Atlantoaxial Instability (IAA) (2023)

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Craniocervical instability and atlantoaxial instability are diagnoses that often cause great disability and confusion. We're going to go through it all here to make sure you know what these terms mean, the common symptoms of these issues, like thesediagnoses are made, which istreatmentoptions imply. Let's dig.

What is Atlanto-Axial Instability (AAI), also known as Craniocervical Instability (CCI)?

CCI means craniocervical instability and AAI means atlantoaxial instability. Before we understand what these terms mean, let's review the anatomy of the craniocervical junction, or where the cervical spine meets the skull.

The upper part of the neck where the spine meets the head is called the craniocervical junction, or CCJ. The seven bones of the spine or neck vertebrae are numbered from C1 to C7. The skull is numbered C0. Bones C0-C2 form the CCJ. In fact, another name for instability in this area is CCJ Instability.

While the lower bones of the neck have a cushioning disc at the front and two joints at the back at each level,the upper part of the neck is constructed differently.

The C1 bone is called the atlas and the C2 bone has a protruding part (dens) that fits into the atlas:

This CCJ area has many ligaments connecting C1 to C2 and C2 to the skull. These main ligaments are:

  • Yes, like that
  • Transversal
  • Accessory

Together, the elements described here function as a functional unit for attaching the skull to the neck. Here's how these ligaments fit together:

Atlantoaxial instability and craniocervical instability basically mean the same thing: that those ligaments that attach the head to the neck are damaged, leading to instability, but they refer to different parts of the same functional unit, the CCJ.

What is instability and why is it so important?

Instability simply means that the bones are moving a lot, usually due to damaged ligaments. In the spine, this can cause nerves to snap and joints to be damaged. At the craniocervical junction, instability can cause the upper cervical spinal nerves to become irritated, leading to headaches. In addition, the C0-C1 andC1-C2 facet jointscan also be damaged. Also, there are other nerves that exit the skull through here that can be irritated, such as the vagus nerve, which can cause a rapid heartbeat.

What is the difference between CCI and AAI? CCI refers to instability at any part of the craniocervical junction, while AAI refers to instability at C1-C2.The only reason to differentiate them is usually that patients with atloaxial instability can be treated with less invasive C1-C2 fixation screws, whereas ICC patients may require more extensive, as you'll see below, surgery is not always the best treatment for these conditions.

What are the symptoms of AAI?

HeCHF symptoms/AAI includes:

  • headaches
  • Dizziness/Imbalance/Vertigo
  • visual disturbances
  • Mental confusion
  • Fast heart rate (tachycardia)
  • Random area of ​​numbness or pain or other symptoms such as an upset stomach.

Mental confusion

Brain fog is one of the characteristic symptoms of craniocervical instability. It is characterized by slow thinking, difficulty concentrating, confusion, lack of concentration, forgetfulness or confused thinking. The severity of symptoms varies from patient to patient. Have you ever had a severe hangover or high fever and had trouble concentrating or performing simple tasks? That brain fog. Some patients describe it as a general confusion of thinking, as if they had cotton wool stuck to their head. In addition to cognitive deficits, many patients also report generalized mental fatigue that makes complex tasks almost impossible. The exact cause of brain fog is unknown. Possible explanations include…

Read more about brain fog

Neck pain/neck pain

Neck pain is also known as neck pain, which is a very common and unpleasant pain. Read here to learn more about symptoms, diagnosis, and treatment options. We will discuss other causes of neck pain. What symptoms are associated with neck pain? How is neck pain diagnosed? What are the treatment options for neck pain? Neck pain is a medical term used to describe neck pain. It is very common and affects approximately 2/3 of the population at some point in their lives. Neck pain is the fourth leading cause of disability. Risk factors include injuries, history of musculoskeletal and neck pain, office-intensive jobs, low social support, job insecurity, physical weakness, and improper computer station setup.

