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ORIGINAL ARTICLE
Anterior Retropharyngeal Approach to the Cervical Spine
S. Behari, D. Banerji, P. Trivedi, V.K. Jain, D.K. Chhabra
Department of Neurosurgery
Sanjay Gandhi Postgraduate Institute of Medical Sciences,
Rae Bareli Road, Lucknow - 226 014, India.
Summary
The anterior retropharyngeal approach (ARPA) accesses anteriorly situated lesions from
the clivus to C3, in patients with a short neck, Klippel Feil anomaly or those in whom the
C2-3 and C3-4 disc spaces are situated higher in relation to the hyoid bone and the angle
of mandible where it is difficult to approach this region using the conventional anterior
approach, due to the superomedial obliquity of the trajectory. The ARPA avoids the
potentially contaminated oropharyngeal cavity providing for a simultaneous arthrodesis
and instrumentation during the primary surgical procedure. Experience of five patients
with high cervical extradural compression, who underwent surgery using this approach
between 1994 and 1999, is presented. The surgical procedures included excision of ossified
posterior longitudinal ligament (n=2); excision of prolapsed disc and osteophytes (n=2);
and excision of a vertebral body neoplasm (n=1). Following the procedure, vertebral
arthrodesis was achieved using an iliac graft in all the patients. Only one patient with
vertebral body neoplasm required an additional anterior cervical plating procedure for
stabilisation the construct. The complications included transient respiratory insufficiency
and neurological deterioration in two patients; and, pharyngeal fistula and donor site
infection in one patient.
Key words : Craniovertebral junction, Corpectomy, OPLL.
Neurol India, 2001; 49 : 342-349
Introduction
The conventional transoral approach traversing the
midline pharyngeal raphe,1-3 and the anterior cervical
approach through the avascular plane between the
carotid sheath and trachea and oesophagus,4-7 are
Correspondence to : Dr. D. Banerji, Department of
Neurosurgery, Sanjay Gandhi Postgraduate Institute of
Medical Sciences, Rae Bareli Road, Lucknow - 226 014,
India.
E-mail : [email protected]
Neurology India, 49, December 2001
adequate to approach the upper (C1-2) and middle
cervical vertebral segments (C3) respectively.8
However, when an approach to this region is required
avoiding the potentially infected oral cavity; and
while approaching the middle cervical segment in
patients with a short neck or Klippel Feil anomaly and
when the C3 vertebra is situated high in relation to the
hyoid bone, the anterior retropharyngeal approach
(ARPA) is the optimum surgical approach.9-13 In this
study, key technical points and indications for ARPA
are discussed.
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Anterior Retropharyngeal Approach
Material and Methods
Patient spectrum
Five patients with high cervical extradural
compression underwent surgery using ARPA to the
cervical spine between 1994 and 1999. Their clinical
presentation is summarized in Table I. The mean age
at presentation was 43.6 years and the average
duration of symptoms, 27.2 months. Their pre- and
postoperative clinical status was defined using
Harsh’s myelopathic grade.14 Plain radiographs of the
cervical spine and magnetic resonance imaging (MRI)
in sagittal and axial cuts were done in all cases. A
computed tomographic scan with sagittal
reconstruction images was also performed in three
patients (cases 1, 2 and 5) to further delineate the bony
pathology. The surgical procedures that were carried
out utilizing the ARPA included excision of ossified
posterior longitudinal ligament (n=2); excision of disc
with osteophytes (n=2); and, excision of a vertebral
body osteochondroma (n=1). Following the
procedure, vertebral arthrodesis was achieved using
an iliac graft in all the patients. Only one patient with
vertebral body neoplasm required an additional
anterior cervical plating procedure in order to stabilize
the construct.13
Surgical procedure
Patient position and incision (Fig. 1a) : The patient is
placed supine on the operating table. Crutchfield
cervical traction is placed to stabilise the neck during
the procedure. The patient is positioned with a pillow
under the shoulder, the head extended on a head ring
and rotated 30o to the contralateral side.13 A
transverse submandiblar incision is placed 2 cm
inferior to the mandible, extending from slightly
across the midline to the anterior border of the
sternocleidomastoid.10,13 The marginal mandibular
branch of the facial nerve runs forwards below the
angle of the mandible under cover of the platysma
and the skin incision 2 cm below and parallel to the
inferior border of the mandible ensures its
preservation.
