Risk of Posterior Semicircular Canal Trauma When Using a Retrosigmoid Approach for Acoustic Neuroma Surgery and Role of Endoscopy: An Imaging Study

The rate of hearing preservation after vestibular schwannoma surgery is variable and is not as high as expected, possibly due to injuries to the posterior semicircular canal while exposing the tumor. The aim of this study was to estimate the risk of posterior semicircular canal injuries using temporal bone computed tomography (CT) scan findings. Temporal bone CT scans of 30 patients selected between 2013 and 2015 were studied. The median age of the patients was 40 years. Two planes were studied: (1) the axial plane that shows the common crus of the posterior semicircular canal and (2) the coronal plane that shows the two crura of the posterior semicircular canal. Five lines were drawn and four angles and three distances were measured. In this study, we divided the patients into three groups consisting of 10 patients each: (1) patients with no evidence of inflammatory or neoplastic disease, (2) those with chronic ear disease, and (3) those with vestibular schwannomas. The portion of the internal auditory canal that was exposed by drilling while preserving the posterior semicircular canal was 53 to 64% and 61 ± 9% in whole temporal bones in the three groups. The mean angle of vision with an endoscope was less than 105° in 56% of cases, which means even with a 30° endoscope, the fundus could not be visualized. Therefore, according to our data, it seemed impossible to expose the whole length of the internal auditory canal from the porus to the fundus without causing injury to the posterior semicircular canal. However, the use of endoscopes may help to prevent injury.

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Enhanced Retrosigmoid Exposure with Posterior Semicircular Canal Resection

Otolaryngology ◽

10.1016/s0194-5998(96)70135-3 ◽

1996 ◽

Vol 115 (1) ◽

pp. 46-48 ◽

Cited By ~ 12

Author(s):

Ltc Moises Arriaga ◽

Maj Michael Gorum

Keyword(s):

Semicircular Canal ◽

Cerebellopontine Angle ◽

Internal Auditory Canal ◽

Hearing Preservation ◽

Middle Fossa ◽

Posterior Semicircular Canal ◽

Acoustic Neuromas

A subset of patients with acoustic neuromas and useful hearing have tumors that are inadequately approached by both middle fossa and retrosigmoid techniques. The enhanced retrosigmoid technique combines the hearing preservation of posterior semicircular canal ablation to achieve lateral internal auditory canal exposure with the ample cerebellopontine angle exposure of the standard retrosigmoid technique.

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Transcranial translabyrinthine approach to vestibular schwannomas

The Journal of Laryngology & Otology ◽

10.1017/s0022215100122364 ◽

1993 ◽

Vol 107 (2) ◽

pp. 111-114 ◽

Cited By ~ 2

Author(s):

Joseph G. Feghali ◽

Allen B. Kantrowitz

Keyword(s):

Facial Nerve ◽

Temporal Bone ◽

Semicircular Canal ◽

Internal Auditory Canal ◽

Endolymphatic Sac ◽

Vestibular Schwannomas ◽

Translabyrinthine Approach ◽

Vestibular Aqueduct ◽

Temporal Bones ◽

Suboccipital Approach

Surgeons who utilize the suboccipital approach for the removal of large vestibular schwannomas, can perform a planned labyrinthectomy from within the intracranial cavity via the suboccipital exposure. This transcranial translabyrinthine approach provides one of the major advantages of the conventional transmastoid translabyrinthine approach, namely, unambiguous identification of the facial nerve as it exits the internal auditory canal, without the need for complete mastoidectomy and labyrinthectomy. The labyrinthectomy is best performed prior to the complete exposure of the internal auditory canal. The approach requires the surgeon to identify the endolymphatic sac intracranially, then drill the temporal bone and follow the vestibular aqueduct to the utricle. The lateral and superior semicircular canal ampullae, the superior vestibular nerve, Bill's bar, and the facial nerve at the lateral end of the internal auditory canal can then be identified. After testing on multiple cadaver temporal bones, this approach was used in patients with large tumours that extended far laterally in the internal auditory canal. The steps in the technique are described in detail.

