Temporal lobe structural evaluation after transsylvian selective amygdalohippocampectomy

Abstract

<jats:sec><jats:title>OBJECTIVE</jats:title><jats:p>Mesial temporal lobe epilepsy (MTLE) is the most common type of focal epilepsy in adolescents and adults, and in 65% of cases, it is related to hippocampal sclerosis (HS). Selective surgical approaches to the treatment of MTLE have as their main goal resection of the amygdala and hippocampus with minimal damage to the neocortex, temporal stem, and optic radiations (ORs). The object of this study was to evaluate late postoperative imaging findings on the temporal lobe from a structural point of view.</jats:p></jats:sec><jats:sec><jats:title>METHODS</jats:title><jats:p>The authors conducted a retrospective evaluation of all patients with refractory MTLE who had undergone transsylvian selective amygdalohippocampectomy (SAH) in the period from 2002 to 2015. A surgical group was compared to a control group (i.e., adults with refractory MTLE with an indication for surgical treatment of epilepsy but who did not undergo the surgical procedure). The inferior frontooccipital fasciculus (IFOF), uncinate fasciculus (UF), and ORs were evaluated on diffusion tensor imaging analysis. The temporal pole neocortex was evaluated using T2 relaxometry.</jats:p></jats:sec><jats:sec><jats:title>RESULTS</jats:title><jats:p>For the IFOF and UF, there was a decrease in anisotropy, voxels, and fibers in the surgical group compared with those in the control group (p &lt; 0.001). An increase in relaxometry time in the surgical group compared to that in the control group (p &lt; 0.001) was documented, suggesting gliosis and neuronal loss in the temporal pole.</jats:p></jats:sec><jats:sec><jats:title>CONCLUSIONS</jats:title><jats:p>SAH techniques do not seem to totally preserve the temporal stem or even spare the neocortex of the temporal pole. Therefore, although the transsylvian approaches have been considered to be anatomically selective, there is evidence that the temporal pole neocortex suffers structural damage and potentially functional damage with these approaches.</jats:p></jats:sec>

Transsylvian amygdalohippocampectomy for mesial temporal lobe epilepsy: Comparison of three different approaches

“…TU‐AH was proposed by Coppens et al as an alternative for approaching the temporal horn by adopting an anteromesial route through the piriform cortex of the uncus 18 . In addition to temporal neocortex preservation, the TU‐AH approach showed relative preservation of the UF, as demonstrated by imaging studies and postmortem dissections 3,16,18 . The UF is described as the tract responsible for the structural connectivity between the temporal lobe (uncus, entorhinal cortex, perirhinal cortex, and temporal pole) and frontal lobe (lateral orbitofrontal cortex and frontal pole) 26 .…”

“…We then changed our surgical strategy to the TU‐AH approach to avoid direct damage to TS components (uncinate fasciculus [UF], inferior fronto‐occipital fasciculus [IFOF], and the anterior portion of the optic radiations) 3 . However, our late postoperative MRIs demonstrated prominent atrophy of the temporal pole following both TI‐AH and TU‐AH 16 . In light of evidence of temporal pole atrophy, gliosis, and possible loss of function following selective TI‐AH and TU‐AH approaches, we have used a new transsylvian strategy (TP‐AH) since 2013 17,19 …”

“…Many groups have focused on comparisons between selective amygdalohippocampectomy and standard ATL. However, literature is still controversial regarding the benefits of transsylvian approaches, and only a few studies have evaluated the effects of using different strategies other than ATL 16 . The purpose of this study was to evaluate seizure control, TS damage, VFDs, and neuropsychological performance following three transsylvian techniques: temporopolar (TP‐AH), transinsular (TI‐AH), and transuncus (TU‐AH) amygdalohippocampectomy 17–19 …”

Temporopolar amygdalohippocampectomy: seizure control and postoperative outcomes

“…The selective transsylvian approach for amygdalohip- 4 which is suggestive of gliosis and a possible loss of function. Concerning TP function, the participation of this structure in cognitive performance is a matter of debate.…”

“…3 Although use of the selective transsylvian approach is intended to preserve the lateral temporal neocortex, postoperative imaging analyses of our patients revealed a frequent temporal pole (TP) atrophy, likely attributable to that surgical approach, as well as a high incidence of temporal stem (TS) damage. 4 Additionally, meta-analyses and systematic reviews report significant improvement in seizure control, or at least a tendency toward better outcomes, following anterior temporal lobectomy (ATL) compared to selective approaches. [5][6][7][8] This critical information, coupled with our own experience, supported utilizing an anterior opening of the Sylvian fissure to remove the TP, with the limen insula as the posterior limit, to gain better exposure of the uncus and the anterior portion of the temporal horn.…”