Cervical dissection (Fig. 1b) : The superficial cervical
fascia including the platysma is incised transversly in
line with the skin incision and retracted, thus exposing
the investing lamina of the deep cervical fascia
enclosing in different fascial sheaths, the
sternocleidomastoid muscle, the strap muscles,
trachea, oesophagus and the recurrent laryngeal nerve.
The investing lamina of the deep cervical fascia is
opened and the retromandibular branches of the
common facial vein ligated. The facial artery is
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retracted superolaterally towards the mandible. The
exposed mandibular gland is elevated superolaterally,
carefully preserving its duct in order to prevent a
salivary fistula (Fig 1c). The intermediate tendon of
posterior belly of digastric muscle is held to the body
and the greater cornu of the hyoid bone by a fibrous
loop. This fibrous loop is incised mobilising the
digastric muscle and retracting it superiorly. The
stylohyoid muscle is also divided and retracted
superiorly.12,13 This permits the exposure of the
hypoglossal nerve, which is also carefully dissected
free and retracted cranially, exposing the hyoglossus
muscle and the greater cornu of the hyoid bone
(Fig. 1d). This procedure allows a medial retraction of
the hyoid bone and hypopharynx.
Wide dissection of the fascial plane between the
sternocleidomastoid and the carotid sheath laterally
and the hypopharynx, trachea and oesophagus
medially, permits exposure of the retropharyngeal
space and the prevertebral fascia covering the longus
colli muscles (Fig. 1e). Care is taken not to injure or
stretch the superior laryngeal nerve which courses
deep to the internal carotid artery along the constrictor
muscles of the pharynx.13 The retropharyngeal areolar
tissue and the prevertebral fascia are opened exposing
the anterior surface of the anterior arch of atlas and the
C2 and C3 vertebrae (Fig. 1f).
Bony drilling : An orientation to the midline is gained
by noting the attachment of the longus colli muscle on
both sides as they converge towards the anterior
tubercle of atlas as well as the anterior longitudinal
ligament in the midline. The amount of rotation of the
atlas may be gauged by palpating the anterior tubercle
of the atlas. Using a monopolar cautery, the anterior
surface of the vertebral bodies is exposed. The medial
segment of the vertebral bodies is removed using a
cutting burr till the inner cortical shell remains and
this is further removed using diamond burr and
Kerrison’s punch. A wide midline gutter of 1.2 to 1.5
mm is made in the vertebral bodies leaving the lateral
pillars intact.5,10 The posterior longitudinal ligament
is excised exposing a bulging dura.5 During the
drilling of the inner cortical bone, there may be severe
bleeding from the epidural veins which is controlled
by bipolar coagulation and surgicel. In case there has
been a breech in the dura, it can be covered by a thin
layer of fat and lumbar drainage instituted for three
days along with acetazolamide administration.
Bony arthrodesis : A tricorticate iliac graft is
positioned into the corpectomy defect after applying
manual traction on the mandible to distract the
vertebral bodies. Once the graft has snugly fitted into
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Neurology India, 49, December 2001
Table I
Clinical Summary of Patients who Underwent Anterior Retropharyngeal Approach to the Upper Cervical Spine
Name,
age,
sex
Clinical
presentation
KP,
48,F
Spastic
quadriparesis
grade III,
spinothalamic
and posterior
column
impairment
KS
32,F
Preoperative
Harsh grade
Surgery
Postoperative
course
V
OPLL against
C2-C3
vertebrae,
prolapsed
disc at C3-4,
C4-5
ARPA+ partial C2,
total C3,4
corpectomy,
OPLL excision and
Iliac bone grafting.
