Yutaka Hayashi, Masashi Kinoshita, Mitsutoshi Nakada and Jun-ichiro Hamada
Disturbance of the arcuate fasciculus in the dominant hemisphere is thought to be associated with language-processing disorders, including conduction aphasia. Although the arcuate fasciculus can be visualized in vivo with diffusion tensor imaging (DTI) tractography, its involvement in functional processes associated with language has not been shown dynamically using DTI tractography. In the present study, to clarify the participation of the arcuate fasciculus in language functions, postoperative changes in the arcuate fasciculus detected by DTI tractography were evaluated chronologically in relation to postoperative changes in language function after brain tumor surgery.
Preoperative and postoperative arcuate fasciculus area and language function were examined in 7 right-handed patients with a brain tumor in the left hemisphere located in proximity to part of the arcuate fasciculus. The arcuate fasciculus was depicted, and its area was calculated using DTI tractography. Language functions were measured using the Western Aphasia Battery (WAB).
After tumor resection, visualization of the arcuate fasciculus was increased in 5 of the 7 patients, and the total WAB score improved in 6 of the 7 patients. The relative ratio of postoperative visualized area of the arcuate fasciculus to preoperative visualized area of the arcuate fasciculus was increased in association with an improvement in postoperative language function (p = 0.0039).
The role of the left arcuate fasciculus in language functions can be evaluated chronologically in vivo by DTI tractography after brain tumor surgery. Because increased postoperative visualization of the fasciculus was significantly associated with postoperative improvement in language functions, the arcuate fasciculus may play an important role in language function, as previously thought. In addition, postoperative changes in the arcuate fasciculus detected by DTI tractography could represent a predicting factor for postoperative language-dependent functional outcomes in patients with brain tumor.
Yutaka Hayashi, Mitsutoshi Nakada, Shingo Tanaka, Naoyuki Uchiyama, Yasuhiko Hayashi, Daisuke Kita and Jun-ichiro Hamada
Fluorescence-guided surgery using 5-aminolevulinic acid (5-ALA) has been broadly recognized as a beneficial tool for the resection of glioblastoma multiforme (GBM). Fluorescence in the ventricular walls, which were apparently free of macroscopic tumor or MR imaging enhancement indicative of CSF dissemination, was detected during surgery for GBM. To evaluate the clinical significance of the 5-ALA fluorescence, the authors resected ventricle wall tissue together with the adjacent tumors for pathological examination and then followed up the clinical courses of the patients.
Seven consecutive GBMs located near the lateral ventricle were surgically treated using a fluorescence-guided technique with 5-ALA at the authors' hospital since acquiring instrumentation for the detection of 5-ALA fluorescence in 2007. All of the procedures were performed using a ventricular entry, and 5-ALA fluorescence of the ventricular wall was detected despite the absence of macroscopic tumor invasion of the wall.
A pathological examination of the resected ventricular wall tissues revealed tumor cells in 6 of the 7 cases and disruption of the ependymal cell layer in all 7 cases. Delayed communicating hydrocephalus followed surgery in all 7 patients, and ventricular wall enhancements on MR imaging were demonstrated after hydrocephalus in 2 of the patients.
Data in this study suggest that 5-ALA fluorescence of the ventricular wall may be predictive of postoperative hydrocephalus associated with CSF dissemination even in cases without evidence of CSF dissemination on MR imaging studies before surgery. The authors also speculate that postoperative radiotherapy covering the whole ventricular system may be a better therapeutic option for these patients.
Masashi Kinoshita, Harumichi Shinohara, Osamu Hori, Noriyuki Ozaki, Fumiaki Ueda, Mitsutoshi Nakada, Jun-ichiro Hamada and Yutaka Hayashi
Recently, intraoperative mapping has disclosed that, in addition to the classic language centers (that is, the Broca and Wernicke centers), other cortical regions may also play an important role in language organization. In the prefrontal cortex, although the lateral superior frontal gyrus (LSFG) could have language-related functions, there are no detailed reports that demonstrate the anatomical connection between the LSFG and other well-known language cortices, such as the Broca center. To show the existence of the structural connection, white matter association fibers between the inferior frontal gyrus (IFG) and the LSFG were examined using fiber dissection (FD) and diffusion tensor (DT) imaging–based tractography.
Eight cadaveric cerebral hemispheres were dissected to reveal the association fibers between the IFG and LSFG. The DT imaging–based tractography studies targeting the prefrontal cortex were obtained in 53 right-handed patients who had no organic cerebral lesions.
The association fiber tract between Brodmann area 44/45 (the Broca center in the dominant hemisphere) and LSFG were detected in all specimens by FD. In the DT imaging–based tractography studies, the tract was identified in all patients bilaterally, except for the 4 in whom the tract was detected only in the left hemisphere. This tract was spread significantly wider in the left than in the right hemisphere, and left lateralization was evident in male patients.
Based on its character, this tract was named the Broca-LSFG pathway. These findings suggest a close relationship between this pathway and language organization. The structural anatomy of the Broca-LSFG pathway may explain speech disturbances induced by LSFG stimulation that are sometimes observed during intraoperative language mapping.