Craniocervical instability

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A cervical MRI is assessed for possible craniocervical instability.

Craniocervical instability (CCI) is a pathological condition of increased mobility at the craniocervical junction, the area where the skull meets the spine. In CCI the ligamentous connections of the craniocervical junction can be stretched, weakened or ruptured.[1] This can lead to compression of the brainstem, upper spinal cord, or cerebellum and result in myelopathy, neck pain and a range of other symptoms.[2]

CCI usually develops as a result of physical trauma such as a car accident, an inflammatory disease such as rheumatoid arthritis or a congenital disorder such as Down's syndrome.[3] More recently, physicians have reported an increased prevalence of CCI in patients with hereditary disorders of connective tissue such as Ehlers Danlos Syndromes (EDS).[4] There have also been anecdotal reports of patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) who were later diagnosed with CCI,[5][6][7] although no scientific publication on this subject exists.

Symptoms[edit | edit source]

Symptoms of craniocervical instability include occipital headache, neck pain and neurological abnormalities such as numbness, motor weakness, dizziness, and gait instability.[8][9][10][11][12] Patients sometimes describe the feeling that their head is too heavy for their neck to support (“bobble-head”).[4] No particular symptom is mandatory for a diagnosis of CCI and each symptom listed might have a cause other than CCI.

Other symptoms reported in patients with CCI include:

Risk factors and comorbidities[edit | edit source]

Established risk factors for CCI include physical trauma, inflammatory disease, neoplasms and congenital disorders.[3][25]

More recently, physicians have reported an increased prevalence of CCI in patients with hereditary connective tissue disorders.[4] According to Brodbelt & Flint, however, an "increased range of joint movement, caused by ligamentous laxity, is not the same as spinal instability resulting from trauma or major inflammatory arthropathies such as (historically) rheumatoid arthritis."[26] Others have argued that "pathological instability at the cranio-cervical junction has not been clearly established in the literature for the hypermobility population."[4]

Cause of instability Example
Physical trauma[27] Car accident[28][29], blow to the head.[30]
Infection & inflammatory disease Rheumatoid arthritis[31], tuberculosis[32]
Neoplasms Tumors[25] such as haemangioma, aneurysmal bone cyst
Congenital Down’s syndrome[33], os odontoideum[34], dwarfism
Hereditary connective tissue disorder Ehlers Danlos Syndromes[13][14]

It is not unusual for CCI to co-occur with other structural neurological abnormalities such as atlantoaxial instability (AAI) and chiari malformation (CM).[35][13]

Diagnosis[edit | edit source]

Dr. Paolo Bolognese discusses methods of imaging and measurement for diagnosis.

The diagnosis of CCI is based on symptom presentation, a supportive history, demonstrable neurological findings and abnormal imaging.

Imaging[edit | edit source]

CCI is typically diagnosed via a cervical MRI, whether supine or upright. If supine, a 3 Tesla MRI is preferred over a 1.5 Tesla. Most neurosurgeons prefer upright MRI with flexion and extension.[36] According to Henderson FC, “ventral brainstem compression may exist in flexion of the cervical spine, but appear normal on routine imaging.”[4]

Imaging Sensitive for
Upright MRI with flexion/extension Horizontal instability
CT scan with rotation Rotational instability
Invasive cervical traction (ICT) with fluroscopy Vertical instability

Measurements[edit | edit source]

More than twenty radiological measurements have been proposed or used in the diagnosis of CCI. However, three measurements are most commonly used: the Grabb-Oakes line, which measures ventral brainstem compression; the Clivo-Axial Angle (CXA), which measures brainstem deformity by the odontoid process; and the Basion Dens Interval, which measures vertical instability (cranial settling). According to a 2013 consensus statement on the assessment of CCI a CXA of 135 degrees or less should be considered as "potentially pathological."[37] as it is reported to be uncommon in the healthy population.[38][39][40] Others have argued that these radiological measurements are "not accepted internationally as indicating instability."[26]

