Spinal cord injury in I-cell disease.

I-cell disease (ICD), mucolipidosis II, is an autosomal recessive syndrome resulting from defective phosphorylation of acid hydrolases. The diagnosis is made in early childhood and in most cases death occurs by age 5 as a result of cardiorespiratory complications. Pathologic changes are limited to mesenchymal tissues. We treated two children with ICD who developed atlantoaxial dislocation and myelopathy following minor injuries. The first child developed cardiovascular instability with manipulation of the C1 ring at operation, necessitating removal of the arch of C1 and fusion from occiput to C2. The second child was quadriplegic following anatomic reduction of the C1-C2 dislocation at operation during which somatosensory evoked potentials (SSEPs) showed no deleterious change. The atlantoaxial joint is unstable in ICD due to an incompetent transverse ligament infiltrated by storage cells. A cartilaginous, rather than calcified, odontoid process may contribute to the instability. The intraoperative neural injury occurred during attempts to effect anatomical reduction of the chronically dislocated C1-C2 joints and could have resulted from inadvertent trauma to the vertebral arteries and subsequent infarction of the cord. The lack of change in the intraoperative SSEPs was probably due to relative sparing of the posterior columns during the cord injury. We recommend that children with ICD and atlantoaxial instability undergo closed reduction of any existing malalignment followed by posterior C1-C2 fusion as long as the operative risk is not prohibitive. If preoperative closed reduction is not readily feasible and the cord is severely compromised, the C1 arch should be removed and the occiput fused to C2. Forceful attempts at anatomical reduction of the chronically dislocated C1-C2 segments should be avoided.