Is there a condition where people are born without the top three vertebrae of the spine?

Congenital Absence of Upper Cervical Vertebrae

Yes, there is a rare congenital condition where individuals can be born with absent or severely hypoplastic upper cervical vertebrae, though complete absence of all three top vertebrae (C1, C2, C3) is extremely rare. The most clinically relevant condition is absence of vertebra, which occurs at a rate of approximately 1.2 per 100,000 pediatric patients 1.

Specific Conditions Involving Upper Cervical Vertebral Absence

Klippel-Feil Syndrome

• Klippel-Feil syndrome (KFS) is the primary condition associated with congenital fusion or absence of cervical vertebrae, occurring at a rate of 4.3 per 100,000 pediatric patients 1.
• KFS can present with vertebral malformations including fused (block) vertebrae, hemivertebrae, or sagittally clefted (butterfly) vertebrae in the cervical region 2.
• Approximately 25% of patients with KFS have cervical spine instability, particularly at the C1-C2 level, which significantly impacts morbidity 2.

Isolated Vertebral Absence

• Complete absence of vertebra is documented but extremely rare at 1.2 per 100,000 cases 1.
• More commonly, patients present with hemivertebrae (incomplete vertebral segments) at a rate of 9.1 per 100,000, which represents partial rather than complete absence 1.

Associated Cervical/Occipital Anomalies

Cervical and occipital anomalies are found in almost all children with certain skeletal dysplasias, though they are rarely clinically consequential 3. However, surgical intervention may occasionally be required 3.

Critical Screening Recommendations

• One-time screening for cervical spinal anomalies and instability with radiography, including atlas-dens measurements in flexion and extension, is recommended around age 4 years 3.
• MRI is the preferred imaging modality for evaluating cervical vertebral anomalies and associated neural abnormalities, providing detailed visualization of soft tissue, bone marrow, and spinal canal 2.

Clinical Implications and Complications

Neurological Risks

• Patients with cervical vertebral anomalies require thorough neurological examination focusing on signs of myelopathy or radiculopathy 2.
• Focal neurological findings, muscle weakness, or abnormal deep tendon reflexes may require brain MRI for further evaluation 3.

Anesthetic Considerations

• Airway management is a major concern in patients with upper cervical vertebral anomalies due to limited neck mobility and difficult intubation 2.
• This is particularly critical for surgical procedures and pregnant women requiring delivery 2.
• Operative vaginal delivery should be avoided when possible, as approximately 25% of patients with skeletal dysplasias have C1-C2 instability that places the spinal cord at risk 2.

Associated Systemic Anomalies

Congenital vertebral anomalies rarely occur in isolation. Patients with vertebral abnormalities have high rates of concurrent systemic anomalies:

• Cardiac anomalies are the most common concurrent finding at 6.5% overall 1.
• Diastematomyelia (split cord malformation) patients have the highest rate of other anomalies at 70.1% 1.
• Full MRI workups should be considered in all patients with spinal abnormalities to detect potentially devastating perioperative complications 1.

Common Pitfalls

• History and physical examination alone demonstrate only 62% accuracy for diagnosing intraspinal anomalies, even in the presence of obvious vertebral malformations 3.
• A negative neurological examination does not predict a normal MRI, making imaging essential even in asymptomatic patients 3.
• Delayed presentations of serious systemic anomalies are common, requiring ongoing surveillance 1.