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Department of
Otolaryngology
Endoscopic Endonasal Dissection of the Pterygopalatine fossa, Infratemporal fossa, and Poststyloid compartment. Anatomical Relationships and Importance of Eustachian Tube in the
Endoscopic Skull Base Surgery
Carlos M Rivera-Serrano,
1
MD ;
Ramon
1
Terre-Falcon ;
2
MD ;
2
MD ;
Juan Fernandez-Miranda
Daniel Prevedello
Carl H Snyderman
2
1,2
1,2
Gardner MD ; Amin Kassam MD ; Ricardo L Carrau MD
University of Pittsburgh, Department of Otolarngology1 and Department of Neurosurgery2
1,2
MD ;
Paul
INTRODUCTION
Endoscopic surgery has revolutionized the
treatment of skull base disorders and is routinely
used in some centers for the treatment of
neoplastic and non-neoplastic cranial base
pathology. The group of minimally invasive
endoscopic techniques used to approach the
cranial base are also known as expanded
endoscopic approaches (EEA), which are
classified in a modular fashion under two main
categories: sagittal (or cranio-caudal) and coronal
(or medio-lateral). Figure 1
The goals of this project are to develop an
anatomical model to facilitate the study of the
anatomy of the infratemporal fossa (ITF),
pterygopalatine fossa (PPF), and post-styloid
space from the endoscopic endonasal
perspective, and to determine the most
important anatomical landmarks in the endonasal
endoscopic approach to these areas.
MATERALS AND METHODS
Eight pterygopalatine and infratemporal fossas
were dissected in four adult heads injected with
colored latex. Rod-lens endoscopes with 0, 30
and 45 degrees lenses, a neurosurgical
microscope, and microsurgical endoscopic
instruments were used for dissection. A transantral approach was performed to access the
pterygopalatine fossa, and a transpterygoid
approach was used to access the infratemporal
fossa and post-styloid space.
RESULTS
Transantral and transpterygoid approaches
allowed dissection of pterygopalatine and
infratemporal structures. Dissection and
resection of the sphenopalatine artery, and
dettachment of the medial and
lateral
pterygoid muscles were essential to gain access
to deeper structures. The lateral pterygoid plate
was the most useful landmark for location of
the foramen ovale and the mandibular branch
of the trigeminal nerve. The Eustachian tube,
medial pterygoid plate, and styloid process
were the most useful landmarks used to locate
post-styloid anatomic structures (internal
parapharyngeal carotid artery, internal jugular
vein, cranial nerves IX and X).
REFERENCES
1.Kassam, A.B., et al., Expanded endonasal approach: fully endoscopic,
completely transnasal approach to the middle third of the clivus, petrous
bone, middle cranial fossa, and infratemporal fossa. Neurosurg Focus,
2005. 19(1): p. E6.
2.Kassam, A., et al., Expanded endonasal approach: the rostrocaudal axis.
Part II. Posterior clinoids to the foramen magnum. Neurosurg Focus, 2005.
19(1): p. E4.
3.Kassam, A., et al., Expanded endonasal approach: the rostrocaudal axis.
Part I. Crista galli to the sella turcica. Neurosurg Focus, 2005. 19(1): p. E3.
4.Snyderman, C.H., et al., Endoscopic skull base surgery: principles of
endonasal oncological surgery. J Surg Oncol, 2008. 97(8): p. 658-64.
5.Fortes, F.S., et al., Endoscopic anatomy of the pterygopalatine fossa and
the transpterygoid approach: development of a surgical instruction model.
Laryngoscope, 2008. 118(1): p. 44-9.
6.Rhoton, A.L., Jr., The temporal bone and transtemporal approaches.
Neurosurgery, 2000. 47(3 Suppl): p. S211-65.
7.Alfieri, A., et al., Endoscopic endonasal approach to the pterygopalatine
fossa: anatomic study. Neurosurgery, 2003. 52(2): p. 374-78; discussion
378-80.
CONTACT
Carlos M. Rivera-Serrano, MD
Ricardo L Carrau
[email protected]
Figure 1. Bilateral transmaxillary approach to the cranial base. On the right side,
modular trans-pterygoid approaches in numbered boxes: Area 1 or medial
petrous apex. Area 2 or petroclival union. Area 3 or cuadrangular space. Area
4 or superior cavernous sinus. Area 5 or medial cranial fossa/infratemporal fossa.
