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Klippel-Feil Spectrum


KEY FACTS

Terminology

  • Synonyms: Klippel-Feil syndrome (KFS)

  • Congenital spinal malformation characterized by segmentation failure of ≥ 2 cervical vertebrae ± thoracic, lumbar segmentation failure

Imaging

  • Single- or multiple-level congenital cervical segmentation and fusion anomalies

  • C2-3 (50%) > C5-6 (33%) > craniovertebral junction, upper thoracic spine

  • Vertebral bodies usually smaller than normal

  • Vertebral body narrowing (“wasp waist”) at fused rudimentary disc space ± fusion of posterior elements

Top Differential Diagnoses

  • Juvenile idiopathic arthritis

  • Surgical fusion

  • Chronic sequelae of discitis

  • Ankylosing spondylitis

Pathology

  • No universally accepted etiology; embryonic insult postulated between 4th and 8th weeks

  • Sporadic; familial genetic component with variable expression identified in many patients

Clinical Issues

  • Classic triad (33-50%): Short neck, low posterior hairline, and limited cervical motion

  • In practice, however, wide variation in clinical, anatomical expression

Diagnostic Checklist

  • Much KFS morbidity and nearly all mortality related to visceral system dysfunction

  • Look for instability, progressive degenerative changes, cord/brainstem compression

Sagittal graphic (KFS 2) shows congenital fusion
of the C5-C6 vertebrae and spinous processes, with characteristic rudimentary disc space and distinctive “waist” typical of congenital fusion.

Lateral radiograph (KFS type 2) demonstrates typical C2/3 congenital segmentation failure (“fusion”) with characteristic rudimentary disc space
and fusion of the facets and spinous processes. The disc space appearance helps distinguish from postcervical fusion.

Sagittal bone CT (KFS 1) reveals extensive fusion of all cervical vertebrae and posterior elements, with the characteristic hypoplastic appearance of the vertebrae and intervertebral disc spaces. In this patient, there is additionally incorporation of C1 into the skull base (“occipitalization of the atlas”).

Axial bone CT (KFS 1, severe segmentation anomalies) demonstrates the vertebral articulation of a unilateral left omovertebral bone
.

TERMINOLOGY

Synonyms

  • Klippel-Feil syndrome (KFS)

Definitions

  • Congenital spinal malformation characterized by segmentation failure of ≥ 2 cervical vertebrae ± thoracic, lumbar segmentation failure

IMAGING

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