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Relative Preservation of Superior Semicircular Canal Architecture in CHARGE Syndrome

Otolaryngology ◽

10.1177/0194599818824306 ◽

2019 ◽

Vol 160 (6) ◽

pp. 1095-1100 ◽

Cited By ~ 1

Author(s):

Kareem O. Tawfik ◽

Brittany A. Leader ◽

Zoe A. Walters ◽

Daniel I. Choo

Keyword(s):

Temporal Bone ◽

Semicircular Canal ◽

High Frequency ◽

Care Center ◽

Internal Auditory Canal ◽

Charge Syndrome ◽

Venous Anatomy ◽

Temporal Bone Imaging ◽

Temporal Bones ◽

Clinical Diagnostic Criteria

Objectives (1) Describe common patterns of semicircular canal (SCC) anomalies in CHARGE syndrome (CS) and (2) recognize that in CS, the architecture of the superior SCC may be relatively preserved. Study Design This is a retrospective review of temporal bone imaging studies. Setting Quaternary care center. Subjects and Methods A sample of 37 patients with CS. All subjects met clinical diagnostic criteria for CS. The presence/absence of anomalies of the middle ear, mastoid, temporal bone venous anatomy, inner ear, and internal auditory canal was recorded. Anomalies of each SCC were considered separately and by severity (normal, dysplasia, aplasia). Results Thirty-seven subjects (74 temporal bones) were reviewed. Thirty-four (92.0%) patients demonstrated bilateral SCC anomalies. Three (8.0%) had normal SCCs. In patients with SCC anomalies, all canals demonstrated bilateral abnormalities. Thirty-two (86.5%) patients had bilateral horizontal SCC aplasia. These 32 patients also demonstrated posterior SCC aplasia in at least 1 ear. Of 74 temporal bones, 37 (50.0%) had superior SCC dysplasia. All dysplastic superior SCCs showed preservation of the anterior limb. Complete superior SCC aplasia was found in 28 (37.8%) temporal bones. Conclusion SCC anomalies occur with high frequency in CS. Complete absence of the horizontal and posterior canals is typical and usually bilateral. By contrast, the superior SCC often demonstrates relative preservation of the anterior limb.

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A Temporal Bone Study of Posterior Semicircular Canal Resection for Exposure of the Internal Auditory Canal (PSCC Resection)

Acta Oto-Laryngologica ◽

10.1080/00016489950180171 ◽

1999 ◽

Vol 119 (8) ◽

pp. 858-862 ◽

Cited By ~ 1

Author(s):

Jeffrey T. Vrabec, Ravi Pachigolla

Keyword(s):

Temporal Bone ◽

Semicircular Canal ◽

Internal Auditory Canal ◽

Posterior Semicircular Canal

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Cerebrospinal Fluid Leak During Stapes Surgery: The Importance of Temporal Bone CT Reconstructions in Oblique Anatomically Oriented Planes

Ear Nose & Throat Journal ◽

10.1177/0145561320984569 ◽

2021 ◽

pp. 014556132098456

Author(s):

Massimo Re ◽

Mirko Giannoni ◽

Alfonso Scarpa ◽

Claudia Cassandro ◽

Massimo Ralli ◽

...

Keyword(s):

Cerebrospinal Fluid ◽

Temporal Bone ◽

Internal Auditory Canal ◽

Cerebrospinal Fluid Leak ◽

High Resolution Computed Tomography ◽

Temporal Bone Ct ◽

Patients At Risk ◽

Bone Structures ◽

Fluid Leak

Stapes gusher is a massive flow of perilymph and cerebrospinal fluid leak that fills the middle ear immediately after surgical opening of the labyrinth, such as during stapedectomy. Stapes gusher usually occurs as the result of a congenital malformation that causes an abnormal communication between the perilymphatic space and the subarachnoid space involving the internal auditory canal or the cochlear duct. To date, the potential risk of stapes gusher cannot be assessed preoperatively, as there are not pathognomonic signs suggestive of this complication. However, high-resolution computed tomography scan (HRCT) of the temporal bone can provide information that may help recognizing patients at risk. Recently, an anatomic evaluation of the inner ear with oblique reformation at HRCT has been described. This reformation offers a new and more detailed topographic vision of temporal bone structures compared to the classic axial and coronal planes and may help identifying anatomical alterations otherwise not visible. In this article, we present a case of stapes gusher and the role of preoperative HRCT with oblique reformation in its prevention.

