Craniocervical instability: what it is, how it is assessed and what the evidence says

The craniocervical junction is the region where the base of the skull sits on the first two bones of the neck (the atlas, C1, and axis, C2). It allows a wide range of nodding and turning movements and is held together by strong ligaments. The brainstem and the upper spinal cord pass through it.

Craniocervical instability is the term used when those ligaments are thought to allow too much movement. A paper published in Neurosurgical Review describes it as occurring in conditions of weakened ligaments, such as trauma, infection and connective tissue disorders. Because the brainstem is nearby, the concern is that excess movement could compress or irritate it, a proposal sometimes called cervicomedullary syndrome.

The topic is controversial. The UCL research summary says it has been proposed that hypermobility of the craniocervical junction is a major cause of headaches, neck pain and other neurological symptoms in joint hypermobility disorders, and that this has been said to be diagnosable by upright dynamic MRI and treatable by craniocervical fixation surgery, but that this imaging technique is yet to be validated.

The NHS says hypermobile Ehlers-Danlos syndrome is the most common type of EDS and that people with it may have joint hypermobility, loose, unstable joints that dislocate easily, joint pain and clicking joints, extreme tiredness, skin that bruises easily, digestive problems and dizziness and an increased heart rate after standing up. It says the diagnosis is based on a person's medical history and a physical examination, and that people who do not meet the criteria may be diagnosed with hypermobility spectrum disorder, which is treated in the same way.

The NHS joint hypermobility page describes symptoms such as joint pain and stiffness, sprains and strains, joints that dislocate, poor balance or co-ordination and tiredness, and says physiotherapy, occupational therapy or podiatry can help reduce pain and the risk of dislocations and improve muscle strength, fitness, posture and balance. Neither NHS page makes a claim about craniocervical instability itself, so the discussion of the neck in this context rests on specialist and research sources.

The UCL summary describes people with hypermobility disorders who frequently suffer from headaches, neck pain and other neurological symptoms. The surgical literature, for example the paper by Henderson and colleagues, lists severe headache and neck pain, lower cranial nerve deficits, myelopathy and the cervical medullary syndrome among the features in the patients it studied.

These symptoms are not specific. They overlap with migraine, tension-type headache, postural tachycardia, autonomic problems, anxiety, sleep disorders, fibromyalgia and a range of other conditions that are far more common. For this reason an assessment has to consider the whole picture rather than the neck alone.

• Neck pain and a feeling that the head is heavy or hard to hold up.

• Headaches, often at the back of the head or worse when upright or after movement.

• Dizziness, light-headedness, visual disturbance, or tinnitus.

• Difficulty swallowing, voice change, or sleep problems.

• Tingling, numbness or weakness in the limbs, or clumsiness, which should be assessed promptly.

A GP will usually begin with a history and examination, including a neurological examination, and consider other explanations for headache and dizziness. Referral may be made to neurology, rheumatology, a hypermobility clinic or, for structural questions, a spinal or neurosurgical service. Standard MRI of the brain and cervical spine is used to look for conditions such as Chiari malformation, tumours or cord compression.

The role of upright or dynamic imaging is where views differ. The UCL study, which is registered on the Health Research Authority site, is comparing upright dynamic MRI in healthy controls, people with hypermobility without symptoms and people with hypermobility and symptoms, in order to establish normal ranges and test whether the abnormalities relate to symptoms. Its stated rationale is that the results will either support larger surgical trials or provide data against potentially unnecessary invasive and expensive neurosurgical treatment.

Clinicians generally take care with any examination that stresses the neck. Anyone undergoing assessment should ask who is responsible for interpreting dynamic imaging and what criteria are being used.

Most people with neck pain and hypermobility are managed without surgery, with physiotherapy to improve muscle control and posture, pacing and pain management, treatment of coexisting headache or autonomic problems, and support for sleep and mood. The NHS says that in hypermobility physiotherapy can help to reduce pain and the risk of dislocations and to improve muscle strength, fitness, posture and balance.

Surgery, usually occipito-cervical fusion, is performed in a small number of centres for selected patients. The Henderson paper reports a retrospective outcomes analysis of 53 patients with EDS who underwent fusion after failed non-operative management and found significant improvement in headache, neck pain and function. It is a single-surgeon retrospective series from the USA, without a control group, so it cannot show how the same patients would have fared without surgery, and it is not UK guidance.

The UCL summary expresses the uncertainty plainly: if their results support the hypothesis, they would provide evidence supporting larger surgical trials, and if not they would provide data against potentially unnecessary invasive treatment. Anyone considering fusion should weigh the permanent loss of neck movement, the risks of a major operation and the limits of the evidence.

Call 999 or go to A&E for a sudden severe headache, weakness or numbness down one side of the body, face drooping, slurred speech, loss of consciousness, difficulty breathing, or new loss of bladder or bowel control, particularly after a neck injury. The NHS lists weakness or numbness down one side, blurred vision or loss of sight, dizziness or falling over and a severe headache among the symptoms of stroke and advises calling 999.

Neck problems after significant trauma, with fever, or with progressive limb weakness or clumsiness also need prompt assessment. These features are not explained by hypermobility alone.

Practical measures include pacing activity, avoiding positions that provoke symptoms, supporting the head and neck with pillows, ergonomic adjustments at work, and a tailored exercise programme supervised by a physiotherapist familiar with hypermobility. The NHS suggests that people with joint hypermobility can improve joint and muscle strength and reduce strain through self-care and exercise.

Chronic pain and uncertain diagnoses can be exhausting. Peer support from groups such as EDS Support UK and the Hypermobility Syndromes Association can help, although information on the internet varies widely in quality, and it is sensible to compare claims with NHS and academic sources.

On the NHS, assessment is through the GP, then neurology, rheumatology or a hypermobility service, with neurosurgical or spinal opinion where structural disease is suspected. There is no single national pathway for craniocervical instability specifically, and practice varies between regions.

Some people seek private upright MRI or surgical opinions, including overseas. These can be costly, and the interpretation of dynamic imaging is not standardised. It is reasonable to ask any clinician what criteria they use, what the alternatives to surgery are, how many such operations they perform and what their outcomes are, and to share any private findings with your NHS clinicians.