Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_4368_Библиотеки_им_академика_М_И_Перельмана
.pdf
Endoscopic Approaches to the Craniovertebral Junction
https://t.me/med1917
ET
ET
*
ET
a
SP
CD
S
b
c
d
Rt
ET
g i
Fig. 21.6 Stepwise demonstration of intraoperative endoscopic photographs. (a) A vertical incision was made on nasopharyngeal
mucosa. ET, eustachian tube; S, suction tip; SP, soft palate. Asterisk, Bovie electrocautery. (b–e) The tumor (arrow) was removed
in piecemeal with curved curette (pound signs). CD, clival dura. (f) Tumor erosion of the lower clivus was drilled (arrow head) and
resected. (g) The angled endoscopes were used for visual confi rmation of radical resection of the tumor. (h) The operative space was
packed with Gelfoam and fat graft, and was sealed with fi brin glue. (i) Endoscopic follow-up photograph taken after weeks of surgery
demonstrated good healing and epithelialization of the operative wound (circle); Rt ET, right eustachian tube.
h
21.3 Common Pathologies of
Craniovertebral Junction
The CVJ supports the cranial vault over the cervical spine
and allows movements in sagittal, coronal, and axial
planes in humans. The unique anatomic, developmental
and biomechanical characteristics of CVJ are drastically
different in humans than other quadrupedal vertebrae
animals. Harboring the critical neural structure and
functioning as one of the most mobile vertebral segments,
the CVJ strikes a precise balance to achieve maximum
Fibrin
glue
SP
mobility while maintaining reliable stability. Any
deviation of functions or structures will lead to severe
neurologic sequelae in this critical area. The pathologies
in this area include developmental, rheumatological,
traumatic, neoplastic, and infectious processes.
21.3.1 Developmental Anomalies
The CVJ has an unique embryonal development. The
development of CVJ includes “pro-atlas” comprising of
the fourth occipital sclerotome to form the tip of dens,
dorsal cranial articulating facet, and occipital condyle.
fe
Rt
ET
225
Endoscopic Approaches to the Craniovertebral Junction
https://t.me/med1917
a b
e
Fig. 21.7 Serial images of a patient with severe deformity at the craniovertebral junction. (a–c) Preoperative sagittal view of T2W
MRI (a) and sagittal (b) and axial (c) reformatted CT demonstrated severe bony deformity causing cord compression (arrows).
(d–f) Postoperative CT including three-dimensional reformatted (d), sagittal (e), and axial (f) view demonstrated the extent of
decompression after the fi rst-stage anterior transnasal transpharyngeal surgery. The patient was scheduled for posterior correction
and fi xation but he declined the surgery.
The “primitive atlas” is derived from the cranial portion
of the first cervical sclerotome and caudal portion of
the fourth occipital sclerotome to form the lateral mass,
pedicle, and lamina of the atlas and the remainder
part of the odontoid process. The “primitive axis” is
derived from the caudal portion of the first and cranial
portion of the second cervical sclerotome and forms
the body and posterior elements of C2 and the C2–C3
intervertebral disc.
14
Os odontoideum is a rare condition involving the
presence of an ossicle with smooth circumferential
cortical margins that has no osseous continuity with the
vertebral body of C2. The clinical importance of this entity
is that the attachment of transverse atlantal ligament
(TAL) onto this mobile or incompetent ossicle jeopardizes
the restraining effect of atlantoaxial motion and inflicts
atlantoaxial instability. The etiology of os odontoideum
remains controversial, with evidence supporting both
acquired and congenital causes.
15
A similar but more
common condition is ossiculum terminale, which means
the nonunion of the dens tip at the secondary ossification
center. Ossiculum terminale is typically distal to the
attachment of TAL and thus theoretically does not cause
atlantoaxial instability. However, certain cases can also
have hypoplastic basal dental segments with short dental
pivot, which may inflict atlantoaxial instability and high
cervical cord compression.
14
Basilar invagination and basilar impression are
uncommon conditions in which the superior part of the
odontoid migrates upward into the foramen magnum.
The terms basilar invagination and basilar impression
are often used interchangeably to indicate the upwards
migration of the upper cervical spine. Basilar invagination
is defined as upward displacement of vertebral elements
into the foramen magnum due to a developmental anomaly
of the structures surrounding the foramen magnum.
Alternatively, basilar impression typically refers to an
upward displacement secondary to softening of bones at
the base of the skull in certain pathologic conditions such
as generalized osteopenia, osteomalacia, Paget’s disease,
hyperparathyroidism, osteogenesis imperfecta, cretinism,
achondroplasia, osteopetrosis, and mucopolysaccharidoses.
Local bone destruction by neoplasm, infection or trauma
is also included in basilar impression. “Cranial settling” is
typically applied to CVJ changes associated with rheumatoid
arthritis.
16
Goel proposed that basilar invagination is a
result of chronic atlantoaxial instability and can best be
addressed with segmental atlantoaxial fixation with facet
arthrodesis.
17
Thus, the anterior transoral approach might
not always be necessary. He classified facetal malalignments
into three types. Type 1 means the facet of atlas is
dislocated anterior (anterior slippage) to the facet of axis
on lateral imaging. More often in cases with group A basilar
invagination, such alignments are typically seen in mobile
c
fd
226
NS
https://t.me/med1917
Endoscopic Approaches to the Craniovertebral Junction
OT
a
d
Rt ET
Rt ET
OT
DM
SP
AT
b
OT
e
c
Rt ET
f
SP
NS
g
Fig. 21.8 Stepwise demonstration of intraoperative endoscopic photographs. (a) A vertical mucosal incision was made directly on
the nasopharyngeal wall. NS, nasal septum; Rt ET, right eustachian tube; SP, soft palate. (b) Anterior tubercle of C1 and the anteriorly
displaced odontoid process were exposed. AT, C1 anterior tubercle; OT, odontoid tip of C2. (c–e) Bony structures’ compression of
the spinal cord were drilled and removed. DM, dural matter; OT, odontoid tip. (f–g) The operative cavity was packed with Gelfoam
and fat graft, and was sealed with fi brin glue. NS, nasal septum; Rt ET, right eustachian tube; SP, soft palate. (h–i) The lower part of
the operative wound with fat graft (arrow) was visualized from a transoral angle of view. A suture stitch (arrow head) was made for
fi xation of fat graft and approximation of wound. T, tongue.
and reducible atlantoaxial dislocations. The odontoid
process is displaced posteriorly and superiorly, resulting in
atlantoaxial dislocation as manifested by an increase in the
atlantodental interval and basilar invagination. The odontoid
process directly indents into the craniocervical cord and
results in symptoms related to direct neural compression
in a relatively acute fashion. Type 2 refers to posterior
dislocation of atlas facets in relation to the facet of axis. Type
SP
h
i
T
3 is when the facets are in alignment and the instability is
diagnosed on the basis of clinical and radiologic evidence
and, more importantly, it is diagnosed by direct surgical
manipulation during surgery. In types 2 and 3 atlantoaxial
facetal dislocations, the atlantodental interval is not altered
and the odontoid process does not directly indent into the
neural structures. Types 2 and 3 facetal dislocations are
more often associated with group B basilar invagination and
227
Endoscopic Approaches to the Craniovertebral Junction
https://t.me/med1917
b ca
d e f
Fig. 21.9 Comparison of pre- and postoperative images of a patient who underwent endoscopic trans-oral odontoidectomy.
(a–c) Preoperative MRI (a) and CT (b and c) demonstrated severe deformity and spinal cord compression even after posterior
decompressive surgery with intended fusion 3 months ago. The hard palate (arrow) was as high as the midclivus level, which
precluded endoscopic transnasal odontoidectomy. (d–f) Postoperative MRI (d) and CT (e and f) demonstrated the extent of
decompression.
cases with Chiari’s malformation and syringomyelia.18 The
primary goal of treatment is realignment and segmental
stabilization, best achieved with facet arthrodesis or
posterior fixation.
or suboccipital decompression is only needed in certain
cases with severe or precipitating symptoms.