Measurement Units Description Normal Range Borderline Range Pathological Range Alternate Ranges Instability Measured Pathology Measured Refs
Clivo-axial angle (CXA) Degrees Angle between clivus line and the posterior axial line 170 -150 149 -136 ≤ 135 More sensitive for horizontal Brainstem deformity [41]
Grabb-Oakes mm Distance from the dura to the line drawn from the basion to the posterior inferior edge of the C2 vertebra < 6 ≥ 6 and < 9 ≥ 9 Some use pathological ≥ 8 More sensitive for horizontal Brainstem compression [42][4]
Basion-Axial Interval (BAI) mm Distance from tip of basion to posterior axial line < 12   ≥ 12 [43]
Basion-Dens interval (BDI) mm Vertical distance between the basion and the dens < 12 ≥ 12 Some use pathological ≥ 10 Vertical Cranial settling [43][4]
Translational BAI mm Change in BAI between flexion and extension positions of the head < 1 ≥ 1 and ≤ 2 > 2 For surgery > 4 needed Horizontal Skull sliding over spine [44][13]
Translational BDI mm Change in BDI between flexion and extension positions of the head
Dynamic BDI mm Change in BDI value when the head is pulled upward with traction force of typically up to 35 lbs Vertical Cranial settling
Dens Over Chamberlain mm How far tip of the dens extends above Chamberlain's line < 2 ≥ 2 and ≤ 3 ≥ 3 Vertical Basilar invagination [45]

Some of the measurement ranges in the above table are also to be found in the 2nd International CSF Dynamics Symposium Consensus Statement (2013).[37]

Traction[edit | edit source]

Manual traction, halo and invasive cervical traction are often used to aid in the diagnosis of CCI. Symptomatic improvement with traction can help determine whether a patient with abnormal measurements will benefit from craniocervical fusion surgery.

Treatment[edit | edit source]

Dr. Fraser Henderson presents the results a five-year follow-up study.

Conservative treatment[edit | edit source]

Treatment of CCI can include “conservative measures” such as rest, pain management, bracing with a cervical collar, or physical therapy to strengthen neck muscles.[46] Many conservative therapies have little to no supporting evidence of efficacy.

There is no evidence for the efficacy of experimental treatments for CCI such as prolotherapy and upper cervical chiropractic.

Surgery[edit | edit source]

When non-invasive treatments for CCI fail to work, occipito-cervical fusion (OCF) can be considered.[13] OCF is a surgery that aims at a biomechanical stabilization of the craniocervical junction. Patients with objective radiological findings, a clinical picture supportive of the diagnosis, a positive response to traction, and who are significantly impaired may be candidates for this surgery. A common method involves internal fixation of the upper spine to the skull by mechanical rods and screws. (However, rod-wire, rigid rod-screws, occipital hooks and cervical claws are all methods currently in use.[47]) During surgery, titanium hardware is used to fixate the occiput, axis and atlas (i.e., C0 to C2) while rib graft or cadaver bone graft is used to help the bones fuse together. Wire methods are less biomechanically stable than rod methods and have high rates of dural laceration.[47] Screw and rod fixation methods have lower complication rates and higher rates of successful fusion.[48] Fusion rates across all hardware methods range from 89 to 100%.[47] When cervical instability is present below C2, additional vertebrae may also be fused if the patient is symptomatic.

Outcomes, risks & complications[edit | edit source]

The outcome of OCF is generally favorable with most patients experiencing symptom relief post-surgery.[13] The complications of OCF however can be serious[49] and occur in an estimated 7% to 33% of patients.[3][48][2][50][47] Common complications include screw failure, wound infection, dural tear and cerebrospinal fluid leakage[2] In some cases revision surgery is needed to treat infection or to remove hardware. Severe complications can include meningitis and accidental injury of the vertebral artery by misplaced screws.[51]

A meta-study of 2274 procedures across 22 studies[47] found the following complication rates:

