Article Figures & Data
Figures
- Fig 1.
Flow chart of the procedures. Post OP indicates postoperative; preOP, preoperative; DOF, deformation; EPio, intraoperative electrophysiology; EPpo, postoperative electrophysiology; Navi, Navigation (Sequence); pre, before; post, after; VAT, volume of activated tissue; highres, high-resolution.
- Fig 2.
3D renditions of the corticospinal tract. A, Depiction of a left CST (red) in the fiber-tracking software (StealthViz DTI; Medtronic) but already depicted as a DICOM hull structure. B, Bilateral visualization of the transferred DICOM structure in the planning software (FrameLink 5.0; Medtronic Surgical Navigation). Blue probe simulations indicate intraoperatively tested electrode positions (test el.). PG indicates precentral gyrus; test el. (sim.), simulated test electrode position.
- Fig 3.
Evaluation based on intraoperative electrophysiology: corticospinal tract depiction in axial, coronal, and sagittal (A–C) planes. A, Red dot indicates post hoc simulation of the intraoperative position of the test electrode in the planning software (Framelink 5.0; Medtronic Surgical Navigation) according to microTargeting Drive settings. In this example, 5 mA of intraoperative stimulation resulted in “gaze palsy” as capsular effect. The shortest spatial distance to the medial CST border of 5.5 mm is indicated with a blue circle. Both coordinates (electrode tip, medial border of CST) were recorded and later plotted (Fig 4). Note that the CST is located posterior and lateral relative to the positon of the electrode (A).
- Fig 4.
Postoperative electrophysiologic evaluation by using CT depiction of the DBS electrode artifacts. The 3D helical postoperative CT is superimposed on the planning data. Reconstruction along the main DBS electrode (white) axis, quasiaxial (A) and coronal (B). The minimal spatial distance to the medial border of the CST is 4.0 mm. B, The DBS electrode (inset; geometry; DBS lead model 3389; Medtronic) is seen as a white structure in the STN region. In this example, electrode contact 0 (EC0, deepest contact, 2.3 mm from the electrode tip) elicited capsular effects during postoperative clinical testing. C, 3D rendering of the right (rt) and left (lt) CSTs with DBS electrode artifacts from helical CT.
- Fig 5.
Graphic depiction of the EPio experiment results. Atlas templates in axial (A, 6.2 mm below the midcommissural point [MCP]) and coronal sections (B, 2 mm behind the MCP) (idealized according to Schaltenbrand and Wahren46). Intraoperative electrode positions are represented by black dots. Black lines represent the shortest distance in space to the CST as depicted with the DTI technology. Blue dots show the individual CST penetration in space. Shaded circles indicate estimated volumes of activated tissue around a test electrode, specific to the current that was applied to elicit an electrophysiologic CST response according to Ranck (1975), (Fig 1).20 CST (blue dots) corresponds nicely with electric field borders, indicating that medial CST definition with DTI reliably predicts the CST border as measured with electrophysiology. RN indicates red nucleus. (Of note in A, the CST is always located posterior and lateral to the STN region.)
- Fig 6.
A, Bland-Altman plot, intraoperative measurements. Gray labels indicate individual patients. B, Bland-Altman plot, postoperative measurements. Gray labels indicate individual patients.
