Craniocervical ligament injuries: Focus on the alar ligament

Ross Hauser, MD.

As with most cervical spine ligament injuries, the alar ligament injury takes its place among the controversial findings of difficult to treat and difficult to understand cervical spine instability and cervicocranial instability. What makes the alar ligament injury so controversial? It centers around how important or non-important the alar ligament is in certain instances of cervical spine instability.

As we are in the practice of healing ligaments, all ligaments are very important to us. But each ligament has a purpose and each ligament interacts with its surrounding ligaments, bones, and tendons. It is, as we have practiced and understood ligament healing, that a ligament works within a complex of ligaments. To fix one ligament, all the ligaments it interacts with should be treated as well. Ligament injuries are rare injuries that sit in isolation. General instability of the cervical spine is typically not a problem of a single ligament but interaction and weakness of many ligaments.

In this article, we will address the problem of chronic and degenerative or post-traumatic ligament injury and the many neurologic, cardiovascular, and psychiatric-type symptoms and conditions certain ligaments may present. We will see research that suggests that ligament injuries may be misunderstood, including the role of the alar ligament injury.

The learning points: Craniocervical ligament injuries: Focus on the alar ligament

My doctors say the conditions and symptoms I have could not possibly exist

The idea that alar ligament injury is misunderstood is certainly not a new idea to people who have been diagnosed or suspected of having alar ligament “involvement.” Involvement of course is the MRI type word that many people have seen and read in their MRI interpretation of what is going on in their neck. Here are some of the types of stories we hear from people in their journey to understand their cervical spine instability and their alar ligament involvement:

My doctors have told me there is no treatment they can offer me at this point.

My doctors have told me there is no treatment they can offer me at this point. I have been diagnosed with advanced cervical spine instability. I have been to several neurologists. They tell me that the symptoms I have of dizziness and vertigo, blurred and distorted vision, hyperacusis (sound disturbance or intolerance to sounds), occipital nerve pain, and headache, are not coming from the advanced, degenerative problems in my neck. They are also not interested in talking about damaged ligaments. They also told me the conditions and symptoms I have could not possibly exist. There is no reason for them.

I have an MRI that demonstrates atlantoaxial instability, and damage to the ligaments at c2, alar ligament, and the transverse ligament. I have bone spurs at c6/c7. The only treatment that they want to offer me is pain medications as there is not yet enough damage to my neck to warrant a fusion surgery.

I have an MRI that shows injury to my transverse and alar ligaments

Three years ago I was involved in an accident. I have seen many specialists and neurologists and now I am seeing pain management specialists. I am not getting any help. Almost any rotation or movement of my head will cause pain of varying degrees. I do however have constant pain in my right occipital area. I have an MRI that shows injury to my transverse and alar ligaments. The doctors I am seeing don’t want to treat C1-C2 and would prefer to limit treatments further down my cervical spine. I have had facet joint injections further down my spine and nerve ablation with no improvement.

The displaced C1

We will also hear the story of a chiropractic adjustment gone awry. The patient will be a regular, sometimes long-term patient of a favored chiropractor. One day there will be an adjustment that sets things in the wrong direction. In some people, this focuses on an adjustment of the C1. X-rays will reveal that the C1 is now displaced. Further chiropractic adjustments were able to put the C1 back in place but the adjustment does not hold for long. The patient then will report the familiar neurologic-type symptoms of dizziness, brain fog, general poor health, and pain.

Post-Concussion Syndrome and headaches

People will contact us following an impact to the head injury in which they suffered a concussion. At our center, we generally see one type of patient with a diagnosis of post-concussion syndrome. It is the patient who has long-term, unexplained conditions and symptoms and their post-concussion syndrome has now turned into a persistent post-concussion syndrome. Then this group of patients is further divided into The younger athlete with persistent post-concussion syndrome. The whiplash accident injuries people with persistent post-concussion syndrome. The “I have had many concussions” people. For more information on this condition please see our article When persistent post-concussion syndrome turns into a neurologic mystery.

