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Clinical Anatomy 00:00–00 (2014)
ORIGINAL COMMUNICATIONS
Trautmann’s Triangle Anatomy With Application
to Posterior Transpetrosal and Other Related
Skull Base Procedures
R. SHANE TUBBS,1,2,3 CHRISTOPH GRIESSENAUER,1 MARIOS LOUKAS,2
SHAHERYAR F. ANSARI,4 MICHAEL H. FRITSCH,5 AND AARON A. COHEN-GADOL4*
1
Pediatric Neurosurgery, Children’s Hospital of Alabama, Birmingham, Alabama
Department of Anatomic Sciences, St. George’s University School of Medicine, St. George’s, Grenada
3
Centre of Anatomy and Human Identification, Dundee University, United Kingdom
4
Goodman Campbell Brain and Spine, Department of Neurological Surgery, Indiana University School of
Medicine, Indianapolis, Indiana
5
St. Vincent Medical Center, Indianapolis, Indiana
2
Trautmann’s triangle (TT) faces the cerebellopontine angle and is exposed during posterior transpetrosal approaches. However, reports on the morphometric
analysis of this structure are lacking in the literature. The goal was to better
understand this important operative corridor. TT was exposed from an external
approach (transmastoid) in ten cadavers (20 sides) and from an internal
approach on 20 dry adult temporal bones. Measurements included calculation
of the area of TT and the distance of the endolymphatic sac from the anterior
border of the sigmoid sinus. The area range of TT was 45–210 mm2 (mean 151
mm2; SD 37 mm2). Three types of triangles were identified based on area.
Type I triangles had areas less than 75 mm2, Type II areas were 75–149 mm2,
and Type III areas were 150 mm2 and greater. These types were observed in
37.5%, 35%, and 27.5% of sides, respectively. The distance from the jugular
bulb’s anterior border to the posterior border of the posterior semicircular canal
ranged from 6 to 11 mm (mean 8.5 mm). The endolymphatic sac was located
in the inferior portion of TT and traveled anterior to the sigmoid sinus. The horizontal distance from the anterior edge of the sigmoid sinus to the posterior
edge of the endolymphatic sac ranged from 0 to 13.5 mm (mean 9 mm). Additional anatomic knowledge regarding TT may improve neurosurgical procedures in this region by avoiding intrusion into the endolymphatic sac and
sigmoid sinus. Clin. Anat. 00:000–000, 2014. VC 2014 Wiley Periodicals, Inc.
Key words: skull base; neurosurgery; posterior cranial fossa; mastoid bone;
Trautmann’s triangle
INTRODUCTION
During posterior transpetrosal approaches to the
posterior fossa, the dura mater on the posterior side
of the temporal bone that faces the cerebellopontine
angle is opened. This triangular-shaped area is
referred to as Trautmann’s triangle (TT) (Moritz
Trautmann, 1833–1902) and is bordered by the
superior jugular bulb at the inferior vertex, the
sino-dural angle along the superiorly directed base
C
V
2014 Wiley Periodicals, Inc.
*Correspondence to: Aaron A. Cohen-Gadol, MD, MSc, Goodman Campbell Brain and Spine, Indiana University Department
of Neurological Surgery, 355 W. 16th Street, Suite #5100, Indianapolis, IN 46202, USA. E-mail: [email protected]
Received 20 September 2013; Revised 26 November 2013;
Accepted 26 November 2013
Published online in Wiley Online Library (wileyonlinelibrary.com).
DOI: 10.1002/ca.22363
2
Tubbs et al.
During a retrolabyrinthine presigmoid approach,
the posterior temporal bone is drilled out and TT is
exposed. The dura of TT is then opened parallel to the
sigmoid sinus posteriorly and the superior petrosal
sinus and floor of the middle cranial fossa superiorly
(Oppel and Mulch, 1979; Al-Mefty et al., 1988) (Fig.
2). Currently, the approach through TT is performed in
nière’s disthe surgical management of intractable Me
ease, during which the endolymphatic sac is opened
and a shunt is placed (Paparella et al., 1988). The retrolabyrinthine approach was originally developed for
vestibular neurectomies for intractable vertigo and
has since been used for resection of petroclival meningiomas and other related lesions ventral to the brainstem as part of partial petrosectomy (Miller et al.,
1993). Since TT and its associated structures are
exposed in the surgical field and are best left intact,
the authors performed this study to better characterize some anatomic relations within this important
area.
MATERIALS AND METHODS
(Gonzalez et al., 2004), and anteriorly by the posterior semicircular canal (Fig. 1) (Sincoff et al., 2007).
TT, also referred to as the retromeatal trigone, represents much of the area resected in the approach
to the posterior petrosectomy (Miller et al., 1993;
Gonzalez et al., 2004).
TT was exposed from an external approach (transmastoid) in 10 cadavers (20 sides) (Fig. 3) and from
an internal approach on 20 dry adult temporal bones
(Fig. 4). The cadaveric specimens were derived from
five male and five female specimens with an age
range at death of 29–88 years (mean 75 years).
