Download Superior semicircular canal dehiscence: evaluation by thin

Superior semicircular canal dehiscence: evaluation by thinsection computed tomography with reformations in the
planes of Stenver and Pöschl.
Poster No.:
C-1704
Congress:
ECR 2011
Type:
Educational Exhibit
Authors:
A. L. CUNHA, A. A. S. M. Santos, R. A. Medina, M. L. O. Santos,
C. A. P. Fontes, C. E. L. Cabral; Niterói - Rio de Janeiro, RJ/BR
Keywords:
Technical aspects, Outcomes analysis, Observer performance,
CT, Head and neck
DOI:
10.1594/ecr2011/C-1704
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Learning objectives
•
•
Demonstrate the importance of using thin-section computed tomography
(CT), whether additional reformations in the planes of Stenver and Pöschl
change the diagnostic interpretation for semicircular canal dehiscence
(SCD) when compared with the diagnostic interpretation of standard coronal
reformations.
To review the cases treated and underwent CT scan of the mastoid, with the
objective of alerting health professionals of the existence of this disease by
addressing its main clinical and diagnostic features
Background
•
•
150 mastoid CT scans were retrospectively studied. The examinations were
reviewed by two radiologists independently, and subsequently reviewed by
the authors, and the results achieved by consensus.
On routine examination, were performed with slices of 1.0 mm, in axial
and coronal planes, with subsequent reconstructions: oblique coronal (with
angulation of 45° / pitch 1.5) - Stenvers plan and oblique sagittal (with 45°
angle / pitch 1.5) - Pöschl plan semicircular canal.
ANATOMY:
•
The human auditory system is divided into three parts each with its own
functions and the three are essential for the proper functioning of hearing
(FIG.1):
#External ear
#Middle ear
#Inner ear
•
•
The semicircular canals are three half-circular, interconnected tubes located
inside each ear. The three canals are the horizontal semicircular canal (also
known as the lateral semicircular canal), superior (or anterior) semicircular
canal and the posterior semicircular canal (FIG.2).
The canals are aligned approximately orthogonally to one another.
# The horizontal canal detects horizontal head movements, while the superior and
posterior canals detect vertical head movements
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# The superior and posterior canals are aligned roughly at a 45 degree angle to a vertical
plane drawn from the nose to the back of the skull.
# Thus, the horizontal canal detects horizontal head movements, while the superior and
posterior canals detect vertical head movements
•
•
Each canal is filled with a fluid called endolymph and contains a motion
sensor with little hairs (cilia) whose ends are embedded in a gelatinous
structure called the cupula. As the skull twists in any direction, the
endolymph is thrown into different sections of the canals. The cilia detect
when the endolymph rushes past, and a signal is then sent to the brain.
The semicircular canals are a component of the bony labyrinth (FIG 3,4).
Semicircular canal dehiscence:
•
•
•
Semicircular canal dehiscence (SCD) is an unusual abnormality of the
temporal bone. Patients most frequently experience dizziness induced by
loud noises (Tullio phenomenon). Since its initial description in 1998, SCD
has rapidly become an accepted diagnosis in the evaluation of vertigo.
The normal bony covering over the apex of the superior semicircular canal
is absent in patients with superior semicircular canal dehiscence (SSCD) the
most frequent semicircular canal stricken.
The most affected age group was described in the literature around the 4th
decade. In this study, the mean age was 48,27 years, with no preference for
sex.
Images for this section:
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Fig. 1: Schematic figure of the division of human auditory system
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Fig. 2: Three-dimensional VR CT image (view from the dissected medial portion of the
temporal bone) shows the inner ear, including the cochlea (Co), vestibule (Ve), superior
semicircular canal (SSCC), lateral semicircular canal (LSCC), and posterior semicircular
canal (PSCC). The internal auditory canal (IAC) and the bony canal for the facial nerve
(FN) are also seen.
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Fig. 3: Normal anatomy of the bony labyrinth. Three-dimensional VR CT image
(anterolateral view) shows the normal bony labyrinth, which consists of the cochlea (Co),
vestibule (Ve), and semicircular canals (SCC). FN = facial nerve canal, IAC = internal
auditory canal, OW = oval window.
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Fig. 4: Three-dimensional VR CT image (posteroinferior view) shows the singular canal
(SC), through which courses a branch of the inferior vestibular nerve. The inferior
vestibular nerve innervates the posterior semicircular canal (PSCC).
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Imaging findings OR Procedure details
IMAGING FINDINGS:
•
•
•
The diagnosis of Semicircular canal dehiscence is confirmed by high
resolution Computed Tomography of the temporal bone, in which there is
exposure (gap) of the canal wall by the lack of bone overlying it.
It is recommended, to reduce the number of false positives, use slices <
1mm (of 0.5mm) and / or reconstruction of the images in the plane of the
semicircular canal.
All examinations were performed on helical device (bone filter / 130 kV /
mAs 135), performed without intravenous contrast, with serial sections of 1.0
mm thickness and interval with subsequent reconstruction:
# Axial: fixed position of the head and slightly bent, and the cutting plane parallel to
orbitomeatal line or the hard palate, taking care with the lens
# Coronal: head secured with cervical hyperextension avoiding vertebro-basilar
insufficiency during hyperextension, with the cutting plane perpendicular to the maximum
angle
# Coronal oblique: (angled 45 ° / pitch 1.5) - Stenvers (FIG. 1)
# Sagittal oblique: (angled 45 ° / pitch 1.5) - Pöschl (FIG. 2,3)
•
•
•
•
In 150 patients, the transverse images, coronal and oblique reformations in
planes of Stenver and Pöschl proved semicircular canal dehiscence in 11
patients (7,5%). One case was bilateral dehiscence (FIG.4-8).