Read more about Cervicalgia / Neck pain

chronic fatigue

Have you ever done a challenging all-day hike, athletic endeavor, or worked a double shift and felt exhausted the next day? Later that day or the next morning, moving around the room may have seemed almost impossible and had Herculean power. Now imagine this happening daily without any provocation. Simple tasks 24/7 are almost impossible due to lack of strength and energy. This is chronic fatigue and is one of the common symptoms associated with craniocervical instability. Severity can vary, and in severe cases, patients are confined to their beds. Aggravating and palliative factors often cannot be identified.

Read more about chronic fatigue

chronic headaches

Do you suffer from chronic headaches? Maybe it's a daily problem, maybe once a week, maybe even less often, but one thing is for sure: when a chronic headache strikes, it can be a real headache - literally. To effectively deal with chronic headaches, you must first determine whether the pain is caused by a neck problem. Let's take a look at some neck problems that can cause headaches: Weak Neck Muscles – The average head weighs around ten pounds, so when your neck muscles are weak, it can make your head feel weak, a bit like a bowling ball that your neck can't balance. There are many muscles that, along with the cervical spine, work together to help support the neck and facilitate movement...

Read more about chronic headaches

Gastrointestinal (GI) issues

Gastrointestinal (GI) issues can be debilitating and affect a person's well-being and ability to participate in life with confidence. Symptoms vary and may include nausea, bloating, constipation, diarrhea, delayed motility, abdominal pain, irritable bowel-like symptoms, heartburn, and reflux. Gastrointestinal problems can be caused by structural and functional problems within the intestine itself. Examples include hiatal hernia and bacterial overgrowth. Less appreciated is the fact that many patients with craniocervical instability (CCI) can also have significant gastrointestinal problems. Unfortunately, many of these patients undergo extensive and expensive GI evaluations, only to be told that their tests and studies are normal. This can be extremely frustrating. For these patients...

Read more about gastrointestinal (GI) issues

Muscle pain after cervical fusion surgery

Cervical fusion is major surgery that involves joining one or more bones in the spine using screws, pins, and plates (1). The hardware can be placed in front (anterior) or behind (posterior) of the cervical spine. The disc between the bones in the spine is usually removed and replaced with a bone graft or spacer. The neck is formed by 7 bone blocks numbered from 1 to 7. The letter C is associated with numbers to designate the cervical spine. Therefore, the neck bones are C1 to C7. Interspersed between the bones of the neck are important shock absorbers called discs. Cervical fusion surgery removes...

Read more about muscle pain after cervical fusion surgery

Neck pain and dizziness

Our body's balance system is made up of three separate systems that work together to keep the body in balance: the eyes, the inner ear, and the upper cervical spine. The upper cervical spine contains and processes information about your position in space and communicates this information to your inner eyes and ears via nerves. There is a constant road of electrical signals between the cervical spine, inner ear and eyes that keep us upright, make us aware of our position and allow us to walk, move and run. This balance system requires the inner ear, eyes and cervical spine to be operational...

Read more about neck pain and dizziness

Pain at the base of the neck and skull

The base of the skull is a complex area. It involves the upper cervical spine, facet joints, muscles, tendons, ligaments and nerves. Irritation or injury to any of these structures can cause pain at the base of the skull. Unfortunately, many providers don't understand this area. This can lead to a delay in treatment and unnecessary pain and suffering. Treatment options depend on the underlying cause of the pain. Conservative therapy in the form of physiotherapy, when appropriate, is the best first-line treatment. Steroids are often recommended but should be avoided as they are toxic to orthopedic tissue and have significant side effects...

Read more about pain at the base of the neck and skull

fast heart rate

A rapid heart rate can be debilitating, compromising your well-being and ability to perform the easiest of tasks, and is unfortunately a common symptom of craniocervical instability or other upper cervical conditions. The normal heart rate for an adult at rest is between 60 and 85 beats per minute. Tachycardia is a medical term for a heartbeat of 100 beats per minute. Most of us have experienced a rapid heartbeat after exertion or strenuous exercise. Remember how your heart raced after wind races or chasing your dog over the fence? Your heart is beating rapidly in your chest. Unfortunately, for some patients, this is the baseline.