19
Transoral or transnasal decompression
21.3.2 Rheumatological, Traumatic,
Neoplastic, and Other Disease
Processes
Rheumatoid disease can cause bony and ligamentous
destruction in CVJ most commonly presented as
atlantoaxial instability (25% of rheumatoid arthritis
patients), basilar invagination (8% of rheumatoid arthritis
patients), and pannus formation around the odontoid. The
pannus can produce collagenases and other proteolytic
enzymes capable of destroying ligaments, tendons,
cartilage, and bone in the joint. These damages potentially
cause ligamentous laxity and bone erosions, which may
lead to subluxation and instability. Subluxation also
causes the anterior shift of the C1 arch and a decrease
in the dimension of the spinal cannel by the posterior
arch of the atlas. Anterior decompression is mandatory
when ventral compression is significant. Reduction with
external traction is prudent prior to posterior fixation to
achieve best surgical results.
The CVJ is vulnerable to trauma because of the large lever arm formed rostrally by the cranium and the relative
high freedom of movement of the CVJ, which depends
disproportionately on ligamentous structures rather than
on intrinsic bony stability. Injuries disrupt the structural integrity, and vital damage to the spinal cord carries
a high likelihood of death or severe neurologic sequelae.
However, the traumatic condition of CVJ has a great variety and therefore is beyond the scope of this chapter.
All types of neoplasm can arise in this area from osseous structure or soft tissue surrounding this area.
Osseous tumors include chordoma, chondrosarcoma,
plasmacytoma, osteoblastoma, fibrous dysplasia, eosinophilic granuloma, metastatic tumor, and giant
cell tumor. Extra-axial lesions include meningioma,
neurinomas, paragangliomas, and glomus tumors, and
less frequent are dermoid, teratomas, neurenteric cysts,
and arachnoid cysts.
unique pathologies at CVJ with their origin presumably from remnant notochord. These locally aggressive
malignant tumors are most commonly located at the
sphenooccipital and sacrococcygeal segments of the
axial skeleton. In fact, 25 to 39% of chordomas arise at
the clivus.
complete tumor removal provides the best long-term
22
Most reports have indicated that radical or
21
Chordomas are uncommon but
20
228
Endoscopic Approaches to the Craniovertebral Junction
https://t.me/med1917
U
DM
OP
OP
T
a
b
c
U
d
Fig. 21.10 Stepwise demonstration of intraoperative photographs. (a) The uvula and soft palate were retracted superiorly, and
a vertical incision was made on oropharyngeal mucosa. Two traction sutures (arrow) were done on both sides of the wound for
better exposure. Most steps of the procedure were done under microscope but the upmost portion could only be approached with
endoscope. T, tongue; U, uvula. (b, c) The anterior tubercle of C1 and odontoid process were drilled and removed. DM, dural matter;
OP, odontoid process. (d–f) After decompression, the mucosal wound was sutured with several stitches. U, uvula.
outlook for survival; however, several factors influence
such a resection, the optimal surgical approaches, the
associated complications, and even the survival benefit
achieved by such a resection, which remain controversial. The surgical approaches to skull base chordoma
can be broadly classified as anterior midline approaches
and lateral approaches. The anterior midline approaches
include extended subfrontal, transmaxillary, transmandibular, endoscopic endonasal, transcervical, and
e
f
ligamentous laxity and instability and then the bone to
cause destruction and collapse. It usually takes an insidious
clinical course from months to years to produce symptoms
characterized by cervicomedullary compression, cranial
nerve deficits, atlantoaxial instability, and abscess forma-
27,28
tion.
The mainstay of treatment includes optimal antibiotic coverage and surgical decompression/fixation if neurologic deterioration has developed and/or instability has
occurred.
transoral approaches. The lateral approaches include
frontotemporal orbitozygomatic, anterior transpetrosal,
preauricular infratemporal, combined supra- and infratentorial transtemporal, and extreme lateral transcon-
22,23
dylar.
Selection of an approach must take into consideration the location of the main tumor bulk and its
relation to the carotid, the vertebral and basilar arteries,
the cavernous sinus, and the brainstem.
