LABORATORY INVESTIGATION J Neurosurg Pediatr 25:331–339, 2020 Anterior peri-insular quadrantotomy: a cadaveric white matter dissection study *Pablo Gonzalez-Lopez, MD, PhD,1 Giulia Cossu, MD,2 Etienne Pralong, MD,2 Matias Baldoncini, MD,3 Mahmoud Messerer, MD, MSc,2,4 and Roy Thomas Daniel, MD, MCh2,4 1Department of Neurosurgery, Hospital General Universitario Alicante, Spain; 2Department of Neurosurgery, University Hospital of Lausanne, Switzerland; 3Department of Neurological Surgery, San Fernando Hospital, Buenos Aires, Argentina; and 4Faculty of Medicine and Biology, University of Lausanne, Switzerland OBJECTIVE Anterior quadrant disconnection represents a safe surgical option in well-selected pediatric patients with a large frontal lobe lesion anterior to the motor cortex. The understanding of the anatomy of the white matter tracts con- necting the frontal lobe with the rest of the cerebrum forms the basis of a safe and successful disconnective surgery. The authors explored and illustrated the relevant white matter tracts sectioned during each surgical step using fiber dissection techniques. METHODS Five human cadaveric hemispheres were dissected to illustrate the frontal connections in the 3 planes. The dissections were performed from lateral to medial, medial to lateral, and ventral to dorsal to describe the various tracts sectioned during the 4 steps of this surgery, namely the anterior suprainsular window, intrafrontal disconnection, anterior callosotomy, and frontobasal disconnection. RESULTS At the beginning of each surgical step, the U fibers were cut. During the anterior suprainsular window, the superior longitudinal fasciculus (SLF), the uncinate fasciculus, and the inferior fronto-occipital fasciculus (IFOF) were vi- sualized and sectioned, followed by sectioning of the anterior limb of the internal capsule. During the intrafrontal discon- nection, the SLF was cut, along with the corona radiata. At the medial surface the cingulum was sectioned. The anterior callosotomy disconnected the anterior third of the body of the callosum, the genu, and the rostrum. The frontobasal disconnection addressed the last remaining fibers connecting the frontal lobe with the rest of the hemisphere, namely the anterior limb of the anterior commissure. CONCLUSIONS The anterior peri-insular quadrantotomy aims at effectively treating children with large lesions of the frontal lobe anterior to the motor cortex. A precise understanding of the gyral anatomy of this lobe along with the several white matter connections is crucial to avoid motor complications and to ensure complete disconnection. https://thejns.org/doi/abs/10.3171/2019.10.PEDS19472 KEYWORDS epilepsy surgery; anterior quadrantotomy; disconnective surgery; frontal lobe OCAL epilepsies restricted to the frontal lobe account frontal lobe anterior to the precentral gyrus and is com- for 20% of patients with refractory epilepsy, and posed of the superior, middle, and inferior frontal gyri on they represent the second most common cause for the lateral surface of the cerebrum, the cingulate gyrus Ffocal epilepsy syndromes after temporal lobe epilepsy.10,11 and the anterior part of the callosum on the medial sur- Small lesions are treated by simple lesionectomy, while face, and the orbital gyri and gyrus rectus on the basal larger lesions have been traditionally treated by frontal lo- surface. Patients with well-defined epileptogenic lesions bectomy. 3,8 Disconnective surgery, such as hemispheroto- of the frontal lobe and with sparing of the perirolandic my or anterior and/or posterior quadrantotomy, has gained cortex and preserved motor functions are ideal candidates increasing acceptance for treating the large hemispheric for an anterior peri-insular quadrantotomy that keeps the and/or subhemispheric lesions that are frequently seen in motor cortex and the posterior quadrant and their projec- the pediatric population.3–6 tions intact, thereby maintaining neurological functions. The anterior quadrant is defined as the portion of the Disconnective surgery avoids the classical complications ABBREVIATIONS IFOF = inferior fronto-occipital fasciculus; SLF = superior longitudinal fasciculus. SUBMITTED August 12, 2019. ACCEPTED October 21, 2019. INCLUDE WHEN CITING Published online December 20, 2019; DOI: 10.3171/2019.10.PEDS19472. * P.G.L. and G.C. contributed equally to this work. ©AANS 2020, except where prohibited by US copyright law J Neurosurg Pediatr Volume 25 • April 2020 331 Unauthenticated | Downloaded 10/09/21 10:40 AM UTC Gonzalez-Lopez et al. associated with large brain resections.3,11 We recently pub- lished the technical details of this surgery along with a case description of a 9-year-old child.2 Due to the rarity of these cases, reports from the literature