Atlantoaxial dislocation (AAD)

Atlantoaxial dislocation (AAD) The loss of normal alignment and stability of the first cervical (atlas) and second cervical (axis) vertebrae with respect to each other is called Atlantoaxial dislocation. Atlas is the first cervical vertebra in the neck and this is the bone right below the head which supports the head, the next bone is the axis the second cervical vertebra these vertibrae help balance the whole body. This is a very crucial region because this is the place where the spine starts. The occiput (the bone on the back of the skull), the atlas (C1), and the axis (C2) form one functional unit (the occipitocervical articulation) which gives a high degree of mobility and little bony stability to the neck. The strong ligaments facilitate movement and keep these structures in place. The head rotation occurs mainly at this junction, and the odontoid bone is the axis that allows this rotation. The extension and flexion movement of the head is allowed because of the atlantooccipital joint. This joint gives movement to the neck allows the head to move front and back and on either side. The connection between the very critical structures of the brain and the rest of the body is called the craniocervical junction. This is a very complex region because of the requirement of stability and movement, anything which goes wrong here can be disastrous and dangerous. AAD is a challenging disorder of the craniocervical junction. The condition must be diagnosed and treated to prevent deformity, spinal instability, and potential neurologic injury. How is Atlantoaxial dislocation caused? AAD is caused due to traumatic, congenital, and pathologic causes. Atlantoaxial dislocation (AAD) is often caused by trauma, tumors or congenital malformations, infection, connective tissue, and autoimmune disorders. AADs are mainly caused by odontoid fracture or rupture of the transverse ligament. -Traumatic AAD caused by a fall or accident is the most common type of AAD. -Sometimes AAD can be seen from birth due to developmental problems in the neck which are called congenital atlantoaxial dislocations it is the second most common type of AAD. -The pathologic type of AAD which is least common is caused by tuberculosis, infection, or tumors of the atlas or axis. Symptoms of AAD 

•Patients with traumatic AAD often complain of neck pain and limitation of movement (especially rotation) after injuries to the neck or head. Muscle spasm in the neck, tenderness, and torticollis(twisted neck) may be found on physical examination. Some of the patients feel they need to keep holding their heads with their hands because of a terrible feeling of neck loss.

•    When the medulla or spinal cord is being compressed, patients may complain of numbness and weakness in the extremities, sphincter dysfunction, disordered circulation, and respiration center dysfunction, which may end in paralysis and even death if the respiratory center is affected.

•    Patients with AAD due to congenital deformities in the craniocervical junction symptoms include neck pain, limitation of neck movement, and numbness and weakness in the limbs.

•    Tuberculosis may destroy the lateral mass of the atlas leading to atlantoaxial instability and dislocation which is more common in children.

•    Rotational dislocation occurs if one side of the lateral mass collapses where the patient complains of neck pain and shows torticollis.

•    AAD can also be caused by tumors in the upper cervical vertebrae, continuous occipital and cervical pain is usually the early symptoms, more severe at night, and often accompanied by torticollis or awkward postures. Neck movement may increase the pain. The pain may also intensify if the tumor invades the soft tissue around the vertebrae. Pain in the zone served by nerves from the related segment can occur due to compression of the spinal cord or nerve root by a tumor. Compression of the medulla or spinal cord by an enlarging tumor can lead to limb numbness, movement problems.

•    Spontaneous atlantoaxial subluxation is a type of AAD seen in children, which is usually associated with pharyngeal or neck infection, early symptoms are continuous neck pain and limitation of cervical movement which may gradually intensify. Diagnosis Radiography is important in the diagnosis of AAD.

Radiography, CT, or MRI examination can identify AAD associated with malformations in the craniocervical junction and compression of the upper spinal cord, allowing a final definite diagnosis. Treatment The treatment of AAD includes reduction, decompression, fixation, and fusion. With the deep location and intricate anatomic structure, the craniocervical junction always poses technical challenges for spine surgeons because of its deep location and intricate and complex anatomic structures. Treating this portion of the neck is highly complex, It is treated by decompressing or making sure the nerve or spinal cord is cleared of any compression, and then it is fixed into the position using titanium screws and rods so that it is stabilized. By fixing the atlantoaxial dislocation the patient gets relieved of most of the symptoms but sometimes it takes time for some of the symptoms to resolve, the surgical fixation of the atlantoaxial dislocation is very important to prevent the ongoing damage of the crucial junction of the brain and spine. With recent developments in medical science, great progress has been made in the diagnosis and treatment of AAD, efficacious treatment strategies, various novel operation techniques including innovative posterior or transoral anterior reduction, and novel fixation instruments. The various new technologies have transformed this complex surgery which was highly morbid some years ago into a relatively safer procedure achieving good clinical results. Visit us if you’re worried about any symptoms you’re experiencing and for early detection of Atlantoaxial dislocation.