PMC4533461_01
A-C: Magnetic resonance (MR) images before the first surgery demonstrating a tumor in the left frontal lobe. A: The tumor is hypoin-tense on T1-weighted images. B, C: The tumor is heterogeneous and hyperintense on T2-weighted images. The tumor is mainly located in the inferior frontal gyrus (IFG). The anterior part of the tumor shows a strong high intensity area, while the posterior part of the tumor shows a weak high intensity area. Arrow indicates the pre-central sulcus. D-F: MR images after the first surgery. D: Axial T1-weighted image showing a resection cavity. E, F: T2-weighted images showing that the strong high intensity area has been removed and that the weak high intensity area remains.
nmc-54-587-g1.jpg
PMC4533461_01_nmc-54-587-g1.jpg
F1
T1-weighted images (T1WI) and as a heterogeneous high intensity area on T2-weighted images (T2WI) (Fig. 1A-C). The tumor was mainly located in the left IFG. T2WI was removed (Fig. 1D-F). The pathological diagnosis was oligoastrocytoma and no adjuvant therapy was proposed.
A: Intraoperative view before resection. Dotted line shows the resection margin. B: Intraoperative neuronavigation view demonstrates that each cross point indicates a site that elicited speech arrest. C: Intraoperative view after resection. Arrows indicate the pre-central sulcus. Arrowheads indicate the diagonal sulcus. L: site that elicited speech arrest, T: primary motor area of tongue, F: primary motor area of face.
nmc-54-587-g2.jpg
PMC4533461_01_nmc-54-587-g2.jpg
F2
Stimulator, Integra Radionics, Inc., Burlington, Massachusetts, USA) was used to apply electrical stimulation with a biphasic current intensity between 2 and 6 mA (50 Hz pulse frequency, 1-2 seconds pulse contact). Stimulations allowed the primary orofacial motor area (Fig. 2A). No function was found within the strong high intensity area of the tumor on intraoperative T2WI, which corresponded to the pars opercularis and triangularis (Fig. 2A). Meanwhile, stimulation of the gyrus between the diagonal and pre-central sulcus elicited speech arrest (biphasic current intensity of 4 mA) (Fig. 2A). T2WI (Fig. 2B). The strong high intensity area of the tumor was removed using the diagonal sulcus as the posterior limit and the inferior frontal sulcus as the superior margin (Fig. 2C).
A-C: MR images before the second surgery demonstrating regrowth of the residual tumor just posterior to the prior resection cavity. A: The tumor is hypointense on T1-weighted images. B: The tumor is hyperintense on T2-weighted images. C: The tumor is hyperintense on sagittal FLAIR images. Arrow indicates the pre-central sulcus. D-F: MR images after the second surgery showing that the tumor has been subtotally removed. D: Axial T1-weighted image. E: Axial T2-weighted image. F: Sagittal FLAIR image. FLAIR: fluid attenuated inversion recovery, MR: magnetic resonance.
nmc-54-587-g3.jpg
PMC4533461_01_nmc-54-587-g3.jpg
F3
MR images showed that the recurrent tumor was located just posterior to the prior resection cavity and had partially invaded in the pre-central gyrus (Fig. 3A-C). Postoperative MRI demonstrated that the tumor was sub-totally removed (Fig. 3D-F).
A: Intraoperative view before resection. Dotted line shows the resection margin. B: Intraoperative neuronavigation view demonstrates that each cross point indicates a site that elicited speech arrest during the second surgery. C: Intraoperative view after resection. Arrows indicate the pre-central sulcus. L: site that elicited speech arrest in the first surgery. Circle L: site that elicited speech arrest in the second surgery. Circle W: white matter site that elicited speech arrest in the second surgery. Circle T: primary motor area of tongue. Circle F: primary motor area of face.
nmc-54-587-g4.jpg
PMC4533461_01_nmc-54-587-g4.jpg
F4
Although this area had involved the language area at the first surgery (Fig. 4A), no active functional response was elicited on the tumor surface (biphasic current intensity of 6 mA). Alternatively, speech arrest elicited area was recognized on the ventral part of pre-central gyrus (biphasic current intensity of 2-4 mA) (Fig. 4A). Primary orofacial motor area was confirmed on the cranial side of this area in the precentral gyrus (Fig. 4A). Electrical functional mapping suggested that the language area had shifted posterolaterally, corresponding to an extratumoral area on intraoperative neuronavigation (Fig. 4B). The tumor was removed using the pre-central sulcus as the posterior limit (Fig. 4C).