5
Other locally
advanced metastatic tumors or malignancies arise from
the local structure, such as nasopharyngeal carcinoma,
while other head and neck cancers can also use these
approaches to resect. As the approaches became more
extensive, the techniques to reconstruct the skull base
defects evolved simultaneously to minimize untoward
complications, especially with CSF leakage.
24–26
An infectious process can involve the CVJ to cause ligamentous destruction and instability. Take tuberculosis for
instance; the primary infection is usually of a pulmonary
or mediastinal lymph node and the disease progresses
with lymphatic spread to the synovial lining of CVJ. Subsequently, it extends to the surrounding ligaments to cause
21.4 Complications and Their
Avoidance
There are many critical anatomic structures around the
CVJ, including vascular and neural tissues. Injury of them
could cause serious neurologic deficits or functional impairment. For example, injury to the brain stem, cranial
nerves, or spinal cord could result in quadriparesis, respiratory failure, and aspiration. Injury to the vertebral
artery, carotid artery, or basilar artery could also be problematic and even fatal. This endoscopic surgery per se is
minimally invasive to the CVJ and rarely causes velopharyngeal insufficiency or difficulty of phonation, as there
are little alterations to the surrounding musculatures of
the nasopharynx and the larynx. Persistent postoperative CSF leakage might eventually cause meningitis or
encephalitis, although sometimes the CSF leakage would
be self-limiting. Care must be taken to repair the dural
incision, for example, with autologous fat and bone grafts
229
Endoscopic Approaches to the Craniovertebral Junction
https://t.me/med1917
for smaller defects or a nasoseptal mucosal flap for larg-
11
er.
Postoperative bed rest or CSF diversion (i.e., lumbar
drainage) could also be beneficiary in cases of low-flow
and low-pressure CSF leakage.
Surgical tips to avoid complications include thorough
preoperative evaluations, use of intraoperative image
guidance, meticulous dissection, and reconstruction.
Preoperative thin-cut CT scans is extremely useful for depiction of the bony anatomy around the CVJ. Moreover,
CT angiography provides good knowledge of the course
of major vessels of its neighborhood. During the operation, identification of the midline is essential, and can be
assisted by navigation system. For particular cases, it is
an advantage to have intraoperative fluoroscopy at hand
for real-time assessment of the cranial-caudal location as
well as the extent of surgical field. The deeply seated target of surgery can be visualized under the endoscope, and
some lateral lesions can also be seen using angled endoscopes. However, some of them may be difficult to reach
with currently available instruments, even with those
specially designed endoscopic tools. Furthermore, the
endoscopic views are two-dimensional and there is inevitably less tactile feedbacks when using the long-shaft
surgical instruments. Therefore, meticulous dissection is
warranted during surgery. Hemostasis could be more difficult than traditional microsurgery, which is performed
under three-dimensional microscopic visualization. Last
but not least, efforts are necessary for repair of durotomy
to minimize the chance to postoperative CSF leakage and
subsequent infection of the central nervous system.
References
1. Agrawal A, Cavalcanti DD, Garcia-Gonzalez U, et al. Comparison
of extraoral and transoral approaches to the craniocervical junction: morphometric and quantitative analysis. World Neurosurg
2010;74(1):178–188
2. Enepekides DJ, Donald PJ. Transoral approaches to the clivus and
nasopharynx. Otolaryngol Clin North Am 2001;34(6):1105–1121, ix
3. Hsu W, Wolinsky JP, Gokaslan ZL, Sciubba DM. Transoral
approaches to the cervical spine. Neurosurgery 2010;66(3, Suppl):119–125
4. Menezes AH. Surgical approaches: postoperative care and complications “transoral-transpalatopharyngeal approach to the craniocervical junction”. Childs Nerv Syst 2008;24(10):1187–1193
5. Dlouhy BJ, Dahdaleh NS, Menezes AH. Evolution of transoral
approaches, endoscopic endonasal approaches, and reduction
strategies for treatment of craniovertebral junction pathology:
a treatment algorithm update. Neurosurg Focus 2015;38(4):E8
6. Moshel YA, Schwartz TH. Endoscopic transnasal versus transoral
approaches to the craniovertebral junction. World Neurosurg
2010;74(6):568–569
7. Weissler MC. Transoral approaches to the skull base. Ear Nose
Throat J 1991;70(9):587–592
8. El-Sayed IH, Wu JC, Ames CP, Balamurali G, Mummaneni PV.
Combined transnasal and transoral endoscopic approaches to
the craniovertebral junction. J Craniovertebr Junction Spine
2010;1(1):44–48
9. El-Sayed IH, Wu JC, Dhillon N, Ames CP, Mummaneni P. The importance of platybasia and the palatine line in patient selection for
endonasal surgery of the craniocervical junction: a radiographic
study of 12 patients. World Neurosurg 2011;76(1–2):183–188,
discussion 74–78
10. Wu JC, Huang WC, Cheng H, et al. Endoscopic transnasal transclival odontoidectomy: a new approach to decompression: technical case report. Neurosurgery 2008;63(1, Suppl 1):ONSE92-4,
discussion E94
11. Yen YS, Chang PY, Huang WC, et al. Endoscopic transnasal odontoidectomy without resection of nasal turbinates: clinical outcomes of 13 patients. J Neurosurg Spine 2014;21(6):929–937
12. Kuo CH, Yen YS, Wu JC, et al. Primary endoscopic transnasal transsphenoidal surgery for giant pituitary adenoma. World Neurosurg
2016;91:121–128
13. Kuo CH, Yen YS, Wu JC, Chen YC, Huang WC, Cheng H. Primary
endoscopic transnasal transsphenoidal surgery for magnetic resonance image-positive Cushing disease: outcomes of a series over
14 years. World Neurosurg 2015;84(3):772–779
14. Pang D, Thompson DN. Embryology and bony malformations of
the craniovertebral junction. Childs Nerv Syst 2011;27(4):523–564
15. Rozzelle CJ, Aarabi B, Dhall SS, et al. Os odontoideum. Neurosurgery 2013;72(Suppl 2):159–169
16. Smoker WR. Craniovertebral junction: normal anatomy, craniometry, and congenital anomalies. Radiographics 1994;14(2):255–277
17. Goel A. Craniovertebral junction instability: a review of facts
about facets. Asian Spine J 2015;9(4):636–644
18. Goel A. Basilar invagination, Chiari malformation, syringomyelia: a
review. Neurol India 2009;57(3):235–246
19. Chang PY, Yen YS, Wu JC, et al. The importance of atlantoaxial fixation after odontoidectomy. J Neurosurg Spine 2015;13:1–9
20. Colli B, Al-Mefty O. Chordomas of the craniocervical junction: follow-up review and prognostic factors. J Neurosurg
2001;95(6):933–943
21. Menezes AH. Craniovertebral junction neoplasms in the pediatric
population. Childs Nerv Syst 2008;24(10):1173–1186
22. Sen C, Triana AI, Berglind N, Godbold J, Shrivastava RK. Clival chordomas: clinical management, results, and complications in 71 patients. J Neurosurg 2010;113(5):1059–1071
23. Shidoh S, Toda M, Kawase T, et al. Transoral vs. endoscopic endonasal approach for clival/upper cervical chordoma. Neurol Med Chir
(Tokyo) 2014;54(12):991–998
24. Horowitz PM, DiNapoli V, Su SY, Raza SM. Complication avoidance in endoscopic skull base surgery. Otolaryngol Clin North Am
2016;49(1):227–235
25. Klatt-Cromwell CN, Thorp BD, Del Signore AG, Ebert CS, Ewend
MG, Zanation AM. Reconstruction of skull base defects. Otolaryngol Clin North Am 2016;49(1):107–117
26. Tien DA, Stokken JK, Recinos PF, Woodard TD, Sindwani R. Comprehensive postoperative management after endoscopic skull base
surgery. Otolaryngol Clin North Am 2016;49(1):253–263
27. Qureshi MA, Afzal W, Khalique AB, Pasha IF, Aebi M. Tuberculosis of
the craniovertebral junction. Eur Spine J 2013;22(Suppl 4):612–617
28. Suarez-Almazor ME, Russell AS. Anterior atlantoaxial subluxation in
patients with spondyloarthropathies: association with peri pheral
disease. J Rheumatol 1988;15(6):973–975
230
Chapter 22
https://t.me/med1917
22.1 Surgical Technique 232
The “Far Medial”
(Transcondylar/
Transtubercular)
Approach to the
Inferior Third
of the Clivus
22.2 Complications, Tips
and Tricks 235
22.3 Case Example 235
22.4 Conclusion 235
The “Far Medial” (Transcondylar/Transtubercular) Approach to the Inferior Third of the Clivus
https://t.me/med1917
22 The “Far Medial” (Transcondylar/Transtubercular)
Approach to the Inferior Third of the Clivus
Martin Corsten, Srikant S. Chakravarthi, Juanita M. Celix, Sammy Khalili, Melanie Fukui, Richard Rovin, Amin Kassam
Introduction
The expanded endonasal approach (EEA) has been
described as a minimally invasive approach to access lesions of the anterior portion of the foramen magnum and
inferior one-third of the clivus.