On the left side: main anatomic structures of these areas. (IMa: Internal maxillary
artery, APha: ascending pharyngeal artery, CICa: cavernous internal carotid artery, 2nd
genu of ICA: second genu of internal carotid artery, IPICa: petrosal internal carotid
artery (dotted line), PPICa: parapharyngeal internal carotid artery, CS: cavernous sinus,
V1: ophthalmic branch of trigeminal nerve, V2: maxillary division of trigeminal nerve, V3:
mandibular division of trigeminal nerve, IOn: infraorbital nerve, GPn: greater palatine
nerve, VI CN: VI cranial nerve, Hypophysis: hypophysis, ET: cartilaginous portion of the
eustachian tube (partially resected and replaced by a plastic translucent tube), Sync:
synchondrosis, SPHA: stylopharyngeal aponeurosis (partially resected), LCm: longus
capitis muscle, ITF: infratemporal fossa, Clivus: clivus, MCF floor: floor of the middel
cranial fossa, MCF dura mater: dura mater of the middle cranial fossa, NF: nasal
floor).
Figure 2. A, view of the right maxillary sinus after medial endoscopic antrostomy.
B, access to PPF was obtained by performing an endoscopic trans-antral
approach using Kerrison rongeurs. (Vomer: vomer bone resected, Eth. Crest:
ethmoidal crest of the palatine bone, Sp. Sinus: sphenoid sinus, Spa: sphenopalatine
artery, SpF: sphenopalatine foramen, Post. Wall of Max. Sinus: posterior wall of
maxillary sinus, Inf. Turbinate: inferior turbinate, DPa: descending palatine artery,
Surrounding fat tissue of ITF and PPF: Surrounding fat tissue of infratemporal fossa
and pterygopalatine fossa, Periosteum of Post. Wall of Max. Sinus: periosteum of the
posterior wall of the maxillary sinus. Pictures were taken with a 0 degree rod lens
endoscope).
Figure 3. A, view of the right pterygopalatine fossa. The subjacent periosteum and fat
pad were dissected, discovering the internal maxillary artery (IMa) and its branches.
Identification of each branch was ocassionally difficult due to the high anatomical
variability of the distal third of the IMa. However, it was possible to identify all IMa
divisions after dissecting one or more of its major branches, such as the infraorbital,
descending palatine or sphenopalatine arteries. Despite the high anatomical variability,
other minor branches (posterior superior alveolar and pharyngeal arteries) were also
identified. B, view of the distal third of the internal maxillary artery after resection of
surrounding bone and fat. (IMa: internal maxillary artery, IOa: infraorbital artery, DPa:
descending palatine artery, Spa: sphenopalatine artery, PSAa: posterosuperior alveolar
artery, Pha: pharyngeal artery, Septal Post. art.: Posterior Septal artery, DTa: deep temporal
artery, IOn: infraorbital nerve. Pictures were taken with a 0 degree rod lens endoscope).
Figure 5. A, view of right infratemporal and pterygopalatine fossas after resection of
internal maxillary artery and dettachment of lateral pterygoid muscle from the lateral
pterygoid plate. In this specimen, the vidian and palatovaginal canals had a common
entrance orifice. B, view of the right drilled pterygoid “wedge” (dotted black triangle).
The vidian nerve was resected and followed until the second genu of internal carotid
artery. (Zn: zygomatic nerve, V2: maxillary division of the trigeminal nerve, SPg:
sphenopalatine ganglion, GPn: greater palatine nerve, LPn: lesser palatine nerves, IOn:
infraorbital nerve, LPm: lateral pterygoid muscle, Tm: temporalis muscle, 2nd genu of ICA:
second genu of internal carotid artery, ICA: internal carotid artery, VC / PV: vidian and
palatovaginal canals common entrance. Pictures were taken with 0 degree rigid endoscope).
Figure 6. A, view of the right infratemporal fossa after resection of the surrounding fat.
The buccal and pterygoid nerves were observed traveling in between the superior and
inferior heads of the lateral pterygoid muscle. B. View of the mandibular division of the
trigeminal nerve (V3) and branches through the right foramen ovale. The V3 division
divided itself in two minor trunks: anteromedial and the posterolateral. The buccal nerve
is the first and only sensitive branch of the anteromedial trunk, and innervates the skin of
the cheek. The other branches of the anteromedial trunk (deep temporal nerves, lateral
and medial pterygoid nerves, and masseteric nerve) are motor in nature. The
posterolateral trunk is sensitive and is divided in: lingual nerve, inferior alveolar nerve and
auriculotemporal nerve. The V3 division was the first important landmark in the location
of the post-styloid space, as it was always anterior and in very close proximity. (Zn:
zygomatic nerve, Bn: buccal nerve, Ptn: medial and lateral pterygoid nerves, GPn: greater
palatine nerve, LPn: lesser palatine nerve, IOn: infraorbital nerve, Ln: lingual nerve, IAn: inferior
alveolar nerve, Vn: vidian nerve, SPg: sphenopalatine ganglion, LPm: lateral pterygoid muscle,
FO: foramen ovale, VC: vidian canal, IMa: internal maxillary artery. B picture was taken with 0
degree rod lens endoscope).
