Case Studies » craniovertebral Junction
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8 Year old boy
An 8 year old boy presented with difficulty in walking,
frequent falls and weakness of all 4 limbs
He had a condition known as AAD (atlanto-axial dislocation)
which is due to dislocation of the C2 vertebra. The C2
vertebra is an important bone instrumental in supporting the
weight of the head on the upper part of the neck.
The dislocation causes a potentially fatal compression of
the spinal cord and therefore weakness of the limbs.
Sometimes, even more dangerously, the C2 vertebra can
telescope into the base of the skull through the opening in
the base of the skull. This opening is known as foramen
magnum and is the passage for the brain stem to continue
into the neck as the spinal cord.
This kind of telescoping into the foramen magnum causes
brain stem compression and has the potential to cause
respiratory paralysis and sudden death.
Sagittal T2 MRI showing the part of the C2 vertebra (odontoid
process) that has dislocated backwards into the spinal canal
(white arrow) causing severe compression of the brainstem
and spinal cord. The cord is showing signs of damage due to
compression (the white signal within the cord – black
arrow).
TA CT scan picture showing the bony patho-anatomy of the
dislocation. The finger-like odontoid process is seen
clearly in its abnormal position inside the foramen magnum
(delineated by two white arrows). The normal space for the
spinal cord is reduced to less than 1/3rd.
The patient required a two-stage procedure. The first stage
was to decompress the spinal cord and brainstem by removing
the abnormally located bone. This requires a procedure
called TRANS-ORAL ODONTOIDECTOMY, which is an extremely
challenging procedure done through the patient’s mouth. The
odontoid is reached through an incision in the back of the
throat and the abnormal bone is drilled out and removed.
This requires specialized instrumentation such as an
operating microscope and a high-speed drill.
Above is the post-operative CT scan showing complete
excision of the abnormally located odontoid. The spinal cord
is now adequately decompressed. The black line indicates the
position of the excised bone.
The second stage involves stabilizing the now unstable spine
with the use of metal implants. Here the skull is joined to
the spine with a titanium rod and special screws augmented
with a bone graft.
This boy did extremely well after surgery, has gone back to
school and is ambulating nearly normally, except for mild
residual stiffness in the legs.
24 Year old gentleman
This young gentleman was involved in a road traffic accident
9 months before presenting with severe neck pain. His Xrays
and CT scan showed a fracture of the odontoid (part of the
C2 vertebra which is responsible for supporting the head on
the neck and is also critical in movements like head
turning). This type of fracture is inherently highly
unstable and will fail to heal if not treated.
Xray of the cervical spine showing the fracture line (black
arrows). The upper fragment is displaced forwards. The lower
fragment does not move in conjunction with the upper
fragment causing it to protrude into the spinal canal (the
part of the spine which accommodates the spinal cord) which
can cause spinal cord compression.
A CT scan showing the fracture site (white arrow). The lower
fragment is impinging on the spinal cord (black arrow). The
black line demonstrates the impingement on the spinal cord
As the fracture was more than 6 months old, direct methods
of fracture repair were not possible. He underwent a C1-C2
fusion using the Vertex system. In this method of fusion,
screws are inserted into the C1 vertebra (known as the
atlas) on both sides. Screws are also inserted into the C2
vertebra. Screw insertion into C2 is technically challenging
as the screw has to traverse a critical part of the bone
between the spinal cord on one side and the vertebral artery
on the other. The vertebral artery is the major blood vessel
supplying critical areas of the brain and brain stem. Any
damage to the vertebral artery can cause a serious,
life-threatening stroke causing permanent major disability
or death. Screw passage in this area has to be technically
perfect to prevent any untoward complications from
occurring.
Post-operative Xray showing the screws in both C1 and C2 on
both sides. The fracture has reduced. The fusion has been
augmented with an additional cable to fuse C1-C2. The black
arrows indicate the screws in C1 and C2 and the white arrow
represents the braided cable.
A sagittal CT section showing the screws in C1 & C2. The C2
screw has traversed without compromising the vertebral
artery notch (white arrow).
Axial CT section showing the screws in C2. The spinal canal
is outlined in black. The cable is seen behind along with
the bone graft used to augment the fusion (White arrow).
The patient has done well following the surgery and has
returned to gainful employment. Xrays done at 3 months
showed good integration of the graft.
Odontoid Fracture
Post-operative CT scan images of a patient with an odontoid
fracture. He has undergone a C1-C2 fusion with C1 lateral
mass screws and C2 pedicle screws to achieve a rigid
stabilization of the spine. This has been augmented with an
iliac crest bone graft (black arrow) and a C1-C2 cable
(white arrow).
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