Orthopaedic Surgery - Klippel–Feil Syndrome

Basics

Klippel–Feil syndrome is a congenital disorder characterized by failure of normal segmentation of the cervical vertebrae during embryonic development, resulting in congenital fusion of two or more cervical vertebrae.

The classic clinical triad is:

A short neck, low posterior hairline, and restricted cervical range of motion.

However, the complete triad is present in only a minority of patients.

Associated Abnormalities

Klippel–Feil syndrome frequently occurs with abnormalities in other organ systems.

Common associations include:

Congenital scoliosis, Sprengel deformity, hearing impairment, synkinesis, congenital heart disease, renal abnormalities, and spinal dysraphism.

Classification

A traditional classification divides the disorder according to the distribution of vertebral fusion.

Type I

Type I consists of extensive fusion involving the:

Cervical and upper thoracic vertebrae.

Type II

Type II involves fusion confined predominantly to the cervical spine.

One or several cervical motion segments may be fused.

Type III

Type III describes cervical fusion associated with additional congenital fusion involving the:

Lower thoracic or lumbar spine.

Prevention

There are no established preventive measures because the condition develops during embryogenesis.

Epidemiology

The congenital segmentation abnormality develops early in fetal life.

The age at diagnosis varies considerably according to the severity of the fusion and associated abnormalities.

Early Presentation

Extensive cervical fusion is more likely to be recognized during early childhood, sometimes around 2–4 years of age, because of visible neck shortening, limited motion, or associated deformity.

Later Presentation

Less extensive disease may remain asymptomatic for many years.

Some patients are diagnosed incidentally during imaging, while others first become symptomatic when adjacent-segment degeneration, stenosis, or instability develops later in life.

Sex

A slight female predominance has been described, with historical female-to-male ratios around 1.5:1.

Neurologic Symptoms

Most children are neurologically normal.

Symptomatic cervical stenosis or adjacent-segment degeneration may become more apparent in adulthood, particularly during the fourth decade and beyond.

Symptoms may include sensory disturbance, weakness, gait abnormality, or myelopathic findings.

Incidence

Congenital cervical fusion has historically been reported in approximately 0.7% of the population, although prevalence varies according to imaging technique and diagnostic criteria.

Risk Factors and Associated Developmental Abnormalities

Associated abnormalities include:

Spina bifida and congenital renal malformations.

The presence of one congenital anomaly should prompt consideration of others.

Genetics

Klippel–Feil syndrome is genetically heterogeneous.

Many cases are sporadic, while familial cases may follow different inheritance patterns.

Inheritance

Autosomal dominant forms have been documented, and autosomal recessive forms are also recognized in some genetic subtypes.

Molecular Associations

Abnormalities involving genes that regulate vertebral segmentation and embryonic development have been implicated.

Research has identified associations with pathways involving somitogenesis and Notch signaling, while specific families have demonstrated chromosomal abnormalities such as an inversion involving 8q22.2–q23.3.

The genetic basis is therefore variable rather than attributable to one universal mutation.

Etiology

The fundamental developmental abnormality is incomplete segmentation of the cervical sclerotomes during embryogenesis.

Normally, adjacent portions of developing vertebral segments separate and reorganize into individual vertebrae.

Failure of this process produces congenital block vertebrae.

Proposed Mechanisms

Additional proposed mechanisms include:

Abnormal facet-joint segmentation, vascular disruption, fetal hypoxia, or other developmental insults affecting vertebral formation.

These mechanisms remain incompletely defined.

Associated Conditions

Musculoskeletal Abnormalities

Common musculoskeletal associations include:

Sprengel deformity, congenital or idiopathic scoliosis, spinal stenosis, cervical instability, and spina bifida occulta.

Sprengel Deformity

Sprengel deformity results from failure of normal descent of the scapula during development.

The affected scapula remains elevated and may contribute to:

Restricted shoulder motion, cosmetic asymmetry, and cervical or upper thoracic deformity.

Scoliosis

Scoliosis has been reported in up to approximately 60% of patients in some series.

Curves may be congenital, compensatory, or idiopathic.

Spinal Stenosis

The cervical spinal canal may be congenitally narrow or may become stenotic later because of:

Adjacent-segment degeneration, osteophyte formation, disc degeneration, or instability.

Craniofacial and Neurologic Associations

Possible abnormalities include:

Hearing loss, extraocular muscle palsy, synkinesis, and other cranial nerve abnormalities.

