Working in a specialised hypermobility practice has given me a lot of exposure to less understood conditions such as upper cervical instability in hypermobility. Very often, these patients’ routine neurological and radiological examinations appear normal, so it is up to the hypermobility-aware health practitioner to recognise the problem. In this blog post I will attempt to explain the link between hypermobility and upper cervical instability and their complex intermingling relationships with other related comorbidities.
What is Hypermobility?
Hypermobility is a connective tissue disorder. Contrary to popular belief, hypermobility does not only affect the joints. Being a spectrum, individuals with hypermobility can range from those who are asymptomatic to those with widespread complex symptoms with nearly every organ system affected.
Emerging research is showing that Hypermobility Spectrum Disorders (HSD) and hypermobile Ehlers-Danlos Syndrome (hEDS) are far more common than previously thought. The prevalence of general hypermobility in the adult population ranges from 10 to 30% (1, 2). Most individuals with general hypermobility remain asymptomatic throughout their lives, but compared to those who are not hypermobile, they have an increased risk of musculoskeletal complaints (2), especially in the neck, back and upper body (1, 2).
For more information on hypermobility and its relationship with pain and fatigue, see my previous Physio Network reviews here.
Hypermobility and Upper Cervical Instability
The cranio-cervical junction is the most mobile part of the spine. Upper cervical instability, particularly cranio-cervical instability (CCI) and atlanto-axial instability (AAI), are potential complications of hypermobility (3). Connective tissue laxity in the upper cervical region can compromise the spinal cord, brain stem, and vascular system leading to neurological symptoms. Whilst CCI and AAI are well accepted in patient population with conditions such as rheumatoid arthritis, Down’s Syndrome, and osteogenesis imperfecta, the same recognition is not afforded to the hypermobility syndromes (4).
In a study of 223 patients, the prevalence of the common comorbidities associated with EDS are reported as follows (5):
- Postural Orthostatic Tachycardia Syndrome (POTS) – 88%
- Mast Cell Activation Syndrome (MCAS) – 81%
- Tethered Cord Syndrome – 40%
- Chairi Malformation – 24%
- Craniocervical Instability (CCI) (21%)
- Complex Regional Pain Syndrome (20%)
There is a lot of symptom overlap with the comorbidities reported above. Of the same cohort of patients in the study, 52% of patients with EDS have symptoms suggestive of CCI when a Chiari malformation is present, and CCI is reported to nearly always occur with POTS and MCAS.
Cranio-cervical Instability (CCI) versus Atlanto-axial Instability (AAI)
The difference between CCI and AAI is in the region of instability. CCI is more commonly reported in the hypermobility literature than AAI.
Cranio-cervical instability (CCI) in hypermobility is related to incompetent ligamentous connections from the skull to the spine (3). Biomechanically, flexion/extension is the most prominent movement at the atlanto-occipital (CO/1) junction (3, 4). CCI can result in the deformation of the brainstem, cranial nerves, upper spinal cord, vertebral artery, and affect cerebrospinal fluid (CSF) flow from the cranium.
CCI is associated with basilar invagination (or ventral brainstem compression), resulting in a range of neurological symptoms such as limb weakness, abnormal reflexes, paraesthesia, headache, neck pain, dizziness, altered vision and hearing, dyspnoea, dysphonia, altered gait, sexual function and bladder/bowel problems.
The atlanto-axial junction (AAJ) is the most mobile joint of the body (3), with its mechanical stability determined predominantly by the alar and transverse ligaments. In children, hypermobility of the AAJ is common and over 40 degrees of rotation may be observed unilaterally, but in the adult, at 35 degrees of rotation of C1 over C2 the contralateral vertebral artery gets overstretched and kinked (3).
The common presenting features of AAI are neck pain, and suboccipital headaches.
There may be vertebral artery disruption related symptoms such as (3):
- Visual changes
Other symptoms include (3):
- Facial pain
- Respiratory issues
Neurological findings may include hyper-reflexia, dysdiadochokinesia, and hypoesthesia to pinprick (3).
There are lots of overlaps in the symptoms associated with CCI and AAI. In some literature, these overlapping symptoms are referred to as the “cervical medullary syndrome” (3, 6).
CCI and AAI diagnoses are dependent on: 1) history and clinical findings of cervical medullary syndrome, 2) neurological findings, and 3) radiological findings (3, 6). Below I discuss my general approach to assessing my patients with suspected upper cervical instability.