Extradural bleeding,
dural breech
Transient
respiratory
insufficiency required
tracheostomy
and ventilatory support.
Transient neurological
deterioration
IIIC
1.5 months,
↕Spasticity,
power
grade IV,
Construct in
place
Pain in nape
of neck radiating
upto vertex
0
Expansile, osteolytic
lesion of C3 vertebral
body. Pedicles and
posterior elements intact.
Loss of subarachnoid
space anterior to cord
ARPA + C3
corpectomy,
iliac bone grafting and
A-O plating C2 to C4
Tumour firm, avacular
Uneventful.
Biopsy:
osteochondroma
0
1.5 months,
No pain,
No deficit.
Construct in
place
RPS
50,M
Spastic
quadriparesis
grade IV with
urinary
hesitancy
II
OPLL from
odontoid to C4
vertebral body
ARPA + partial C2,
complete C3,C4
corpectomy with C3-4
and C4-5 discectomy with
excision of OPLL and
iliac bone grafting.
Incomplete removal of
OPLL on left side,
dural breech
Transient left upper
limb weakness,
transient respiratory
insufficiency required
tracheostomy and
ventilatory support
IIIC
3 months,
Residual
spasticity,
quadriparesis
Construct in
place
LS
35,M
Spastic
quadriparesis
grade IV with
spinothalamic and
posterior column
impairment
Osteophytes with
disc prolapse at
C3-4,4-5, 5-6,
maximum at C3-4 level
ARPA + C3-4 Cloward’s
procedure and Dowel
grafting from iliac crest
Uneventful.
II
1 year Spasticity↕
power grade V.
Construct in
place
CS
53,M
Neck pain
with spastic
quadriparesis
grade IV with,
spinothalamic
posterior column
derangement
Fixed atlantoaxial
dislocation with C2-3
fusion with significant
C3-4 disc prolapse
with anterior and
posterior osteophytes
at C5-6
ARPA + C3-4
Cloward’s procedure
and Dowel grafting
from iliac crest.
Developed pharyngeal
fistula and donor
site infection.
II
3 months,
Spasticity ↕
power and
hypoaesthesia
improved.
Walking without
support. Construct
in place
IIIC
IIIB
Harsh
grade at
follow up
Follow up
Behari et al
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Radiology
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Anterior Retropharyngeal Approach
Fig. 1 : Diagrams showing, (a) the patient position and incision, (b) the soft tissue exposure following reflection of the skin flap
showing the carotid sheath, the hypoglossal nerve, the stylohyoid and digastric muscle, the submandibular gland and the hyoid
bone, (c) the submandibular gland is retracted superolaterally towards the mandible, (d) the digastric and stylohyoid muscles are
mobilised and the hypoglossal nerve is also retracted cranially, (e) traversing the facial plane between the carotid sheath laterally
and the hypopharynx, trachea and oesophagus medially exposes the longus colli muscle and the anterior surface of the upper
cervical vertebrae, (f) the prevertebral fascia is opened exposing the longus colli and the anterior longitudinal ligament covering
the anterior surface of upper cervical vertebrae. The arrow shows the superomedial trajectory of the approach.
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Behari et al
Fig. 2 : (Case 2): Preoperative MRI T2WI, sagittal image
showing anterior obliteration of the subarachnoid space at
the level of collapse of C3 vertebra.
the gutter, the manual traction is released and the
traction removed. In one of the patients, in whom the
osteochondroma was involving the lateral part of the
vertebral body, an anterior cervical plating was also
performed (Figs. 2, 3). A bicorticate purchase was
obtained on the vertebral bodies above and below the
level of the corpectomy and the correct position
confirmed by using an intraoperative image
intensifier. One screw was also passed into the
allograft. However, this did not traverse the posterior
surface of the graft.