Complication type Prevalence rate
Hardware failure after fusion non-union 7%
Wound infection 3.8%-11%
Vertebral artery damage 1.3%-4.1%
Dural tears 0% to 4.2%

Meta-studies place the rate of death from fusion surgery at 0-0.6%.[47][48]

Side effects[edit | edit source]

OCF causes a substantial reduction in the neck’s range of motion, estimated at approximately 40% of total cervical flexion–extension.[52]

Cost[edit | edit source]

OCF is estimated to cost tens of thousands of dollars, although some insurance schemes fully cover the cost of surgery depending on the country located and neurosurgeons involved.

Stem cell therapy[edit | edit source]

Some clinics offer stem cell therapy in order to regenerate the area, ligaments, connective and other tissues that may be damaged in the area.[citation needed]

Dysautonomia and CCI in EDS[edit | edit source]

As CCI might lead to a compression of the brain stem, some researchers speculate this might cause some of the autonomic symptoms such as tachycardia and orthostatic intolerance that are frequently seen in patients with Ehlers Danlos Syndromes (EDS). In a 2007 influential paper Milhorat et al. followed-up on patients with Chiari malformation who did not improve with treatment and surgery. The authors discovered that many of these patients suffered from EDS and had other structural abnormalities at the upper spine such as CCI and cranial settling. Milhorat et al. speculated that the resulting compression of the brainstem might be the cause of the autonomic and other symptoms these patients were suffering from.[53] In conference presentations, neurosurgeons have indicated that they think CCI can cause dysautonomia symptoms such as postural orthostatic tachycardia syndrome (POTS) [54][55][37]

Henderson et al. tested this theory by following 20 CCI patients with comorbid Chiari Malformation and hereditary hypermobility connective tissue disorders for a period of 5 years after OCF-surgery. Patients were satisfied with the surgery and experienced significant improvements in some CCI-related symptoms such as vertigo, headaches, imbalance, dysarthria dizziness or frequent daytime urination. There was however only a small increase in objective outcomes such as work resumption with 60% of patients remaining unable to work or go to school. Participants attributed this to other medical problems related to EDS such as musculoskeletal pain, fatigue, gastrointestinal issues and POTS, indicating these were not significantly improved after OCF-surgery.[13]

Mechanical basis theory[edit | edit source]

Five ME/CFS patients diagnosed with CCI (some also had EDS) reported to have experienced remarkable improvements and even remission of their ME/CFS symptoms following OCF-surgery.[56][57] They speculate that mechanical compression of the brainstem due to CCI has the potential to cause characteristic ME/CFS symptoms such as post-exertional malaise[58], although this theory is currently not supported by scientific evidence. The current literature does not suggest a connection between ME/CFS and CCI. Others have raised concerns about CCI surgery in patients with ME/CFS given the lack of research on OCF in this patient population.[59]

Synonyms[edit | edit source]

  • Syndrome of Occipitoatlantialaxial Hypermobility[14]
  • Hypermobility of the Craniocervical Junction[60]

See also[edit | edit source]

Learn more[edit | edit source]

References[edit | edit source]