Read more about rapid heart rate


Conventional wisdom holds that torticollis symptoms can be treated with non-surgical remedies. However, not all torticollis symptoms are benign, and leaving a stiff neck untreated can lead to limited range of motion that can affect your overall health and quality of life. A stiff neck can cause pain, tightness, clicks and pops and affect daily activities. A thorough examination of torticollis symptoms can determine the exact condition that affects torticollis. Where does the neck hurt? Neck stiffness can occur from the base of the head up to the shoulders. This can be associated with pain, crepitus or popping sensations and can...

Read more about torticollis


Do you remember the ringing in your ears after a loud rock concert or a very intense sporting event? It's that ringing or buzzing sound that slowly gets better the next day over the course of several hours. Unfortunately for some people, ringing in the ears is not due to an external event. Even worse is that it doesn't resolve with time. This condition is called tinnitus. It is a medical condition characterized by tinnitus or other noise in one or both ears that is NOT caused by external sound. Other people cannot hear the ringing that patients describe. It's a common problem. It affects approximately 15-20% of people.

Read more about tinnitus

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How is the AAI tested? (Exams and Diagnosis)

ICC and AAI are often diagnosed through the patient's symptoms and a manual test by the physician or therapist or diagnostic imaging. However, remember that for many patients it is difficult to obtain adequate tests to confirm the diagnosis. let's dive

Highly trained upper cervical chiropractors and manual physical therapists can usually diagnose CCI using manual techniques. This means that the patient is seeing an upper cervical chiropractic specialist (NUCCA or Atlas-Orthogonal) and the patient is only getting temporary relief from manual adjustments. Or, if the patient is seeing a manual physiotherapist (very specialized PT focusing on the spine), then specific diagnostic practice tests (allar stress test) are done.

There are many different types of images that can be taken to help make a diagnosis:

  • Dynamic Motion X-Rays (DMX)
  • motion computed tomography
  • Static MRI of the upper neck
  • dynamic magnetic resonance

Dynamic Motion X-Rays (DMX)

This is a real-time x-ray of the neck. The aim is to allow the patient to move around and see how the bones line up or move a lot. To learn more, watch my video below:

motion computed tomography

Computed tomography is a specialized 3D radiography and, in this case, it is performed with the patient's head turned to the right or left. Excessive movement, usually at C1-C2, can be used to make a diagnosis of CCI.

Static MRI of the upper neck

This test can be performed in two ways. The first is a routine MRI, where different measurements can be taken, such as:

  • Grabb Oakes
  • Axial Tilt-Angle (CXA)
  • power ratio

To learn more about Grabb-Oakes, check out my video below:

power ratio:

dynamic magnetic resonance

MRI scans are usually done with the patient lying very still on their back in a tube, but they can also be done with the patient sitting with movement. This can be used to see if the bones in the upper part of the neck move too much with movement.

How is atlantoaxial instability treated?

There are three main types of treatment:

  • Conservative Care: Chiropractic and Physical Therapy
  • injections
  • Surgery

conservative care

There are two main disciplines in chiropractic which are NUCCA (National Upper Cervical Chiropractic Association) and AO (Atlas-Orthogonal). This usually involves measuring the angles of the bones in the upper neck on an X-ray and then specific manipulations to move them back into place. Patients who get only temporary relief are more likely to be chronically unstable. There are also highly trained physical therapists and osteopaths who specialize in the upper neck. These providers may also offer manipulative care with the same caveats as above.


There are several different types of injections here, including:

  • Intra-articular facet injections
  • proloterapia posterior
  • IPLC procedure

Intra-articular facet injectionscervical superiorfacet joints are very specific and difficult to perform. These are joints in the neck that can be hit or damaged when there is CCI or AAI (AAI impactingC1-C2). There are only a handful of doctors in the United States who have a lot of experience injecting these joints using X-ray guidance and contrast to ensure placement. These joints may be injected with substances such as PRP or bone marrow concentrate, which can help reduce pain or heal damage.

