An implantable electrode arrangement for a cochlear implant system is described. An electrode lead contains a lead structure control element configured to control a lead shape of the electrode lead between an insertion state wherein the electrode lead within a mastoid tunnel has a longitudinal lead axis lying entirely along the tunnel axis, and a post-insertion state wherein a facial recess portion of the electrode lead fitting within a limited diameter portion of the mastoid tunnel associated with a facial recess portion of the mastoid bone has a longitudinal lead axis along the tunnel axis, and a storage portion of the electrode lead fitting within an enlarged diameter portion of the mastoid tunnel lateral to the facial recess portion has a longitudinal lead axis coiled in a helical shape radially around the tunnel axis.
