Introduction
Following the wider utilisation of semicircular canal obliteration for persistent benign paroxysmal positional vertigo and superior semicircular canal dehiscence, we have gained a better understanding of the surgical outcomes and the reaction of the inner ear to surgical manipulations.Reference Beyea, Agrawal and Parnes1,Reference Deschenes, Hsu and Megerian2 Such knowledge has led to the development of novel treatment methods for dealing with patients with intractable vertigo.
Over 10 years ago, Yin et al. introduced three-semicircular-canal obliteration as an alternative method for managing patients with Ménière's disease.Reference Yin, Chen, Yu, Wu, Shi and Zhou3 The promising initial results, showing good control of vestibular symptoms and hearing preservation in most patients, were further supported by the promising long-term outcomes of a recent large retrospective series.Reference Zhang, Lv, Han, Li, Li and Wang4
However, the available information on three-semicircular-canal obliteration remains limited, and a detailed description and demonstration of the surgical technique are lacking. The current work aimed to demonstrate the surgical technique of three-semicircular-canal obliteration, highlighting key aspects and surgical considerations.
Materials and methods
Settings and patient selection
A pilot case series with prospectively collected data was performed in a tertiary, university centre between January and December 2019. The local ethical board approved this study as an audit.
Two patients with intractable Ménière's disease scheduled to undergo elective three-semicircular-canal obliteration were enrolled. They had both previously received intratympanic steroid and gentamicin injections, with additional vestibular physiotherapy, without any definite control of their vertiginous symptoms. Following detailed consultation about the available options, the patients were scheduled for the above procedure.
The present study focused on the surgical technique, including the duration of the procedure, any complications and side effects, and the length of in-patient stay.
Pre- and post-operative average pure tone audiometry thresholds (in accordance with the American Academy of Otolaryngology and Head and Neck Surgery minimal reporting standard for audiometric data in clinical research) and Dizziness Handicap Inventory scores were also included, to assess the outcome. Morbidities that could affect the outcome were additionally recorded.
All patients had undergone pre-operative magnetic resonance imaging to rule out a retrocochlear pathology and computed tomography of the temporal bone to assess the bony anatomy.
The post-operative data presented here are based on short-term (six-week or two-month) and long-term (one-year) post-operative assessment findings.
Surgical technique including surgical anatomy
Following a post-auricular approach and harvesting of little pieces of temporalis fascia and temporalis muscle, cortical mastoidectomy was performed; bone dust was harvested and mixed with a non-ototoxic antibiotic (bone pâté) for use as further graft material.
All three semicircular canals were gradually identified and carefully ‘blue lined’ until the endosteum was clearly visible, without disrupting its continuity, to prevent any perilymph leak and inner-ear trauma. After adequate exposure, the canals were plugged in very slowly with small pieces of muscle (as demonstrated in a short video, available on The Journal of Laryngology & Otology website; Appendix 1). The obliteration was subsequently covered by fascia and bone pâté (Figures 1 and 2).
Fig. 1. The semicircular canal (patient one, left ear) opened and obliterated in two sites each (numbered), with two pieces of muscle occluding the lateral semicircular canal (LSCC), two occluding the posterior semicircular canal (PSCC) and two occluding the superior semicircular canal (SSCC) (a), covered by temporalis fascia (b) and bone pâté (c). MF = middle fossa
Fig. 2. All three semicircular canals (patient two, right ear) opened and obliterated in one site each (numbered) (part (a) shows a still from the video), covered by temporalis fascia (b) and bone pâté (c). LSCC = lateral semicircular canal; MF = middle fossa; SSCC = superior semicircular canal; PSCC = posterior semicircular canal
In the first case, all three semicircular canals were ‘blue lined’ and obliterated with muscle in two different sites for each semicircular canal (Figure 1). However, in the second case, all three semicircular canals were ‘blue lined’ in one site only, with wider exposure of the membranous labyrinth, to achieve robust obliteration of the lumen (Appendix 1) (Figure 2).
Results
Two female patients, aged 42 and 65 years respectively, were included. Both patients suffered from unilateral Ménière's disease, affecting the left ear (patient one) and the right ear (patient two) (Table 1).
