Management of Cranio-Vertebral Junction Anomalies Recommendations

Management of Cranio-Vertebral Junction Anomalies:

WFNS Spine Committee Recommendations

1-Chiari Malformation: Diagnosis, classifications, natural history, and conservative
management.

Chiari Malformation: Diagnostic Criteria and Outcome Measures

1-Chiari Syndrome is the clinical manifestation of the following diagnostic criteria: 
* Headache, usually occipital or suboccipital, of short duration (< 5 minutes) and provoked/precipitated by cough or other Valvalsa-like maneuvers
* Symptoms and/or signs of brainstem (ie nystagmus, dysfagia, sleep apnea), cerebellar (ataxia) and/or cervical cord dysfunction (ie muscles hypotrophy, sensory and motor deficits)
2-Additional clinical manifestation of CS may be vestibular symptoms, transient visual symptoms and scoliosis.
3-There are no specific clinical evaluation models related to Chiari Syndrome. An accurate Clinical Assessment, performed by specialist, is the most reliable evaluation model
4-The Chicago Chiari Outcome Scale (CCOS) may be used to assess the post-operative outcome in CM during the short-term follow-up time. Analyzes of disease-free survival and re-OP rate
are suggested to evaluate the long-term outcome

Chiari Malformation: Classification and Radiology

5-Chiari Malformation (CM) in adults is classified in type 1 and 2. The most common form in adult is type 1; type 2 is associated with myelo-meningocele and hydrocephalus from childhood. Further sub-classifications are available and can be used.
6-For diagnosis of type 1 CM, MRI is the exam of choice in order to show variable degree of tonsillar herniation, overcrowded posterior fossa or the absence of cisterna magna. Dynamic flexion-extension (Xray or CT scan) and/or MRI with CSF dynamic-flow study may be useful in specific cases.

Chiari Malformation: Natural History and Conservative Treatment

7-The natural history of patients with asymptomatic CM type 1 has a favorable evolution. Patients with asymptomatic or with mild symptoms may improve over time or stabilize with conservative treatment. According to clinical and radiological findings we recommend that:
* Patients with asymptomatic CM type 1 and syringomyelia should be treated conservatively with clinical-radiological monitoring * Mild symptomatic CM type 1 patients with or without syringomyelia may undergo somato-sensory evoked potentials (SSEP) and motor evoked potentials (MEP), brainstem auditory evoked potentials
and polysomnography
sleep-related breathing disorders and/or cough headaches

2-Chiari Malformation: Indications for surgery and surgical options. Indications of surgery for Chiari malformation

1-In presence of CM type 1 with characteristic symptoms, surgery is indicated. In asymptomatic patients, surgery may be an option if MRI shows progression.

Osteo-ligamentous decompression alone for Chiari malformation

2-Based on short-term outcome, the pediatric osteo-ligamentous decompression alone is recommended in population, presenting patients with suboccipital headache only, not associated syringomyelia.
3-The failure rate of osteo-ligamentous decompression alone is higher in: syringomyelia, adult population. 

Extra-arachnoid approach, dural opening and grafting for Chiari malformation

4-Symptomatic patients with CM type 1 with/without syrinx may have foramen magnum decompression with duraplasty.
5-Although available recent literature shows no significant advantage of subarachnoid dissection over extra-arachnoid approach, arachnoid opening could be done in patients with failed previous surgery.
6-For patients with CM, the extra-arachnoid approach is a safe procedure showing globally fewer complications than the subarachnoid dissection in short-term follow-up.
 

Cerebellar tonsil resection and arachnoid dissection for Chiari malformation

7-Arachnoid membrane may be opened when arachnoid morphological changes are seen during surgery.
8-In the short-term follow-up, tonsillar shrinking has slightly better clinical efficacy when compared to decompression alone, however, it may lead to a higher complication.

Posterior C1-C2 fusion for Chiari malformation

9-Atlanto-axial fixation alone is not recommended to treat CM1 patients without basilar
invagination (BI) and atlanto-axial instability (AAI).

Surgery for Chiari malformation and associated syringomyelia

10-The available scientific data suggest that syringomyelia is a manifestation of CSF obstruction at cranio-vertebral junction and does not represent a separate entity in CM type 1.
11-Decompression of CVJ in CM in the form of either PFD (bony decompression with band excision) or PFDD (bony decompression with duraplasty) is sufficient to control the associated syringomyelia in most of the cases. In case of previously failed surgery, symptomatic patients with enlarging syrinx re-exploration or duraplasty may be considered. Syrinx drainage is the last option.