Postoperative management : The patients were
weaned off the ventilatory support as soon as possible
and were mobilised on a hard cervical collar. At
follow up after one and a half and three months, their
clinical status was evaluated again using the Harsh’s
functional myelopathic grade14 and lateral cervical
radiographs were obtained to assess for the stability
of the construct.
Results
Three of the five operated patients had significant
improvement in spasticity and power (Cases 1, 4, and
5). Case 2 had no preoperative myelopathy but
significant pain in the nape of neck which completely
resolved following stabilization. Case 3 with OPLL
spanning several vertebral segments, in whom the
significant extadural venous bleeding precluded total
removal of the OPLL, the residual spasticity and
unilateral deterioration in power by one grade
Neurology India, 49, December 2001
Fig. 3 : (Case 2): Postoperative lateral cervical radiograph
showing arthrodesis between C2 and C4 using iliac bone
graft and anterior cervical plating.
persisted at follow up (Fig. 4). The lateral radiograph
of the cervical spine at follow up in all the five patients
revealed that the construct was well placed and there
was no lysthesis. The complications of the procedures
included transient respiratory insufficiency requiring
ventilatory support as well as neurological
deterioration in two patients; and, pharyngeal fistula
and donor graft site infection in one patient. There was
no perioperative mortality. Though two patients with
OPLL had dural breech during the surgery, there was
no postoperative cerebrospinal fluid leak. None of the
patients in the series developed hypoglossal nerve
paresis.
Discussion
Approach
A number of studies have established the usefulness
of ARPA in providing a wide exposure from the
basiocciput of clivus and anterior rim of foramen
magnum to the rostral cervical spine upto C4.9-13 An
additional caudal dissection in the fascial plane
between the carotid sheath laterally and the trachea
and oesophagus medially gives access to the entire
cervical spine.10 According to the normal anatomy,
the C1-2 disc space corresponds to the angle of
mandible, the C2-3 disc space to the lower border of
the mandible and the C3 body to the hyoid bone.4 The
standard anterior approach to the subaxial spine
allows an easy exposure of the anterior cervical spine
from C3 to C7.6,7 However, in three patients in this
series, the ARPA rather than the conventional anterior
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Anterior Retropharyngeal Approach
Fig. 4 : (Case 3) Preoperative MRI T2WI, sagittal image
showing OPLL from odontoid to C4 body.
approach was used to treat prolapsed intervertebral
disc at C3-4 level (n=2) and osteochondroma of the
C3 vertebra (n=1). The indications for using ARPA in
the two patients with C3-4 disc prolapse (Cases 4 and
5) were the presence of a short neck in one patient
and a coexisting craniovertebral junction anomaly in
the other. The preoperative lateral radiographs of the
cervical spine in these cases had revealed the
existence of the C3-4 disc space at a higher level
than the hyoid bone and the lower border of the
mandible. In the patient with C3 osteochondroma,
the anterior cervical plating necessitated the complete
exposure of C2 vertebral body and the passage of a
bicortical screw through it. Thus approaching the C34 disc space in the former and the exposure and
instrumentation of C2 vertebra in the latter using the
conventional anterior approach would have been
difficult due to the superomedial obliquity of the
trajectory and would have required significant
traction on the soft tissues.
Vender et al13 have summarised the advantages of
ARPA in accessing anteriorly situated lesions from C1
to C3. Besides achieving a wide, bilateral exposure,
the approach avoids the potential contamination of the
oropharyngeal cavity and thus provides for a
simultaneous arthrodesis and instrumentation during
the primary surgical procedure. It also provides a safer
environment for a simultaneous intradural procedure
and management of a cerebrospinal fluid fistula.
