title: Longitudinal evaluation of corticospinal tract in patients with resected brainstem cavernous malformations using high-definition fiber tractography and diffusion connectometry analysis: preliminary experience.
abstract: OBJECTIVE
  Brainstem cavernous malformations (CMs) are challenging due to a higher symptomatic hemorrhage rate and potential morbidity associated with their resection. The authors aimed to preoperatively define the relationship of CMs to the perilesional corticospinal tracts (CSTs) by obtaining qualitative and quantitative data using high-definition fiber tractography. These data were examined postoperatively by using longitudinal scans and in relation to patients' symptomatology. The extent of involvement of the CST was further evaluated longitudinally using the automated "diffusion connectometry" analysis.
  
  
  METHODS
  Fiber tractography was performed with DSI Studio using a quantitative anisotropy (QA)-based generalized deterministic tracking algorithm. Qualitatively, CST was classified as being "disrupted" and/or "displaced." Quantitative analysis involved obtaining mean QA values for the CST and its perilesional and nonperilesional segments. The contralateral CST was used for comparison. Diffusion connectometry analysis included comparison of patients' data with a template from 90 normal subjects.
  
  
  RESULTS
  Three patients (mean age 22 years) with symptomatic pontomesencephalic hemorrhagic CMs and varying degrees of hemiparesis were identified. The mean follow-up period was 37.3 months. Qualitatively, CST was partially disrupted and displaced in all. Direction of the displacement was different in each case and progressively improved corresponding with the patient's neurological status. No patient experienced neurological decline related to the resection. The perilesional mean QA percentage decreases supported tract disruption and decreased further over the follow-up period (Case 1, 26%-49%; Case 2, 35%-66%; and Case 3, 63%-78%). Diffusion connectometry demonstrated rostrocaudal involvement of the CST consistent with the quantitative data.
  
  
  CONCLUSIONS
  Hemorrhagic brainstem CMs can disrupt and displace perilesional white matter tracts with the latter occurring in unpredictable directions. This requires the use of tractography to accurately define their orientation to optimize surgical entry point, minimize morbidity, and enhance neurological outcomes. Observed anisotropy decreases in the perilesional segments are consistent with neural injury following hemorrhagic insults. A model using these values in different CST segments can be used to longitudinally monitor its craniocaudal integrity. Diffusion connectometry is a complementary approach providing longitudinal information on the rostrocaudal involvement of the CST.
authors.affiliation: Departments of 1 Neurological Surgery and.
authors.forename: Amir H
authors.initials: AH
authors.lastname: Faraji
authors.affiliation: Departments of 1 Neurological Surgery and.
authors.forename: Kumar
authors.initials: K
authors.lastname: Abhinav
authors.affiliation: Department of Psychology, University of Pittsburgh; and.
authors.forename: Kevin
authors.initials: K
authors.lastname: Jarbo
authors.affiliation: Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania.
authors.forename: Fang-Cheng
authors.initials: FC
authors.lastname: Yeh
authors.affiliation: Departments of 1 Neurological Surgery and.
authors.forename: Samuel S
authors.initials: SS
authors.lastname: Shin
authors.affiliation: Department of Psychology, University of Pittsburgh; and.
authors.forename: Sudhir
authors.initials: S
authors.lastname: Pathak
authors.affiliation: Otolaryngology, University of Pittsburgh Medical Center;
authors.forename: Barry E
authors.initials: BE
authors.lastname: Hirsch
authors.affiliation: Department of Psychology, University of Pittsburgh; and.
authors.forename: Walter
authors.initials: W
authors.lastname: Schneider
authors.affiliation: Departments of 1 Neurological Surgery and.
authors.forename: Juan C
authors.initials: JC
authors.lastname: Fernandez-Miranda
authors.affiliation: Departments of 1 Neurological Surgery and.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Friedlander
mesh_terms: D016880:Anisotropy; D056324:Diffusion Tensor Imaging; D005260:Female; D020786:Hemangioma, Cavernous, Central Nervous System / Q000601:surgery*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008137:Longitudinal Studies; D008297:Male; D010291:Paresis / Q000209:etiology / Q000628:therapy; D011183:Postoperative Complications / Q000473:pathology / Q000628:therapy; D011712:Pyramidal Tracts / Q000473:pathology*; D016896:Treatment Outcome; D066127:White Matter / Q000473:pathology / Q000601:surgery; D055815:Young Adult
keywords: ADL = activities of daily living; CC = corpus callosum; CM = cavernous malformation; CN = cranial nerve; CST = corticospinal tract; DSI = diffusion spectrum imaging; DTI = diffusion tensor imaging; FDR = false discovery rate; HDFT = high-definition fiber tractography; ICH = intracerebral hemorrhage; QA = quantitative anisotropy; ROI = region of interest; SRS = stereotactic radiosurgery; brainstem cavernous malformations; corticospinal tract; diffusion MRI; diffusion connectometry; fiber tractography; quantitative anisotropy; vascular disorders