Temporal Lobe Structural Evaluation after Transsylvian Selective Amygdalohippocampectomy

Introduction: Temporal lobe epilepsy (TLE) is the most common type of focal epilepsy in adults and in 65% of cases it is related to hippocampal sclerosis. Selective surgical approaches to the treatment of TLE have as primary goal the resection of the amygdala and hippocampus with minimal aggression to the neocortex, temporal stem (TS) and optic radiations (OR).

Objectives: To define the postoperative consequences to the temporal lobe (TL), from the structural point of view, through imaging methods.

Methods: We performed a retrospective evaluation of 56 patients with refractory TLE who underwent surgical treatment with selective amygdalohippocampectomy techniques: transinsular (TI) in 29 patients and transuncus (TU) in 27 patients. The surgical group was compared to a control group of 30 adults with TLE and indication of surgical treatment but not submitted to the procedure. The inferior fronto-occipito fasciculus (IFOF), uncinate fasciculus (UF) and OR were evaluated by diffusion tensor image analysis (DTI). The changes detected in the tractography maps were evaluated for fractional anisotropy, number of voxels and fibers. The neocortex T2 relaxometry was also compared between the control group and the surgical group.

Results: There were interruptions in the IFOF fibers in 50% of the patients who underwent surgical treatment (23/29 in the TI group and 5/27 in the TU group), whereas in the control group all the patients had this fasciculus preserved. The UF was interrupted in 94.64% of the patients in the surgical group (29/29 in the TI group and 24/27 in the TU group), while the tractography of the UF was preserved in all the cases in the control group. Therefore, in relation to IFOF and UF, there was a decrease in anisotropy, voxels and fibers in the surgical group compared to the control group (p < 0.05). The tractography analysis of the OR showed fibers interruption in 8.92% of the patients, only in the TI group (5/29), with preservation in all patients of the TU and control groups. Increase in relaxometry time of the surgical group compared to the control group (p < 0.05) was also documented.

Conclusion: Selective amygdalohippocampectomy techniques do not seem to preserve the TS from a structural point of view as initially proposed, since postoperative imaging tests with DTI showed impairment of the TL fascicles. In addition, there is a marked increase in gliosis in the remaining TL, evidenced by the increase in the relaxometry time.

No conflict of interest has been declared by the author(s).