Measurements included calculation of the area of TT
(Image J, imagej.nih.gov/ij/), the distance from the
jugular bulb’s anterior border to the posterior border
of the posterior semicircular canal, and the distance of
the endolymphatic sac from the anterior border of the
sigmoid sinus along a horizontal line. The latter measurements were made with microcalipers (Mitutoyo,
Kawasaki, Japan) and observations/photographs
under a surgical microscope (Zeiss, Germany) or digital camera. The endolymphatic sac was observed as a
Fig. 2. Schematic drawing of the operative approach
through TT. The left image demonstrates the predural
opening. The right image shows the dural opening and
elevation and exposure of deeper structures. Note that
the endolymphatic sac is normally located anterior to the
sigmoid sinus, superior to the jugular bulb, and approximately in the midportion of TT. In this schematic drawing,
the endolymphatic sac is not in anatomic position. [Color
figure can be viewed in the online issue, which is available
at wileyonlinelibrary.com.]
Fig. 1. Schematic drawing illustrating the left TT from
an external approach. Copyright The Neurosurgical Atlas,
Aaron A. Cohen-Gadol, MD, MSc. Used with permission.
[Color figure can be viewed in the online issue, which is
available at wileyonlinelibrary.com.]
Trautmann’s Triangle
3
(Fig. 4C) had areas of 150 mm2 and greater. These
types were observed in 15 (37.5%), 14 (35%), and
11 (27.5%) of sides, respectively. The distance from
the jugular bulb’s anterior border to the posterior border of the posterior semicircular canal ranged from
6 to 11 mm (mean 8.5 mm). The endolymphatic sac
was located in the inferior portion of TT and traveled
Fig. 3. Right-sided cadaveric specimen that has
undergone a retrolabyrinthine exposure with TT exposed.
[Color figure can be viewed in the online issue, which is
available at wileyonlinelibrary.com.]
thickening of dura mater between the sigmoid sinus
posteriorly and the posterior semicircular canal anteriorly. The endolymphatic sac is typically located inferior
to the posterior semicircular canal. Using the prominence of the horizontal semicircular canal, Donaldson
line (a line drawn through the horizontal semicircular
canal and extended into the mastoid cavity) is identified to approximate the position of the endolymphatic
sac. The endolymphatic sac should be located inferior
to this line (Ammirati et al., 1995). Statistical analysis
was performed using Statistica for Windows (10.0)
with statistical significance set at P < 0.05. No specimen was found to have gross intracranial pathology.
RESULTS
The area of TT ranged from 45 to 210 mm2 (mean
151 mm2; SD 37 mm2). Although TT appeared to be
somewhat smaller in female specimens, this difference did not reach statistical significance. We classified the triangles into three types. The definitions of
these types were as follows: Type I triangles (Fig. 4A)
had areas of less than 75 mm2; Type II triangles (Fig.
4B) had areas of 75–149 mm2; and Type III triangles
Fig. 4. A: From an internal view (left side), a Type I
TT. B: From an internal view (right side), a Type II TT.
C: From an internal view (left side), a Type III TT. [Color
figure can be viewed in the online issue, which is available
at wileyonlinelibrary.com.]
4
Tubbs et al.
medial to the sigmoid sinus and inferior to the posterior semicircular canal (Fig. 2). The horizontal distance
from the anterior edge of the sigmoid sinus to the
posterior edge of the endolymphatic sac ranged from
0 to 13.5 mm (mean 9 mm). This sac was, in general,
a few millimeters posterior to the posterior semicircular canal. The anterior inferior cerebellar artery and
subarcuate artery approached TT in 40% (n 5 8) and
30% (n 5 6) of sides, respectively. None of the measurements were statistically different when comparing
left or right sides.
DISCUSSION
The surface area of TT is highly variable and largely
dependent on the location of the sigmoid sinus in the
mastoid cavity (Paparella et al., 1988). For example,
when the sigmoid sinus occupies a truly lateral position within the mastoid bone, TT will occupy the posterior wall of the mastoid space (Paparella et al., 1988).
Three types of TT have been described in the otolaryngology literature based on the location of the sigmoid sinus (Sarmiento and Eslait, 2004). Sarmiento
and Eslait (2004) described a posteriorly, anteriorly,
and medially displaced sigmoid sinus in 22.3%,
57.5%, and 20.2%, respectively. Naturally, an anteriorly and medially displaced sigmoid sinus will diminish
the area of TT. In their Type I, the sigmoid sinus is
located posteriorly in the mastoid cavity, thus enlarging the triangle. In Type II, the sigmoid sinus is
located more anteriorly thereby diminishing the size
of TT. In Type III, the sigmoid sinus is displaced medially, which also reduces the size of the triangle (Sarmiento and Eslait, 2004).
