RADIOLOGICAL AND PATHOLOGICAL ANALYSIS OF CALCIFIED THORACIC DISCAL HERNIATION: 13 CASES

Abstract

Purpose: Calcified thoracic discal herniation is an uncommon entity. The purpose of this study was to analyse the population concerned to search for radiological signs of sequellar Scheuermann disease and the characteristic features of hernias in this context and to compare computed tomography (CT) and magnetic resonance imaging (MRI) findings with intraoperative and histological findings.

Material and methods: A retrospective series of 13 patients with symptomatic calcified thoracic discal herniation (CTDH) who underwent surgery from 1996 to 2001 was analysed. Mean age was 50.7 years. The population included ten men and three women. CT was performed in all cases, with myelography in two. MRI was performed in eleven cases with DTPA-gadolinium injection in six. Two neuroradiologists blinded to intraoperative findings reviewed the images independently to search for radiological signs predictive of dural adherence and/or penetration and the presence of Scheuermann squellae. Pathology data were available for five patients.

Results: All herniations occurred in the mid to lower thoracic level in patients in their fourth or fifth decade. The disk was calcified at the zone of herniation in all cases. The hernia occupied more than half of the spinal canal in 70% of patients. The nature of the lesion was analysed on axial CT and T1/T2 weighted MRI sequences with fat suppression. Images confirmed the pathological findings: the majority of the calcified herniations were composed of mature haversian bone. In ten of the eleven cases, the radiological interpretation of the hernia/dural interface was found to correspond to the intraoperative observation.

Discussion: The sensitivity and specificity of T2 weighted MRI with gadolinium injection of the hernia/dural interface is superior, enabling prediction of dural penetration. Sequellae of Scheuermann disease found in five patients confirmed a probably non-fortuitous association.

Conclusion: The natural history of CTDH starts with discal calcification in a degenerative spine during posterior migration, followed by bone metaplasia which can involve neighbouring structures such as the longitudinal ligament and lead to penetration of the dura by the mature ossified lesion.