In these people, their initial contact with us will reveal that an MRI has been taken and that in their case the alar ligament(s) have been damaged in their impact injury. The focus on the alar ligament is being used as an explanation for the worsening of the post-concussion syndrome symptoms. Some of these people report that physical therapy and adjustments help a little and that they have taken to wearing a cervical collar to help minimize pain, discomfort, and constant headaches.

Whiplash injury

The transverse ligament and the two alar ligaments are what specifically afford the stable anatomic relationship between the cranium and C1-C2. These ligaments are tiny, yet among the toughest in the body. Inevitably, however, the magnitude of the forces, even at low speed, in whiplash, can result in transverse and alar ligament injury. The forces imparted by the whiplash effect of the motor vehicle crash can result in ligamentous strain – that is, irreversible stretch (without treatment) – and in ligamentous edema. With sufficient force, the ligament can actually tear.

If we have all these problems in people why is there controversy over the alar ligament involvement?

Above is a very small sampling of the types of stories and medical histories we hear. We have seen many more complex cases. The question is, why is the alar ligament a focus of misunderstanding? Why will some doctors not understand its involvement? Let’s start trying to understand ourselves.

“The alar ligament is an important structure in restraining the rotational movement at the atlantoaxial joint.”

In December 2021, doctors at the Department of Neurosurgery, Westchester Medical Center, New York Medical College, Maimonides Medical Center, Zucker School of Medicine at Hofstra/Northwell, and the University of New Mexico School of Medicine presented a case history in the journal Spinal cord series and cases. (5) It is the story of a woman who had alar ligament damage and did not respond to conservative care and ultimately went to surgery. Here is the case:

“The alar ligament is an important structure in restraining the rotational movement at the atlantoaxial joint. While bony fractures generally heal, rupture of ligaments may heal poorly in adults and often requires surgical stabilization. Atlantoaxial rotatory subluxation (Rotational subluxation or dislocation of C1 on C2) is a rare injury in adults, and the prognostic importance of the presence of alar ligament injury with regard to the success of nonoperative management is unknown.

Case presentation: A 28-year-old woman presented after a traumatic Type I Atlantoaxial rotatory subluxation without evidence of osseous (bone damage) injury, but MRI demonstrated evidence of unilateral alar ligament disruption. Initial conservative management with closed reduction (the C1-C2 are manipulated back into place without open surgery) and maintenance in a rigid cervical collar proved unsuccessful, with worsening pain and failure to maintain reduction. She subsequently underwent open reduction and surgical fixation of C1-C2, resulting in resolution of her pain and maintenance of alignment. . . Alar ligament rupture may be a negative prognostic indicator in the success of nonoperative management of type I atlantoaxial rotatory subluxation.”

The atlantooccipital joint is not disrupted and the craniovertebral junction is not destabilized in alar ligament injury

In October 2021 (6) Doctors at the Department of Neurosurgery, Kırıkkale University Faculty of Medicine in Turkey reported on an isolated bilateral alar ligament injury. As you will see in this excerpt from this published report, medical information, specifically patient outcomes, on isolated alar ligament injury is rare.

“Only seven cases of isolated unilateral rupture of the alar ligament had been previously reported. The authors report the first adult female case of this rare injury. The patient in their case, a 36-year-old female presented after trauma due to falling, and at that moment, she had fainted due to a sudden pain between the neck and head. The radiological examinations [magnetic resonance imaging (MRI) and X-rays] had been interpreted as normal.” It was later revealed the extent of her injury, an asymmetrically left-sided odontoid process (the dens of the C2 was tilted) and a new MRI revealed a right-sided alar ligament rupture.

This patient did not have surgery but was treated with a bilateral greater occipital nerve block together with pulse radiofrequency and trigger point injection at splenius capitis, levator scapula, and trapezius followed by the application of a halo orthosis to be worn for 3 months. The patient was found to be pain-free in the follow-up examinations.

The findings of interest here were: “With pure unilateral alar ligament rupture, the atlantooccipital joint is not disrupted and the craniovertebral junction is not destabilized.

