Imaging description

Skeletal abnormalities occur in approximately 25–40% of NF I cases. Scoliosis is the most common skeletal manifestation in NF I. The vertebrae are often abnormal showing posterior scalloping and enlarged intervertebral foramina due to dural ectasia or neurofibromas of the nerve roots. Posterior scalloping is believed to be mainly due to dural ectasia whereas anterior and lateral scalloping are the result of mesodermal dysplasia (Figure 79.1). In the rib cage the underlying mesenchymal abnormality combined with the erosions by intercostal neurofibromas result in ribbon-like deformities of the ribs. Bowing in the long bones in patients with NF I should suggest the possibility of early or ensuing congenital pseudoarthrosis of the tibia (Figure 79.2). Non-ossifying fibromas of the long bones in the lower extremities are also a feature of NF I.

Lateral thoracic meningoceles are the result of protrusion of the dura and arachnoid through the neural foramina (Figure 79.3). This is most common at the apex of the scoliotic curve and the majority of meningoceles are right sided. Chest films of patients with thoracic meningoceles exhibit a short focal scoliosis of the upper thoracic spine convex toward the lesion. The neural foramina appear enlarged and the pedicles show thinning with increased interpediculate distance. The distance between some adjacent ribs may increase.