Atlantoaxial Instability and Cervical Cord Compression in Morquio Syndrome

A15-YEAR-OLD WOMAN had mucopolysaccharidoses type 4A (Morquiosyndrome). Recent neck pain, progressive weakness, and numbness in 4 extremities were described. Physical examination revealed decreased muscle power, increased deep tendon reflex, and positive Hoffman sign. A brain and cervicalcordmagneticresonanceimage was obtained and showed mild atlantoaxial subluxation, odontoid hypoplasia, and thickened soft tissue without contrast enhancement anterior to the cord, which contributed to cervical cord compression (Figure). The patient was later referred to another hospital for surgical intervention. COMMENT Odontoid hypoplasia is a characteristic finding in Morquio syndrome, causedbyimpairedossificationofthe odontoid process. Odontoid hypoplasia and adjacent ligamentous laxity create instability and frequent movementofatlantoaxialjunction,resultinginatlantoaxialsubluxationand thickenedfibrocartilaginoustissueanterior to the cervical cord and causing further cord compression. Patientswithatlantoaxialinstabilityare prone to sudden death after a minor fall. 1 Similarconcernsmayariseinindividuals with other types of mucopolysaccharidoses, Down syndrome, and connective tissue disorderssuchasEhlers-Danlossyndrome. 2 Asaresult,prophylacticcer