 I then used the cutting and diamond burs to incise the skull above the external auditory canal so as to expose the dura underneath this and extended it posteriorly to the sigmoid sinus, dissecting or exposing the dura to the level of the jugular bulb. 
I then used the cutting and diamond burs to incise the skull above the external auditory canal so as to expose the dura underneath this and extended it posteriorly to the sigmoid sinus , dissecting or exposing the dura to the level of the jugular bulb .