Intraoperative MRI–based elastic fusion for anatomically accurate tractography of the corticospinal tract: correlation with intraoperative neuromonitoring and clinical status

OBJECTIVETractography is a useful technique that is standardly applied to visualize subcortical pathways. However, brain shift hampers tractography use during the course of surgery. While intraoperative MRI (ioMRI) has been shown to be beneficial for use in oncology, intraoperative tractography can rarely be performed due to scanner, protocol, or head clamp limitations. Elastic fusion (EF), however, enables adjustment for brain shift of preoperative imaging and even tractography based on intraoperative images. The authors tested the hypothesis that adjustment of tractography by ioMRI-based EF (IBEF) correlates with the results of intraoperative neuromonitoring (IONM) and clinical outcome and is therefore a reliable method.METHODSIn 304 consecutive patients treated between June 2018 and March 2020, 8 patients, who made up the basic study cohort, showed an intraoperative loss of motor evoked potentials (MEPs) during motor-eloquent glioma resection for a subcortical lesion within the corticospinal tract (CST) as shown by ioMRI. The authors preoperatively visualized the CST using tractography. Also, IBEFs of pre- and intraoperative images were obtained and the location of the CST was compared in relation to a subcortical lesion. In 11 patients (8 patients with intraoperative loss of MEPs, one of whom also showed loss of MEPs on IBEF evaluation, plus 3 additional patients with loss of MEPs on IBEF evaluation), the authors examined the location of the CST by direct subcortical stimulation (DSCS). The authors defined the IONM results and the functional outcome data as ground truth for analysis.RESULTSThe maximum mean ± SD correction was 8.8 ± 2.9 (range 3.8–12.0) mm for the whole brain and 5.3 ± 2.4 (range 1.2–8.7) mm for the CST. The CST was located within the lesion before IBEF in 3 cases and after IBEF in all cases (p = 0.0256). All patients with intraoperative loss of MEPs suffered from surgery-related permanent motor deficits. By approximation, the location of the CST after IBEF could be verified by DSCS in 4 cases.CONCLUSIONSThe present study shows that tractography after IBEF accurately correlates with IONM and patient outcomes and thus demonstrates reliability in this initial study.

THE ASSOCIATION BETWEEN LOCATION OF BRAIN LESION AND FINDINGS OF FLEXIBLE ENDOSCOPIC EVALUATION OF SWALLOWING (FEES) IN STROKE PATIENTS: WHICH EXERCISE IS BENEFICIAL?

Background: Dysphagia is a frequent occurrence following stroke. Various brain regions have been shown to control deglutition. However, it is still controversial as to which of the two hemispheres plays more important role in deglutition, and which injured hemisphere is more likely to cause the specific patterns of dysphagia seen in stroke patients. An accurate estimate of the incidence of dysphagia will be critical to assess benefits of dysphagia interventions. Objective: To investigate whether patterns of dysphagia are associated with the location of brain lesion in stroke patients and to examine whether pharyngeal strengthening exercise and hyolaryngeal exercise are proper for patients, based on the findings of FEES and location of brain lesion. Methods: The subjects were stroke outpatients who visited our clinic from January 2016 to April 2018. To localize brain lesion, Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) have been employed. The locations of brain lesions were classified into cortical, subcortical, and brain stem. FEES was conducted to assess the patterns of deglutition disorders. These data were collected via retrospective chart review. Results: Of the 11 subjects, mean age (SD) was 62.73 (8.67) years and seven (63.64%) subjects were male. All subjects got ischemic stroke, eight (72.73%) had right hemispheric lesion and three (27.27%) had left hemispheric lesion. By brain lesion, there were nine subcortical, five cortical, and four brain stem lesions. All FEES findings, especially standing secretion, penetration, residue, and reduced hypopharynx sensitivity were higher in subcortical lesion, followed by brain stem and cortical lesion successively. Conclusion: Right hemisphere was involved more than left hemisphere in dysphagia patients. Standing secretion, penetration, residue, and reduced hypopharynx sensitivity occurs more often in subcortical lesion. Further studies on big samples in a perspective structure are needed. Based on this result, there is a place for pharyngeal strengthening exercise and hyolaryngeal complex range of motion and strengthening exercise to be implemented to the patients with neurogenic dysphagia after stroke.