✓Cervicomedullary compression at the foramen magnum in patients with achondroplasia can be associated with apnea, neurological deficits, and sudden death. Decompressive operations are often performed in symptomatic patients. In asymptomatic patients, the indications for prophylactic decompression are controversial. The authors present the case of a previously neurologically intact 4-month-old girl with achondroplasia who presented with severe hemiparesis after a low-velocity motor vehicle accident. Imaging studies demonstrated osseous compression of the medulla and upper cervical spinal cord with associated parenchymal signal changes. To the authors' knowledge this is the first reported case of a new neurological deficit after a minor trauma in this patient population. The authors review the relevant literature, focusing on the indications for cervicomedullary decompression in infants with achondroplasia. They propose that asymptomatic patients with achondroplasia and osseous compression at the foramen magnum should be offered prophy-lactic surgery if T2-weighted magnetic resonance imaging signal changes in the spinal cord are observed. Prophylactic surgery can be considered an option in patients whose imaging studies do not show signal changes in the spinal cord but demonstrate significant osseous compression and absence of visible subarachnoid spaces.