We classified the triangles into three types based
on their surface area, which is more objective and
accurate than the approximate position of the sigmoid
sinus as described in the previous studies (Sarmiento
and Eslait, 2004). Such classification is important as it
correlates with the position of the endolymphatic sac
and the available operating space between the posterior semicircular canal and the sigmoid sinus. In Type
I triangles, the surgical window for exposure is highly
contracted due to anteriorly positioned sigmoid sinus
and surgical manipulation may lead to endolymphatic
sac injury and poor exposure of the posterior fossa.
Therefore, the exposure of the brainstem and the surgeon’s working angles are limited due to a narrow
“keyhole” exposure. Type II triangles can be useful
surgically, and although not ideal, can be chosen for
maximal effectiveness based on the location of the
endolymphatic sac. The Type III triangles can be
expected to provide a wider operative corridor to
expose the posterior fossa with a high likelihood of
preserving the endolymphatic sac. Nitek et al. (2002)
have also measured the surface area of TT and found
that on average, this was 175.9 mm2 and was always
large enough to insert standard otosurgical instruments and endoscopic devices. Lastly, Tedeschi and
Rhoton (1994) have reported that anteroposterior and
craniocaudal measurements of TT were 7–8 mm and
14–16 mm, respectively.
Anatomical variations of TT have also been associ nière’s disease
ated with chronic otitis media and Me
(Paparella et al., 1988; Rhoton, 1993). Patients with
nière’s disease may have a larger and anteromeMe
dially displaced sigmoid sinus resulting in a smaller TT
(Paparella et al., 1988). The endolymphatic sac is
normally located anterior to the sigmoid sinus, superior to the jugular bulb, and approximately in the midportion of TT (Tos, 2000). We found that the
endolymphatic sac was usually located in the inferior
portion of TT in Type I and traveled medial to the sigmoid sinus and inferior to the posterior semicircular
canal. This sac was, in general, a few millimeters posterior to the posterior semicircular canal. A line drawn
through the horizontal semicircular canal and extended
into the mastoid cavity, referred to as Donaldson’s
line, usually indicates the approximate location of the
normal endolymphatic sac (Rhoton, 1993). Anatomical
variation has been linked to underdevelopment of the
endolymphatic duct and sac, periaqueductal cells, and
mastoid air cells, leading to endolymphatic malabsorption followed by endolymphatic hydrops with manifes nière’s disease (Paparella et al., 1988). In
tations of Me
up to 10% of endolymphatic sac operations for
nière’s disease, the endolymphatic sac may not be
Me
identified at surgery (Friberg et al., 1988).
During posterior petrosectomy, TT is used as part
of the approach to posterior fossa lesions (Gonzalez
et al., 2004). The transpetrosal approach is further
subdivided into translabyrinthine (essentially a labyrinthectomy in combination with the approach through
TT), retrolabyrinthine, and transcochlear approaches.
Each of these operative corridors can be used
to approach petroclival lesions with transcochlear
approaches favored for tumors with extensive prepontine extension. Translabyrinthine, transotic, and transcochlear approaches do not preserve hearing. The
surface area of TT is primarily relevant to the retrolabyrinthine approach; the translabyrinthine and transcochlear approaches provide substantially more room
and anterior exposure from removing portions of the
inner ear. One study analyzed the postauricular, transpetrous, presigmoid approach for extensive petroclival
skull base tumors (Tedeschi and Rhoton, 1994; Behari
et al., 2010). Lesions included petroclival meningiomas, cranial nerve schwannomas, glomus jugulare
tumors, and petrous aneurysmal bone cysts. In contrast to a posterior retrosigmoid approach where cranial nerves, blood vessels, cerebellum, and brain stem
obliterate the surgical corridor, the transpetrosal route
allows access to the petroclival region and cerebellopontine angle from an anterolateral trajectory. However, the risk of complications such as deafness, facial
nerve palsy, and cerebrospinal fluid leak increases as
the extent of the petrosal bony resection increases
(Gonzalez et al., 2004).
The wide surgical corridor provided through the
petrosectomy route facilitates maximal tumor resection through numerous working angles and allows
microsurgical dissection of important perforators
under direct microsurgical inspection without risky
retraction on surrounding neurovascular structures. In
selected cases, this approach has been combined with
retrosigmoid, suboccipital craniectomy, infratemporal,
extreme lateral transcondylar, or translabyrinthine
approaches to achieve even wider access. Ligation
Trautmann’s Triangle
and division of the superior petrosal sinus and tentorium cerebelli as well as posterior retraction of a skeletonized sigmoid sinus will widen this corridor (Behari
et al., 2010). Based on our study, the surgeon will
have approximatley 1 cm from the anterior wall of the
superior jugular bulb until the posterior wall of the
posterior semicircular canal is reached.
CONCLUSIONS
Additional anatomic knowledge regarding TT may
improve neurosurgical procedures in this region. The
surface area typing of this triangle, based on our
study, is more objective and accurate than the one
from previous studies and may be useful to clinicians
for estimating the chances of success using a presigmoid approach. Depending on the triangle size, success of surgery through TT may be predicted to a
greater degree.
ACKNOWLEDGEMENT
The authors are grateful to the donors of the specimens used in this study.
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