CRANIOCERVICAL INSTABILITY
ATLANTOAXIAL INSTABILITY
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CCI and AAI are two forms of spinal instability, affecting the skull-C1 vertebrae (CCI) and C1-C2 vertebrae (AAI). They are both structural instabilities that can lead to pathological deformation of the brainstem and upper spinal cord.
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This page mainly focuses on CCI+AAI caused by lax ligaments failing to keep the craniocervical junction stable.
SYMPTOMS
Symptoms include
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Headache
Neck pain
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Altered vision
Diplopia
Nystagmus
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Tinnitus
Hearing loss
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Dysautonomia​
Postural orthostatic tachycardia (high heart rate upon standing)
Orthostatic intolerance
(Pre) syncope
Dizziness
Vertigo
Urinary tract dysfunction, urgency, frequency
GI dysfunction, constipation
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Weakness
Spasticity
Clumsiness
Altered sensation, numbness (dysesthesia, paresthesias)
Abnormal gait
Paralysis
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Sleep apnea
Sleep disorders
Fatigue
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Choking, dysphagia
Trouble breathing
Slurred speech, dysarthria
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DIAGNOSIS
CCI and AAI is diagnosed based on three things - 1) imaging, 2) symptoms and 3) positive neurological findings.
A neurosurgeon will look at a patient's imaging and take certain measurements, such as the clivo-axial angle, which if abnormal suggests CCI or AAI. However these measurements cannot stand alone.
A neurosurgeon will also go through the patients symptoms, past medical history and do a neurological exam. The symptoms and neurological findings are important to make a final diagnosis while also assessing the severity of the patient's condition.
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For diagnosing CCI, an upright flexion extension MR(uMRI)I is the gold standard. A digital motion xray(DMX) can be used to further confirm the diagnosis. An ordinary supine brain MRI should also be done to rule out or diagnose comorbidities such as intracranial pressure issues, chiari malformation etc.
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For diagnosing AAI, a rotational CT scan is considered the gold standard. An upright MRI with rotation can also be used to make a diagnosis.
MEASUREMENTS
CAUSES
There's a number of different conditions that can cause CCI and AAI, some which are widely recognized, while others are still relatively unknown by many medical professionals.
The common ones include
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Autoimmune connective tissue disorders such as rheumatoid arthritis and lupus
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Genetic conditions such as downs syndrome and osteogenesis imperfecta
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Conditions causing tumors in the craniocervical junction, such as Neurofibromatosis
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Other acquired bone conditions such as Paget's disease
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Severe trauma to the craniocervical junction and head
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Less commonly known is
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Hereditary connective tissue disorders, also known as hypermobility syndromes, such as Ehlers-danlos syndrome and the hypermobility spectrum disorders
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Trauma to the craniocervical junction(CCJ) , that would usually be considered less severe, such as whiplash
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Grisel syndrome, subluxation of the atlantoaxial joint (C1/2) due to inflammatory ligamentous laxity following an infectious process in the head and neck
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In these two conditions the instability do not stem from a malformation or degeneration of the bone, but from the ligaments in the CCJ being too lax, to properly stabilize the vertebra. In conditions such as ehlers-danlos syndrome, the laxity comes from a genetic defect of the connective tissue, while in cases of trauma, the laxity stems from the ligaments being stretched during the traumatic incident.
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MANAGEMENT
Unfortunately there's no cure for CCI and AAI, but there is different ways to manage it.
The main ones being physical therapy, symptom management, bracing, and as a last resort a spinal fusion surgery can be done.
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In mild to moderate cases, physical therapy, bracing and treating symptoms can be enough to manage the patient's condition.
The physical therapy and symptom management will vary from patient to patient, however isometric neck exercises are one of the most common recommendations. Symptom management might include treating conditions caused or exacerbated by CCI and AAI, such as dysautonomia, medications to manage pain, nausea etc
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In severe cases this won't be enough to manage the condition, and spinal fusion will be recommended.
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SURGERY
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