Neurofibromatosis type 1 (musculoskeletal manifestations)

Musculoskeletal manifestations of neurofibromatosis type 1 (NF1), or von Recklinghausen disease, are relatively common among these patients, with skeletal abnormalities occurring in up to 50% ¹.

For a general discussion of the underlying condition, please refer to the article on neurofibromatosis type 1. 

Clinical presentation

Mass effect and pressure-induced changes caused by skin and soft tissue enlargement associated with plexiform neurofibromas may cause deformities on the underlying bone.

Spinal deformities are common in patients with NF1, occurring in up to 50%. Scoliosis is most common and can occur in 21% of NF1 patients ¹.

Bowing and pseudarthrosis are related to mesodermal dysplasia and can occur in a variety of bones, but commonly affects the tibia. 

Neoplasms

In result of the inactivation of a tumor suppressor gene, NF1 is also associated with increased incidence of numerous tumors, such as rhabdomyosarcoma.

Radiographic features

The imaging spectrum includes

• kyphoscoliosis

• vertebral scalloping: can be associated with dural ectasia or neurofibromas

• intrathoracic meningocele

• dural ectasia

• hypoplastic posterior elements: thinning of the pedicles, transverse processes, and lamina

• transverse process spindling

• enlarged neural foramina

• ribbon rib deformity, rib notching, and dysplasia

• extrinsic pressure may result in deficient bone formation that could be expressed as cortical thinning, erosive defects, sclerosis, and periosteal proliferation

• tibial pseudoarthrosis or, less commonly, ulnar pseudoarthrosis

• bony dysplasias: especially affecting tibia

• severe bowing: both lateral and anterior

• multiple non-ossifying fibromas: metaphysis of long bones well-defined, expansile lucent lesions with sclerotic margins

• limb hemihypertrophy

• atrophic thinned / absent fibulas

• lambdoid suture defect: radiolucency present near the lambdoidal suture

• localized gigantism