Table 1. Summary of demographics and recorded factors of enrolled patients
* Duration of operation refers to ‘skin-to-skin’ (entire surgery) duration, with the cortical mastoidectomy performed by a supervised resident. †Pure tone audiometry threshold in accordance with American Academy of Otolaryngology and Head and Neck Surgery minimal reporting standard for audiometric data in clinical research. Pt no. = patient number; mins = minutes; PTA = pure tone audiometry; pre-op = pre-operative; post-op = post-operative; wk = weeks; F = female
Patient one had no measurable hearing prior to the operation in the affected ear; she was also suffering from degenerative lower spine changes with disc prolapse (lumbar spine vertebrae L4/L5) and anxiety. Her Dizziness Handicap Inventory score improved to 68 following the obliteration procedure (vs a score of 88 pre-operatively). She had a 3-day in-patient stay in light of balance disturbances following the surgery. One year following the surgery, her symptoms were stable, with a Dizziness Handicap Inventory score of 66. Additionally, she had managed to come off antidepressant medication, which she had required prior to surgery for a prolonged period of time.
The post-operative disequilibrium in patient one led the surgeon to obliterate each semicircular canal through one site only in patient two. This latter patient spent 1 day in the hospital post-operatively. Patient two had an average hearing threshold of 82.5 dB pre-operatively, which was preserved after surgery (her post-operative hearing threshold was 85 dB). Her Dizziness Handicap Inventory score improved from 54 pre-operatively to 30 following the three-semicircular-canal obliteration. One year following the surgery, she was completely asymptomatic, with a Dizziness Handicap Inventory score of 0.
There were no surgical complications in either case.
Discussion
Surgical considerations
The present study, which focuses on the surgical aspects of three-semicircular-canal obliteration, demonstrates vestibular symptom improvement in patients with intractable Ménière's disease who underwent this procedure. There are two main noteworthy surgical aspects: (1) the ‘blue-lining’ and occlusion of the semicircular canal in one site only, instead of the two-site approach, which has commonly been utilised in cases of benign paroxysmal positional vertigo (posterior semicircular canal) and superior semicircular canal dehiscence;Reference Beyea, Agrawal and Parnes1,Reference Deschenes, Hsu and Megerian2 and (2) the obliteration material (muscle supported by fascia and bone pâté).
With respect to ‘blue-lining’ and obliterating the semicircular canal only in one site, this appears to provide adequate exposure of the lumen, allowing the advance of the obliterating material into the semicircular canal. The initial case series of three-semicircular-canal obliteration, reported by Yin et al., also described a one-site fenestration only.Reference Yin, Chen, Yu, Wu, Shi and Zhou3 However, the authors recommended a small fenestration (1 mm) to avoid inner-ear trauma.Reference Yin, Chen, Yu, Wu, Shi and Zhou3 In the present work, the surgeon used a wider fenestration, taking care not to breach the membranous labyrinth. This aspect was helpful, as it facilitated trouble-free advancing of the muscle and occlusion of the lumen. The post-operative recovery period and the surgery duration were shorter when ‘blue-lining’ all three semicircular canals only in one site. Although the number of cases reported here is minimal, the recovery and the previously reported larger seriesReference Yin, Chen, Yu, Wu, Shi and Zhou3,Reference Zhang, Lv, Han, Li, Li and Wang4 indicate that fenestrating only one site in each canal in the three-semicircular-canal obliteration technique is preferable to fenestration and obliteration of each canal in two sites.
The number of reported cases is very limited, but the findings indicate that three-semicircular-canal occlusion can be a viable alternative for selected patients. Gill et al. recently reported the promising outcomes of three cases, based on class of vertigo and pure tone thresholds. Of note, we did aim to collect data from additional patients, but the current pandemic prevented this; we hope to collect these data in the near future.