Posterior prolotherapy involves injecting the ligaments at the back of the neck (not the alar, transverse, or accessory ligaments). While this may help patients with CCI or AAI, unfortunately, in our experience, most patients do not get relief with subsequent prolotherapy.

The PICL procedure involves direct injection of two ligaments that support the head (alar, transverse, or accessory ligaments) from the front. This is a very complex procedure that involves an endoscopy for direct visualization of the back of the throat area, specialized anesthesia, a specialized mouthpiece, and X-ray guidance. In our experience, this procedure can help many patients avoid the need ofneck fusion. Watch our video below to learn more:


The surgical approach here involves fusion, which means the doctor inserts screws and plates to fuse various parts of the upper cervical bones together. These are all higher risk procedures than a mid-level or lower-level routine procedure.cervical fusion. These are the main surgeries:

  • Fixation with screws C1-C2
  • C0-C2 Fusion (Goel and Harms Technique)
  • Occipital-cervical fusion (skull base to C2)

Fixation with C1-C2 screws is probably the most common procedure we see. This involves placing a screw in the C1-C2 joint and is involved in atlantoaxial instability (AAI). The main problems have been:

  • Lack of fusion of the C1-C2 joint. If this joint does not fuse (grow together with the bone), the joint is now destroyed due to surgery and causes pain. In this case, it may be necessary to repeat the procedure.
  • Occipital nerve sacrifice. This is the nerve that runs to the head, so damage to this nerve causes chronic headaches.
  • Screw displacement. The most common thing we see is the screw being placed too deep and into the C0-C1 joint, leading to arthritis in that joint.

A C0-C2 fusion occurs when the doctor inserts screws into the vertebral bodies rather than through the joint itself. This is a longer procedure than fixing with C1-C2 screws. It has many of the same possible complications, including non-fusion and nerve damage.

An occipital-cervical fusion involves extending the hardware to the base of the skull. This is the largest of the three surgeries. It has all the same potential complications, which are usually higher for this procedure as it is the most invasive.

cervical fusion

Cervical fusion is often recommended when chronic neck pain problems get worse over time. What exactly? Cervical fusion is major surgery that involves joining one or more bones in the spine using screws, pins, and plates (1). The hardware can be placed in front (anterior) or behind (posterior) of the cervical spine. The disc between the bones in the spine is usually removed and replaced with a bone graft or spacer. The neck is made up of 7 bone blocks numbered from 1 to 7. The letter C is associated with the numbers to designate the Cervical Column.

Read more about cervical fusion


The other day I was evaluating a patient and reviewing treatment options for his back condition. After discussing the above treatments, we come to the topic of pain relief medications. He explained that he took mostly anti-inflammatories (NSAIDs) and then told me to take a lot of what he has been taking for many years... he takes about 2 grams (2000 milligrams) daily which is about 9-10 medicine capsules per day. I was surprised considering she was pre-diabetic and had high blood pressure, plus her PCP (Primary Care Physician) was ok with it...

Read more about NSAIDs

Occipital Cervical Fusion

An occipital cervical fusion, also known as Occipitocervical Susion, is a major surgery. It is not a routine operation and is a challenging procedure due to the complex anatomy of the upper neck. The procedure involves rods, plates and screws that are placed in the cervical and occipital spine. A plate secured with screws is placed at the base of the occiput. Screws are also placed in one or more cervical bones. The rods then connect the occipital plate to the cervical screws as shown below. The objective of Cervical Occipital Surgery is a bony fusion between the skull and the neck and to relieve…

Read more about Occipital Cervical Fusion

IPLC procedure

CCI stands for Cranial Cervical Instability, which means that the ligaments that support the head are too loose. To solve this problem, we have developed a new procedure called PICL, which stands for Percutaneous CCJ Implant. This is still an experimental procedure that has already changed many lives and helped patients avoid the complication-laden upper cervical fusion. Given the interest in the PICL procedure by patients with ICC, many questions arise. Since the procedure is not yet covered by insurance, some question why it costs more than the copayment and deductible if they decide to have a more invasive cervical fusion.