Seven cases were found with associated changes: thickening of the
tympanic membrane, incomplete pneumatization of the mastoid,
mastoidectomy, acute otomastoiditis, chronic otomastoiditis with
cholesteatoma, chronic otitis (FIG. 9).
CT has become the method of complementary examination of choice for
evaluating patients with vestibular, since it allows to observe the internal
organs with greater accuracy, without superimposition of images, reducing
the time of diagnosis and treatment of patients with vestibular symptoms
(dizziness and imbalance chronic) and avoiding inappropriate diagnostic or
therapeutic approaches (such as anti-vertigo medications).
CT reformations in the planes of Stenver and Pöschl change the diagnostic
interpretation for superior semicircular canal dehiscence (SSCD)
when compared with the diagnostic interpretation of standard coronal
reformations.
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Images for this section:
Fig. 1: Plane of Stenver. (a) Angle of reformation demonstrated on transverse scout
image. (b) Intact superior semicircular canal (arrowhead). (c) Dehiscent superior
semicircular canal (arrow).
Fig. 2: Plane of Pöschl:(a) Angle of reformation demonstrated on transverse scout image.
(b)Intact superior semicircular canal (arrowhead). (c)Dehiscent superior semicircular
canal (arrow).
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Fig. 3: Plane of Pöschl:(a) Plane of reconstruction (white line) through the roof of the
superior semicircular canal. (b) Oblique sagittal image shows integrity of the bone in the
roof of the superior semicircular canal (SSC), as well as a normal appearance of the facial
nerve (FN) and the lateral semicircular canal (LSC). (c) Single-oblique sagittal image
shows dehiscence of the SSC (arrow).
Fig. 4: In 150 patients, the transverse images, coronal and oblique reformations in planes
of Stenver and Pöschl proved semicircular canal dehiscence in 11 patients (7,5%).
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Fig. 5: Female, 72yo, right hearing loss.
Fig. 6: Female, 83 yo, right otalgia.SSCD. Coronal oblique reformation (plane of Stenver),
in the right picture and sagittal oblique reformation (Plane of Pöschl) in the left one.
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Fig. 7: Female, 74 yo, left otalgia.SCCD. Coronal oblique reformation (plane of Stenver),
in the right picture and sagittal oblique reformation (Plane of Pöschl) in the left one.
Fig. 8: Male, 14 yo, asymptomatic. SSCD. Coronal oblique reformation (plane of
Stenver), in the right picture and sagittal oblique reformation (Plane of Pöschl) in the left
one.
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Fig. 9: Male, 56 yo, pain. SSCD. Coronal oblique reformation (plane of Stenver), in the
right picture and sagittal oblique reformation (Plane of Pöschl) in the left one. Associated
change: Chronic otomastoiditis with cholesteatoma.
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Conclusion
•
The CT scan is the gold standard for diagnostic confirmation of superior
semicircular canal dehiscence and it is important to note that images should
be obtained with smaller slices than 1.0 mm thick with reformation plans
Stenvers and Pöschl.
Personal Information
Alexandre Limpias Cunha.
Student of the Specialization Course in Radiology - Institute of Postgraduate Medical
Carlos Chagas (IPGMCC). Rio de Janeiro. Brazil.
Email: [email protected]
Alair Augusto Sarmet M. D dos Santos. MD, PhD.
Corresponding Author. Associate Professor, Department of Radiology and Head of the
Radiology and Diagnostic Imaging Service of University Hospital Antônio Pedro (HUAP) /
UFF (Federal Fluminense University) - Niterói, RJ, Brazil. Coordinator of Image CenterHCN (Hospital Clinicas de Niterói) and Coordinator of the Specialization Course in
Radiology Institute of Postgraduate Medical Carlos Chagas (IPGMCC).Rio de Janeiro,
Brazil.
Email: [email protected]
e-curriculum: http://lattes.cnpq.br/1215394507629695
Rafael de Araújo Medina.
Student of the Specialization Course in Radiology - Institute of Postgraduate Medical
Carlos Chagas (IPGMCC). Rio de Janeiro. Brazil.
Email: [email protected]
Maria Lucia Oliveira Santos. MD, PhD.
Associate Professor, Department of Radiology University Hospital Antônio Pedro
(HUAP) /UFF (Federal Fluminense University) - Niterói, RJ, Brazil.
Page 14 of 16
Email: [email protected]
Cristina Asvolinsque Pantaleão Fontes. MD.
Assistent Professor. Departament of Radiology, and Diagnostic Imaging Service of
University Hospital Antônio Pedro (HUAP) /UFF (Federal Fluminense University) Niterói, RJ, Brazil.
Medical radiologist in Image Center-HCN (Hospital Clinicas de Niterói).
Email: [email protected]
Carlos Eduardo Lassance Cabral.MD
Assistent Professor of the Specialization Course in Radiology Institute of Postgraduate
Medical Carlos Chagas (IPGMCC).Rio de Janeiro, Brazil.
Medical radiologist in Image Center-HCN (Hospital Clinicas de Niterói).RJ. Brazil.
Email: [email protected]
Study site
Hospital de Clínicas de Niterói, Institute of Postgraduate Medical Carlos Chagas
(IPGMCC) and Federal Fluminense University (UFF) - Niterói, Rio de Janeiro, Brazil.
Potential Conflict of Interest
No potential conflict of interest relevant.
Funding Sources
This study did not have funding source.
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