Introduction: Stereotactically guided lead placement for deep brain stimulation requires a carefully planned out trajectory and approach. Point of entry at the cortex is usually selected to be over a gyrus avoiding veins. The angle of lead entry into the skull is different from the perpendicular direction of burr drill. If the burr hole is not placed properly the inner plate of skull may be in a way of the lead trajectory, which creates a snowball effect of complications from trajectory readjustment to improperly fitting hardware.
Methods: The trigonometric principles were applied to the set up of stereotactic lead insertion in order to elucidate a mathematical equation that would predict precise position of the burr hole in order for the lead to enter exactly in the middle of the opening at the dural level.
Further, twenty DBS patients were reviewed retrospectively in order to elucidate which variables of the equation (angle of lead entry, angle of skull plate, and skull thickness) could be safely generalized for all patients
Results: The resulting equation, that will be presented, is a function of Tangent dependent on skull thickness and the two angles mentioned above. Patient population review showed that the variable may be generalized, however individual application of the equation is more likely to produce favorable results.
Conclusions: This new mathematical equation allows for precise determination of burr hole placement and reduces operator-dependent variability. The equation may be integrated into current navigation software improving precision and safety of the lead placement in DBS surgery. Findings could further be extrapolated to all stereotactic procedures requiring a burr hole for approach.
Patient Care: Use of the equation will potentially reduce OR time related to fixing the complications associated with incorrect burr hole placement and therefore improve safety and outcomes of the DBS surgery.
Learning Objectives: By the conclusion of this session, participants should be able to understand why careful burr hole placement is essential and how to improve the precision in selecting the entry point on the skull.