Chapter 7
Technique of Transoral Odontoidectomy
P.J. Apostolides, A.G. Vishteh, R.M. Galler, V.K.H. Sonntag
Modified from Operative Techniques in Neurosurgery, 1:58 – 62, Apostolides, Vishteh, and Sonntag,
“Technique of transoral odontoidectomy,” copyright 1998, with permission from Elsevier.
7.1
Terminology
The transoral approach to the craniovertebral junction
is an excellent surgical technique for treating ventral
midline extradural compressive pathology. The target
region is reached by an approach crossing the oral cavity through the open mouth (“transoral”).
7.2
Surgical Principle
The transoral operation provides direct midline access
to the ventral craniovertebral junction to facilitate decompression of the lower brain stem and upper cervical
spinal cord. The surgical exposure typically extends
from the inferior third of the clivus to the top of the C3
vertebra (Fig. 7.1) and is limited primarily by the paa
Fig. 7.1. a Routine transoral
exposure. This exposure may
be increased superiorly with
a transpalatal extension or
inferiorly with a transmandibular extension. b Sagittal
view showing routine transoral exposure with normal
and pathological anatomy
(inset). With permission from
Barrow Neurological Institute
b
7
36
Cervical Spine – Odontoid
tient’s ability to open his or her mouth. The standard
transoral exposure can be extended superiorly with a
transpalatal or transmaxillary approach [3 – 5, 16 – 23],
or inferiorly with a mandibulotomy and median glossotomy (Fig. 7.1a, b) [3, 8, 14, 16 – 20].
located within or ventral to the lesion. The transoral
approach is usually inappropriate for intradural pathology because of the significant risks of CSF leakage
and meningitis associated with the frequent inability to
achieve a watertight dural closure [7, 10 – 12, 21].
7.3
History
7.7
Patient’s Informed Consent
The approach was described first by Kanavel in 1917
[15]. Since then and especially since the application of
the surgical microscope, the approach has been described by many authors mainly for the extirpation and
treatment of extradural lesions [3, 7, 8, 11, 13, 18, 22].
Informed consent of the patients should include explanations of the potential complications such as lesions to the
tongue, postoperative hematoma, irritation, and sensory
deficits in the oral cavity. It should also include the risk of
disturbed senses of taste and smell or swallowing due to
postoperative swelling of the intraoral structures. The
risk of postoperative infection and the necessity for antibiotic medication should be emphasized.
7.4
Advantages
This approach is the direct and unobstructed way to the
anterior part of the craniocervical junction. The anterior bony structures (inferior third of the clivus, anterior
arch of C1, and anterior part of C2 and C3) can be exposed by dissection of the posterior wall of the pharynx. The apex of the odontoid process as well as the anterior part of the foramen magnum can be exposed after resection of the anterior arch of C1.
7.5
Disadvantages
The approach is limited by the surgical corridor provided through the open mouth. There is a considerable
risk of severe complications such as infection with or
without involvement of the meninges, disturbances of
wound healing, cerebrospinal fluid (CSF) leakage as
well as complications arising from trauma to the uvula
and soft palate. In patients with rheumatoid arthritis
involving the mandibular joints, the approach is occasionally limited by the inability to open the mouth sufficiently (> 2.5 cm).
7.6
Indications and Contraindications
The primary indication for a transoral procedure is an
irreducible midline extradural lesion that compresses
the cervicomedullary junction. A transoral procedure
occasionally may be required to obtain a tissue diagnosis or to debride an infection.
Transoral surgery is contraindicated if the patient
has an active nasopharyngeal infection or reducible
ventral lesion, or if the vertebral or basilar arteries are
7.8
Surgical Technique
7.8.1
Preoperative Preparation
All transoral surgeries are performed under general
anesthesia administered via a fiber-optically placed
orotracheal tube that can be retracted from the surgical
field to provide optimal exposure of the posterior oropharynx. Routine tracheostomy is rarely necessary unless severe preoperative bulbar or respiratory disturbances are present [1, 2, 9, 13, 23]. All patients receive
routine perioperative antibiotics (cefuroxime, 1.5 g).
Unlike some authors, [6, 18, 23] we do not obtain routine preoperative nasal and oropharyngeal cultures unless an active infection is suspected based on the patient’s history or clinical examination.
Continuous intraoperative somatosensory evokedpotential monitoring and brain stem auditory evokedpotential monitoring are used to assess the physiologic
status of the spinal cord and brain stem during the procedure.
7.8.2
Positioning
The patient’s head is secured with a Mayfield clamp and
the patient is placed in the supine position. The head is
placed in a neutral position and the neck is slightly extended.