In this study and in the initial description of three-semicircular-canal plugging,Reference Yin, Chen, Yu, Wu, Shi and Zhou3 temporalis muscle was used as an occlusion material. Despite the utilisation of bone pâté in previous series, targeting either the superior or the posterior semicircular canal,Reference Beyea, Agrawal and Parnes1,Reference Deschenes, Hsu and Megerian2 the authors are sceptical about the direct application of bone pâté in the inner ear, in case the continuity of the membranous labyrinth has been disrupted. However, to date, there is no evidence against the usage of bone pâté. The temporalis muscle has been utilised by the surgeon without any issues in a series of superior semicircular canal obliteration cases (unpublished data). In addition to the muscle, the overlying temporalis fascia and bone pâté, which can support the obliteration and prevent any perilymph leak, is an important detail.
Finally, with respect to pre-operative diagnostic methods, we found the computed tomography scan very useful in determining pneumatisation of the temporal bone and the accessibility of all three canals. In patients with superior semicircular canal dehiscence, the temporal bone is well pneumatised;Reference Tikka and Kontorinis5 however, in patients with Ménière's disease, this may vary.
Technique strengths and limitations
The three-semicircular-canal obliteration technique is associated with high rates of hearing preservation.Reference Yin, Chen, Yu, Wu, Shi and Zhou3,Reference Zhang, Lv, Han, Li, Li and Wang4 This provides us with a good alternative to labyrinthectomy (essentially three-semicircular-canal occlusion is a selective, partial, hearing-preserving labyrinthectomy). It also helps us to improve our understanding of the inner ear's tolerance to surgical trauma. Being able to obliterate and bypass part of the inner ear without causing deafness opens up new ways of accessing deeper areas such as the petrous apex, in a less invasive, more sophisticated way.
Previous experimental three-semicircular-canal occlusions in guinea pigs showed promising results in managing rotatory dizziness with hearing preservation.Reference Yin, Yu, Li and Wang6 In a similar fashion, the first animal study on three-semicircular-canal occlusion also showed superior outcomes compared to labyrinthectomy.Reference Gianoli, Duff, Kartush and Bouchard7 Despite the differences between animal and human models, the reported outcomes in humans support the use of such a technique. As the semicircular canals control angular accelerations, in cases where rotatory dizziness is intractable, selective obliteration of the semicircular canals – the part of the vestibular organ responsible for such symptoms – should be considered a worthwhile treatment method.Reference Yin, Chen, Yu, Wu, Shi and Zhou3,Reference Zhang, Lv, Han, Li, Li and Wang4,Reference Gill, Muzaffar, Kumar and Irving8 This was also highlighted in a recent study focusing on long-term, symptom-centred, positive outcomes, further supporting the current findings;Reference Gill, Muzaffar, Kumar and Irving8 unfortunately, that study lacked surgical details.
In the currently described surgical technique, a cautious, step-by-step approach is essential to avoid inner-ear trauma. During and after the ‘blue-lining’ of all three semicircular canals, economy of movements and avoidance of excess manipulations are crucial. Should a leak occur, additional care should be taken to avoid inner-ear trauma.
• Triple semicircular canal occlusion is a feasible, hearing-preserving surgical option for patients with Ménière's disease resistant to less invasive treatment
• Three-semicircular-canal obliteration targets the angular acceleration (controlled by semicircular canals), and can eliminate rotatory vertigo
• So far, outcomes indicate that such ‘selective labyrinthectomy’ techniques can be used to access deeper lesions, with hearing-preserving intent
• An atraumatic technique, with semicircular canal ‘blue-lining’ and careful occlusion of all canals, is crucial in hearing preservation
In conclusion, the three-semicircular-canal obliteration technique is a useful treatment option for selected patients with intractable Ménière's disease, as it can safely control rotatory vertigo. ‘Blue-lining’ of each semicircular canal in one site, and occlusion with temporalis muscle supported by fascia and bone pâté, is a safe technique.
Supplementary material
The supplementary material for this article can be found at https://doi.org/10.1017/S002221512100387X.
Competing interests
None declared
Appendix 1. Supplementary video material
A short video, demonstrating the ‘blue-lining’ of all three semicircular canals in one site (right ear), and subsequent occlusion with temporalis fascia, is available online at The Journal of Laryngology & Otology website, at https://doi.org/10.1017/S002221512100387.