“The strength of the alar ligament has been described inconsistently”

In a September 2021 paper in the journal Global Spine Journal (7) The strength of the alar ligament has been described inconsistently, possibly because of the nonphysiological biomechanical testing models, and the inability to test the ligament with both attachments simultaneously. The researchers of this study sought to understand what it actually takes to rupture an alar ligament. In cadaver studies, they found when both the right and left alar ligament were included, the total alar ligament failure occurred at an average force of 394 Newtons. The alar ligament failed before the transverse ligament. What are 394 Newtons? Simple physics and math tell us that if you had an object weighing 88 pounds strapped around your neck and you dropped it a meter – it would snap the alar ligaments. As noted the alar ligament failed before the transverse ligament.

Now let’s look further at the transverse ligament. A March 2021 study in the Global Spine Journal (8) wanted to know at what force does the transverse ligament fail in the elderly. This was a cadaver study on donors under 80 years old and over 80 years old.  Here is what they wrote:

“The transverse ligament is the strongest ligament of the craniocervical junction and plays a critical role in atlanto-axial stability. The goal of this cadaveric study, and the subsequent study (part II), was to reevaluate the force required for the transverse ligament and alar ligament to fail in a more physiological biomechanical model in elderly specimens.”

In the research above we discussed 394 Newtons as the force needed to rupture alar ligaments. The average force required for the transverse ligament to fail was 236 Newtons or for example, a 53-pound weight tied around your neck and dropped from a meter. The researchers concluded: “The transverse ligament’s failure in elderly specimens occurred at an average force of 236 Newtons, which was lower than that reported in the previous literature. The ligament’s failure force in younger patients differs and may be similar to the findings published to date.”

What are we seeing in the image below? The interaction and relationships of the ligaments of the cervical spine

In this image, we are looking at an example of what may happen in a sports injury, whiplash injury, or accident involving the neck. This image’s heading is a brief mention of MRI and DMX. These are the imaging tools to help identify cervical spine injuries. We will discuss this further below. Here the focus of this image is on the soft tissue. For a more comprehensive discussion of imaging tests, please see my article by Ross Hauser, MD. Reviews of Diagnostic Imaging Technology for Cervical Spine Instability.

Understanding the ligament complex at C1-C2

The main stability of the C0-C2 joints comes from the integrity of their ligament support. The ‘big three’ ligaments for the C1-C2 junction have long been thought to be the transverse, alar, and apical ligaments because of their attachment to their anterior location to stabilize the dens, while the capsular ligaments which surround the C1-C2 facet joints located posteriorly have taken backstage. The ‘big one,’ the transverse ligament, positions the dens against the anterior arch of the atlas. This allows the desired rotation of the neck but prevents anterior-posterior translation of C1 on C2, which would jeopardize the spinal cord. The alar ligament, a secondary stabilizer of the dens, connects the cranium to C1 from the sides of the dens to the lateral borders of the foramen magnum. The alar ligaments function to prevent excessive axial rotation at the atlanto-occipital joint (to the right by the left alar and vice versa). Additional support to the occiput-atlantoaxial joints is provided by the apical ligaments.

For the person with alar ligament damage that is symptomatic, we have shown that tightening the capsular ligaments of C1-C2 can normalize C1-C2 motions and stability.

It is likely the symptoms of whiplash associated disorder are due to the posterior ligaments, especially the capsular ligaments

If the head is turned or turns to the side during whiplash, the chances increase significantly that upper cervical injury will occur.  A rotating head at the time of impact can also lead to significantly more transverse ligament injuries as did front-end versus rear-end collisions. The alar ligament restrains rotation of the upper cervical spine, whereas the transverse ligament restricts flexion as well as anterior displacement of the atlas. It should be noted that minor alar and transverse ligament injuries as seen on MRI after whiplash injuries did not correlate with the symptoms of the whiplash-associated disorder. What this means is that the symptoms of the most whiplash-associated disorder are not related to injuries to these ligaments.  Since most of us spend time with our necks flexed, it is likely the symptoms of the whiplash-associated disorder are due to the posterior ligaments, especially the capsular ligaments. The capsular ligaments are discussed below.

In this image, we see two alar ligaments, the left side, and the right side. For the purpose of this illustration, they are shown with class III type tears. We also see a dura mater / tectorial membrane complex tear III tear illustrated. This highlighted membrane acts as a ligament as it is an extension of the posterior longitudinal ligament. This membrane can be seen as a backup or redundancy system to help the alar and transverse ligaments stabilize the cervical spine. This is especially true in neck flexion or the motion of looking down with the chin in the chest. The tectorial membrane helps prevent the odontoid process from moving backward and impinging into the cervical canal.

