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

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

Ear Nose & Throat Journal ◽

10.1177/0145561318097001-223 ◽

2018 ◽

Vol 97 (1-2) ◽

pp. 24-30

Author(s):

Ali Kouhi ◽

Varasteh Vakili Zarch ◽

Ali Pouyan

Keyword(s):

Temporal Bone ◽

Semicircular Canal ◽

Internal Auditory Canal ◽

Imaging Study ◽

Hearing Preservation ◽

Neoplastic Disease ◽

Posterior Semicircular Canal ◽

Temporal Bone Ct ◽

Temporal Bones

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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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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Posterior Semicircular Canal Dehiscence Arising From Temporal Bone Fibrous Dysplasia

Otology & Neurotology ◽

10.1097/mao.0b013e3181be6b12 ◽

2010 ◽

Vol 31 (9) ◽

pp. 1516-1517 ◽

Cited By ~ 1

Author(s):

Andrew A. McCall ◽

Hugh D. Curtin ◽

Michael J. McKenna

Keyword(s):

Fibrous Dysplasia ◽

Temporal Bone ◽

Semicircular Canal ◽

Posterior Semicircular Canal ◽

Canal Dehiscence

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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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The Singular Canal: A Valuable Landmark in Surgery of the Internal Auditory Canal

Otolaryngology ◽

10.1177/019459988809800207 ◽

1988 ◽

Vol 98 (2) ◽

pp. 138-143 ◽

Cited By ~ 27

Author(s):

Herbert Silverstein ◽

Horace Norrell ◽

Eric Smouha ◽

Thomas Haberkamp

Keyword(s):

Hearing Loss ◽

High Resolution ◽

Sensorineural Hearing Loss ◽

Semicircular Canal ◽

Internal Auditory Canal ◽

Retrosigmoid Approach ◽

Posterior Semicircular Canal ◽

Vestibular Neurectomy ◽

Acoustic Neuromas ◽

Acoustic Neuroma Surgery

The singular canal transmits the posterior ampullary nerve between the inferior part of the internal auditory canal (IAC) and ampulla of the posterior semicircular canal. The anatomy of the singular canal was studied in temporal bone dissections, in surgical dissections, and in high-resolution computerized tomography scans. Measurements were taken for distances between the origin of the singular canal in the IAC, the porus acousticus, the vestibule, and posterior canal ampulla. The location and importance of the singular canal are demonstrated for retrosigmoid-IAC vestibular neurectomy, retrosigmoid acoustic neuroma surgery, and transcochlear cochleovestibular neurectomy. The main purpose for the use of the retrosigmoid approach to the internal auditory canal during vestibular neurectomy and excision of acoustic neuromas is preservation of hearing. A major concern when the contents of the internal auditory canal are exposed through this approach is fenestration of the labyrinth, which results in sensorineural hearing loss. In the retrosigmoid approach, the singular canal has been found to be a vital landmark in prevention of fenestration during surgery of the internal auditory canal.

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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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Image-Guided, Endoscopic-Assisted Drilling and Exposure of the Whole Length of the Internal Auditory Canal and Its Fundus With Preservation of the Integrity of the Labyrinth Using a Retrosigmoid Approach: A Laboratory Investigation

Operative Neurosurgery ◽

10.1227/01.neu.0000343521.88537.16 ◽

2009 ◽

Vol 65 (suppl_6) ◽

pp. ons53-ons59 ◽

Cited By ~ 7

Author(s):

Promod Pillai ◽

Steffen Sammet ◽

Mario Ammirati

Keyword(s):

High Resolution ◽

Semicircular Canal ◽

Image Guidance ◽

Internal Auditory Canal ◽

Posterior Wall ◽

Retrosigmoid Approach ◽

Slice Thickness ◽

Posterior Semicircular Canal ◽

Computed Tomographic ◽

Reference Markers

Abstract Objective: Hearing loss after removal of vestibular schwannomas with preservation of the cochlear nerve can result from labyrinthine injury of the posterior semicircular canal and/or common crus during drilling of the posterior wall of the internal auditory meatus. Indeed, there are no anatomic landmarks that intraoperatively identify the position of the posterior semicircular canal or of the common crus. We investigated the usefulness of image guidance and endoscopy for exposure of the internal auditory canal (IAC) and its fundus without labyrinthine injury during a retrosigmoid approach. Methods: A retrosigmoid approach to the IAC was performed on 10 whole fresh cadaveric heads after acquiring high-resolution computed tomographic scans (120 kV; slice thickness, 1 mm; field of vision, 40 cm; matrix, 512 × 512) with permanent boneimplanted reference markers. Drilling of the posterior wall of the IAC was executed with image guidance. Its most lateral area was visualized using endoscopy. Results: Target registration error for the procedure was 0.28 to 0.82 mm (mean, 0.46 mm; standard deviation, 0.16 mm). The measured length of the IAC along its posterior wall was 9.7 ± 1.6 mm. The angle of drilling (angle between the direction of drill and the posterior petrous surface) was 43.3 ± 6.0 degrees, and the length of the posterior wall of the IAC drilled without violating the integrity of the labyrinth was 7.2 ± 0.9 mm. The surgical maneuvers in the remaining part of the IAC, including the fundus, were performed using an angled endoscope. Conclusion: Frameless navigation using high-resolution computed tomographic scans and bone-implanted reference markers can provide a “roadmap” to maximize safe surgical exposure of the IAC without violating the labyrinth and leaving a small segment of the lateral IAC unexposed. Further exposure and surgical manipulation of this segment, including the fundus without additional cerebellar retraction and labyrinthine injury, can be achieved using an endoscope. Use of image guidance and an endoscope can help in exposing the entire posterior aspect of the IAC including its fundus without violating the labyrinth through a retrosigmoid approach. This technique could improve hearing preservation in vestibular schwannoma surgery.

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