7.8.3
Surgical Steps
A low-profile self-retaining transoral retractor system
(Spetzler-Sonntag, Aesculap, San Francisco, CA) is
7 Technique of Transoral Odontoidectomy
Fig. 7.2. Superior (a) and lateral
(b) views of patient positioning
and the retractor system used in
the transoral approach. The
patient’s head is secured with a
Mayfield clamp. The patient is
placed in the supine position
with the head in the neutral position and the neck slightly extended. The rectangular retractor
frame is placed over the patient’s
mouth and attached to the operating room table via crossbars.
With permission from Barrow
Neurological Institute
a
used to achieve wide exposure of the posterior oropharynx. The rectangular retractor frame is placed
over the patient’s mouth and attached to the operating
room table via crossbars to stabilize the instrumentation and to allow the table to be rotated during the procedure (Fig. 7.2a, b ). The tongue and endotracheal tube
are retracted caudally with a rigid wide-blade retractor.
To avoid severe swelling or necrosis, the tongue should
be inspected carefully to ensure that it is not pinched
between the retractor blade and the patient’s teeth. The
soft palate and uvula are retracted superiorly with a
malleable-blade retractor. Adjustable, telescoping
tooth-bladed retractors are attached to the retractor
frame and inserted into the oropharynx to retract the
pharyngeal flaps laterally to widen the exposure.
The oropharynx and the retractors are sterilized
with Betadine solution. An intraoperative radiograph
often is obtained to judge spinal alignment after positioning and to confirm the extent of the rostral and caudal exposure provided by the retractor system. The table is often placed in the Trendelenburg position to
provide the best perspective of the craniovertebral
junction. The surgical microscope is used immediately
to improve lighting, to provide variable magnification,
and to allow the co-surgeon to observe and assist during the procedure. The surgeon sits above the patient’s
head and has a direct view of the patient’s mouth and
oropharynx (Fig. 7.3a).
The C1 tubercle is palpated to verify the position of
the midline (Fig. 7.3b). The midline posterior oropharyngeal mucosa is infiltrated with 0.5 % or 1 % lidocaine with 1/200,000 epinephrine. A vertical midline
b
37
38
Cervical Spine – Odontoid
Fig. 7.3. a Surgeon’s view of
patient’s mouth and oropharynx after placement of the
low-profile, self-retaining retractor system. b Anatomical
relationships of the anterior
aspects of the clivus, C1-C2,
and the adjacent vascular
structures underlying the
posterior oropharynx mucosa
and muscles. The C1 tubercle
is a key landmark that verifies the position of the midline. c Anatomical relationships of the alar and apical
ligaments fixating the dens to
the occiput. With permission
from Barrow Neurological
Institute
a
b
c
a
b
Fig. 7.4. Transoral odontoidectomy. a A vertical midline incision is made in the median raphé of the posterior oropharynx to expose the anterior arch of C1 and the body of C2. b The inferior portion of the anterior C1 arch is resected to expose the base of
the odontoid process.
7 Technique of Transoral Odontoidectomy
c
d
e
Fig. 7.4. (cont.) c The dens is transected at its base. d The dens is
removed to complete the decompression. e The incision is
closed in a single layer with a running 2 – 0 vicryl suture. With
permission from Barrow Neurological Institute
incision is made in the median raphé of the posterior
pharyngeal wall mucosa, pharyngeal muscles, and the
anterior longitudinal ligament using either monopolar
cauterization or a Shaw scalpel (Fig. 7.4a). If possible, a
palatal incision is avoided because it can cause nasal re-
gurgitation, dysphagia, and a nasal tone of voice. The
layers of the posterior oropharynx are maintained as a
single thick layer to facilitate a strong tissue closure.
Periosteal elevators are used to dissect the anterior longitudinal ligament subperiosteally and to separate the
tissue flap from the anterior surfaces of the C1 arch, the
C2 vertebral body, and the inferior clivus.
Curettes and periosteal elevators are used to define
the boundaries of the clivus, the anterior arch of C1, the
base of the odontoid process, and the C2 vertebral
body. The inferior one-third to two-thirds of the anterior C1 arch is resected to expose the base of the odontoid
process using a high-speed air drill and Kerrison rongeurs (Fig. 7.4b). We try to limit the resection of the anterior C1 arch to preserve the structural integrity of the
C1 ring. However, enough bone must be removed to expose the dens adequately. If necessary, the anterior C1
arch should be resected completely.
After the base of the dens has been exposed satisfactorily, the lateral margins of the odontoid are defined.
The alar and apical ligaments are detached sharply with
curved curettes. The base of the dens is partially transected with a cutting burr (Fig. 7.4c); the osteotomy is
completed by removing the posterior cortex with a
small Kerrison rongeur or diamond burr. The dens is
grasped with a toothed odontoid rongeur and removed
en bloc (Fig. 7.4d). The dens can be removed in a piecemeal fashion, but it is often more difficult to access its
apex.
