Rib head dislocation causing spinal canal stenosis in a child with neurofibromatosis, type 1

Abstract

A 10-year-old female with neurofibromatosis type 1 and severe dystrophic scoliosis presented with a two-month history of difficulty ambulating due to low back pain.  The patient did not have any neurological symptoms. MRI of the thoracolumbar spine demonstrated subluxation of the right posterior tenth and eleventh ribs through their respective neural foramina, with mild mass effect on the thecal sac without abnormal cord signal or cord compression.   Groups of neurofibromas were present along the right ribs and paravertebral soft tissues around these levels.   CT evaluation was completed for greater osseous definition. Cases of rib head dislocation into the central canal in the setting of dystrophic scoliosis were documented in only a limited sample of case reports.  The angulated short-segment curvature in dystrophic scoliosis causes vertebral body rotation, foraminal enlargement, spindling of transverse processes, and penciling of the apical ribs.  These changes can alter the articulation of the rib along the transverse process.  The enlarged foramina can also create a larger space into which a rib may displace.  As a result, in most reported cases, the subluxed ribs were on the convex apex of the curve in the mid-to-lower thoracic region.  The risk of cord injury from rib head dislocation makes the complete depiction of the anatomy essential for proper surgical management.