347
Moreover, in case the occipito-atlantoaxial
configuration is not disturbed, the stabilisation
procedure excludes the occipito-axial joint, thus
preserving the vital lateral rotatory movements at the
neck. Thus, the technique is specially favourable for
dealing with ventrally situated lesions extending from
C1 - C3, especially when long vertebral segments are
involved as in OPLL, cervical spondylosis and bony
tumours and especially when a simultaneous anterior
vertebral arthrodesis and instrumentation is also
required.10 However, the anterior decompression of
the cervicomedullary junction restricted to the level
of clivus and the anterior arch of atlas is not usually
preferred using the present approach because the
trajectory of the approach is superomedial and the
head is also rotated towards the contralateral side
causing a simultaneous rotation of the arch of atlas.
This makes it difficult for the surgeon to orient
himself regarding midline of the cervical spine as a
direct anterior visualisation of the vertebral bodies at
this level is not possible.10 In such patients the
transoral approach1-3,16 can be utilised which has the
advantage of being a straight midline approach
through an avascular median raphe. This also ensures
direct anterior bony exposure of upper cervical
segment through a familiar anatomy. Moreover, it
allows foramen magnum decompression in neck
extension which is especially useful while dealing
with atlantoaxial dislocations. However, the surgery
is performed at the depth of a narrow field with vital
cervicomedullary centers underneath and therefore
carries the inherent risk of neurological deterioration.
Passage through a potentially infected oral cavity may
produce infection and precludes a simultaneous
intradural access or a stabilisation procedure during
the primary surgery.3 This approach does not provide
a good caudal access to the cervical spine without
combining it with a mandibular osteotomy and tongue
splitting,15 the lateral exposure also being limited to
3-4 cm, due to the emergence of the hypoglossal
nerves, the vertebral artery and the eustachian tube
laterally.16 Wide excision of the osteoligamentous
components may produce instability which requires a
separate procedure for stabilisation.2 The
disadvantages of the transoral route can be avoided
utilising the ARPA especially when access to the
middle and lower spinal segments is simultaneously
being sought along with access to the upper cervical
segment and also when an anterior bony arthrodesis is
being considered.
Complications
Two patients out of five developed respiratory
insufficiency requiring ventilatory support. The
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Behari et al
patients with a high cervical cord compression show
the syndrome of afferent respiratory dysfunction. A
number of cumulative factors like laryngeal oedema
due to retraction, pent up larygobronchial secretions,
compromise of the diaphragmatic function, weakness
of accessory respiratory muscles and increased
thoraco-abdominal muscle tone contribute to this
complication. Both patients were vulnerable to sleep
induced apnoea and required assisted ventilation.
However, the respiratory functions improved with
time and both patients could be weaned off the
ventilator. Transient neurological deterioration also
occurred in two patients, however, it was more
sustained in the second case. In the latter patient, there
was brisk extradural bleeding during the OPLL
removal, and a part of the compressing segment of the
OPLL could not be removed. This perhaps was
responsible for the sustained neurological
deterioration at follow up. During the drilling of the
vertebrae, application of a lateral rather than a
downward pressure and leaving a thin posterior
cortical surface of bone which is removed using
Kerrison’s punches,18 is recommended to prevent
potential neuraxial injury. It is also important for the
surgeon to gain orientation to the midline. The
rotation of head away from the midline, which also
rotates the anterior arch of atlas, can be assessed by
palpating the mental protruberance of the mandible.10
Maintaining this orientation throughout the anterior
decompression of the spinal cord ensures that the
drilling is carried out far enough laterally to permit a
wide decompression of the cord and its expansion into
the gutter created but not so far laterally so as to
endanger the vertebral arteries.10 A simultaneous
stabilisation during the primary procedure avoided the
danger of neurological deterioration due to
instability.13
The pharyngeal fistula occurred in one patinets, due to
retractor injury to the thin layer of superior constrictor
muscle that separates the hypopharynx from the area
of dissection.10 In such cases, if the injury is detected
during surgery, then the fistula can be closed in two
layers using absorbable sutures. In our patient, the
placement of nasogastric tube for seven days,
restricting the oral feeds and providing a broad
spectrum antibiotic coverage sufficed in overcoming
the complication.
