Stereotactic guide assemblies and methods of using same

A stereotactic guide assembly comprising:

• an implantable body having an interior chamber and a first passageway that extends through the implantable body into communication with the interior chamber, the implantable body having a stepped-down configuration wherein the implantable body comprises an upper portion connected to a lower portion, the upper portion at least partially defined by an external coupling feature and having an outer diameter greater than an outer diameter of the lower portion, the implantable body sized and dimensioned to fit within a burr hole located in a cranium of a human subject;
• and
• a fastener configured to fit in the interior chamber, the fastener having a second passageway extending therethrough and an internal coupling feature adapted to releasably engage the external coupling feature.