Read more about the PICL procedure

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Our doctors who treat AAI

Atlantoaxial Instability (IAA) (1)

Dr. Christopher J. Centeno

Christopher J. Centeno, MD is an international expert in interventional orthopedics and the clinical use of bone marrow concentrate in orthopedics. He is certified in physical medicine and rehabilitation with a subspecialty in pain medicine by the American Board of Physical Medicine and Rehabilitation. The Doctor. Centeno is one of the few physicians in the world with extensive experience in expanding the culture and clinical use of adult bone marrow concentrate for the treatment of orthopedic injuries. His clinic incorporates a variety of revolutionary pain management techniques to bring relief and results to his vast patient base. Dr. Centeno treats patients from across the United States who…

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Atlantoaxial Instability (IAA) (2)

Dr. John Schultz

John R. Schultz MD is a national expert in interventional orthopedics and the clinical use of bone marrow concentrate for orthopedic injuries. He is board certified in Anesthesiology and Pain Medicine and has trained in both. Dr. Schultz has extensive experience with same-day as well as expanded bone marrow concentrate for culture, seeing patients at the CSC Clinic in Broomfield, Colorado, as well as the Regenexx Clinic in Grand Cayman. The emphasis of Dr. Schultz is in the evaluation and treatment of thoracic and cervical disc, facet, nerve and ligament injuries, including the non-surgical treatment of craniocervical instability (CCI). Dr. Schultz trained at the School of…

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Other Resources for AAI

  • New Atlas of Interventional Orthopedics

    Writing a textbook is a huge undertaking. By creating the first comprehensive book of its kind on interventional orthopedic procedures, authors Williams, Sussman, and Pitts have set a new benchmark in the field. Congratulations to the authors for their dedication, vision and commitment to the advancement of Interventional Orthopedics. What is interventional orthopedics? Interventional Orthopedics...continued

  • Understanding measures of cervical spine instability

    Cervical Spine Instability Measurements: How to Accurately Interpret Them Everything was a blur. He was waiting for the red light to change when a large truck slammed into his vehicle. He didn't see the approaching vehicle, but he heard the tires skidding. Brain fog, dizziness, and fatigue did not respond to conservative therapy. …continued

  • What is the range of Atlantodens? A quick start guide

    Headaches and dizziness became progressive in nature and responded to conservative care. Chiropractic adjustments provided only temporary relief as she was unable to stay in shape. A surgeon reviewed her history, symptoms, and radiographic studies. He mentioned different measurements that were abnormal. What is the Atlantodens Interval? What is Atlas? What is the axis...continued

  • Your Grabb Oakes Measurement: What Does It Mean?

    The headaches, mental confusion and balance problems were progressive in nature and did not respond to conservative care. After what seemed like endless consultations and examinations, her chiropractor believes it to be craniocervical instability. During a surgical evaluation, the MRI was reviewed and several measurements were taken, all of which were confusing. What is the Skull? What is it …continued

  • Gymnastics and yoga were easy since you were super flexible. With continued training, your shoulders and knees would shift. A series of minor but significant traumas has left you marginalized both in sports, academically and socially. Brain fog and fatigue were common themes. You've consulted countless doctors with conflicting information. Your chiropractor...continued

  • What are the long-term effects of untreated whiplash?

    You were waiting for the red light to turn when you heard the brakes squeal. Out of nowhere, he is hit by a large SUV and pushes his vehicle into the intersection. Your neck and shoulder hurt and you're not processing all the information. Your doctor thinks you have whiplash. What is whipping? What are the…continued


Atlantoaxial Instability (IAA)? ›

Trauma as the sole cause of atlantoaxial instability is a unique entity, usually resulting from a disruption of the transverse, alar, or apical ligaments. This type of injury is commonly associated with head trauma. Fractures of C1 or C2 also are traumatic causes of atlantoaxial instability.

What is the most common cause of atlantoaxial instability? ›

Trauma as the sole cause of atlantoaxial instability is a unique entity, usually resulting from a disruption of the transverse, alar, or apical ligaments. This type of injury is commonly associated with head trauma. Fractures of C1 or C2 also are traumatic causes of atlantoaxial instability.