Genitourinary Abnormalities

Renal anomalies occur in a substantial minority of patients, historically reported in up to approximately 30%.

These may include:

Unilateral renal agenesis, ectopic kidney, collecting-system abnormalities, or other congenital renal malformations.

Cardiovascular Abnormalities

Congenital heart defects may occur and should be investigated when clinically suspected.

Diagnosis

Signs and Symptoms

The classic triad consists of:

Short neck, low posterior hairline, and restricted cervical motion.

The full triad is found in only approximately 40–50% of patients.

Limited Motion

Restricted cervical motion is one of the most common findings and has been reported in up to approximately 75% of affected patients.

Short Neck

Visible neck shortening and a correspondingly low posterior hairline are present in fewer than half of patients.

Incidental Diagnosis

Some patients have no obvious clinical abnormalities and are diagnosed after cervical fusion is discovered incidentally on radiographs or other imaging.

Other Presentations

Additional findings may include:

Scoliosis, shoulder asymmetry, hearing impairment, neurologic symptoms, renal anomalies, or congenital heart disease.

Physical Examination

A systematic examination should include both the cervical spine and screening for associated abnormalities.

Inspection

Assess:

Neck length, posterior hairline, head posture, cervical alignment, shoulder height, scapular position, and scoliosis.

Cervical Range of Motion

Document:

Flexion, extension, lateral bending, and rotation.

The degree of limitation depends on the number and location of fused segments.

Neurologic Examination

A complete neurologic examination is essential.

Assess:

Upper- and lower-extremity strength, sensation, reflexes, gait, coordination, pathologic reflexes, and signs of myelopathy.

Myelopathic Findings

Findings such as:

Hyperreflexia, clonus, pathologic reflexes, gait imbalance, hand clumsiness, or weakness

may indicate cervical spinal cord compression.

Examination for Associated Anomalies

The physical examination should also assess for:

Sprengel deformity, scoliosis, limb abnormalities, renal or genitourinary anomalies, hearing impairment, and cardiovascular findings.

Imaging

Plain Radiographs

Conventional cervical radiographs demonstrate varying patterns of congenital vertebral fusion.

Findings range from:

A single block vertebra to multiple contiguous fused segments.

Fusion Patterns

Different portions of the vertebra may be fused.

Historical series have reported combinations involving the:

Vertebral bodies, posterior elements, or lateral components.

Some patients demonstrate fusion of both anterior and posterior elements.

Spina Bifida Occulta

Associated posterior-element abnormalities, including spina bifida occulta, may be visible.

Adjacent-Segment Degeneration

Mobile segments immediately above or below a congenital fusion are exposed to greater mechanical stress.

Over time, they may develop:

Disc degeneration, facet arthrosis, instability, subluxation, or stenosis.

Flexion-Extension Radiographs

Dynamic lateral flexion and extension radiographs are useful for assessing:

Occult instability and excessive motion at adjacent segments.

These studies are particularly important before procedures requiring manipulation of the cervical spine, including anesthesia and intubation when instability is suspected.

MRI

MRI is indicated when there is concern for:

Spinal cord compression, nerve-root compression, stenosis, disc disease, congenital spinal cord abnormalities, or neurologic symptoms.

It is also useful before cervical spine surgery.

CT

CT may be useful for defining:

Complex bony anatomy, fused posterior elements, congenital anomalies, and preoperative surgical anatomy.

Pathological Findings

The primary abnormality is congenital fusion of cervical vertebrae.

Intervertebral Discs

Discs at the fused levels may be:

Narrow, rudimentary, or absent.

Adjacent Discs

Remaining mobile discs may undergo accelerated degeneration because they compensate for the lost movement at fused levels.

Degenerative Changes

Progressive abnormalities can include:

Degenerative disc disease, facet arthrosis, spinal stenosis, and subluxation.

Differential Diagnosis

Important alternative causes of a short or stiff neck include:

Postsurgical cervical fusion, muscular torticollis, cervical spinal stenosis, and other congenital vertebral segmentation disorders.

Treatment

General Principles

Management depends on:

Neurologic status, cervical stability, severity of stenosis, pain, associated deformity, and involvement of other organ systems.

Most asymptomatic patients do not require cervical surgery.

Evaluation of Associated Organ Systems

All patients should be assessed for associated congenital abnormalities.

