What is Klippel-Feil syndrome in the spine?

Klippel-Feil Syndrome in the Spine

Klippel-Feil syndrome (KFS) is a rare congenital disorder characterized by the abnormal fusion of two or more cervical vertebrae, resulting in a classic triad of short neck, limited neck range of motion, and low posterior hairline, though less than half of affected individuals display all three features. 1

Pathophysiology and Classification

• KFS occurs due to failure of cervical somite segmentation and differentiation during embryonic development, appearing either as a sporadic mutation or associated with specific genetic factors 1
• The most commonly affected vertebral levels are C2-C3 and C5-C6 1
• KFS can be classified according to the Samartzis system:
  • Type I: Single level fusion
  • Type II: Multiple non-contiguous fused segments
  • Type III: Multiple contiguous fused segments 2

Clinical Presentation

• Pain is experienced by over 90% of KFS patients, with median age of onset at 16 years and worsening at 28 years 2
• Pain is primarily located in the shoulders/upper back (76%), neck (72%), and back of head (50.7%) 2
• Pain quality is typically described as tightness (73%), dull/aching (67%), and tingling/pins and needles (49%) 2
• Type III fusions (multiple contiguous segments) are significantly associated with greater nerve pain, headache/migraine pain, and joint pain compared to other fusion types 2
• Neurological symptoms may include balance and gait disturbances, particularly in patients with more severe disease 2

Associated Conditions

• KFS can be associated with various congenital anomalies:
  • Orthopedic conditions: Sprengel deformity, congenital scoliosis, and other cervical spine abnormalities 1
  • Neurological conditions: Split cord malformation (SCM) 3
  • Cardiovascular abnormalities 4
  • Genitourinary malformations 1
• Split cord malformations associated with KFS may present with vertebral malformations including hemivertebrae, sagittally clefted (butterfly) vertebrae, or fused (block) vertebrae 3
• Anterior cervical meningomyelocele is a rare association with KFS that may require surgical intervention if causing nerve root compression or myelopathy 5

Diagnostic Evaluation

• MRI is the preferred imaging modality for evaluating KFS and associated neural abnormalities, providing detailed visualization of soft tissue, bone marrow, and spinal canal 3
• Radiographs can identify vertebral fusion, spondylosis, malalignment, or spinal canal stenosis 3
• CT scans may be useful as supplementary imaging, especially when evaluating bony structures 6
• Neurological examination should focus on signs of myelopathy or radiculopathy 3
• Airway assessment is crucial in KFS patients who may require anesthesia, as difficult airway management is common 3

Management

• Asymptomatic individuals with KFS generally require observation only 1
• Pain management options include:
  • Oral over-the-counter medications (rated 3/5 for effectiveness) 2
  • Oral prescribed medications (rated 3/5 for effectiveness) 2
  • Injections (rated 2/5 for effectiveness) 2
  • Surgery (rated 3/5 for effectiveness) 2
• Surgical intervention is indicated for:
  • Progressive neurological deficits 5
  • Myelopathy 5
  • Severe pain unresponsive to conservative treatment 2
  • Correction of significant deformity 1
• Cervical disc arthroplasty (CDA) is a feasible surgical option for KFS patients with symptomatic adjacent segment disease, as it preserves segmental and global mobility 7
• Patients who undergo surgical treatment typically have more comorbidities and neurological symptoms than those managed non-surgically 2

Special Considerations

• Sports participation recommendations should be individualized based on the level and number of vertebrae involved in the fusion 1
• Pregnant women with KFS require special anesthetic planning for delivery due to potential airway management difficulties 3
• A multidisciplinary approach involving neurosurgery, orthopedics, and other specialties is recommended for complex presentations 1

Prognosis

• The natural course of KFS is variable, with many patients remaining asymptomatic 1
• Pain tends to worsen with age, with median age of pain worsening at 28 years 2
• Patients with Type III fusions (multiple contiguous segments) generally experience more significant pain and neurological symptoms 2
• Surgical outcomes are generally favorable for appropriately selected patients, with improvement in neurological function and pain relief 5, 7