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Study of Sigmoid Sinus Variations in the Temporal Bone by Micro Dissection and its Classification – A Cadaveric Study

International Archives of Otorhinolaryngology ◽

10.1055/s-0039-1688455 ◽

2019 ◽

Vol 23 (03) ◽

pp. e311-e316 ◽

Cited By ~ 1

Author(s):

Anup Singh ◽

David Victor Kumar Irugu ◽

Kapil Sikka ◽

Hitesh Verma ◽

Alok Thakar

Keyword(s):

Temporal Bone ◽

Semicircular Canal ◽

Sigmoid Sinus ◽

Point Of View ◽

Posterior Semicircular Canal ◽

Mastoid Pneumatization ◽

Clinical Point ◽

Temporal Bones ◽

Grade Iii

Introduction Sigmoid sinus (SS) variations have been classified variously in the literature. These classifications suffer from some form of shortcoming from a clinical point of view for their application. Objective We propose a clinically relevant classification of the SS in relation to the posterior semicircular canal (PSCC) and to the exposure of the presigmoid dural plate. The positioning of the SS was analyzed with reference to the volume of the mastoid and to the level of mastoid pneumatization. Methods A total of 94 formalin-preserved human cadaveric temporal bones were microdissected to carry out a complete mastoidectomy. The SS, the presigmoid dural plate, and the PSCC were exposed, and the position of the former was analyzed in relation to the latter two in order to classify the position of the SS into three grades. Results Grade I had the best exposure of the presigmoid dura and of the PSCC, while grade III had the poorest exposure of the presigmoid dura and of the PSCC. Grade I SS was associated with good pneumatization and higher mastoid volumes compared with grades II and III. Conclusions The SS exhibits considerable anatomic variability. A favorable positioning of the SS is associated with a large mastoid volume and pneumatization. A careful preoperative study of the imaging may help in understanding the positioning of the SS and the safety of various transmastoid approaches.

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Schuknecht’s Temporal Bone Bank in Boston

10.1093/med/9780190600129.003.0018 ◽

2016 ◽

Author(s):

Robert W. Baloh

Keyword(s):

Temporal Bone ◽

Semicircular Canal ◽

Clinical Syndrome ◽

Posterior Semicircular Canal ◽

Provocative Test ◽

Posterior Canal ◽

Left Posterior ◽

Test Position ◽

Set Up ◽

Paroxysmal Positional Vertigo

When Harold Schuknecht arrived at Harvard in 1961, he immediately set up a temporal bone laboratory and began collecting specimens. Schuknecht obtained two specimens from patients with a typical clinical picture of benign paroxysmal positional vertigo (BPPV). In these specimens, Schuknecht identified a prominent granular basophilic staining mass attached to the cupula of the left posterior semicircular canal. Based on his findings, Schuknecht coined the term “cupulolithiasis” (“stones on the cupula”) to explain the clinical syndrome of BPPV. He assumed that substances having a specific gravity greater than endolymph and thus subject to movement with changes in the direction of gravitational force come into contact with the cupula of the posterior semicircular canal. With the head in the erect position, the posterior canal ampulla is located inferiorly, whereas in the provocative test position (supine, head hanging, ear down) the posterior canal assumes a superior position.

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Schuknecht and His Breakthrough on Benign Paroxysmal Positional Vertigo

10.1093/med/9780190600129.003.0017 ◽

2016 ◽

Author(s):

Robert W. Baloh

Keyword(s):

Temporal Bone ◽

Semicircular Canal ◽

Benign Paroxysmal Positional Vertigo ◽

Assistant Professor ◽

Clinical Instructor ◽

Posterior Semicircular Canal ◽

Positional Vertigo ◽

Patient Reported ◽

The University ◽

Paroxysmal Positional Vertigo

In 1949, Harold Schuknecht completed his residency in John Lindsay’s Otolaryngology Department at the University of Chicago and stayed first as a clinical instructor and then as an assistant professor. Schuknecht reviewed the temporal bone specimens from the patient reported by his mentor, John Lindsay, and from patients reported by Charles Hallpike and colleagues and was struck by the similarity in the pathologic changes. He concluded that in each case damage to the labyrinth resulted from occlusion of the anterior vestibular artery. Schuknecht believed that the delayed positional vertigo that occurred in these cases must have originated from the posterior semicircular canal. He reasoned that with degeneration of the superior vestibular labyrinth, otoconia would be released from the otolithic membrane of the utricular macule and that, in certain positions of the head, the otoconia would respond to gravity and thereby activate the cupula of the posterior semicircular canal.

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