Figure 7. A, view of ITF before and after resection of the pterygoid plates. After the
lateral pterygoid muscle was displaced laterally, it was necessary to perform two
osteotomies at the inferior insertion of the pterygoid plates. This step permitted the gain
of important working space (once the muscles that insert in the pterygoid fossa were
lateralized). B, view of the muscular insertions in the pterygoid fossa after the remaining
pterygoid plates were drilled from medial to lateral and from rostral to caudal. For
location of deeper structures, the medial pterygoid muscle and the tensor veli palatini
muscle were dissected and laterally displaced. (Bn: buccal nerve, Zn: zygomatic nerve, IOn:
infraorbital nerve, Ln: lingual nerve, GPn: greater palatine nerve, LPn: lesser palatine nerve, Vn:
vidian nerve, SPg: sphenopalatine ganglion, MCF floor: medial craneal fossa floor, FO: foramen
ovale, MPm: medial pterygoid muscle, LPm: lateral pterygoid muscle, TVPm: tensor veli palatini
muscle, Tm: temporalis muscle, IMa: internal maxillary . A and B pictures were taken with a 0
degree rod lens endoscope)
Figure 9. A, endoscopic view of the right post-styloid space after resection of
the stylopharyngeal aponeurosis (SPHA). The cranial nerve IX was located in
between the internal jugular vein and the internal carotid artery (ICA), literally
encased in the SPHA. A1, Magnified view of the post-styloid space (of figure 9
A) reveals the intimal relationship of the ICA and the eustachian tube (ET).
The IJV was posterior to ICA and styloid process. B, view of the right cranial
nerve X after ICA reflection. B1, Magnified view (of figure 9 B) of posterior
structures to the ICA. The cranial nerves XI and XII were identified posterior
to cranial nerve X, but they could not be dissected at this level due to its
posterior, lateral and inferior location to the ICA. (ET: eustachian tube, TT: torus
tubaris, LVPm: levator veli palatini muscle, IMa: internal maxillary artery, MMa:
medial meningeal artery, APhv: ascending pharyngeal vein, APha: ascending
pharyngeal artery, PPv: pterygoid plexus vein, ICA: internal carotid artery, IJV:
internal jugular vein, XI-XII: XI and XII cranial nerves, IX: IX cranial nerve, X: X
cranial nerve, Ln: lingual nerve, IAn: inferoalveolar nerve, ChTn: chorda tympani
nerve, V3: mandibular division of the trigeminal nerve, SP: styloid process. A and B
pictures were taken with a 30 degree rigid endoscope.
Figure 10. A, anterior view of the right Eustachian tube (ET) after lateral
displacement of the medial pterygoid muscle and resection the tensor veli
palatini muscle. The ET had a posterosuperior direction of approximately 4045 degrees towards the cranial base and 30-35 degrees towards the bony
palate. The torus tubaris relates to the posterior border of the medial
pterygoid plate anteriorly and the nasopharyngeal mucosa and longus capitis
muscle posteriorly. The levator palatini muscle has a very close relationship
with the stylopharyngeal aponeurosis (SPHA) and internal carotid artery. B,
view of the post-styloid space after resection of the SPHA. The ET relates
with the post-styloid space and the internal carotid artery (ICA)
posterolaterally. The ET relates anterolaterally with V3 and the medial
meningeal artery, at the level of the foramen ovale and spinosum respectively.
