Background: Intervertebral disc herniation has two common types, extrusion and protrusion, which may affect the adjacent vertebrae.In addition, it is associated with significant signal changes in T1 MRI (short TR/TE) and T2 MRI (long TR/TE).
Methods: The present study is a cross-sectional analytic one, in which sampling was performed retrospectively. Cases were randomly selected from the patients undergoing discectomy in our department in a one-year period. Before surgery, MRI images, T1-weighted and T2-weighted sagittal cuts were interpreted by an expert radiologist. Signal intensity of the upper and the lower adjacent vertebra and the operated herniated disc were compared with the normal discs, both in T1-weighted and T2-weighted. Changes in signal intensity were recorded in qualitative variables. Statistical analysis was then performed between two groups.
Results: In the present study, we have evaluated 170 patients undergoing lumbar disc herniation surgery, which included 97 protruded and 86 extruded discs. The patients' age ranged from 21 to 78 years old, with an average of 43.03 ±11.4 years. Evaluating the type of discopathy with the presence of signal changes (hypo or hyper signal changes) demonstrated more signal changes in upper adjacent vertebrae in T2-weighted MRI (45.3%). However, patients with protruded discs showed less changes (30.9%). It showed that the difference was statistically significant (P<0.05).
Conclusion: Extruded discs are associated with increased signal in T1-weighted MRI (short TR/TE) in the upper adjacent vertebrae. Signal changes in T2-weighted MRI (long TR/TE) in upper adjacent vertebrae are significantly more common in extruded discs, in comparison with protruded discs.
Keywords: Extrusion; Lumbar disc herniation; MRI; Protrusion; Signal change.