Glioma infiltration of the corpus callosum: early signs detected by DTI

Abstract

The most frequent primary brain tumors, anaplastic astrocytomas (AA) and glioblastomas (GBM): tend to invasion of the surrounding brain. Histopathological studies found malignant cells in macroscopically unsuspicious brain parenchyma remote from the primary tumor, even affecting the contralateral hemisphere. In early stages, diffuse interneural infiltration with changes of the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) is suspected. The purpose of this study was to investigate the value of DTI as a possible instrument of depicting evidence of tumor invasion into the corpus callosum (CC). Preoperatively, 31 patients with high-grade brain tumors (8 AA and 23 GBM) were examined by MRI at 3 T, applying a high-resolution diffusion tensor imaging (DTI) sequence. ADC- and FA-values were analyzed in the tumor-associated area of the CC as identified by fiber tracking, and were compared to matched healthy controls. In (MR-)morphologically normal appearing CC the ADC values were elevated in the tumor patients (n = 22; 0.978 × 10(-3) mm²/s) compared to matched controls (0.917 × 10(-3) mm²/s, p < 0.05), and the corresponding relative FA was reduced (rFA: 88 %, p < 0.01). The effect was pronounced in case of affection of the CC visible on MRI (n = 9; 0.978 × 10(-3) mm²/s, p < 0.05; rFA: 72 %, p < 0.01). Changes in diffusivity and anisotropy in the CC can be interpreted as an indicator of tumor spread into the contralateral hemisphere not visible on conventional MRI.

Fig. 1

Boxplot of rFA values of patients with (CC-affect) and without (CC-normal) obvious affection of the corpus callosum and healthy controls demonstrating significant asterisk differences between the two patient groups and controls as well as between the patient groups

Fig. 2

The Kaplan–Meier-curve comparing the five patients with the lowest ADC-values to the five patients with highest ADC-values and without visible CC infiltration demonstrates a longer survival with low or normal ADC-values

Fig. 3

The 3D-fiber tracts are projected on the sagittal midline 2D-image from the T1 dataset demonstrating the localization of the passage of the CC (a). The fiber tracts originating from a glioblastoma crossing the truncus of the CC—marked in solid red (b)—identify an area mainly in region 2 [16] marked in light blue (b)—Without any abnormal signal or contrast enhancement (c). The follow-up examination 12 months later reveals recurrent tumor infiltrating of the CC with contrast enhancement in the previously identified area (d)