3-Pediatric Chiari Malformation
1-In pediatric population with CM type 1, surgery performed before puberty reduces scoliosis progression and foramen magnum decompression is recommended.
2-In children with scoliosis and CM type 1 without syringomyelia there is an indication of surgery if there is no other cause for scoliosis.
3-Decompression of foramen magnum with duraplasty is recommended in children with CM type 1 associated with syringomyelia. In children with CM type 2, the recommendation is to perform urgently tailored decompression of foramen magnum and cervical canal.
4-Cranial vault expansion is recommended in pediatric CM associated with craniosynostosis.
5-Children with CM type 1 can play sports because of the low risk of clinical worsening.

4-Syndromic atlanto-axial instability: Screening and surveillance, sports clearance and treatment options

Down's and Morquio's: Conservative and Surgical Treatment

1-In asymptomatic Down- and Morquio syndrome patients with proven atlanto-axial instability, preventive stabilization might be considered. Neurological symptoms deriving from atlanto-axial instability are an indication for stabilization in these patients. The indication and timing of surgery is insufficiently covered in literature, especially if a surgery is offered for nonneurological symptoms or prophylaxis.
2-The surgical approach must be tailored individually to each patient. However, in literature, Goel-Harms C1-C2 stabilization technique is most frequently described. 
 

Down's and Morquio's: Screening and Surveillance of AAI and Sports Practice

3-In Morquio's patients older than 5 years-old, it is recommended to perform an annual detailed neurological examination and, when possible, correlate it with imaging studies of the spine to detect early spinal stenosis or instability compromising the cervical cord.
4-Morquio's patients require radiological surveillance of the entire spine. For AAI the recommended screening should include: 
* Cervical spine lateral radiograph in controlled flexion/extension projections, at first visit and every 1-2 years.
* Dynamic cervical MRI or craniovertebral junction CT represents complementary examinations
5-Down's patients require close neurological screening from birth up to 5 years of life, and yearly thereafter. Yearly, neuroradiological screening may be used to detect AAI. Relatives should be informed and counseled to avoid Down's children's participation in full contact sports (football, soccer), or sports that might cause cervical injury like gymnastics, wrestling, diving, and trampoline use.

6-Down's children presenting with symptoms are recommended to proceed with flexion/extension X rays, MRI and CT studies. In case AAI on screening radiographs is detected they should be followed closely, at least annually, with repeat neurologic examinations. In selected cases, preventive stabilization might be considered.
7-Clearance for sports competition should include a focused history and neurological examination of patients with DS. Patients without AAI and neurological intact are cleared to unrestricted sports.
DS patients with symptoms but without AAI or spinal cord compression can participate in most Special Olympics sports training and competition activities. However, they shall not be permitted to integrate sports which, by their nature, result in hyperextension, radical flexion or direct pressure on the cervical spine.
There is no evidence available to clear Down's patients for sports, after posterior cervical decompression/fusion.
8-Morquio patients can participate in activities, such as swimming or hippotherapy, while contact sports should be avoided. There are no recommendations in the literature regarding competition in Special Olympics for Morquio patients.

5-Diagnosis, classification and treatment of os odontoideum

Diagnosis and Classification

1-There are no specific symptoms afflicting patients with os odontoideum. CT and MRI are required to better qualify the anatomical diagnosis. Two anatomical types, orthotropic and dystopia have been confirmed. Caution must be done in the assessment of transverse ligament position regarding the odontoid tip defect.
2-The natural history of asymptomatic os odontoideum patients is not well defined. The propensity toward development of neurological deficit or progressive instability in osodontoideum left untreated in unknown.
3-Clinically, os odontoideum patients can be classified into four main categories:
1. asymptomatic patients
2. neck pain only
3. cervical myelopathic symptoms and signs
4. symptoms related to vertebrobasilar ischemia
 

Surgical Treatment

4-All symptomatic patients and those presenting with spinal cord compression on MRI should have a C1-2 joint stabilization and fusion procedure. Incidentally discovered OO surgery factors should be offered on an individual basis, considering predictive for neurological deterioration and the expertise of the counseling surgeon.

