what-when-how
In Depth Tutorials and Information
placement should be performed initially or should fol-
low realignment of the craniocervical junction.
9
Posterior
decompression fusion can be performed for cases with
reducible BI; halo traction should precede the surgical
decompression.
9
Irreducible ventral pathology of the craniocervical
region has historically been addressed with posterior
and anterolateral approaches. In the past, treatment
generally consisted of suboccipital decompression or
upper cervical laminectomy; however, clinical out-
comes were disappointing.
14
The traditional approach
to the occipitocervical junction is through the transoral-
transpharyngeal route.
22,24,25
Transorally, the pharyn-
geal muscles are vertically incised and the ventral C1
ring and rostral part of C2 are exposed and drilled.
These bony structures and the ligamentous complex
are completely resected and the ventral thecal sac is
exposed. This allows direct decompression of the high-
riding dens peg. This approach, however, is not benign
and may be associated with risks including CSF leak,
meningitis, pharyngeal wound healing problems and
recurrence of pathology.
In cases where exposure of the craniocervical junction
and the upper cervical vertebrae is required the open
traditional or endoscopic transmaxillary approach can
be used to treat pathologies of the craniocervical junc-
tion.
26,27
The transmaxillary approach requires a superior
sublabial incision; a unilateral dissection of the soft tissue
up to the infraorbital foramen and a maximal antrotomy
that preserves the neurovascular structures coming from
the infraorbital foramen at the surgical field.28
28
Removal
of the medial wall of the antrum, the palatine vertical
lamina and the medial aspect of the posterior wall of the
antrum is performed, considering the pterygoid process
as the posterior limit. Exposure and coagulation or liga-
tion of the sphenopalatine artery to prevent unexpected
rupture is recommended.
28
A gastric feeding tube, prolonged intubation and
tracheostomy, and prolonged hospitalization may be
required in a subset of these cases.
3
This approach has
been proven efficacious in the vast majority of cases;
however, its challenges include a limited operative view,
a deep working distance and potential contamination by
normal oral flora. Serious complications have been pre-
viously reported and include dehiscence of the posterior
pharynx, alteration in phonation secondary to the effects
of surgery on the pharynx, tongue, edema and the poten-
tial need for prolonged intubation.
1,29
The transmandibular circumglossal approach and
Le Fort osteotomies can provide a wider corridor and
can increase the exposure. The surgical technique
for the transmandibular-retropharyngeal-circumglossal
approach has been previously described.
30
The proce-
dure is performed in combination with the maxillofacial
and/or otorhinolaryngology-head and -neck surgery
FIGURE 36.3
Radiographic measurements utilized in diagnosing BI.
Solid: McGregor's line; Dashed: Chamberlain's line; Double line: McRae's
line.
(Reproduced with permission). Copyright © 2014 Jean-Paul Wolinsky.
radiographs have been proposed as diagnostic criteria
for BI: the Chamberlain's and McGregor's lines and the
angle between the plane of the hard palate and the plane
of the atlas (
Figure 36.3
).
21
TREATMENT
The hallmark of basilar impression in OI and its
related syndromes is the bone softening state. This results
in infolding of the squamous-occipital bone, the floor of
the posterior fossa being elevated in the margins of fora-
men magnum curving upward. The basiocciput becomes
elevated and shortened, and the clivus becomes horizon-
tally oriented, creating an obtuse basal angle. The petrous
portion of the temporal bones elevates; thus, the clivus-
atlas-odontoid complex assumes an abnormally rostral
location within the foramen magnum further restricting
the space within the posterior fossa.
The general goals of nonsurgical management in OI
are to decrease the incidence of fractures and increase
mobility and independence.
2
If symptomatic BI is pres-
ent, however, only surgical decompression and stabiliza-
tion can halt the progression of deficits and potentially
reverse them.
1,22,23
Axial halo traction followed by pos-
terior occipitocervical fixation may give good long-term
results in patients with BI and symptomatic hydro-
cephalus complicating OI.
14
As suggested by Sawin and
Menezes, ventriculoperitoneal (VP) shunting should be
performed in cases of BI associated with hydrocephalus.
6
However, it is controversial in the literature if VP shunt
