Overview

Klippel-Feil Syndrome (KFS) is a condition acquired congenitally (at birth)that manifests as two or more fused vertebrae in the neck. KFS is estimated to manifest in one birth every 40,000 and is more commonly found in people assigned female at birth (AFAB).¹ Common symptoms of KFS include a shortened neck, a low hairline at the back of the head and reduced neck movement. KFS is also associated with several spinal, neurological and cardiovascular disorders.² However, in many KFS cases, there are no visible deformities and thus the condition may remain undetected for up to a decade.

KFS diagnosis is often found incidentally in imaging studies carried out for other purposes, with X-rays playing a crucial role in this process.³ Although a KFS patient may not initially present symptoms, the pressure caused by the fused vertebrae may lead to degenerative changes in the spine and, as a result, long-term health effects. Lifestyle changes and activity limitations may prevent the worsening of the symptoms.¹ The risk of neck injury associated with KFS makes early detection very important.² Through the generation of a radiographic image of the spine, X-rays help identify KFS features and guide management. 

This article will discuss the power of X-rays in managing this complex, rare condition and how the understanding provided by this imaging tool can help improve outcomes. 

Understanding klippel-feil syndrome

What is klippel-feil syndrome?

Klippel-Feil Syndrome (KFS) is a rare congenital condition of the spine. It presents as one or more fused vertebrae in the spinal cord's neck (cervical) region. KFS patients often present one or more of these three symptoms: 

• Short neck 
• Limited range of motion in the neck
• A low back hairline

However, KFS can also be asymptomatic. Studies show that 34% to 74% of KFS patients present one or more of the characteristics above.⁴

The lack of mobility caused by the fused segments can pressure the neighbouring segments, making them more prone to injury and degeneration. Added pressure on the spinal cord and nerve roots can cause secondary symptoms such as neck pain, chronic headaches,¹ myelopathy and radiculopathy.⁵ 

How common is it?

KFS is a very rare condition that develops between the first three to eight weeks of embryonic development. It is estimated to affect 1/40,000 newborns,¹ but recent studies measure higher numbers.³

​KFS may appear for unknown reasons, but specific cases have been associated with a mutation in the genes responsible for bone development of the embryo (GDF3 and GDF6)  and the gene that controls vertebrae separation (MEOX1). Both gene mutations are inherited, with GDF3 and 6 being dominant mutations and MEOX1 being recessive.¹

Health issues linked to KFS

KFS patients often present other comorbidities that might have a severe impact on their quality of life. The most common linked conditions include: 

• Congenital scoliosis (more than 50% of KFS patients) 
• Deafness (30%) 
• Sprengel's deformity (20-30%)
• Genitourinary issues  (25-35%)
• Cardiovascular abnormalities (4-29%)²

KFS has also been found in some patients in combination with foetal alcohol syndrome ⁶ and Goldenhar syndrome.⁷ 

The variety in the condition's presentation and associated issues makes performing a thorough medical evaluation even more critical. Diagnostic testing for KFS includes a physical examination, multiple imaging studies, and genetic testing. Simple imaging studies, such as X-ray radiography, can help identify KFS and other common musculoskeletal anomalies such as scoliosis and Sprengel's deformity.¹

The cervical spine

Basic anatomy of the neck

KFS is a condition localised in the portion of the spine of the neck known as the cervical spine. The cervical spine serves several purposes– it protects the spinal cord, which carries nerve signals throughout the body, supports the head and allows for head movement. The seven vertebrae in the cervical spine, namely C1-C7,  are separated by cushions (discs) that facilitate neck mobility and stabilise the spine.⁸

What happens in KFS

In KFS, multiple vertebrae in the cervical spine merge together. The segments C2-C3 and C5-C6 are the most likely to be affected.³ The fusion will likely impact daily movement and posture, potentially affecting the health of other spinal regions. The most common sign of KFS is the restriction of the neck's range of motion.² The loss of flexibility in the area increases the pressure on the adjacent vertebrae and discs, which over lengthy time periods may force them to shift. This structural misalignment can compress the spinal cord and nerve roots. As these two structures are responsible for carrying sensation throughout the body, their compression may cause chronic pain in the neck, upper back and back of the head.⁹ The neighbouring spinal segments may try to compensate for the lack of flexibility caused by KFS by increasing their range of motion beyond normal. This hypermobility increases the risk of disc herniation and degeneration and increases the risk of neck injury.²

How x-rays help diagnose KFS

What is an x-ray?