What are the symptoms of Atlantoaxial instability? ›

Signs & symptoms of atlantoaxial instability

change in bowel or bladder control. neck pain or stiffness, or their head stays tilted. new weakness or they become fatigued more easily. a decrease in their activity level or function.

What is atlantoaxial AA instability? ›

Atlantoaxial (AA) luxation is a condition in which instability or excessive movement is present between the first two vertebrae within the neck. This spinal disorder is most commonly seen in young, small breed dogs, such as Toy Poodles, Miniature Poodles, Yorkshire Terriers, Pomeranians, and Chihuahuas.

What is the special test for atlantoaxial instability? ›

The patient is asked to slowly flex the head performing a slight cervical nod, at the same time the examiner presses posteriorly on the patient's forehead. A sliding motion of the head in relation to the axis indicates atlantoaxial instability.

How do you fix atlantoaxial instability? ›

Initially, these patients are treated with a halo brace; however, if this treatment is unsuccessful because of a fixed deformity or recurrent deformity, posterior fusion of C1-2 is required. Posterior cervical spinal fusion can successfully treat symptomatic AAI in many cases.

What are the symptoms of atlantoaxial joint injury? ›

Patients typically complain about unilateral neck pain occurring with the slightest head rotation. The pain ascends unilaterally to the occiput, the parietal skull and sometimes even to the eye.

What is the treatment for atlantoaxial? ›

Treatment of Atlantoaxial Subluxation

Treatment includes symptomatic measures and cervical immobilization, usually beginning with a rigid cervical collar. Urgency of treatment is generally based on symptoms or presence of cord abnormalities on MRI in susceptible patients.

In which condition may atlantoaxial instability be present? ›

Neurologic symptoms can occur when the spinal cord or adjacent nerve roots are involved. This instability can originate from congenital conditions, but in adults, it is primarily seen in the setting of acute trauma or degenerative changes due to the inflammatory pannus of rheumatoid arthritis (RA).

What are the signs of atlantoaxial subluxation? ›

Atlantoaxial subluxation is usually asymptomatic but may cause vague neck pain, occipital headache, or occasionally intermittent (and potentially fatal) cervical spinal cord compression.

How do you fix C1 and C2 vertebrae misalignment symptoms? ›

Some common nonsurgical treatments for C1-C2 include:
  1. Medication. ...
  2. Immobilization. ...
  3. Physical therapy. ...
  4. Chiropractic manipulation. ...
  5. Injection of anti-inflammatory or pain reducing medications such as corticosteroids in the epidural space or the atlantoaxial joint at C1-C2.

What are the neurological symptoms of cervical instability? ›

The symptoms of cervical instability can vary but often include neck pain, stiffness, headaches, dizziness, muscle weakness, tingling or numbness in the arms or hands, and difficulty maintaining balance. Some individuals may also experience pain or discomfort while moving the neck or during certain activities.

What are the symptoms of C1 and C2 instability? ›

What are the symptoms of cervical instability?
  • Inability to hold up the head for an extended period of time.
  • Upper neck pain near the skull.
  • Referred pain to the shoulders.
  • Head feels heavy.
  • Tightness or stiffness in neck muscles.
  • Tenderness.
  • Headaches.
  • Shaking or unstable feeling in neck/head.
Jul 9, 2020

How common is atlantoaxial instability? ›

Atlantoaxial instability (AAI) affects 10–20% of individuals with Down syndrome (DS). The condition is mostly asymptomatic and diagnosed on radiography by an enlarged anterior atlanto-odontoid distance.

What are the symptoms of atlantoaxial dislocation? ›

Symptomatic atlantoaxial dislocation in children with Down syndrome may occur anytime from infancy to the twenties. Females are more often affected than are males. Symptoms include neck pain, torticollis, and an abnormal gait. Spinal cord compression is progressive and leads to quadriplegia and urinary incontinence.


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