We also see injuries to the posterior atlantooccipital membrane or posterior atlantooccipital ligament. This ligament or membrane attaches the base of the skull to the atlas. A groove in this membrane offers just enough room to create an opening of the vertebral artery and suboccipital nerve.

How essential is the essential alar ligament?

At the top of this article, I stated that we treat ligament injury. Therefore every injury of a ligament needs to be addressed. Equally, the focus on treating a single ligament injury in isolation may not lead to the cervical spine instability that we are seeking. Focusing all our attention on the alar ligament without understanding the neck as a whole may not lead to the results we want to have in our treatments.

Contradictory evidence

Here is a paper that appeared in the Journal of Neurosurgery: Spine. February 2019 (1). Here a team of researchers from the Department of Bioengineering, and Scientific Computing and Imaging Institute, at the University of Utah created computer models to demonstrate that the occipitoatlantal capsular ligaments are the primary stabilizers of the occipitoatlantal joint in the craniocervical junction.

Here is what they said and did:

“There is contradictory evidence regarding the relative contribution of the key stabilizing ligaments of the occipitoatlantal joint.” Because cadaveric studies are limited by the nature and the number of injury scenarios that can be tested to identify occipitoatlantal stabilizing ligaments they developed a computer model to analyze five subject-specific craniocervical junction models to investigate the biomechanics of the occipitoatlantal joint and identify the ligamentous structures essential for stability.

The scenarios they created included: Isolated ligamentous injury of either decreasing the stiffness of the occipitoatlantal capsular ligaments (the ligaments of the facet joints at the back of the spine) or completely removing the transverse ligament, tectorial membrane, or alar ligaments. Combination scenarios were also evaluated.

How much instability would there be if the transverse ligament(s) was removed, how much instability there would be if the alar ligament(s) were removed?

Simply, what they tested for was how much instability would there be if the transverse ligament(s) was removed, how much instability there would be if the alar ligament(s) were removed. How much instability would there be if the occipitoatlantal capsular ligaments were “loosened.” Finally, how much instability would there be in combination with these simulations? Here are their results.

Rupture of the alar ligament does cause instability

In a December 2021 paper in the medical journal Spine (2) university researchers in Spain described the anatomical instability they found in cadaver studies when one alar ligament was completely cut. “Unilateral alar ligament transection increased the range of motion of C0-C2 in the three planes of movement (sagittal (forward and back), frontal (side to side), and transverse (up and down) planes) however, intersegmental motion (simultaneous movement) alterations were not always observed. Conclusion: Increases in the range of extension and lateral bending at C0-C1, which had not been reported previously, were observed. Further, the range of rotation on the right and left sides increased, in conjunction with the increased ranges at C0-C1 and C1-C2.”

Let’s stop here to discuss the capsular ligaments.

In 2014 our research team published a study in The Open Orthopaedics Journal (3). In this paper, we explained the role of the capsular ligaments in cervical spine instability. What the researchers above found out through the computer model, is what we discovered in clinical observation seen in our patients and a critical review of the medical literature up until that time.

“The capsular ligaments are the main stabilizing structures of the facet joints in the cervical spine and have been implicated as a major source of chronic neck pain. Chronic neck pain often reflects a state of instability in the cervical spine and is a symptom common to a number of conditions described herein, including disc herniation, cervical spondylosis, whiplash injury, and whiplash-associated disorder, post-concussion syndrome, vertebrobasilar insufficiency, and Barré-Liéou syndrome.

When the capsular ligaments are injured, they become elongated and exhibit laxity, which causes excessive movement of the cervical vertebrae. In the upper cervical spine (C0-C2), this can cause a number of other symptoms including, but not limited to, nerve irritation and vertebrobasilar insufficiency with associated vertigo, tinnitus, dizziness, facial pain, arm pain, and migraine headaches. In the lower cervical spine (C3-C7), this can cause muscle spasms, crepitation, and/or paresthesia in addition to chronic neck pain. In either case, the presence of excessive motion between two adjacent cervical vertebrae and these associated symptoms is described as cervical instability.

