An implantable electrode arrangement for a cochlear implant system comprising: an extracochlear electrode lead configured for carrying one or more cochlear stimulation signals from a proximal end of the electrode lead at a mastoid opening in a patient mastoid bone into the middle ear to a distal end of the electrode lead at a cochlear opening in the outer surface of a patient cochlea; an intracochlear electrode array configured for insertion through the cochlear opening into the patient cochlea, the electrode array having a proximal end connected to the distal end of the electrode lead, and an outer surface with a plurality of stimulation contacts configured for applying the cochlear stimulation signals to target neural tissue within the patient cochlea; and an insertion mechanism comprising: i. a retraction limiter configured to fit around and securely engage a portion of the distal end of the electrode lead, the retraction limiter having a proximal end, a distal end, an outer surface, and a plurality of flexible retraction limiting projections longitudinally distributed along the outer surface of the retraction limiter between the proximal end of the retraction limiter and the distal end of the retraction limiter, ii. an insertion tube configured to fit around the electrode array and the retraction limiter and to engage against the outer surface of the patient cochlea at the cochlear opening, and iii. an insertion plunger configured to fit within the insertion tube and engage against the proximal end of the retraction limiter; wherein the insertion mechanism is operable for the insertion plunger to slide within the insertion tube to push against the proximal end of the retraction limiter to push: i. the electrode array through the cochlear opening into the patient cochlea, and ii. at least a portion of the retraction limiter through the mastoid opening so that when the insertion tube is withdrawn back through the mastoid opening, one or more of the retraction limiting projections displaces out away from the outer surface of the retraction limiter and blocks the mastoid opening so as to prevent retraction of the electrode lead back out from the middle ear. an extracochlear electrode lead configured for carrying one or more cochlear stimulation signals from a proximal end of the electrode lead at a mastoid opening in a patient mastoid bone into the middle ear to a distal end of the electrode lead at a cochlear opening in the outer surface of a patient cochlea; an intracochlear electrode array configured for insertion through the cochlear opening into the patient cochlea, the electrode array having a proximal end connected to the distal end of the electrode lead, and an outer surface with a plurality of stimulation contacts configured for applying the cochlear stimulation signals to target neural tissue within the patient cochlea; and an insertion mechanism comprising: i. a retraction limiter configured to fit around and securely engage a portion of the distal end of the electrode lead, the retraction limiter having a proximal end, a distal end, an outer surface, and a plurality of flexible retraction limiting projections longitudinally distributed along the outer surface of the retraction limiter between the proximal end of the retraction limiter and the distal end of the retraction limiter, ii. an insertion tube configured to fit around the electrode array and the retraction limiter and to engage against the outer surface of the patient cochlea at the cochlear opening, and iii. an insertion plunger configured to fit within the insertion tube and engage against the proximal end of the retraction limiter; i. a retraction limiter configured to fit around and securely engage a portion of the distal end of the electrode lead, the retraction limiter having a proximal end, a distal end, an outer surface, and a plurality of flexible retraction limiting projections longitudinally distributed along the outer surface of the retraction limiter between the proximal end of the retraction limiter and the distal end of the retraction limiter, ii. an insertion tube configured to fit around the electrode array and the retraction limiter and to engage against the outer surface of the patient cochlea at the cochlear opening, and iii. an insertion plunger configured to fit within the insertion tube and engage against the proximal end of the retraction limiter; wherein the insertion mechanism is operable for the insertion plunger to slide within the insertion tube to push against the proximal end of the retraction limiter to push: i. the electrode array through the cochlear opening into the patient cochlea, and ii. at least a portion of the retraction limiter through the mastoid opening so that when the insertion tube is withdrawn back through the mastoid opening, one or more of the retraction limiting projections displaces out away from the outer surface of the retraction limiter and blocks the mastoid opening so as to prevent retraction of the electrode lead back out from the middle ear. i. the electrode array through the cochlear opening into the patient cochlea, and ii. at least a portion of the retraction limiter through the mastoid opening so that when the insertion tube is withdrawn back through the mastoid opening, one or more of the retraction limiting projections displaces out away from the outer surface of the retraction limiter and blocks the mastoid opening so as to prevent retraction of the electrode lead back out from the middle ear.