clival tumors such as chordomas and chondrosarcomas,
and tumors in the anterior foramen magnum (usually
meningiomas). In addition, access via EEA to the odontoid
process (for lesions such as basilar invagination, rheumatoid pannus, odontoid fractures, and tumors) has been
a tremendously successful approach.
benefits of EEA in this setting is that the lateral or posterolateral open approaches (e.g., far lateral, retrolabyrinthine
presigmoid) require manipulation of the lower cranial
nerves or the internal carotid artery (ICA) to gain access
to the lesion; the direct medial-to-lateral approach of EEA
obviates the need for this manipulation of critical neurovascular structures and avoids crossing the plane of the
respective cranial nerves that are located posterolateral.
One significant limitation of the standard EEA approach to the inferior third of the clivus is in the presence
of lateral extension of the tumor along the occipital condyle beyond the hypoglossal canal. However, if the lesion
is located medial to the hypoglossal canal, then the “far
medial” approach affords access to these more medially
placed tumors at the pontomedullary and cervicomedullary junction.
divided into two compartments by the hypoglossal canal:
(1) superiorly, the jugular tubercle, and (2) inferiorly, the
occipital condyle. The transtubercular approach can be
used to gain access to the jugular foramen, to biopsy or
resect lesions such as schwannomas, paragangliomas, and
meningiomas. Resection of the occipital condyle is more
limited, as significant resection of the condyle can result
in spinal instability. As a general rule, if one respects the
plane of the hypoglossal canal, that is, does not cross this
as the lateral limit, then it is much less likely to create
instability as the majority of the condyle and atlantooccipital (AO) joint capsule will be preserved. In addition,
tumors in the hypoglossal canal proper can be biopsied
5,6
Anatomically, the lateral inferior clivus is
1,2
These lesions can include
3,4
One of the main
or excised through this “far medial” approach; in some
cases, the etiology of these lesions may be unknown until
they are exposed through EEA. Lesions such as schwannomas, hemangiomas, extramedullary plasmacytomas,
and lymphomas may occur within the hypoglossal canal,
requiring exposure for tissue diagnosis.
22.1 Surgical Technique
22.1.1 Step 1: Standard Exposure of
the Nasopharynx
The transtubercular approach begins with the removal of
the ipsilateral inferior turbinate. Typically, in endonasal
skull base surgery, the right middle turbinate is removed
to allow room for the endoscope, but in cases involving the nasopharynx or clivus, the inferior turbinate is
removed instead. A nasoseptal flap, if desired, is raised
on the side contralateral to the tumor. A posterior septectomy is performed. The nasopharynx, torus tubarius, and
Eustachian tube (ET) orifice are then visualized.
22.1.2 Step 2: Division of the
Ipsilateral Eustachian Tube
The next maneuver is to enter the ipsilateral parapharyngeal space and to mobilize the ET orifice medially (it will be
resected en bloc with the nasopharyngeal mucosa). The endoscopic scissors are inserted into the mucosa just lateral
to the ET orifice, and oriented vertically at first and spread
to dissect the parapharyngeal space and creating a window
between the carotid and ET. A cut in this vertical direction
at the level of the foramen lacerum would lacerate the petrous carotid artery. Therefore, the scissors are turned from
a vertical to a horizontal plane, making them parallel to the
plane of the horizontal carotid, and only then is the ET transected. This rotation from a vertical to horizontal cannot be
overemphasized to protect the ICA (Fig. 22.1).
