Combined Supra- and Infra-Tentorial Retro-Labyrinthine Pre-sigmoid Approach

Abstract

Purpose of Review
This chapter describes the background, indications and key aspects of the combined supra- and infra-tentorial retro-labyrinthine pre-sigmoid approach. This approach is most commonly used for petrous apex meningiomata and vascular pathologies of the mid and upper basilar trunk.

Recent Findings
Our pre-operative evaluation includes MRI, CT to assess pneumatisation of the petrous bone and vascular imaging where necessary. Audiology and ophthalmology baseline assessments are performed if appropriate.

Summary
The nuances of the operative technique are discussed with an emphasis on avoidance of complications.

Full text

OTOLOGY: TUMORS OF THE EAR AND LATERAL SKULL BASE (G DANESI, SECTION EDITOR)
Combined Supra- and Infra-Tentorial Retro-Labyrinthine
Pre-sigmoid Approach
Nick Thomas
1
&Eleni Maratos
1
&Sinan Barazi
1
Published online: 17 May 2019
Abstract
Purpose of Review This chapter describes the background, indications and key aspects of the combined supra- and infra-tentorial
retro-labyrinthine pre-sigmoid approach. This approach is most commonly used for petrous apex meningiomata and vascular
pathologies of the mid and upper basilar trunk.
Recent Findings Our pre-operative evaluation includes MRI, CT to assess pneumatisation of the petrous bone and vascular
imaging where necessary. Audiology and ophthalmology baseline assessments are performed if appropriate.
Summary The nuances of the operative technique are discussed with an emphasis on avoidance of complications.
Keywords Supra- and infra-tentorial .Retro-labyrinthine pre-sigmoid approach
Background
Access to pathologies at the petrous apex and the rostral
brainstem is surgically demanding. There are a number of
possible approaches including the retrosigmoid craniotomy,
the orbito-zygomatic craniotomy, the anterior and lateral
petrosectomy and other trans-petrous approaches. The focus
of this chapter is the combined supra- and infra-tentorial retro-
labyrinthine pre-sigmoid approach. By removing the petrous
bone and cutting the tentorium, this approach allows for the
creation of a large corridor of access to expose the antero-
lateral brainstem, petrous apex and upper and mid basilar
trunk and its branches and provides access both above and
below the tentorium. This follows the skull base concept of
creating space by removing the bone and therefore minimising
brain retraction. Other approaches do not create such
exposure.
This approach has a number of advantages. For example, it
obviates the need for the Sylvian fissure split that is required
with the orbito-zygomatic approach. The access also enables
early identification of cranial nerves that are displaced lateral-
ly by a tumour (particularly the third, fourth and fifth).
Introduction
In the early 1960s, the operating microscope was introduced
to neurosurgery. The superior illumination, optics and magni-
fication enabled dissection of the brain and vasculature to be
performed more safely at depth with improved haemostasis,
ultimately leading to reduced morbidity and mortality.
Pertinent to skull base approaches, House and Hitselberger
refined the anatomical definition of the temporal bone and
popularised the trans-labyrinthine approach to vestibular
schwannoma and reported on combining this approach with
the sub-occipital access[1•].
In the early 1970s, King and Morrison [2•] at the London
Hospital described extending a standard trans-labyrinthine ap-
proach with ligation of the superior petrosal sinus enabling the
surgical field to be widened.
Hakuba noted that division of sigmoid sinus employed to
increase exposure occasionally resulted in venous infarction.
He developed the anterior petrosectomy approach dividing the
superior petrosal sinus.
Spetzler [3••] reported on 46 petroclival lesions where an
anterior petrosectomy was performed either trans-labyrinthine
or retro-labyrinthine, combining this with a temporal
This article is part of the Topical Collection on OTOLOGY: Tumors of the
Ear and Lateral Skull Base
*Nick Thomas
nick.thomas1@nhs.net
1
Department of Neurosurgery, King’s College Hospital, London SE5
9RS, UK
Current Otorhinolaryngology Reports (2019) 7:195–199
https://doi.org/10.1007/s40136-019-00226-0
#The Author(s) 2019
Content courtesy of Springer Nature, terms of use apply. Rights reserved.