The most lateral aspect of the cartilaginous portion of the ET limits with the
ICA. C, superolateral view of the ET once the vidian canal is drilled. The
medial and postero-superior aspect of the torus tubaris is in intimal
relationship with the foramen lacerum and the second genu of the ICA
(through the synchondrosis). D, view of the infratemporal fossa after
resection of the ET (ET has been replaced by a plastic translucent tube). The
ascending pharyngeal artery and vein are located at the level of the posterior
aspect of the cartilaginous ET, in between the ICA and the ET. All extracranial
portions of the ICA are represented. Dotted black line = petrous internal
carotid artery and a portion of the parapharyngeal internal carotid artery (ET:
eustachian tube, LVPm: levator veli palatini muscle, MPm: medial pterygoid
muscle, Clivus: clivus, IMa: internal maxillary artery, MMa: medial meningeal
artery, APhv: ascending pharyngeal vein, PPv: pterygoid plexus vein, APha:
ascending pharyngeal artery, Sync: synchondrosis, Ln: lingual nerve, IAn: inferior
alveolar nerve, ChTn: chorda tympani nerve, GPn: greater palatine nerve, DTn:
deep temporal nerve, IOn: infraorbital nerve, VI CN: VI cranial nerve, CS: cavernous
sinus, MCF dura mater: middle cranial fosa duramater, FL: foramen lacerum, 2nd
genu of ICA: second genu of internal carotid artery, NF: nasal floor, SPHA:
stylopharyngeal aponeurosis, PPICa: parapharyngeal internal carotid artery, IPICa:
intrapetrosal internal carotid artery, CICa: cavernous internal carotid artery, ICA:
internal carotid artery, TT: torus tubarius, V3: mandibular division of the trigeminal
nerve, V2: maxillary division of the trigeminal nerve, V1: ophthalmic division of the
trigeminal nerve. B and C pictures were taken with 30 and 45 degree rod lens
endoscopes respectively).
CONCLUSIONS
Along with more traditional surgical approaches to the ITF, PPF and post-styloid
space, the endoscopic technique is a feasible surgical option. Precise anatomical
knowledge from a endonasal endoscopic perspective should further increase safety
and efficacy.
The most important landmarks in the transnasal endoscopic approach to the ITF and
post-styloid space are the pterygoid plates, V3, the Eustachian tubre and the styloid
process.
The most important landmark for the location of post-styloid structures is the
cartilaginous portion of the Eustachian tube. The Eustachian tube is always anterior
and medial to the parapharyngeal internal carotid artery.
Figure 4. A, view of the right infratemporal and pterygopalatine fossae after resection
of the internal maxillary artery and its branches. Neural structures were identified
posterior to the vascular structures. The origin and number of the lesser palatine
nerves were variable. B, closer view of the right pterygoid “wedge” (dotted black
triangle). Vidian nerve and sphenopalatine ganglia were easily identified. (LPn: lesser
palatine nerves, IOn: infraorbital nerve, GPn: greater palatine nerve, SPg: sphenopalatine
ganglion, V2: maxillary division of the trigeminal nerve, Vn: vidian nerve, Va: vidian artery.
Tm: temporalis muscle, FR: foramen rotundum, PvC: palatovaginal canal, VC: vidian canal,
ICA: internal carotid artery. A and B pictures were taken with 0 degree rod lens
endoscope).
Figure 8. A, endoscopic view of pre-styloid space after lateral displacement of the
lateral pterygoid muscle and resection of the tensor veli palatini muscle. The
junction of the cartilaginous and bony eustachian tube was the most important
landmark in the location of the ICA (covered by the stylopharyngeal aponeurosis
(SPHA)). B, View of the internal carotid artery after lateral displacement of the
SPHA. (LPTm: lateral pterygoid muscle, MPTm: medial pterygoid muscle, TVPm: tensor
veli palatini muscle, ET: eustachian tube, TT: torus tubarius, LVPm: levator veli palatini
muscle, TT: torus tubarius, SPHA: stylopharyngeal aponeurosis, PPv: pterygoid plexus
vein, APhv: ascending pharyngeal vein, APha: ascending pharyngeal artery, ICA: internal
carotid artery).
The principal obstacles to locate the parapharyngeal internal carotid artery and the
glosopharyngeal nerve are the stylopharyngeal fascia and the tensor veli palatini
muscle. Dissection in this area is difficult due to their fibrousmuscular nature and
attachments to the surrounding structures.
Via an endoscopic endonasal approach, the cranial nerve X nerve is located behind
the parapharyngeal carotid. Cranial nerves XI and XII are not easily manipulated due
to the posterior location to cranial nerve X and to limitation of access by the
nasal/maxillary floor. The IX cranial nerve is located in between internal carotid artery
and internal jugular vein, enclosed by the stylopharyngeal aponeurosis, and is
potentially the most susceptible nerve for injury during an endonasal endoscopic
approach to the post-styloid space.