Dilation system and method of using the same

Directional sequential and blunt stimulating dilation systems (10) and related methods for accessing a patient's spine (2) though the patient's psoas muscle (4) include sequential directional dilators (30, 40) or a blunt stimulating dilator (100, 100′) with at least one channel formed therein. Neural elements or nerves (9) of the psoas muscle are preferably mapped using a stimulating probe (20). The stimulating probe is inserted through the psoas muscle toward the patient's spine. The directional sequential dilators may be inserted to dilate the tissue on any side of the stimulating probe without significantly impacting tissue on the opposite side of the stimulating probe, which may be located, proximate the neural elements. The dilators are rendered directional by having bores (35, 45), by means of which they can be inserted over each other and over the probe, which are offset from their longitudinal axes (31, 41).