Renal Evaluation

A renal ultrasound is commonly used to screen for congenital renal anomalies.

Cardiac Assessment

Cardiac evaluation is indicated when examination, history, or associated congenital findings raise concern for structural heart disease.

Hearing Assessment

Because hearing loss is a recognized association, formal audiologic assessment should be considered, especially in children.

Pre-Anesthetic Assessment

Because some patients have occult cervical instability, careful cervical evaluation is important before general anesthesia.

When clinically indicated, flexion-extension radiographs or advanced imaging should be reviewed before airway manipulation.

Anesthesia personnel should be informed of the cervical fusion and any instability.

MRI Before Spine Surgery

MRI should be obtained when neurologic compromise is suspected and before operative treatment of cervical stenosis or instability.

Activity Modification

Patients with significant cervical fusion, instability, or stenosis should avoid activities that create excessive risk of neck trauma.

This may include:

Collision sports, high-impact activities, and occupations or recreational activities with substantial risk of head or cervical injury.

Restrictions should be individualized according to anatomy and stability.

Nonoperative Treatment

For symptomatic but neurologically stable patients, treatment may include:

Activity modification, analgesics, short-term cervical support, and physical therapy.

Cervical Collar

A cervical collar may provide temporary symptomatic relief but should not routinely be used indefinitely because prolonged immobilization can weaken cervical musculature.

Physical Therapy

Physical therapy may be useful for:

Posture, general conditioning, shoulder-girdle strength, balance, and maintenance of available cervical and thoracic mobility.

Forceful manipulation of the cervical spine should be avoided in patients with congenital instability or stenosis.

Medication

Medication is directed at symptom control.

First-Line Analgesia

NSAIDs may be used for pain when there are no contraindications.

Acetaminophen is another option.

Long-Term Opioids

Chronic maintenance opioid therapy generally has no routine role.

Other Treatments

Selected patients with radicular symptoms may undergo specialist-directed interventions such as epidural steroid injection, although treatment should be tailored to the specific neurologic pathology.

Surgery

Surgery is generally reserved for patients with:

Neurologic deficits, progressive myelopathy, documented instability, significant spinal stenosis, or disabling pain that has failed appropriate nonoperative treatment.

Cervical Fusion or Decompression

Operative treatment may involve:

Decompression, stabilization, fusion, or a combination of procedures, depending on the site of stenosis and instability.

Preoperative Evaluation

Because associated renal and cardiac abnormalities are common, patients undergoing major surgery may require assessment by:

Anesthesiology, internal medicine, cardiology, or other appropriate specialists.

Compensatory Spinal Curves

Scoliosis or compensatory curves below the congenital cervical fusion should be monitored carefully.

Some curves can progress substantially during growth.

Bracing

Bracing may be appropriate for selected flexible progressive curves.

Fusion

Progressive structural deformity that cannot be controlled nonoperatively may require spinal fusion.

Surgery for Associated Anomalies

Surgical treatment may also be required for associated disorders such as:

Sprengel deformity, severe scoliosis, cervical rib-related symptoms, or other congenital musculoskeletal abnormalities.

Follow-Up

Prognosis

Many patients remain asymptomatic or minimally symptomatic for years.

Others develop:

Neck pain, radiculopathy, weakness, myelopathy, or adjacent-segment degeneration later in life.

Outcome depends largely on the number and location of fused vertebrae and the presence of associated neurologic, renal, cardiac, or musculoskeletal abnormalities.

Complications

Spinal Stenosis

Cervical spinal stenosis may become progressively symptomatic with age.

Adjacent-Segment Degeneration

Hypermobile segments adjacent to congenital fusion are subjected to increased stress and may develop premature degenerative disease.

Instability

Excessive motion at unfused segments can lead to:

Subluxation, nerve-root compression, or spinal cord compromise.

Neurologic Injury

Patients with extensive cervical fusion or stenosis may be more vulnerable to neurologic injury after trauma.

Severe injury can result in:

Weakness, paraparesis, quadriparesis, or paralysis.

Patient Monitoring

Patients should be followed periodically by an orthopaedic or spine specialist, particularly during growth or when symptoms change.

Follow-up should assess:

Cervical range of motion, pain, neurologic status, spinal alignment, adjacent-segment degeneration, and development of instability or stenosis.

Patients with associated renal, cardiac, hearing, or other systemic abnormalities should also receive appropriate long-term follow-up with the relevant specialists.