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Pablo Gonzalez-Lopez, Giulia Cossu, Etienne Pralong, Matias Baldoncini, Mahmoud Messerer, and Roy Thomas Daniel


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 connecting 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.


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.


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 visualized and sectioned, followed by sectioning of the anterior limb of the internal capsule. During the intrafrontal disconnection, 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.


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.

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Giulia Cossu, Sebastien Lebon, Margitta Seeck, Etienne Pralong, Mahmoud Messerer, Eliane Roulet-Perez, and Roy Thomas Daniel

Refractory frontal lobe epilepsy has been traditionally treated through a frontal lobectomy. A disconnective technique may allow similar seizure outcomes while avoiding the complications associated with large brain resections. The aim of this study was to describe a new technique of selective disconnection of the frontal lobe that can be performed in cases of refractory epilepsy due to epileptogenic foci involving 1 frontal lobe (anterior to the motor cortex), with preservation of motor function. In addition to the description of the technique, an illustrative case is also presented.

This disconnective procedure is divided into 4 steps: the suprainsular window, the anterior callosotomy, the intrafrontal disconnection, and the frontobasal disconnection. The functional neuroanatomy is analyzed in detail for each step of the surgery. It is important to perform cortical and subcortical electrophysiological mapping to guide this disconnective procedure and identify eloquent cortices and intact neural pathways.

The authors describe the case of a 9-year-old boy who presented with refractory epilepsy due to epileptogenic foci localized to the right frontal lobe. MRI confirmed the presence of a focal cortical dysplasia of the right frontal lobe. A periinsular anterior quadrant disconnection (quadrantotomy) was performed. The postoperative period was uneventful, and the patient was in Engel seizure outcome Class I at the 3-year follow-up. A significant cognitive gain was observed during follow-up.

Periinsular anterior quadrantotomy may thus represent a safe technique to efficiently treat refractory epilepsy when epileptogenic foci are localized to 1 frontal lobe while preserving residual motor functions.

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Giulia Cossu, Pablo González-López, Etienne Pralong, Judith Kalser, Mahmoud Messerer, and Roy Thomas Daniel


Surgery for frontal lobe epilepsy remains a challenge because of the variable seizure outcomes after surgery. Disconnective procedures are increasingly applied to isolate the epileptogenic focus and avoid complications related to extensive brain resection. Previously, the authors described the anterior quadrant disconnection procedure to treat large frontal lobe lesions extending up to but not involving the primary motor cortex. In this article, they describe a surgical technique for unilateral disconnection of the prefrontal cortex, while providing an accurate description of the surgical and functional anatomy of this disconnective procedure.


The authors report the surgical treatment of a 5-month-old boy who presented with refractory epilepsy due to extensive cortical dysplasia of the left prefrontal lobe. In addition, with the aim of both describing the subcortical intrinsic anatomy and illustrating the different connections between the prefrontal lobe and the rest of the brain, the authors dissected six human cadaveric brain hemispheres. These dissections were performed from lateral to medial and from medial to lateral to reveal the various tracts sectioned during the three different steps in the surgery, namely the intrafrontal disconnection, anterior callosotomy, and frontobasal disconnection.


The first step of the dissection involves cutting the U-fibers. During the anterior intrafrontal disconnection, the superior longitudinal fasciculus in the depth of the middle frontal gyrus, the uncinate fasciculus, and the inferior frontooccipital fasciculus in the depth of the inferior frontal gyrus at the level of the anterior insular point are visualized and sectioned, followed by sectioning of the anterior limb of the internal capsule. Once the frontal horn is reached, the anterior callosotomy can be performed to disconnect the genu and the rostrum of the corpus callosum. The intrafrontal disconnection is deepened toward the falx, and at the medial surface, the cingulum is sectioned. The frontobasal disconnection involves cutting the anterior limb of the anterior commissure.


This technique allows selective isolation of the epileptogenic focus located in the prefrontal lobe to avoid secondary propagation. Understanding the surface and white matter fiber anatomy is essential to safely perform the procedure and obtain a favorable seizure outcome.

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Claudio Pollo, François Vingerhoets, Etienne Pralong, Joseph Ghika, Philippe Maeder, Reto Meuli, Jean-Philippe Thiran, and Jean-Guy Villemure


The authors describe a new method of localizing electrodes on magnetic resonance (MR) images and focus on the positions of both the most efficient contact and the electrode related to the MR imaging target.


Thirty-one patients who had undergone bilateral subthalamic nucleus (STN) deep brain stimulation (DBS) were included in this study. Target coordinates were calculated in the anterior commissure–posterior commissure referential. A study of the correlation between the artifact and the related contact allowed one to deduce the contact position from the identification of the distal artifact on MR imaging. The best stimulation point corresponded with the contact resulting in the best Unified Parkinson’s Disease Rating Scale (UPDRS) motor score improvement. It was compared (Student t-test) with the dorsal margin of the STN (DM STN), which was determined electrophysiologically. The distance between the target and the electrode was calculated individually in each axis.

The best stimulation point was located at anteroposterior −2.34 ± 1.63 mm, lateral 12.04 ± 1.62 mm, and vertical −2.57 ± 1.68 mm. This point was not significantly different from the DM STN (p < 0.05). The postoperative UPDRS motor score was 28.07 ± 12.16, as opposed to the preoperative score of 46.27 ± 13.89. The distance between the expected and actual target in the x- and y-axes was 1.34 ± 1.02 and 1.03 ± 0.76 mm, respectively. In the z-axis, 39.7% of the distal contacts were located proximal to the target.


This approach proposed for the localization of the electrodes on MR imaging shows that DBS is most effective in the dorsal and lateral part of the STN and indicates that the DBS electrode can be located more proximally than originally expected because of the caudal brain shift that may occur during the implantation procedure.