Hernie discale thoracique

Abstract

The techniques of modern imaging, particularly magnetic resonance (MRI), have shown the high frequency of thoracic herniated discs (THD). One or more THD have been reported in 11% to 37% of asymptomatic subjects. In contrast, symptomatic forms are rare: less than 0.5% of surgical procedures for herniated discs involve a THD. Clinical signs vary widely from spinal pain, nerve root pain to spinal-cord compression. Among symptomatic THD, some are soft and the others hard, impinging on the anterior aspect of the thecal sac. In such cases, the discs are often voluminous and adherent to the thecal sac, and even intradural, making their surgical resection particularly difficult. Information regarding the nature of the lesions and the interface between the herniated disc and the thecal sac are analyzed in the MRI T1-weighted and T2-weighted sequences, respectively. A hypointense lesion on T1 corresponds to a calcified herniated disc. In the midst of a hypointense lesion on T1-weighted sequence, the presence of hyperintense signal that is no longer visible on fat-suppression sequences corresponds to the presence of fatty marrow. This MRI sign indicates that an ossified hernia is involved. The interface between herniated discs and the dura is more visible on T2-weighted sequences. If preoperative T2-weighted sequences do not show a band of hypointense signal between the THD and the thecal sac or if the connecting angles between the PLL and the THD are acute, complete resection of the lesion cannot be achieved without a dural tear. Instead, we recommend preserving a bony chip adhering to the anterior aspect of the dural sheath to prevent a postoperative cerebrospinal fluid fistula. Anterolateral exposure of these lesions by thoracotomy or thoracoscopy is recommended, because posterolateral approach does not provide sufficient exposure to remove this “rock” embedded in the anterior aspect of the spinal cord.