A 5-month-old male with achondroplasia and foramen magnum stenosis presented for posterior fossa decompression. The sagittal image on magnetic resonance imaging of the cranio-cervical junction (image A) demonstrates severe stenosis of the foramen magnum (white line). The spinal cord is compressed between the overgrown opisthion (white arrow) and the tectorial membrane (arrow heads). The axial image (image B) at the level of the dens (arrow head) demonstrates flattening of the spinal cord (white arrow) between the transverse ligament (dashed white arrow) and the opisthion (white dashed line), with complete effacement of the surrounding cerebrospinal fluid spaces.
Foramen magnum stenosis in these patients can lead to central sleep apnea from spinal cord compression at the cervico-medullary junction and may contribute to the increased risk of sudden death during infancy. Midfacial hypoplasia and hypotonia of upper airway muscles predispose these patients to development of obstructive apnea as well.1 Given the potential consequences of spinal cord compression in achondroplasia, there is general consensus on the need for routine surveillance polysomnography in addition to a detailed history and physical exam. Magnetic resonance imaging should only be performed if indicated by abnormal findings with any of the above.2
Preoperative airway assessment requires particular vigilance, and the potential for difficult mask ventilation and intubation attributable to facial anomalies should be anticipated.3 Management of the airway should aim to minimize cervical movement during intubation because of the risk of worsening cervico-medullary compression with neck hyperextension or uncontrolled head positioning. Smaller endotracheal tubes than standard estimated sizes based on age are often necessary because of smaller airway dimensions.3
The authors declare no competing interests.