Transient hoarseness and dysphagia following
anterior cervical spine surgery is attributable to
swelling in the soft tissues of pharynx and larynx due
to retraction.19 The hoarseness may also be due to
neuropraxia of the superior or recurrent laryngeal
Neurology India, 49, December 2001
nerve.4 Compression of the anterior branch of the
recurrent laryngeal nerve between the thyroid lamina
and the endotracheal cuff as the branch passes under
the mucosa of the larynx to the lateral cricoarytenoid
and thyroarytenoid muscles may also be a
contributory factor. A gentle dissection of adequate
length through the fascia situated between the carotid
sheath laterally and the hypopharynx, larynx and
trachea medially; avoiding unduly vigorous retraction;
placement the Cloward’s retractor blades under the
edge of the laterally dissected longus colli muscles;
frequent releasing of the tension on the retractors
especially when they are not actually required such as
when the graft is being harvested, avoids the
hoarseness and dysphagia.
The dural breech, that occurred in the two patients,
whose OPLL was adherent to the outer layer of the
dura, was covered with a fat graft. Acetazolamide
administration and lumbar drainage were instituted to
decrease the cerebrospinal fluid pressure.7,13
Fortunately, there was no leak following removal of
sutures. The other complications that may occur while
utilising this approach include hypoglossal nerve
paresis due to its mobilisation; salivary fistula during
the submandibular gland mobilisation; traction injury
to the facial nerve in the viscinity of the stylomastoid
foramen due to retraction at the base of origin of
stylohyoid or posterior belly of digastric muscle,10
carotid artery occlusion due to prolonged retraction in
association with atherosclerotic disease20 or carotid
artery injury especially due to avulsion of one of its
tethering branches; vertebral artery injury during the
removal of lateral osteophytes or while dissecting the
longus colli laterally using the cutting cautery
especially when orientation to the midline is lost,
injury to the sympathetic chain deep to the longus
colli muscle resulting in Horner’s syndrome,4 and,
graft dislodgement and donor site complications.7
Stabilisation
In the cervical spine, median corpectomy only
partially compromises the anterior spinal support
segment while the lateral segment comprising the
pedicle and facet joints and the posterior segments are
intact. In our series, after the corpectomy or Cloward’s
procedure, this theoretical instability was taken care
of by interposition of autogenous bone graft harvested
from the iliac crest. In four patients, the bone graft
was snugly fitted into the gutter created in the center
of the vertebral bodies by distracting the spine using
manual traction. We did not perform any
instrumentation in these patients in order to facilitate
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postoperative magnetic resonance imaging. Though
an early mobilisation was achieved in all these
patients, with the neck movements only restricted by
a hard cervical collar and not a Minerva jacket or a
halo brace, a good bony construct was noted at follow
up radiological evaluation. In the patient with
osteochondroma, a wider drilling of the lateral
vertebral body pillars prompted an internal fixation
procedure to stabilise the bone graft. An AO plate
system was used and a bicortical purchase through the
vertebrae above and below the level of the pathology
was ensured using intraoperative biplanar
fluoroscopy.7,13
5.
Conclusion
10.
The ARPA is an exteremly useful and safe approach
in accessing anteriorly situated lesions at C1-3
especially in patients with a short neck, Klippel Feil
anomaly or those in whom the C2-3 and C3-4 disc
spaces are situated higher in relation to the hyoid bone
and the angle of mandible. It achieves a wide,
bilateral exposure, avoids the potential contamination
of the oropharyngeal cavity and provides for a
simultaneous arthrodesis and instrumentation during
the primary surgical procedure. For accessing long
cervical vertebral segments, it can be combined with
the conventional anterior approach. However, for
strictly midline lesions restricted to the craniocervical
junction, the superomedial trajectory of the approach
renders it difficult for the surgeon to maintain his
orientation of the midline during the bony drilling.
6.
7.
8.
9.
11.
12.
13.
14.
15.
16.
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Accepted for publication : 21st, October 2000.
Neurology India, 49, December 2001