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).

 
Sita Bhateja Speciality Hospital : Langford Gardens, Bangalore 560025. Ph. +91 80 22210701/22214074