The authors discuss the utility of anterior transposition of the oculomotor nerve from the lateral wall of the cavernous sinus to widen the corridor posterior to the cisternal segment of the oculomotor nerve; this allows exposure of the anterolateral surface of the midbrain. This additional exposure was successfully used for the resection of a large calcified cavernoma in the upper brainstem of a 67-year-old woman who had presented with sudden onset of left hemiparesis and oculomotor palsy. The patient's postoperative course was uneventful and she displayed symptomatic improvement.