SYNOSTOSIS OF CERVICAL SPINE (KLIPPEL-FEIL SYNDROME)
Klippel-Feil syndrome refers to the congenital fusion of two or more cervical vertebrae. In some patients, the entire cervical spine is involved. The fusion is a result of failure of segmentation of the cervical somites during the third to eighth weeks of embryonic development. Although the etiology is not yet determined, the developmental defect is not limited to the cervical spine. Unilateral or bilateral elevation of the scapula occurs in 25% to 30% of patients. Other, less apparent defects in the genitourinary, nervous, and cardiopulmonary systems and hearing loss often occur in patients with Klippel-Feil syndrome.
Clinical Manifestations. The classic clinical signs of the syndrome low posterior hairline, short neck, and limitation of neck motion are not consistent findings; fewer than one half of patients exhibit all three signs. Although the most common finding is limitation of neck motion, many patients with marked cervical involvement maintain a deceptively good range of motion.
Whereas anomalies of the atlantoaxial joint (C1-2) may be symptomatic, fusion of lower cervical vertebrae causes no symptoms. Rather, the problems commonly associated with Klippel-Feil syndrome originate at the open segments adjacent to the area of synostosis, which may become compensatorily hypermobile. As a result of trauma or increased demands placed on these joints, hypermobility can lead to frank instability or degenerative osteoarthritis. Symptoms may be due to mechanical irritation at open articulations, nerve root irritation, or spinal cord compression. The development of symptoms is most likely with fusion of more than four vertebrae; occipitalization of the atlas plus a C2-3 fusion, leading to excessive demands on the atlantoaxial articulation; and an open articulation between two zones of vertebral fusion.
Potentially serious conditions that are associated with Klippel-Feil syndrome include scoliosis or kyphosis (60% of patients); urinary tract abnormalities (33%); congenital heart disease (14%); and deafness (30%). Because the urinary tract problems are often asymptomatic in children but if present require treatment or monitoring, ultrasonography or evaluation by MRI should be performed routinely.
Radiographic Findings. Radiographic examination can be problematic because fixed bony deformities frequently prevent proper positioning of the patient for standard views and overlapping shadows from the mandible, occiput, and foramen magnum may obscure the upper vertebrae. Standard laminagraphic views of the neck on flexion and extension are therefore helpful, and CT with reconstruction views are helpful in delineating the bony anatomy. MRI is a powerful tool in assessing spinal cord morphology and nerve root impingement. Ossification of the vertebral body is not complete until adolescence, and in children the unossified physes may give the false impression of a normal disc space. Therefore, a suspected fusion in a child should be confirmed with lateral flexion-extension radiographs.
The bony cervical defects may extend to the upper thoracic area, particularly in patients with severe involvement. However, narrowing of the vertebral canal, due to degenerative changes or developmental hypermobility, does not usually occur until adulthood.
Treatment. Children with minimal involvement usually lead a normal, active life with minor or no restrictions or symptoms. Symptoms referable to the cervical spine may occur in adulthood as a result of osteoarthritis or instability of the hypermobile articulations. Although conservative treatment is sufficient in most patients, a few require judicious surgical stabilization. Scoliosis must be monitored carefully and treated if necessary. However, the relatively good prognosis of the cervical condition is overshadowed by the hidden or unrecognized associated anomalies. Early recognition and treatment of these problems may spare the patient further deformity or serious illness.