  1. 1.01.11.21.31.41.5 Henderson, Fraser C.; Austin, Claudiu; Benzel, Edward; Bolognese, Paolo; Ellenbogen, Richard; Francomano, Clair A.; Ireton, Candace; Klinge, Petra; Koby, Myles (2017). "Neurological and spinal manifestations of the Ehlers–Danlos syndromes". American Journal of Medical Genetics Part C: Seminars in Medical Genetics. 175 (1): 195–211. doi:10.1002/ajmg.c.31549. ISSN 1552-4876. 
  2. 2.02.12.2 Choi, Sung Ho; Lee, Sang Gu; Park, Chan Woo; Kim, Woo Kyung; Yoo, Chan Jong; Son, Seong (Apr 2013). "Surgical Outcomes and Complications after Occipito-Cervical Fusion Using the Screw-Rod System in Craniocervical Instability". Journal of Korean Neurosurgical Society. 53 (4): 223–227. doi:10.3340/jkns.2013.53.4.223. ISSN 2005-3711. PMC 3698232Freely accessible. PMID 23826478. 
  3. 3.03.13.2 Ashafai, Nabeel S.; Visocchi, Massimiliano; Wąsik, Norbert (2019). "Occipitocervical Fusion: An Updated Review". Acta Neurochirurgica. Supplement. 125: 247–252. doi:10.1007/978-3-319-62515-7_35. ISSN 0065-1419. PMID 30610329. 
  4. 4.04.14.24.34.44.54.6 Henderson, Fraser C. (2016). "Cranio-cervical Instability in Patients with Hypermobility Connective Disorders". Journal of Spine. 05 (02). doi:10.4172/2165-7939.1000299. ISSN 2165-7939. 
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  54. Craniocervical Instability (Dr Henderson the 2012 EDNF Confrence). Minute 12.10.
  55. Dr Milhorat from The Chiari Institute at the 2005 ASAP.
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Myalgic encephalomyelitis (ME) - A disease often marked by neurological symptoms, but fatigue is sometimes a symptom as well. Some diagnostic criteria distinguish it from chronic fatigue syndrome, while other diagnostic criteria consider it to be a synonym for chronic fatigue syndrome. A defining characteristic of ME is post-exertional malaise (PEM), or post-exertional neuroimmune exhaustion (PENE), which is a notable exacerbation of symptoms brought on by small exertions. PEM can last for days or weeks. Symptoms can include cognitive impairments, muscle pain (myalgia), trouble remaining upright (orthostatic intolerance), sleep abnormalities, and gastro-intestinal impairments, among others. An estimated 25% of those suffering from ME are housebound or bedbound. The World Health Organization (WHO) classifies ME as a neurological disease.

ME/CFS - An acronym that combines myalgic encephalomyelitis with chronic fatigue syndrome. Sometimes they are combined because people have trouble distinguishing one from the other. Sometimes they are combined because people see them as synonyms of each other.

Adverse reaction - Any unintended or unwanted response to the treatment under investigation in a clinical trial.

Tachycardia - An unusually rapid heart beat. Can be caused by exercise or illness. A symptom of postural orthostatic tachycardia syndrome (POTS). (Learn more: www.heart.org)

Postural orthostatic tachycardia syndrome (POTS) - A form of orthostatic intolerance where the cardinal symptom is excessive tachycardia due to changing position (e.g. from lying down to sitting up).

Postural orthostatic tachycardia syndrome (POTS) - A form of orthostatic intolerance where the cardinal symptom is excessive tachycardia due to changing position (e.g. from lying down to sitting up).

Post-exertional malaise (PEM) - A notable exacerbation of symptoms brought on by small physical or cognitive exertions. PEM can last for days or weeks. Symptoms can include cognitive impairments, muscle pain (myalgia), trouble remaining upright (orthostatic intolerance), sleep abnormalities, and gastro-intestinal impairments, among others.

Myalgic encephalomyelitis (ME) - A disease often marked by neurological symptoms, but fatigue is sometimes a symptom as well. Some diagnostic criteria distinguish it from chronic fatigue syndrome, while other diagnostic criteria consider it to be a synonym for chronic fatigue syndrome. A defining characteristic of ME is post-exertional malaise (PEM), or post-exertional neuroimmune exhaustion (PENE), which is a notable exacerbation of symptoms brought on by small exertions. PEM can last for days or weeks. Symptoms can include cognitive impairments, muscle pain (myalgia), trouble remaining upright (orthostatic intolerance), sleep abnormalities, and gastro-intestinal impairments, among others. An estimated 25% of those suffering from ME are housebound or bedbound. The World Health Organization (WHO) classifies ME as a neurological disease.

The information provided at this site is not intended to diagnose or treat any illness.
From MEpedia, a crowd-sourced encyclopedia of ME and CFS science and history.