because he had a typical history of BPPV, but no nystagmus could be elicited by the Hallpike's manoeuvre.

RESULTS

All patients were free of vertigo and considered their quality of life improved. The Hallpike's manoeuvre was negative in all cases. A SNHL occurred in two patients, immediately after surgery in one and several months later in the second. The patient with a negative Hallpike's manoeuvre before surgery went back to work 3 weeks after surgery.

Transcanal Approach to the Singular Nerve

OBJECTIVES/HYPOTHESIS

Intractable benign paroxysmal positional vertigo is rare, and surgery is indicated in only a very small number of cases. Transcanal singular neurectomy is considered a difficult and risky procedure possibly leading to hearing loss and vertigo. The objective of this study was to evaluate the feasibility of the singular neurectomy through the external ear canal in an attempt to explain the contradictory results of previous reports of anatomists and of surgeons who abandoned the technique, considering that the singular neurectomy could not be reached via the external auditory canal without damaging the labyrinth.

MATERIALS AND METHODS

Anatomical study on 100 halves of human heads in which the canal of the singular nerve (SN) was identified and opened at its extremities, the internal auditory canal and the ampulla of the posterior semicircular canal, via a posterior fossa approach. Next, the canal of the SN was dissected via the external auditory canal, at the floor of the round window (RW) niche. The relation of the SN canal to the ampulla of the posterior semicircular canal was evaluated.

RESULTS

In 90 cases, the canal was transected medially to and away from the ampulla of the posterior semicircular canal, and in 8, at its emergence from the posterior ampullary recess. In these 98 cases, the RW membrane and the bony labyrinth were kept intact. In two cases, the canal of the SN could not be reached at the floor of the RW niche.

CONCLUSION

Singular neurectomy is feasible via the external auditory canal, without damaging the RW membrane or the labyrinth in 98% of the cases. Because singular neurectomy is indicated in a very small number of cases, it is difficult to master this particular surgical procedure. This may explain why most surgeons abandoned the technique after a few attempts, followed by an unacceptable rate of sensorineural hearing loss.

Surgical Treatment of Peripheral Vertigo and Vertiginous Diseases

Although our understanding of the mechanisms of vertigo and pathophysiology of vertiginous disorders has increased, diagnosis and treatment of various vertiginous diseases is challenging. The objective for the treatment of a vertiginous disease is to eliminate the underlying pathology either with maneuvers or drugs. In vertiginous diseases, surgery is performed either to eliminate the underlying pathologic event or to create stability in the incoming vestibular signals. It is not always possible to treat the underlying disease. Therefore, surgery is usually performed for the relief of vertigo. There are various surgical approaches used to treat a variety of vertiginous diseases. Selection of the approach depends on the type of vertiginous disease. This review mainly focuses on the current status and outcome of the surgeries used in the treatment of a variety of vertiginous diseases.