ET
abc
Fig. 22.1 Avoiding the parapharyngeal carotid artery—vertical to horizontal transection. (a) The vertical position of the scissors along the
parapharyngeal space. (b) Note the horizontal rotation of the upper blade of the scissors. (c) Eustachian tube and torus tubarius transected.
ET, Eustachian tube; FL, foramen lacerum; P-ICA, petrous segment of internal carotid artery; TT, torus tubarius; VN, vidian nerve.
232
Meckel cave
VN
p-
FL
ICA
ET
FL
ET
P- ICA
TT
The “Far Medial” (Transcondylar/Transtubercular) Approach to the Inferior Third of the Clivus
https://t.me/med1917
22.1.3 Step 3: Nasopharyngectomy /
Resection of the Basopharyngeal
Fascia
Next, a nasopharyngectomy is performed. The mucosa
at the superior aspect of the nasopharynx is transected
with electrocautery, and the mucosa of the nasopharynx
is removed. The nasopharyngeal mucosa is extremely adherent to the underlying muscle, especially in the
midline. As such, it is difficult to remove and a variety
of strategies can be employed to remove this mucosa,
including the use of cautery, Kerrison forceps, and/or
the microdebrider. Once the nasopharyngeal mucosa is
removed, the longus capitis muscle is exposed.
At this point, the basopharyngeal fascia needs to be
divided. A wide sphenoidotomy is performed, and the
palatovaginal canal is identified. The basopharyngeal
fascia is continuous with the palatovaginal canal, and
its attachment there is the most adherent. This attachment is divided with a Colorado tip electrocautery. It is
critical to observe here that the basopharyngeal fascia is
also continuous with the cartilaginous ring around the
carotid artery at the foramen lacerum, so division of this
fascia requires attention to avoid injuring the artery. The
division of the basopharyngeal fascia exposes the carotid
artery and foramen lacerum (Fig. 22.2).
22.1.4 Step 4: Completion of
Resection of the Vomer
The next step is to complete the removal of the vomer.
The caudal aspect of the vomer has been removed with
the posterior septectomy, and the cranial aspect can
now be removed en bloc by passing the drill through
the palatovaginal canal bilaterally, then drilling inferior
and superior to the vomer, and fracturing it off laterally.
The removal of the vomer further exposes the longus
capitis, which is removed in a fashion similar to that of
the nasopharyngeal mucosa removal, with a variety of
instruments including cautery, Kerrison forceps, and the
microdebrider (Fig. 22.3).
Meckel
cave
Fig. 22.2 Resection of the basopharyngeal fascia. ET,
Eustachian tube; TT, torus tubarius; V, vomer; VN, vidian nerve.
S
P
A
MP
Fig. 22.3 Removal of vomer and exposure of longus capitis
muscle. ET, Eustachian tube; FL, foramen lacerum; ICA, internal
carotid artery; LC, longus capitis; MP, medial pterygoid; PVC,
palatovaginal canal; SPA, sphenopalatine artery; V, vomer; VN,
vidian nerve.
VN
V
ETTT
ET
Nasopharynx
ICA
VN
FL
VPVC
LC
ET transected
VN
22.1.5 Step 5: Identifi cation of the
Ipsilateral Medial Pterygoid Plate
The identification of the medial pterygoid is the next
step. An endoscopic medial maxillectomy is performed,
the extent of which depends on the nature of the lesion
being exposed (more lateral extension requires more
caudal resection of the lateral nasal wall). The mucosa
over the medial pterygoid plate is then stripped away;
the inferior turbinate artery will often bleed and require
cautery during this step. The descending palatine and
greater palatine arteries are identified at this time and
mobilized laterally. The medial pterygoid plate, once
exposed, is removed with high-speed drill; this step is
critical to achieve lateral visualization (Fig. 22.4). The
removal of the medial pterygoid allows identification of
the medial pterygoid muscle.