craniotomy. Further refinements of the approach have been
reported by Fukushima.
Indications
This approach is suitable for petrous apex lesions such as
meningiomata, intrinsic antero-lateral brainstem lesions such
as cavernomas and upper/mid basilar artery trunk aneurysms
and vascular anomalies.
Pre-operative Evaluation
All tumour cases are discussed in a multi-disciplinary com-
bined neurosurgical and otolaryngological meeting. Similarly,
vascular cases are discussed in a multi-disciplinary setting.
In the skull base tumour clinic, a full history and examina-
tion is performed with a particular attention paid to cranial
nerve function. Informed consent is obtained after the risks
are explained. Due to the risk of a post-operative seizure, the
driving vehicle licence authority in the UK will revoke the
patient’s licence for 1 year.
The pre-operative work-up includes pre- and post-contrast
MR imaging for all lesions and angiography for vascular le-
sions. The relationship of the cranial nerves to the tumour
should be identified if possible. The dominance of the trans-
verse and sigmoid sinuses and the position of the draining
veins particularly the vein of Labbé should be identified.
CT imaging is appropriate to identify the size and extent of
pneumatisation of the petrous bone which will indicate the
ease of surgery and the extent of access. It will also identify
any involvement of the bone with invasive tumours.
Pre-operative speech discrimination audiology should be
performed. Hearing loss may be a presenting complaint. Not
only is it important to document the hearing loss on the side to
be operated upon but also to ensure that there is normal/ ade-
quate hearing on the contralateral side (Fig. 1).
Ophthalmological function may need documenting with
respect to ophthalmoparesis and visual acuity.
Pre-operative Management
If there is evidence of obstructive hydrocephalus associated with
a petrous apex tumour, then ventriculo-peritoneal shunting is
Fig. 1 A 38-year-old with mild
headache and deafness in the right
ear for 1 year and large petrous
apex meningioma
196 Curr Otorhinolaryngol Rep (2019) 7:195–199
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performed a week before definitive tumour resection. We would
advocate placing the shunt on the contralateral side to the tumour
to avoid it interfering with the second stage surgical incision.
All patients with skull base meningiomata are pre-treated
with 5 days of dexamethasone 8 mg once daily with proton
pump inhibitor cover prior to admission. There is no evidence
for the use of prophylactic anti-convulsants in this setting, and
a number of years ago, we witnessed complications related to
anti-convulsants including blood dyscrasias and DRESS syn-
drome. We therefore avoid prophylactic anti-convulsants in
this setting.
Operative Technique
The procedure is carried out under total intravenous anaesthe-
sia (TIVA) with appropriate cardiovascular, respiratory,
bispectral index (BIS) and neuro-monitoring including cranial
nerve, somatosensory-evoked and motor-evoked potentials
(Fig. 2). The TIVA obviates any concerns of interactions be-
tween the anaesthetic and the neuro-monitoring. Urinary cath-
eter insertion is required.
Positioning
The patient is positioned supine in a 3-pin Mayfield head
clamp, reverse Trendelenberg with 30° head-up and rotated
contralaterally approximately 80°.
As cerebrospinal fluid can be drained from the basal cis-
terns and the cisterna magna early after dural opening, we do
not routinely use a lumbar drain. Furthermore, we have
learned that the mastoid cavity repair required to avoid CSF
rhinorrhoea post-operatively does not need to be protected
with a lumbar drain.
We do not routinely use image guidance for these procedures
but it can be helpful in identifying certain anatomical landmarks.
Skin Incision
A large C-shaped skin incision is performed extending from
the temporal region posteriorly around the pinna to the retro-
auricular region and down to just below the mastoid tip.
The skin and sub-cutaneous tissues are dissected to expose
the temporalis muscle and fascia.
The temporalis fascia and muscle are then elevated together
with the pedicle based anteriorly. A small cuff of tissue should
be left peripherally so as to be able to re-suture the muscle in
its appropriate position at the end of the procedure.
Sternocleidomastoid and the sub-occipital musculature are
elevated along with the skin and sub-cutaneous tissue to ex-
pose the mastoid to its tip. The muscles do not need to be
disarticulated separately.
Once the flap is reflected forward and secured, the root of
the zygoma is identified. A line from this to the external oc-
cipital protuberance identifies the horizontal level of the trans-
verse sinus. The posterior limit of the junction of the trans-
verse and sigmoid sinus is approximately 1 cm anterior to the
asterion.
A temporal craniotomy is performed which is approximate-
ly 5 × 5 cm with the antero-inferior extent being at the root of
the zygoma and the posterior limit at the junction of the two
sinuses. Any inferior lip of temporal bone should be drilled so
that the craniotomy is flush with the temporal tegmen.
The middle fossa dura is then elevated to identify the rele-
vant anatomical landmarks including the posterior edge of the
mandibular branch of the trigeminal nerve (V3), the middle
Fig. 2 Positioning and skin incision
TT Trautmann’s triangle.
SS Sigmoid sinus.
JB Jugular bulb.
SPS Superior petrosal sinus.
PSC Posterior semicircular canal. SPS Superior petrosal sinus.
ICA Internal carotid arter
y
.
Fig. 3 Trautmann’s triangle
Curr Otorhinolaryngol Rep (2019) 7:195–199 197
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meningeal artery within foramen spinosum, the greater super-
