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In Depth Tutorials and Information
(OHNS) teams and is divided into two stages.
31,32
The
first stage involves a posterior occipital approach to sta-
bilize the occipitocervical junction. The second stage of
the operation involves the transmandibular circumglos-
sal approach to the anterior craniocervical junction and
ventral cervical spine. The lower lip is split by a mid-
line incision above the mentum that extends inferiorly
to the level of the hyoid bone. A supraomohyoid neck
dissection provides identification of the lingual and
hypoglossal nerves, cranial nerves X and XI, internal
carotid artery (ICA), external carotid artery (ECA) and
internal jugular vein (IJV). A stair-step mandibulotomy
is performed between teeth 24 and 25. A mucosal inci-
sion is made in the floor of the mouth, starting between
the orifices of Wharton's ducts, extending posteriorly to
the anterior tonsillar pillar. The upper limb of the inci-
sion extends to the soft palate, which is separated from
its lateral attachments. The mucosal incision is extended
to the maxillary tuberosity, it turns medially to the hard
palate and extends 1 cm from the gingival margin of
the contralateral side.
33
The lingual nerve is followed
superiorly and identifies the medial pterygoid muscle
on which it lays and the foramen ovale through which
it passes after joining the mandibular nerve. The lower
limb of the incision extends into the hypopharynx, pass-
ing lateral to the tonsils and the orifice of the eustachian
tube.
34,35
However, these approaches are reported to increase
morbidity. Injury to the lingual nerve, malocclusion,
mandibular pseudarthrosis and cosmetically unaccept-
able scarring of the lip have been previously reported.
36
The novel endoscopic transcervical odontoidectomy
was reported in 2007 by Wolinsky and colleagues to have
several advantages over conventional approaches.
36
A standard Smith-Robinson approach to the cervical
spine is performed.
36
The spine is exposed rostrally to
the level of the C-1 tubercle with retraction of the loose
areolar tissue anterior to the spine. Dissecting the longus
colli muscles off the spine exposes the ventral aspect of
C-2. The vertebral arteries should be protected as they
can lie ventral to C-2, especially rostral to the C2-3 disc
space. The resection proceeds first between the poste-
rior aspect of the anterior ring of C-1 and the odontoid.
By utilizing a 4 mm diamond burr, drilling proceeds
rostrally until the tip of the odontoid is encountered.
The resection then proceeds in a “top-down” fashion
throughout the length of the odontoid until all bone
has been removed. The apical and transverse ligaments
are preserved during resection of the odontoid, since
they provide a protective barrier between the osseous
resection and the dura mater. After completion of the
osseous resection the transverse, alar and apical liga-
ments and any pannus present can be removed until the
underlying dura is exposed. After any of these ventral
FIGURE 36.4
(A) Preoperative and (B) postoperative CT images
demonstrating resection of C2 dens through the endoscopic tran-
scervical approach.
(Reproduced with permission). Copyright © 2014
Jean-Paul Wolinsky.
decompressive procedures, there is occipitocervical or
high cervical instability. After completion of the proce-
dure, second-stage occipitocervical fusion or anterior
arthrodesis (in cases of pure C1-2 instability) should be
performed (
Figure 36.4
).
36
This technique does not require traversing the oral
mucosa and therefore decreases the chance of postopera-
tive meningitis if there is a spinal fluid leak and it allows
deep-seated basilar invaginations to be decompressed.
Moreover, the postoperative recovery time is shorter since
the patients are able to ingest food orally shortly after
removal of the endotracheal tube. The risk of postopera-
tive phonation difficulty that may occur with the transoral
approach is avoided with the transcervical approach.
1
Regardless of the surgical approach, resection of
the odontoid and the apical and transverse ligaments
typically renders the occipitocervical junction unsta-
ble. Following the anterior approach, a second-stage
occipitocervical instrumented fusion procedure is often
required.
36
Fixation and arthrodesis across the occipi-
tocervical junction are inherently challenging, particu-
larly in patients with BI. The opisthion is often infolded
and decompression is difficult. Additionally, soft bone
compromises effectiveness of implant fixation in a
highly mobile segment, which can jeopardize successful
arthrodesis. Posterior decompression and instrumented
fusion, therefore, poses unique challenges in patients
with OI. Proper preoperative surgical planning as well as
patient and family counseling are paramount.
CONCLUSION
Basilar invagination is often associated with OI. In
clinically symptomatic patients, direct ventral decompres-
sion followed by posterior occipitocervical stabilization is
