Diffusion tensor imaging correlates with subcortical stimulation for intraoperative pyramidal tract mapping: a preliminary study

Abstract

Objective To evaluate the reliability of diffusion tensor imaging(DTI)-based pyramidal tract(PT)mapping, and to compare with intraoperative subcortical mapping(ISM). Method A prospective study comprised 11 subjects with various intracerebral neoplasms located within or adjacent to PTs was conducted. The PTs were illustrated by the DTI FA maps, and merged with the anatomical structure. During the procedure,DTI- based functional neuronavigation was used for presurgical planning and intraoperative surgical guidance ,whereas ,ISM was regarded as Gold Standard for motor function monitoring. The white matter beneath the resection cavity was electrically stimulated near the PT shown on the functional neuronavigation. Motor response was recorded by compound muscle action potential(cMAP). The distance between PT and the stimulation site was measured. Both techniques of DTI and ISM were compared to assess the accordance for PT mapping.Results ISM verified a high accordance rate with DTI PT mapping in 86% of all subjects(19/22). The cMAP was consistently elicited in 16 stimulation sites. The mean intercept between the positive subcortical stimulation sites and the imaged PTs on DTI was(3.8 ± 1.5)mm. The sensitivity of DTI PT mapping was 100% ,whereas,the specificity was 79%. Conclusions DTI is valuable in delineating PT and visualizing the complicated spatial relationship between the neoplasm and PT. It can be used to identify the descending motor pathways within white matter for presurgical planning, as well as surgical guidance. If possible ,combined usage of DTI -based functional neuronavigation and ISM is recommended for maximal safe resection of tumor in motor area. Key words: Brain neoplasms; Pyramidal tracts; Diffusion tensor imaging; Intraoperative monitoring; Electric stimulation