Deepak Awasthi, MD and H. Bruce Hamilton, MD
Department of Neurosurgery
Louisiana State University Medical Center
New Orleans, Louisiana, USA
[ Introduction | Clinical Presentation | Discussion | References]
Posterolateral Approach to the Cervical Spine
Deepak Awasthi, MD and H. Bruce Hamilton, MD
Department of Neurosurgery
Louisiana State University Medical Center
New Orleans, Louisiana, USA
[ Introduction | Clinical
Presentation | Discussion | References]
Introduction:
The posterolateral approach, with resection of the lamina, facet and
pedicle, has been used primarily in the thoracic spine for treatment of
thoracolumbar fractures, vertebral metastases, disc herniations, ventral
extradural lesions and occasionally for ventral intradural extramedullary
lesions.(1,2,4,5,7,8) Recently, the posterolateral approach has been described
for cervical as well as the thoracic spine for intramedullary lesions of
ventral and ventrolateral spinal cord.(6) Nevertheless, the posterolateral
approach is not commonly used in the cervical spine. Lateral approaches
have also been described to the cervical spine, especially for dumbbell
tumors.(3,9) We describe the posterolateral approach to the cervical spine
for an intradural/ extradural extramedullary tumor (in our case, a dumbbell
shaped neurofibroma). This approach allows excellent ventrolateral exposure
as well as visualization and resection of tumor in the paraspinous region.
As will be seen, this exposure also allows safe access to the vertebral
artery.
Clinical Presentation:
This 27 year old woman presented to the neurourgery clinic with a 2
month progressive history of difficulty walking with accompanied pain in
the left side of the neck and shoulder. Examination revealed a spastic paraparesis,
posterior column signs, cafe au lait spots and a firm, non-tender mass in
the left upper posterolateral neck.
Diagnostic workup included a MRI scan of the cervical spine with and without
contrast. See below:
Note the large extradural extension of the tumor on the T2WI (axial).
This study revealed a large homogeneously enhancing mass at the left
C2-3 area. This mass extended from the spinal canal (occupying greater than
50% of canal) through the neural foramina into the paraspinous region. Given
the tumor extension and the patient's symptoms, a posterolateral approach
and gross total resection of the tumor was proposed.
Operative Technique:
Position and preparation:
The procedure is performed under general anesthesia with the pateint
in the prone position and the head in the Mayfield headrest. The incision
is planned to allow exposure of both laminae, both facets (lateral masses)
and, on the side of the lesion, the transverse process. The level(s) of
the lesion as well as one level above and below are exposed.
Incision:
Two types of incision can be performed- see below:
A: Curvilinear B:Transverse incisions
A curvilinear incision starting in the midline and curving towards the
side of the lesion (as done in our case) can be planned for the upper cervical
spine.
The incision in our case.
A second type of incision is a midline incision combined with a transverse incision that extends laterally at the level of the lesion. This would be more helpful for lower cervical spine.
After the midline incision and dissection, the
dissection is carried through the paraspinous muscle which is elevated
from the lamina, facet and transverse
process. The most important step is a wide muscle dissection allowing the
self-retaining retractors to provide exposure of the transverse process.
Bone removal :
After exposure of the bone at the level of the pathology as well as above
and below, laminectomies are performed at these levels- this involves removal
of the spinous processes and laminae on both sides. Next, the facets and
pedicle at the level of the lesion are removed using standard rongeurs and
a high-speed drill. The pedicle is removed to the level of the floor of
the spinal canal. At this point one can visualize the vertebral artery traversing
in the foramina of the transverse processes:
purple: C1; blue: cervical thecal sac; yellow: vertebral artery traversing
in the transverse processes
This bony removal allows visualization of the intradural as well as the
extradural portion of the tumor:
T: Tumor
The dura can be opened laterally (as shown above) at the level of the
root entry zone allowing gross total resection of the tumor.
Operative Findings and Postoperative Course:
The dumbbell shaped tumor (neurofibroma) was fully resected. In addition,
the lateral exposure allowed a safe dissection of the tumor from the vertebral
artery.
Postoperative course was uneventful in the presented case. The patient's
pre-operative neurological deficits were unchanged, but her shoulder/ arm
pain improved.
Discussion:
The posterolateral approach is used almost routinely in the thoracic
spine for treatment of ventral extradural pathology like fracture fragments,
metastatic tumors and herniated discs.(2,4,5,7) To lesser extent, this exposure
has also been used successfully to resect intradural extramedullary spinal
tumors such as meningiomas and schwannomas, especially in the thoracic spine.(1,8)
Schwannomas/ neurofibromas typically arise from the dorsal root and are
thus located laterally and posteriorly. As shown in this case, these tumors
can also extend far beyond the spinal canal. Typically in these cases (when
the paravertebral mass is large), a two stage procedure is planned- stage
one for removal of the intraspinal portion of the tumor (posterior- laminectomy
approach) and stage two for removal of the extraspinal part.(3) In cases
of cervical dumbbell-shaped tumors extending mostly outside the spinal canal
through an enlarged intervertebral foramen, a lateral or combined anterolateral
(transuncodiscal) can be performed.(3,9) In 1968, Verbiest described a lateral
approach to the cervical spine.(9) Hakuba et al modified this approach and
described the transuncodiscal approach which allows direct access to the
laterally located tumor.(3) In this approach, an anterior dissection is
necessary as well as manipulation of the vertebral artery. The posterolateral
approach avoids potential problems with the anterior dissection and manipulation
of the vertebral artery. This approach can give a wide exposure of a dumbbell-shaped
tumor as well as other tumors located ventrolaterally, allowing their total
resection.
Posterolateral approach:
The posterolateral approach is an extension of the standard posterior
(laminectomy) approach and thus dissection can easily be mastered as compared
to the lateral and anterolateral approaches. This approach provides a wide
exposure of the cervical lateral masses, pedicles and transverse processes.
Subsequent drilling of these bony elements allows an almost lateral view
of the spinal cord, thus making the exposure shallow. The posterolateral
approach can be added, in the middle of the case, if the standard laminectomy
does not provide adequate exposure of the lesion, by extending a tranverse
incision. After opening of the thecal sac, following the posterolateral
approach, dentate ligament sectioning and spinal cord rotation allows excellent
exposure of the ventrolateral surface of the spinal cord (as well as the
dorsal surface of the cord) as far medial as the anterior spinal artery.(6)
Thus, this approach can be used for vascular malformations and/ or intrinsic
lesions of the spinal cord.(6)
Need for Fusion:
Cervical stability does not seem to be compromised by use of this approach.
The anterior and posterior posterior longitudinal ligaments, disc and annulus,
as well as the contralateral facet are not disrupted by this approach. These
structures should provide adequate biomechanical stability. However, a bilateral
removal of the facets or a multilevel laminectomy in children may have to
be fused and internal fixed with instrumentation.(6)
Conclusion:
The posterolateral approach allows wide exposure of lesions located
postero- as well as ventrolaterally in the cervical spinal canal. This exposure
avoids staged procedures for dumbbell shaped tumors. In addition, it allows
safe access to the vertebral artery. The posterolateral approach, thus,
gives the surgeon a reasonable means for addressing large intradural/extradural
lateral tumors as well as ventrolateral lesions in the spinal canal and
cord.
References: