Answer to the Letter to the Editor of A. Hidalgo-Ovejero concerning “Intradural lumbar disc herniation: report of five cases with literature review” (by L. G. Ducati, M. V. Silva, M. M. Brandão, F. R. Romero, M. A. Zanini; Eur Spine J. doi:10.1007/s00586-012-2631-2) - Ducati, Luis Gustavo (Springer-Verlag, 2013)