5-Posterior C1-C2 fixation is the recommended type of surgery in patients with OO, as it is a versatile and effective procedure that leads to the improvement of symptoms and neurological deficits in the vast majority of patients.
6-Routine extension of fixation to the occiput is not recommended in OO patients, unless the following situations are also encountered:
* Atlantooccipital dissociation
* C1 abnormalities, not permitting implantation of screws
* Repeatedly failed attempts of atlantoaxial fusion
* Dystopic os odontoideum with motion
7-Anterior decompression should be avoided to treat irreducible AAD caused by OO. In rare case anterior decompression can be considered.
Instead, neural compression in association with OO should be treated with a reduction of deformity. Since in most cases of OO, the AAD is reducible and additional decompressive surgery is not required.

6-Basilar Invagination: diagnosis, radiology, and classification

1-Basilar invagination can be divided into primary, as a result of CVJ developmental abnormality, or acquired from skull base softening, as seen in rheumatoid arthritis) 
2-Basilar invagination can be classified as Type A (atlantoaxial dislocation) and Type B (without AAD)
3-Clinical signs of BI may be due either to brainstem compression (ataxia, dysmetria, dysphagia, cranial nerve palsy, nystagmus) and/or due to cervical spine cord compression (weakness, neck pain and headache) and instability. There is no symptom-based clinical classification system.
4-A variety of classical measurements are described for the radiological diagnosis of basilar invagination. The most common are:
* McRae for type A
* Chamberlain lines and Boogard for type B.
There are new measurements on CT and MRI; However, further studies are necessary to identify their value.

7-Surgical treatment of basilar invagination

Posterior fossa decompression

1-Based on the limited quality of the existing papers, posterior fossa decompression alone is an option to surgically treat basilar invagination without instability (Type II)

2-There is insufficient scientific data to assess the difference of complications of posterior decompression alone compared to posterior fixation techniques 
 

Posterior C1-C2 Fusion with extension to occiput

3-Most cases of basilar invagination and atlantoaxial instability can be treated by C1-C2 fixation. In selected cases, distraction of the atlantoaxial joint by a spacer or bone graft may be required.
4-Irreducibility criteria of atlantoaxial instability and cranial settling of the odontoid are not clear. There are many options to reduce the basilar invagination. Current evidence is lacking which technique is better.
5-In basilar invagination patients, an occipitocervical fixation can be used in case of atlas assimilation, dysgenesis of C1 lateral mass, in irreducible cases, and if an odontoid resection was done. Occipitocervical fixation may be preferred for revision of failed C1-C2 fixation.
6-Current rigid techniques for occipitocervical fixation (occipital plate, polyaxial screw and rod systems) can provide more fusion and less implant failure than previous semirigid techniques (hook, wire, and plate systems).
7-Occipitocervical fixation significantly restricts head movements and may cause some disability. Complications of the occipitocervical fixation may reach up to 50%. Most of them are implanted related.

Atlanto-axial distraction and fusion

8-C1-C2 facet joint manipulation distraction and fusion is an option to treat BI with AAD or irreducible ADD
9-There is no evidence to treat BI without AAD with C1-C2 facet joint manipulation distraction and fusion

Anterior Fusion

10-The role for anterior fusion for treatment of BI need to be better assessed by further studies
11-For symptomatic cases of irreducible BI, anterior facet distraction and fusion is described. In revision cases, anterior facet fixation is an option preferably through a retromucosal approach

Odontoid Resection

12-In the setting of irreducible anterior compression caused by BI, the anterior odontoidectomy can be indicated. In this case, it may be associated with a posterior decompression and C1-C2/occipital-cervical fusion.
13-There is no sufficient evidence to recommend a trans-nasal approach instead of open transoral odontoidectomy. However, the endoscopic technique may be a better option for pathologies above the level of the hard palate, and transoral approaches may be a better option for pathologies of the C1-C2 region.

8-Basilar Invagination varies with associated Chiari Malformation
1-The incidence of BI and CM in different areas of the world: in Western Europe and US it can be estimated at 8/100000. The incidence for this combination increases with age: children with CM type 1 may develop a basilar invagination in adulthood.
2-Treatment of patients with a combination of BI and CM1 should include appropriate posterior fossa decompression.
3-Chiari Malformation is a modifier in the treatment algorithm