The treatment of skull base deformity (skull base depression, atlantoaxial dislocation) used to require decompression via anterior and posterior approaches respectively, which has long operation time, many complications and high surgical risks. Now we have achieved good results by using posterior repositioning and fixation with bone graft fusion, and the repositioning of the dentate process and posterior decompression can be completed in one operation. The operation time is greatly shortened, and the safety and efficacy of the operation are improved.
The patient was 40 years old, and the skull base deformity (skull base depression and atlanto-axial dislocation) had been found for more than 20 years, and had been treated conservatively. The left limb also began to show symptoms of weakness and numbness. After posterior repositioning and fixation with bone graft fusion, the patient’s symptoms were significantly relieved and he could walk normally and take care of himself.
The preoperative MRI examination indicated depression of the skull base, atlantoaxial dislocation, posterior displacement of the dentate process to compress the brainstem, secondary spinal cord cavity, and significant anterior convexity of the cervical spine.
Posterior dentate repositioning with occipitocervical fusion was adopted for surgery.
First, C2/3 nail and occipital plate were fixed, and the dentate was repositioned by using the stress of the fixation bar.
After repositioning, fixation and bone grafting were performed.
Post-operative 3D CT review Good repositioning of the dentate process
Postoperative 3D CT review Good position of the nail bar
Postoperative CT and MRI showed that the anterior and posterior compressions were released
Most of the skull base deformities (skull base depression, atlanto-axial dislocation) are congenital developmental anomalies, due to atlanto-occipital fusion, flattening of the occipital bone, deformation of the foramen magnum, upward displacement of the dentate and even into the foramen magnum, resulting in a reduction of the anterior and posterior diameters of the foramen magnum. The upwardly displaced foramen can compress the brainstem anteriorly, and the posterior foramen occipitalis and posterior arch of the atlantoaxial spine can compress anteriorly, resulting in secondary spinal cord cavitation. The symptoms gradually worsen with age.
Its main manifestations can be as follows.
1, upper cervical nerve root irritation symptoms
It is mainly due to the stimulation and compression of atlanto-occipital fascia, ligaments and dura mater by the skull base deformity bone, which causes hyperplasia, hypertrophy or formation of fibrous fascia, compressing the upper cervical nerve root. Patients often complain of chronic pain in the occipital region, restricted neck movement, hypesthesia, numbness, pain, muscle atrophy, forced head position, etc. on one or both upper limbs.
2.Posterior group brain nerve disorder symptoms
The posterior group of cerebral nerves is often involved due to brainstem displacement, pulling or arachnoid adhesion, and symptoms of bulbar palsy such as dysphagia, choking, hoarseness, tongue muscle atrophy, slurred speech and weakened gag reflex, as well as facial sensory loss, hearing loss and weakened corneal reflex.
3. Signs of pressure on the medulla oblongata and superior cervical medulla
The symptoms are mainly caused by subungual herniation of the cerebellar tonsils, compression of the medulla oblongata and superior cervical medulla by local pathological tissue and secondary spinal cord cavitation. Patients show weakness of limbs, sensory disorders, positive cone bundle sign, urinary retention, difficulty in swallowing and breathing, impairment of fine finger movements, and loss of position sense; sometimes there is unilateral or bilateral loss of pain and temperature sensation in the cervicothoracic segment of the spinal cord, while tactile and deep sensation exists.
4.Cerebellar dysfunction
Nystagmus is common, mostly horizontal nystagmus, but also vertical or rotational nystagmus. In the late stage, cerebellar ataxia may appear, manifested as unstable walking, slurred speech, inaccurate finger-nose test, unstable heel-knee-shin test, positive closed-eye difficulty sign, etc.
5.Disorders of vertebral artery blood supply
The symptoms are episodic vertigo, visual impairment, nausea and vomiting, ataxia, facial sensory disorder, tetraplegia and ball palsy, etc.
6.Symptoms of increased intracranial pressure
Early stage patients usually do not have intracranial pressure increase, once it appears, it means the condition is serious and mostly advanced. The symptoms are caused by the occurrence of obstructive hydrocephalus, and individual patients who appear earlier may be the cause of combined intracranial tumor or arachnoid cyst. Patients present with severe headache, nausea and vomiting, optic disc edema, and even herniation of the foramen magnum, impaired consciousness, respiratory and circulatory impairment, or sudden respiratory arrest and death.
Previously, the surgical approach was mostly decompression through the anterior cervical or oropharyngeal approach to grind away the tip of the foramen magnum. The posterior approach was then followed by decompression of the posterior margin of the foramen magnum and occipitocervical fusion. Removing the compression via the anterior and posterior approaches, respectively, has a long operative time, many complications, and high surgical risks. Now we have achieved good results by using posterior repositioning and fixation with bone graft fusion, and the repositioning of the foramen magnum and the decompression of the posterior approach can be completed in one operation. This has greatly shortened the operation time and improved the safety and efficacy of the operation.