[Melorheostosis of the HWS in an intraspinal lipoma]

Spinal Melorheostosis Associated with Intradural Fibrous Band and Extensive Lipomatosis Causing Thoracic Cord Tethering and Myelomalacia: A Unique Case Highlighting Importance of MRI in Management

Axial melorheostosis is rare with only few cases reported and even fewer with symptoms. While symptoms secondary to neural foramen or spinal canal stenosis caused by hyperostotic bone are common, only three symptomatic cases of spinal melorheostosis with associated intradural lipomatous lesions have been reported to date. In none of them the fibrous component of lipofibromatous lesion was identified preoperatively on magnetic resonance imaging. We report here a case of 18-year-old male who presented with thoracic myelopathy secondary to widespread spinal melorheostosis associated with extensive intradural lipomatosis and fibrous component in thoracic lipoma, causing tethering of thoracic spinal cord and myelomalacia. The patient was treated with T2 to T9 posterior instrumented stabilization followed by T3 to T8 laminectomy along with selective thoracic lipofibromatous tumor debulking. Detection of the fibromatous component in multilevel extensive intradural lipomatosis associated with melorheostosis is helpful in planning selection of the level of surgical excision and decompression.

Cross-Sectional Imaging Useful in Melorheostosis

Melorheostosis is a rare disease of bone overgrowth that is primarily diagnosed based on imaging studies. Recently, the association of different radiological patterns of the disease with distinct genetic cause was reported. Several case reports have described the radiological findings in patients with melorheostosis. However, the added value of cross‐sectional imaging with CT and MRI beyond X‐rays has not been investigated. The aim of the current study was to investigate this existing gap in knowledge. Forty patients with melorheostosis seen at the National Institute of Health Clinical Center were included in the study, and all their imaging studies were analyzed. The sequence of interpretation was X‐ray followed by CT and then MRI. CT images were extracted from whole‐body 18F‐sodium fluoride positron emission tomography/CT studies. The information from CT reclassified the initial X‐rays based radiological pattern in 13 patients. Additionally, CT comprehensively identified joint involvement and disease extent. In 76% of patients (n = 29) who underwent MRI, additional findings were noted, ranging from soft tissue edema to identification of soft tissue masses and incidental findings. MRI did not provide additional information on skeletal lesions beyond CT scans. However, it revealed the extension of soft tissue ossification into ischiofemoral space in four patients who complained of deep gluteal pain consistent with ischiofemoral impingement syndrome. In addition, MRI revealed soft tissue edema in 20 patients, 9 of whom had bone marrow edema and periosteal edema in the tibias consistent with shin splints. These findings suggest that select patients with melorheostosis should be evaluated with both CT and MRI, particularly patients in whom the distribution of pain does not correlate with the anatomic location of the disease in plain radiographs. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.