Context : The study of dynamical processes in protoplanetary disks is essential to understand planet formation .
In this context , transition disks are prime targets because they are at an advanced stage of disk clearing and may harbor direct signatures of disk evolution .

Aims : We aim to derive new constraints on the structure of the transition disk MWCÂ 758 , to detect non-axisymmetric features and understand their origin .

Methods : We obtained infrared polarized intensity observations of the protoplanetary disk MWCÂ 758 with SPHERE/VLT at 1.04Â \mu m to resolve scattered light at a smaller inner working angle ( 0.093″ ) and a higher angular resolution ( 0.027″ ) than previously achieved .

Results : We observe polarized scattered light within 0.53″ ( 148Â au ) down to the inner working angle ( 26Â au ) and detect distinct non-axisymmetric features but no fully depleted cavity .
The two small-scale spiral features that were previously detected with HiCIAO are resolved more clearly , and new features are identified , including two that are located at previously inaccessible radii close to the star .
We present a model based on the spiral density wave theory with two planetary companions in circular orbits .
The best model requires a high disk aspect ratio ( H / r \sim 0.20 at the planet locations ) to account for the large pitch angles which implies a very warm disk .

Conclusions : Our observations reveal the complex morphology of the disk MWCÂ 758 .
To understand the origin of the detected features , the combination of high-resolution observations in the submillimeter with ALMA and detailed modeling is needed .