MP
*
Fig. 22.4 Identifi cation of ipsilateral medial pterygoid muscle
(MP). The medial pterygoid muscle will be subsequently
stripped away to allow access to the transcondylar window.
Starred (*) symbol indicates the location of the descending
and greater palatine nerve and artery complex. ET, Eustachian
tube; IT, inferior turbinate; LC, longus capitis; VN, vidian nerve.
LC
ET transected
ET
IT
233
The “Far Medial” (Transcondylar/Transtubercular) Approach to the Inferior Third of the Clivus
https://t.me/med1917
22.1.6 Step 6: Transection of the
Parapharyngeal Muscles
The next step is the transection of the parapharyngeal
muscles. The fossa of Rosenmüller is identified, and the
tensor veli palatini muscle is identified and divided. This
muscle’s origin is at the base of the medial pterygoid; it
passes through the pterygoid hamulus and inserts into
the contralateral tensor veli palatini muscle in the palatine aponeurosis. The remaining fibers of the longus capitis muscles as they insert into the lower third of the clivus
and the AO joint are then removed; this exposes the AO
membrane. Deep to the AO membrane is the apical ligament, whereas lateral to it is the alar ligament (Fig. 22.5).
Fig. 22.5 Transection of parapharyngeal muscles, exposure
of atlanto-occipital membrane (AOM).
AOM
22.1.7 Step 7: Resection of
Remaining Inferior One-third
of Clivus
A focal resection of the bone of the inferior one-third
of the clivus is then undertaken, to expose the occipital
condyle. As mentioned previously, the hypoglossal canal
divides the inferior lateral clivus into two portions: the
jugular tubercle superiorly and the occipital condyle inferiorly. The hypoglossal canal then continues obliquely,
dividing the condyle into medial and lateral components.
The supracondylar groove represents a good anatomic
landmark at this time for the hypoglossal canal (Fig. 22.6).
22.1.8 Step 8: Tailored to Lesion
SG
OC
Fig. 22.6 Resection of inferior one-third of clivus, exposure
of supracondylar groove (SG). BF, basopharyngeal fascia; ET,
Eustachian tube; IT, inferior turbinate; OC, occipital condyle.
BF
Being Resected
The resection from this point is dependent on the nature
of the lesion being resected or biopsied. Lesions within
the hypoglossal canal can be exposed through judicious
and targeted drilling at the supracondylar groove continuing inferomedially, with significant use of image guidance
to direct the operator to the exact location of the canal.
The anteromedial aspect of the hypoglossal canal can be
drilled away with impunity, allowing for biopsies of tissue within the canal or decompression of the nerve in the
canal. However, it is critical not to drill away the bone at
the posterolateral aspect of the hypoglossal canal, as this
will result in the removal of more than one-half of the
occipital condyle and result in spinal instability at the AO
7
More importantly, this often requires disruption of
joint.
the synovial joint of the articular facet of C1 and condyle,
further predisposing the patient to instability.
Resection of the ventromedial aspect of the occipital
condyle (taking care to preserve at least one-half of the
condyle and synovial joint capsule, as described earlier)
creates an endonasal ventromedial corridor with lateral
extension that gives access to the vertebral artery at its
insertion into the posterior cranial fossa. We have used
this approach to secure and place a temporary clip on the
vertebral artery extradurally to control a large intradural
vertebrobasilar junction aneurysm.
Meanwhile, the superolateral limit of the tubercular
compartment is the medial aspect of the jugular foramen.
8
OC
*
Fig. 22.7 Removal of tubercular compartment and exposure
of CN IX, X, and XI. Starred symbol (*) indicates location of
superior articular facet of C1. ET, Eustachian tube; OC, occipital
condyle.
This tubercular compartment can be drilled away,
limited by the inferior petrosal sinus superior and lateral
and the hypoglossal nerve inferiorly. As the tubercular
compartment is removed, the nerves of the jugular
foramen (IX, X, XI) are exposed (Fig. 22.7). Access to the
medial jugular foramen may be required to biopsy or
debulk and decompress lesions in this area.
Dura
Foramen
magnum
baslon
ET
IT
ET
234
Соседние файлы в папке Библиотека им академика М.И. Перельмана