High-definition fiber tracking guidance for intraparenchymal endoscopic port surgery

Technical note

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The authors have applied high-definition fiber tracking (HDFT) to the resection of an intraparenchymal dermoid cyst by using a minimally invasive endoscopic port. The lesion was located within the mesial frontal lobe, septal area, hypothalamus, and suprasellar recess. Using high-dimensional (256 directions) diffusion imaging, more than 250,000 fiber tracts were imaged before and after surgery. Trajectory planning using HDFT in a computer model was used to facilitate cannulation of the cyst with the endoscopic port. Analysis of the proposed initial surgical route was overlaid onto the fiber tracts and was predicted to produce substantial disruption to prefrontal projection fibers (anterior limb of the internal capsule) and the cingulum. Adjustment of the cannulation entry point 1 cm medially was predicted to cross the corpus callosum instead of the anterior limb of the internal capsule or the cingulum. Following cyst resection performed using endoscopic port surgery, postoperative imaging demonstrated accurate cannulation of the lesion, with improved quantitative signal from both the anterior limb of the internal capsule and the cingulum. The observed fiber preservation from the cingulum and the anterior limb of the internal capsule, with minor injury to the corpus callosum, was in close agreement with preoperative trajectory modeling. Comparison of pre- and postoperative HDFT data facilitated quantification of the benefits and costs of the surgical trajectory. Future studies will help to determine whether HDFT combined with endoscopic port surgery facilitates anatomical and functional preservation in such challenging cases.

Abbreviations used in this paper: DT = diffusion tensor; EPS = endoscopic port surgery; HDFT = high-definition fiber tracking.

Article Information

Address correspondence to: Johnathan A. Engh, M.D., Department of Neurological Surgery, UPMC Presbyterian, 200 Lothrop Street, Suite B-400, Pittsburgh, Pennsylvania 15213. email: enghja@upmc.edu.

Current address for Dr. Kassam: Brain Tumor Center, Saint John's Health Center, Santa Monica, California 90404.

Please include this information when citing this paper: published online November 27, 2009; DOI: 10.3171/2009.10.JNS09933.

© AANS, except where prohibited by US copyright law.



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    Comparison of standard DT imaging (left) of the temporal portion of the arcuate fasciculus with HDFT imaging (right) of the same fibers by using the Q-Ball algorithm.

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    Preoperative T1-weighted MR images showing a high signal intensity cystic mass extending from the suprasellar to the right prefrontal paraventricular and anterior centrum semiovale region (A, axial view; C, sagittal view; E, coronal view). Postoperative T1-weighted MR images showing subtotal removal (B, axial view; D, sagittal view; F, coronal view).

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    A–C: Preoperative tractographic reconstruction of left (yellow) and right (blue) prefrontal (Prefr) projection fibers. Superior (A), lateral (B), and anterior (C) views are provided. Right prefrontal projection fibers are clearly diminished (or neurapraxic), with a relative volume loss of 63% in comparison with left prefrontal projection fibers. D: Preoperative tractographic reconstruction of left (yellow) and right (green) cingulum (Cing), superior view. The right cingulum has a relative volume loss of 48% in relation to the left cingulum.

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    Presurgical trajectory planning. A, C, and E: A simulated endoscopic port (yellow) was created to estimate the fiber damage associated with the planned transfrontal approach. This trajectory predicts significant disruption to prefrontal projection (Prefr. Proj.) fibers, moderate disruption to the cingulum, and minimal disruption of callosal fibers. Estimated volume of fiber loss was 18.89 ml (A, anterior view; C, lateral view). Selection of long fibers (length > 70 mm) shows volume of damage of 5.37 ml to the prefrontal projection bundle and the cingulum (E). B, D, and F: An alternative trajectory (blue) was placed 1 cm more medially. The new trajectory predicts selective disruption of fibers of the corpus callosum (Corp. Call.), but not of the prefrontal projection fibers or the cingulum. The estimated volume of fiber loss was 19.84 ml (B, anterior view; D, lateral view). When selecting a minimum fiber length threshold of 70 mm, estimated volume loss decreases to 10.28 ml, with the majority of fibers belonging to the corpus callosum (F). NE = Neuroendoport.

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    Intraoperative photographs. A: Frameless image guidance is used to guide the cannulation by following HDFT parameters. B: The bullet-shaped dilator is gently advanced into the white matter. C: The endoscopic port is left in place, and the fluid content of the cyst is evacuated. D: On visualization of the operative field through the endoscopic port, a large amount of lipomatous tissue was noted. E: A large portion of the lesion extends between the right optic nerve and carotid artery within a dilated opticocarotid cistern. F: Following resection, the optic nerve (N.), tract, carotid artery bifurcation, and A1 and M1 segments all can be well visualized within the operative field. ICA = internal carotid artery.

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    Preoperative and postoperative tractographic reconstructions of the anterior corpus callosum (A), cingulum (B), and prefrontal projection fibers (C). There is a confirmed approximate fiber volume loss of 1.8 ml in the anterior corpus callosum. The cingulum shows improved postoperative volume, probably reflecting alleviation of mass effect. Prefrontal projection fibers are completely preserved, and they have partially recovered their normal configuration, with an improvement of volume that represents approximately 31.5% of the prefrontal projection fibers' unilateral volume. D: A parafascicular HDFT-guided surgical approach has been completed between cingulum (green) and prefrontal projection fibers (blue). Minor disruption of the corpus callosum is identified.

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    Postoperative assessment of presurgical damage estimation. A: The presurgically predicted damage (disruption plus disconnection [Disc.]) of fibers is displayed by using a “virtual” port, as in Fig. 3B, D, and F. B: Postoperative assessment of fibers passing through the “virtual” port used for presurgical estimation shows that most of the fibers that had been predicted to sustain damage are really damaged. C: Retroactive simulation of port-related damage to corpus callosum fibers. The length of damaged fibers (red) is approximately one-third the length of disconnected fibers (yellow). D: Postsurgical assessment of fiber damage provides the volume of fiber disruption but not of fiber disconnection. Total fiber damage is formed by disruption and disconnection. E and F: Superior and lateral views of the brain surface displaying the cortical area (right supplementary motor area) affected by fiber damage (red).



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