on this group of patients are scarce. We performed a cadaveric study that details the anato- my of the white matter fibers that are disconnected during the isolation of the frontal lobe from the rest of the cere- brum during the different surgical steps of this procedure. Methods Five human brain specimens were prepared accord- ing to Klingler’s technique for white matter dissection.10 Thus, the brains were extracted when they were as fresh as possible, during the first 12 hours postmortem. The specimens were cleaned under running water and fixed for 8 weeks in a 10% formaldehyde solution. Each piece underwent fixation while hanging upside down by a suture in the basilar artery to avoid morphological disruptions of its shape and size. After the 8-week fixation, the specimens were cleaned under running water again and then frozen to −15°C for 2 weeks. The brains were then thawed and the arachnoid tissue and vessels were carefully dissected and detached from the cortical surface. After this 10-week period, the specimens were ready for the dissection. All the speci- mens were dissected from the lateral, medial, and basal aspects of each frontal lobe, with special attention paid to the sequential removal of underlying white matter tracts. The target in all 3 areas was reaching the frontal horn of the ipsilateral lateral ventricle. Each step of the dissection was photographed to pro- duce high-definition white matter dissection images to show the different tracts exposed, which are those discon- nected during the anterior peri-insular quadrantotomy. Special attention was given to the different connections of all these tracts to determine whether this original surgical procedure allows a complete anterior quadrant disconnec- tion. Results Anatomically, the anterior quadrant is limited posteri- orly by the precentral sulcus on the lateral surface and by the paracentral ascending branch of the cingulate sulcus on the medial surface (Fig. 1A). Below the surface, the anterior quadrant is limited by the anterior part of the cir- cular sulcus and by the anterior perforated substance. As already detailed in our previous report,2 the peri-in- FIG. 1. High-definition white matter dissection images of a right- sular anterior quandrantotomy can be divided into 4 surgi- hemisphere brain specimen in which the 4 sequential corticotomies are cal steps: 1) the anterior suprainsular window, 2) the ante- represented. A: Lateral view of the right hemisphere. The first corticoto- my (1) runs parallel and anterior to the precentral sulcus, disrupting the rior callosotomy, 3) the intrafrontal disconnection, and 4) cerebral cortex of the posterior aspects of F1, F2, and F3. The second the frontobasal disconnection. The details of these discon- corticotomy (2) represents the laterobasal disconnection parallel to the nections are illustrated in Fig. 1. The following paragraphs floor of the anterior fossa through the basal aspect of F3. B: Mediobasal detail the procedure as performed in the cadaver dissec- view of the right cerebral hemisphere showing the medial (3) and basal tion to illustrate the white matter tracts encountered and disconnections (4). The third corticotomy (3) disrupts the cortex of the sectioned during this disconnective procedure. medial gyrus of the frontal lobe as well as the cingulum and corpus cal- losum. FIG. 1. (continued)→ Lateral Dissection Lateral to medial dissection was used to progressively 332 J Neurosurg Pediatr Volume 25 • April 2020 Unauthenticated | Downloaded 10/09/21 10:40 AM UTC Gonzalez-Lopez et al. FIG. 1. C: Basal aspect of the cerebral hemisphere, where the basal corticotomy is represented, disrupting the cortical aspect of the lateral, posterior, and medial fronto-orbital gyri and gyrus rectus: 1, anterior fronto-orbital gyrus; 2, posterior fronto-orbital gyrus; 3, medial fronto-orbital gyrus; 4, lateral fronto-orbital gyrus. For the surgical procedure in patients, the skin incision per- formed is a barn door–type incision, placed in the frontotemporal region, that allows access to perform a frontotemporoparietal craniotomy. This allows adequate exposure of the anterior sylvian point, superior temporal gyrus, inferior and middle frontal gyri, and precentral gyrus (shown in panel A). The cortical incision is placed in the frontal operculum parallel to the sylvian fissure, and this incision is turned superiorly at its posterior end to perform the intrafrontal disconnection. These incisions are deepened to the ventricle, where the anterior callosotomy is performed. The intrafrontal disconnection is then continued medially to reach the interhemispheric fissure by disruption of the frontal cortices at its medial surface (shown in panel B). AC = anterior commissure; aps = anterior perforated substance;