Soft tissue pathology often must be resected to decompress the neural elements adequately. The transverse ligament and tectorial membrane also may need
to be removed to adequately visualize the dura and normal pulsation of the thecal sac. However, the surgeon
must beware of attenuated dura and ligaments that adhere to the dura. Meticulous microsurgical techniques
are necessary to avoid a CSF leak from inadvertent dural entry, which is associated with a high risk of postoperative morbidity and mortality. If an intraoperative
CSF leak occurs, a fascial patch is placed directly over
the dura and secured with fibrin glue. A lumbar drain is
inserted postoperatively, and antibiotic coverage and
the lumbar drain are maintained for at least 5 – 7 days.
The boundaries of the decompression can be assessed intraoperatively by placing iodinated contrast
material into the decompression site and obtaining a
lateral cervical radiograph or by employing stereotactic navigation. Adequate decompression is confirmed
when the dura bows into the wound and assumes its
usual anatomic contour. Once the brain stem and spinal
cord have been decompressed, the wound is irrigated
with antibiotic solution and hemostasis is achieved.
The wound is closed with interrupted or running 2 – 0
vicryl suture in a single layer that includes the mucosa,
pharyngeal muscles, and ligaments (Fig. 7.4e). Multilayer closures are more difficult to perform and can at-
39
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Cervical Spine – Odontoid
tenuate the tissue layers and weaken the incision line. A
nasogastric feeding tube is inserted while directly visualizing the oropharyngeal incision to avoid inadvertent
malpositioning of the tube.
7.9
Postoperative Care
Moderate tongue and pharyngeal swelling can be expected for the first 24 – 72 hours after surgery. The endotracheal tube should be maintained until the swelling subsides because premature extubation can lead to
respiratory distress, respiratory arrest, and death. In
our experience, topical steroids provide little if any
benefit in minimizing soft tissue swelling and therefore
are not used routinely.
Enteral nutrition via the indwelling feeding tube is
started on postoperative day 1 and continued 3 – 5 days.
The patient’s diet is slowly advanced from liquids to soft
regular foods and then to regular foods usually within
14 days. If the feeding tube is inadvertently removed
before oral feedings have been started, appropriate parenteral nutrition should be provided. Replacing the
feeding tube risks penetration of the healing mucosal
incision and inadvertent malpositioning of the tube.
Postoperative spinal instability should be expected
after transoral odontoidectomy. Patients should therefore remain in an external orthosis until spinal stability
can be restored. Although some authors advocate immediate posterior fixation of the spine after transoral
decompression, we prefer to wait several days to reduce
the risk of infection in the posterior cervical wound.
7.10
Hazards and Complications
Medical complications, including pneumonia, urinary
tract infections, deep venous thrombosis, pulmonary
emboli, and myocardial infarctions, are common after
transoral surgery, particularly in patients with severe
preoperative neurological deficits or debilitating medical illnesses. Therefore, it is important to optimize the
patient’s general medical condition before surgery and
to use prophylaxis for deep venous thrombosis during
and after surgery. Postoperatively, pulmonary toilet
should be aggressive, and the patient should be mobilized early after stabilization to limit the development
of these potential complications.
Wound infections should be treated with broadspectrum antibiotics until culture sensitivities are
available. Wound dehiscence at any time requires reoperation and reclosure. Wound dehiscence occurring after the first week should raise the suspicion of a possible underlying retropharyngeal infection or abscess.
CSF leakage represents a significant risk to the patient and should be addressed promptly. Appropriate
treatment includes dural patching, meticulous pharyngeal wound closure, and placement of a lumbar drain. If
a CSF leak stops with lumbar drainage but recurs after
the drain has been closed or discontinued, the patient
requires a lumboperitoneal shunt. If CSF leakage persists despite lumboperitoneal drainage, reoperation
and dural patching are required. Postoperative meningitis should raise the suspicion of a CSF leak. Proper
treatment includes intravenous antibiotics and placement of a lumbar drain.
Neurological deterioration after transoral surgery is
rare. Patients with new neurological deficits should be
evaluated for loss of spinal alignment, persistent cervicomedullary compression, epidural hematoma, epidural abscess, meningitis, or vertebrobasilar occlusion.
7.11
Conclusions
The transoral approach is an effective surgical method
for the direct decompression of irreducible ventral
midline extradural compressive pathology of the craniovertebral junction. Specialized low-profile retractor
systems, the surgical microscope, contemporary microsurgical dissection and dural closure techniques,
and meticulous postoperative radiographic assessment
of spinal stability minimize perioperative complications and facilitate good long-term outcomes.
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