A child with trisomy 21 requires a general anaesthetic. Which cervical spine abnormality must be considered before positioning the patient?

Correct answer: D. Atlantoaxial instability

• A. CERVICAL RIBS are supernumerary ribs arising from C7 that may cause thoracic outlet syndrome. They are unrelated to trisomy 21.
• B. KLIPPEL-FEIL SYNDROME involves congenital fusion of cervical vertebrae producing a short neck and limited movement, but it is a separate condition, not a feature of Down syndrome.
• C. CONGENITAL SCOLIOSIS is a thoracolumbar deformity and is not the specific cervical concern in trisomy 21.
• D. CORRECT. ATLANTOAXIAL INSTABILITY — excessive mobility between C1 and C2 caused by ligamentous laxity — affects roughly 10–20% of people with Down syndrome, with a much smaller proportion symptomatic. Excessive neck extension or flexion risks spinal cord compression, so it is critical during airway management, general anaesthesia and even routine chair positioning. Avoid hyperextending the neck, and enquire about screening status and any symptoms of neck pain, gait change, weakness or altered bladder function.

Note: Other dental considerations in Down syndrome: MACROGLOSSIA with a fissured tongue, mouth breathing, class III tendency with midface hypoplasia, delayed and irregular eruption with hypodontia and microdontia, an unusually LOW caries rate but AGGRESSIVE EARLY-ONSET PERIODONTITIS, and a high prevalence of congenital heart disease (most often an atrioventricular septal defect) requiring assessment for endocarditis prophylaxis.