In practice I would pay particular attention to patients who report persistent neck pain, headaches, dizziness, debilitating fatigue and neurological abnormalities. Some may report feeling like they have a “bobble head”, i.e. difficulty keeping their head on neck or feeling like their head is too heavy for the neck to support. Symptoms can be worse at the end of the day and may be relieved lying down.
It is worth assessing the patient for past head and neck trauma, auto-immune conditions (e.g. systemic lupus and rheumatoid arthritis), cancer, infections, and congenital or genetic conditions (e.g. Down’s Syndrome, Osteogenesis Imperfecta) which can lead to structural instability of their upper cervical spine (6).
In terms of differential diagnosis, be aware that patients with upper cervical instability may report symptoms similar to other diagnoses commonly reported in the hypermobility population (3, 6):
- Postural Orthostatic Tachycardia Syndrome (POTS) and dysautonomia
- Chiari malformation
- Tethered cord syndrome
- Cerebrospinal Fluid leak
- Spontaneous Intracranial Hypotension
- Idiopathic intracranial hypertension (Pseudotumor Cerebri)
I generally refrain from doing upper cervical ligamentous testing (e.g. sharp-purser test, alar ligament, transverse ligament, and tectorial membrane tests) in patients with hypermobility as they have poor diagnostic accuracy (7), and can be highly provocative. Referral to an EDS-aware neurosurgeon is usually made to help confirm diagnosis.
The physical examination includes:
- Neurological – dermatomes, myotomes, upper limb neurodynamic/tension tests, reflexes
- Cervical sensorimotor assessment – cervical proprioception and oculomotor tests. For more information about sensorimotor assessment and rehabilitation of the neck, see Chris Worsfold’s Masterclass
- Posture – tolerance to upright posture and ergonomics
- Neck, jaw and upper body function – including range of motion, joint mobility, and muscle strength.
The problem for those with cervical instability and hypermobility is that most will have a “normal” radiological report, because some radiologists may not recognize instability related to hypermobility. It may also be due to incorrect examination or interpretation of the study itself. For example, the brainstem may appear normal on a routine MRI in the supine position, but present with pathological ventral brainstem compression in the flexion view in upright sitting (3, 4).
At present, there is no universal consensus on the ideal radiological measurements and when they should be used (8). However, I think most would agree on radiological evaluation using an upright MRI in cervical flexion/extension and rotation (8). The upright MRI is helpful in assessing the altered dynamics and effect of gravity on ligamentous laxity of the upper cervical spine, which may otherwise produce borderline findings in a standard supine MRI (6). The upright MRI technology is unfortunately not readily available in most medical facilities which means less accessibility for patients (8).
For CCI, the radiologists may assess three main metrics for diagnosis:
- Clivo-axial angle
- Horizontal Harris
- Grabb-Mapstone Oakes
Others may assess for CCI using a flexion/extension plain radiographs and CT scan (6, 8).
AAI is difficult to assess radiologically, but C1 and C2 rotation is evaluated and benchmarked against normal range (>41 degrees is abnormal) (6,8).
At present the management of CCI and AAI falls under these two categories:
Conservative management of upper cervical instability includes continued patient education, physical therapy and the use of a cervical collar to keep the neck stable. Some patients may benefit from exercising with their neck brace, aiming to gradually wean it off. There are some who need to get into more rigid neck braces such as the Aspen Vista and Miami J collars.
Surgery is the last resort for patients who have failed conservative management. This usually involves occiput to C1/2 stabilisation fusion (3, 9). Anecdotally, some patients have reported substantial recoveries following surgery, but others did not benefit as much (8). However, like all other surgeries, there are many factors that can contribute to surgery success. In 2019, a study on 22 patients with hypermobility reported sustained improvements in pain and function five years after cranio-cervical fusion stabilisation surgery (9). There is otherwise little research surrounding post-surgical outcomes and recovery, and few regarding rehabilitation protocols. Some patients have also been shown to benefit from occipital nerve blocks and cervical epidural or foraminal injections for pain control and symptom relief (8).
Recognition of upper cervical instability in those with hypermobility is still at the early stage, but fast evolving. Much is unknown about the conservative management of upper cervical instability in those with hypermobility. In my experience, a combination of patient education, neck bracing and exercise can help steer some patients away from having to undergo stabilisation surgery. It really helps to work with a supportive multi-disciplinary team who understand hypermobility. Thankfully, awareness is growing and knowledge evolving.