Therefore, we propose that in many cases of chronic neck pain, the cause may be underlying joint instability due to capsular ligament laxity.”

The two studies combined to express an agreement capsular ligament injury resulted in the largest percentage increase in all ranges of motion compared to other ligament injuries.

Let’s return to the Journal of Neurosurgery study for more findings:

CONCLUSIONS: These results demonstrate that the occipitoatlantal capsular ligaments are the key stabilizing ligamentous structures of the occipitoatlantal joint. Injury of these primary stabilizing ligaments is necessary to cause occipitoatlantal instability. Isolated injuries of transverse ligament, tectorial membrane, or alar ligaments are unlikely to result in appreciable instability at the occipitoatlantal joint.

Comment: The transverse ligament, the tectorial membrane, and the alar ligaments are all very important structures in understanding and treating cervical spine instability. However, they are part of a vast array of cervical spine ligaments and membrane weave that hold our head on our neck. Treating anything in isolation can result in diminished treatment results or no results at all.

What are we seeing in this image? A CT Scan showing the offset or subluxation of the C0-C1

What are we seeing in this image? A CT Scan showing the offset if subluxation of the C0-C1

Research: Many doctors do not understand the complexity of the craniocervical junction, neurological deficits, and why there is a normal CT

The above statement will not be shocking nor surprising to many of you. A somewhat normal MRI and continued neurological symptoms are probably at the core of the “hit and miss” treatments you are getting or possibly a referral to a neurological psychiatrist.

In the above image, we see a NOT normal CT scan of the C0-C1. There are obvious displacement and subluxation. We are now going to explore the crosstalk between doctors and researchers in understanding ligament problems in the craniocervical junction, the connection of the skull, atlas, and axis, as they are revealed in imaging studies. Here we will discuss CT scans, MRIs, and Digital Motion X-Ray DMX.

The ligamentous anatomy of the craniocervical junction is complex, and thorough knowledge is a prerequisite for accurate interpretation of the MRI findings

In June 2020, a team of radiologists writing in the Journal of Medical Imaging and Radiation Oncology (4) wrote: “Cervical spine trauma accounts for the majority of spinal injuries, and approximately one-third involve the craniocervical junction. Due to its high sensitivity, magnetic resonance imaging (MRI) has become the standard tool for imaging suspected ligamentous injuries in an unstable spine and in patients with neurological deficits having a normal CT. The ligamentous anatomy of the CCJ is complex, and thorough knowledge is a prerequisite for accurate interpretation of the MRI findings.”

Simply we have doctors having to rely on MRI to understand ligament injuries and for radiologists to understand the challenges of making an accurate interpretation.

These images are from a Digital Motion X-Ray

The digital motion x-ray is explained and demonstrated below. This is one of our tools for demonstrating cervical instability in real-time and motion. When you watch the video, you will see a moving image of this patient’s neck. This gives our clinicians insight into the patient’s range of motion where impingement or compression may be occurring.

The challenges of cervical instability are many. Fixing cervical neck instability is not something that can be treated simply or quickly, it takes a comprehensive non-surgical program to get the patient’s instability stabilized and the symptoms abated. We believe that if you have been going from clinician to clinician, practitioner to practitioner, doctor to doctor, there is a good likelihood that you have problems of cervical neck instability coming from weakness and damage to the cervical ligaments. Our treatments of Comprehensive dextrose Prolotherapy and in some cases Platelet Rich Plasma Prolotherapy can be an answer.

Prolotherapy is an injection of simple dextrose into the unstable cervical spine. The concept is that these injections will strengthen the cervical ligaments thereby providing a stronger or more stable connection between the cervical vertebrae.

In this video Ross Hauser, MD. discusses C0-C1 instability and the problems it creates on C1 nerve root compression.

The Occiput bone smashes against the C1 vertebra

At 0:50 video – the patient’s Digital Motion X-Ray demonstrates that their occiput is violently colliding with their C1 vertebra every time they move their head forward and their chin juts out.