X-rays are high-energy light rays that, thanks to their power, can penetrate soft tissue and lose very little intensity. However, they are not powerful enough to penetrate higher-density materials such as bones. 

In an X-ray scan, light is emitted from an X-ray tube and directed towards the anatomical area of interest, in this case, the spine. A screen on the other side then detects the X-rays that have made it through. In the regions where there is mainly soft tissue, the X-rays will mostly penetrate your body, and the intensity of the light afterwards will remain similar to when it entered. However, solid, dense objects like your bones will absorb most of the X-ray radiation. In those regions, very little light intensity will reach the detector, creating a clear image of the bones and any abnormalities, such as fusions.¹⁰

This process of light absorption creates an image known as a radiograph. Clinicians often use radiographs to assess the health of the skeletal system quickly, as well as to detect gallstones,¹¹ lung infections,¹² and the presence of foreign objects. 

What doctors look for on the x-ray

When diagnosing KFS, an X-ray of the spine is a crucial tool. Radiographs can show the fusion of cervical vertebrae, a key indicator of the condition. The X-ray provides a clear visual of the spine, allowing the healthcare professional to identify any abnormalities or fusions that may be present.

A radiologist may also look for features in your spine, such as abnormalities in spacing, shape and alignment of the vertebrae, which might indicate other associated conditions, such as spinal instability and stenosis in neighbouring segments. These anomalies increase the risk of cervical injury, making their identification and monitoring crucial to the well-being of the patient. ¹³

If you are dealing with KFS, a medical specialist may look for:    

• Number of fusions: Most KFS patients have multiple fusions in the cervical spine. (Samartzis, Ritchey) Cases of KFS with multiple fusions are linked to a higher risk of myelopathy and radiculopathy.² Therefore, prompt identification may provide a chance for early identification of nerve issues
• Location of the fusions: multiple fused segments may or may not be adjacent. Adjacent fusions⁹ and fusions in the lower cervical segments¹⁴ are linked to a higher risk of cervical pain and migraines
• Partial or complete fusion: the extent of the fusion of the segments varies from patient to patient and increases with age. Determining fusion extent may help in differentiating KFS progression from similarly presenting spinal conditions, such as rheumatoid arthritis¹³
• Disease progression: X-rays are a useful monitoring tool in KFS. Radiologists will perform regular follow-up examinations of your spine to check for developing instabilities or protrusions.¹³ KFS symptoms can worsen with age,⁹ and regular imaging plays a crucial role in ensuring your treatment plan remains appropriate for your diagnosis  

Revealing additional anomalies 

KFS is linked with other skeletal conditions, such as spina bifida, scoliosis, and Sprengel's deformity. X-rays produce an almost instantaneous image, providing a quick way to assess the presence of these associated anomalies in KFS patients. 

When more imaging is needed

X-ray radiography is a go-to imaging technique in KFS investigations due to its ability to provide a fast and accurate diagnosis. However, X-rays are limited in the imaging of soft tissue. In cases of KFS-associated neurological symptoms, it is essential to assess the condition using different imaging tools. 

Magnetic Resonance Imaging (MRI): MRI is a powerful imaging tool capable of producing a comprehensive image of your internal anatomy. It can be used to evaluate the health of the soft tissues of the cervical spine, such as nerve roots, the spinal cord, and discs. The pressure caused by the fused segment may affect all these neighbouring structures.¹ MRI is particularly relevant in KFS cases linked to radiculopathy or myelopathy, as it can help identify the location of the nerve damage.¹³

Computed Tomography (CT) scans: CT scans use X-rays to produce a 3D image of your anatomy, providing a more detailed image of your organs for a more complete assessment. This technique allows for visualisation of layers within the spine from different angles. In KFS, this is useful for evaluating the structural health of the core of your vertebrae, especially in suspected cases of stenosis.¹

Summary 

Klippel-Feil Syndrome (KFS) is a rare congenital condition marked by the fusion of two or more cervical vertebrae. While some individuals show physical signs like a short neck or limited mobility, many cases go undiagnosed for decades until incidental findings via imaging.^5,9

X-rays play a key role in diagnosing KFS. They can reveal fused vertebrae, alignment issues, and other structural changes in the cervical spine. Identifying the number, location, and extent of fusion helps guide clinical decisions and assess the risk of complications such as nerve compression, spinal instability, or degeneration. 

Although many KFS patients remain symptom-free during childhood, the condition can lead to long-term spinal problems. Early diagnosis through radiographic imaging allows for proactive care, such as activity adjustments to help reduce the risk of pain or neurological issues.