A method of forming an access opening through a psoas muscle to a patients spine includes laterally inserting a stimulating dilator into the psoas muscle. The stimulating dilator has a stimulation channel formed in an outer surface thereof. An electrical pulse is transmitted via an EMG into the stimulating dilator to locate a position of a nerve in the patients psoas muscle. The stimulating dilator is laterally inserted through the psoas muscle and toward the patients spine in a way that avoids the nerve. A stimulating probe is inserted into the stimulation channel along the outer surface of the stimulating dilator while transmitting an electrical pulse via the EMG into the stimulating probe to verify the position of the nerve.