ficial petrosal nerve and the arcuate eminence, often
representing the superior semi-circular canal.
Dissection of the petrous bone proceeds with a mas-
toidectomy to identify the facial nerve within the
fallopian canal which is skeletonised along with the sig-
moid sinus and jugular bulb in order to maximise bone
resection and operative exposure. The labyrinthine block
is outlined and preserved. An important manoeuvre is to
divide the vestibular aqueduct so as to release the pos-
terior fossa dura from the labyrinthine block—this ma-
noeuvre does not lead to hearing loss.
Bone drilling should expose middle fossa dura, posterior
fossa dura (Trautmann’s triangle) (Fig. 3) and the superior
petrosal sinus. If the jugular bulb is high, then this can be
pushed down up by approximately 1 cm.
In our experience, this should provide enough exposure for
most pathologies and we do not routinely include a
retrosigmoid craniotomy as part of our exposure. Bone, how-
ever, can be removed fromover the sigmoid sinus allowing for
further dural retraction.
A curved dural incision is performed over the middle and
posterior fossae extending towards the sinodural angle which
marks the position of the superior petrosal sinus. The sinus can
then be ligated with haemoclips and divided. The third cranial
nerve is identified with careful elevation of the medial edge of
the tentorium. Dissection can then proceed medial to lateral in
the knowledge that the nerve has been identified.
Identification of the medial edge of the tentorium also ensures
that the tentorial incision is made at the appropriate angle; if
the cut is made lateral to medial without identifying the medial
tentorial edge, it is possible that the angle of incision is too
acute to the medial edge in an anterior direction.
Once the tentorium is completely incised, the operative
field is fullyexposed with minimal brain retraction. In the case
of a medially based petrous apex meningioma, the trigeminal
nerve will usually be evident on the lateral aspect of the tu-
mour along withthe third nerve anteriorly and the fourth nerve
more posteriorly. The other cranial nerves should be identified
and preserved. The origin of tumour on the posterior petrous
bone, with respect to the position of the porus, will determine
how cranial nerves might be displaced or encased by the
tumour.
The basilar artery is often displaced medially by a me-
ningioma. Dissection should proceed in such a way as to be
able to identify the artery and its branches as early as
possible.
SC Superior semicircular canal
LC Lateral semicircular canal
PC Posterior semicircular canal
SCA Superior cerebellar arter
y
Fig. 4 Exposure of surgical field
Fig. 5 Small residuum left to
preserve cranial nerve function.
Mild new V3 paraesthesiae only
198 Curr Otorhinolaryngol Rep (2019) 7:195–199
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Meticulous closure can be difficult particularly around the
superior petrosal sinus (Fig. 4). A small piece of fascia lata is
used to cover the antrum and abdominal fat is harvested to fill
the mastoid cavity defect. Fat in the antrum will compromise
hearing.
Complications
Patients are exposed to the general risks of any neurosurgical
procedure in terms of infection, including meningitis, bleed-
ing, cerebrospinal fluid leak, fits, hemiparesis, thromboembo-
lism and death.
Particular risks pertaining to this approach include cerebro-
spinal fluid rhinorrhoea, sub-cutaneous pseudomeningocoele,
deafness, facial weakness and numbness, ophthalmoplegia,
speech and swallowing difficulties, ataxia and temporal lobe
damage including that which relates to disruption of the vein
of Labbé and brainstem ischaemia as a result of posterior
circulation vessel damage.
Conclusion
This is an important approach to master when faced with large
petrous apex lesions, especially meningiomata. It is also use-
ful in approaching the antero-lateral brainstem and the upper
and mid basilar trunk.
The opening of both the supra- and infra-tentorial compart-
ments gives unparalleled wide exposure of the pathology, im-
proves chances of early identification and preservation of cra-
nial nerves and other structures and avoids brain retraction
(Fig. 5).
Open Access This article is distributed under the terms of the Creative
Commons Attribution 4.0 International License (http://
creativecommons.org/licenses/by/4.0/), which permits unrestricted use,
distribution, and reproduction in any medium, provided you give appro-
priate credit to the original author(s) and the source, provide a link to the
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Publisher’sNote Springer Nature remains neutral with regard to jurisdic-
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References
Papers of particular interest, published recently, have been
highlighted as:
•Of importance
•• Of major importance
1.•Grossi PM, Nonaka Y, Watanabe K, Fukushima T. The history of the
combined supra- and infra-tentorial approach to the petroclival re-
gion. Neurosurg Focus. 2012;33(2):E8 This is an excellent summa-
ry of how the approach has developed over the years.
2.•Morrison A, King TT. Experiences with a trans-labyrinthine
transtentorial approach to the cerebellopontine angle. Technical note.
J Neurosurg. 1973;38:382–90 This is a landmark paper detailing
the expansion of the standard trans-labyrinthine approach.
3.•• Spetzler RF, Daspit CP, Pappas CTE. The combined supra- and infra-
tentorial approach for lesions of the petrous and clival regions: ex-
perience with 46 cases. J Neurosurg. 1992;76:588–99 Spetzler is
one of the key architects of this approach and this paper sum-
marises the surgical technique, which has changed little over the
years.
Curr Otorhinolaryngol Rep (2019) 7:195–199 199
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