IIn this still fame from the video, Dr. Hauser points to the back of the patient's skull, the occiput bone as it smashes into the patient's C1 vertebrae every time they move their head forward and their chin juts out, as in reaching out for something, looking upwards, etc. When this happens the patient's C1 nerve root and vertebral artery are compressed. This compression would lead to headaches, facial pain, and vibrating sensations in the upper lip.

In this still frame from the video, Dr. Hauser points to the back of the patient’s skull, the occiput bone as it smashes into the patient’s C1 vertebrae every time they move their head forward and their chin juts out, as in reaching out for something, looking upwards, etc. When this happens the patient’s C1 nerve root and vertebral artery are compressed. This compression would lead to headaches, facial pain, and vibrating sensations in the upper lip.

Summary and contact us. Can we help you? How do I know if I’m a good candidate?

We hope you found this article informative and that it helped answer many of the questions. Just like you, we want to make sure you are a good fit for our clinic prior to accepting your case. While our mission is to help as many people with chronic pain as we can, sadly, we cannot accept all cases. We have a multi-step process so our team can really get to know you and your case to ensure that it sounds like you are a good fit for the unique testing and treatments that we offer here.

Please visit the Hauser Neck Center Patient Candidate Form

This is a picture of Ross Hauser, MD, Danielle Steilen-Matias, PA-C, Brian Hutcheson, DC. They treat people with non-surgical regenerative medicine injections. Offices are located in Oak Park, Illinois and Fort Myers, Florida.

Brian Hutcheson, DC | Ross Hauser, MD | Danielle Steilen-Matias, PA-C

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1 Phuntsok R, Ellis BJ, Herron MR, Provost CW, Dailey AT, Brockmeyer DL. The occipitoatlantal capsular ligaments are the primary stabilizers of the occipitoatlantal joint in the craniocervical junction: a finite element analysis. Journal of Neurosurgery: Spine. 2019 Feb 15;30(5):593-601. [Google Scholar]
2 Lorente AI, Hidalgo-García C, Rodríguez-Sanz J, Maza-Frechín M, López-de-Celis C, Pérez-Bellmunt A. Intersegmental Kinematics of the Upper Cervical Spine: Normal Range of Motion and Its Alteration After Alar Ligament Transection. Spine. 2021 Dec 15;46(24):E1320-6. [Google Scholar]
3 Steilen D, Hauser R, Woldin B, Sawyer S. Chronic neck pain: making the connection between capsular ligament laxity and cervical instability. The open orthopaedics journal. 2014;8:326. [Google Scholar]
4 Mantripragada S, Kannivelu A, Peh WC. Magnetic resonance imaging of cervical ligamentous anatomy and traumatic ligamentous injuries. Journal of medical imaging and radiation oncology. 2020 Jun;64(3):368-76. [Google Scholar]
5 Ng C, Dominguez JF, Feldstein E, Houten JK, Spirollari E, Gandhi CD, Cole CD, Kinon MD. Does alar ligament injury predict conservative treatment failure of atlantoaxial rotatory subluxation in adults: Case report and review of the literature. Spinal Cord Series and Cases. 2021 Dec 3;7(1):1-7. [Google Scholar]
6 Keskil S, Yüksel U, Babacan A. Unilateral isolated alar ligament rupture in an adult female patient. Agri: Agri (Algoloji) Dernegi’nin Yayin Organidir= The Journal of the Turkish Society of Algology. 2021 Oct 1;33(4):265-7. [Google Scholar]
7 Ishak B, Glinski AV, Dupont G, Lachkar S, Yilmaz E, Iwanaga J, Unterberg A, Oskouian R, Tubbs RS, Chapman JR. Update on the Biomechanics of the Craniocervical Junction, Part II: Alar Ligament. Global spine journal. 2021 Sep;11(7):1064-9. [Google Scholar]
8 Ishak B, Dupont G, Lachkar S, Yilmaz E, Glinski AV, Altafulla J, Kikuta S, Iwanaga J, Chapman JR, Oskouian R, Tubbs RS. Update on the Biomechanics of the Craniocervical Junction—Part I: Transverse Atlantal Ligament in the Elderly. Global Spine Journal. 2021 Mar;11(2):180-6. [Google Scholar]

This article was updated April 24, 2022

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