Vertical perithalamic hemispherotomy: A single-center experience in 40 pediatric patients with epilepsy




The current concept for hemispherotomy includes various lateral techniques and the vertical perithalamic hemispherotomy introduced by Delalande in 1992. We have chosen the vertical approach because of advantages that possibly influence outcome: the possibility to completely disconnect the hemisphere at the level of the thalamus obviating both the need to resect the insula and the need to open and dissect the subarachnoid space of the Sylvian fissure.


We retrospectively analyzed prospectively collected data of all patients who underwent vertical hemispherotomy at the Vienna pediatric epilepsy center. Seizure outcome was classified according to the International League Against Epilepsy (ILAE) proposal 2001.

Key Findings

Follow-up data of 40 patients (22 male/18 female; median age 5.5 years; range 4.4 months to 20.1 years) were analyzed. Hemispherotomy was left in 26 and right in 14 patients. The underlying pathology was ischemic vascular in 19, malformation of cortical development (MCD) in 11, and other pathology in 10. No serious intraoperative complications were encountered. Only two infants (5.0%) needed blood replacement. There was one death on the fourth day after surgery caused by intractable hyponatremic brain edema. Three patients developed cerebrospinal fluid (CSF) disturbances, but only one needed a permanent ventriculoperitoneal (VP) shunt (2.5%). For outcome analysis we included 37 of 40 children with at least 12 months of follow-up. Thirty-four (91.9%) of 37 children were seizure-free (class 1a) after a median follow-up time of 3.7 years (range 12 month to 14.8 years).


We confirm the efficacy and safety of vertical parasagittal hemispherotomy as described by Delalande in a consecutive series of patients treated at our center since 1998. In addition, complete disconnection of the hemisphere in patients with MCD and/or patients with significant involvement of the insula was possible without the complications usually reported with other techniques.

Early onset medically intractable epileptic encephalopathies are often caused by hemispheric pathology such as malformations of cortical development (MCDs), perinatal stroke, Sturge-Weber syndrome, or Rasmussen encephalitis.

Until the late 1960s, complete removal of the affected hemisphere (i.e., anatomic hemispherectomy) was the preferred surgical treatment modality for these patients, and approximately 70–80% of them have been reported to become seizure-free. However, early and delayed surgical complications including significant blood loss, coagulopathy, metabolic imbalances, superficial cerebral hemosiderosis, and hydrocephalus with mortality rates up to 30% lead to a significant decline in use (Krynauw, 1950; Oppenheimer & Griffith, 1966; Rasmussen, 1973; Vining et al., 1997; Bahuleyan et al., 2012).

Following the concept of functional hemispherectomy introduced by Rasmussen, various disconnection techniques have been developed during the last two decades. The common goal of these techniques is to avoid/reduce the above-mentioned complications without minimizing postoperative seizure outcome (Rasmussen, 1983; Delalande et al., 1992, 2007; Schramm et al., 1995; Villemure & Mascott, 1995; Carson et al., 1996; Peacock et al., 1996; Vining et al., 1997; Shimizu & Maehara, 2000; Cook et al., 2004; Villemure & Daniel, 2006; Limbrick et al., 2009; Bahuleyan et al., 2012; Schramm et al., 2012).

In practice, two different approaches for hemispheric disconnection are currently used: lateral periinsular hemispherotomy with various modifications that has consistently been reported to be safe and effective and vertical parasagittal hemispherotomy introduced by Delalande et al. (Villemure & Daniel, 2006; Delalande et al., 2007; Schramm et al., 2012).

Compared with the lateral techniques, the vertical approach seems to have the following advantages: It allows the complete disconnection of the hemisphere at the level of the thalamus, obviating the need to open and dissect the subarachnoid space of the Sylvian fissure and to resect the insula.

However, apart from Delalande′s report published in 2007, no studies from other centers replicating his results and/or reporting long-term experience with this technique have been reported (Chandra et al., 2008; Kawai et al., 2013).

At the Vienna pediatric epilepsy center, vertical parasagittal hemispherotomy has been performed since 1998. We report on our experience in 40 children and adolescents with special emphasis on long-term efficacy and safety.


Presurgical evaluation

Presurgical evaluation followed a standardized protocol including thorough neurologic, ophthalmologic, neuropsychological, and psychiatric assessment as well as intensive video–electroencephalography (EEG) monitoring, and high-resolution magnetic resonance imaging (MRI) (Olbrich et al., 2002; Mayer et al., 2004).

2-[18F]Fluoro-2-deoxy-d-glucose positron emission tomography (FDG-PET) was performed in all patients to document the functional status of the contralateral hemisphere (Sasaki et al., 1998; Moosa et al., 2013).

If the dominant hemisphere of adolescent patients was going to be disconnected and functional magnetic resonance imaging (fMRI) was inconclusive or not possible, a WADA test for language lateralization was performed.

All patients were discussed at a multidisciplinary seizure conference. Indications for hemispherotomy were intractable epilepsies due to unilateral hemispheric syndromes such as Rasmussen encephalitis, Sturge-Weber disease, hemimegalencephaly, polymicrogyria, and extensive hemispheric infarcts. If the information obtained during the noninvasive presurgical evaluation process consistently pointed toward a more circumscript area of the brain as being the site of seizure onset and/or eloquent brain areas had to be preserved, partial disconnections/resections were preferred (Dorfer et al., 2013).

Shortly before surgery, antiepileptic drug (AED) monotherapy with a well-tolerated AED was established in all patients to guarantee the best possible developmental outcome after successful surgery.

Surgical technique

The step by step disconnection of the hemisphere was performed—with slight modifications—as described by Delalande. A small (2.5 × 4 cm) parasagittal precentral craniotomy was performed with the help of the neuronavigational system, as the anatomy in this patient group varies significantly. Access to the lateral ventricle was accomplished via a maximal 2 × 2 cm cortical resection or via an enlarged superior frontal sulcus, depending on the individual anatomy and the need to gain a histologic specimen.

In cases with a porencephalic cyst after middle cerebral artery infarction, an effort was made to initially access the ventricle medial to the cavity. In addition, fibrin glue was used to seal the subdural space overlying the cyst in the area just lateral to the access, and in some cases the pia-cortex layer was fixed to the dura with 5.0 sutures, in an attempt to reduce the risk of a collapse of the cyst.

Disconnection started with transsection of the posterior part of the body of the corpus callosum following the surface of the splenium in a subpial fashion until the visualization of the deep veins confluence into the vein of Galen through the pia-arachnoid plane. After cutting the crus of the fornix at the level of the trigone, the perithalamic incision was performed starting at the trigone with the choroid plexus in the temporal horn serving as guiding structure. Callosotomy was completed anteriorly following the subpially visualized pericallosal artery (Fig. 1).

Figure 1.

(A) Axial T2-weighted and (B) T2 fluid-attenuated coronal inversion recovery MR image depicting the perithalamic disconnection site via the vertical approach.

After subpial suction/resection of the subcallosal area and posterior gyrus rectus, an incision was made through the floor of the frontal horn and the medial caudate nucleus with the optic nerve, the chiasm, and the A1 segment of the anterior cerebral artery subpially coming into view.

After detaching the choroid plexus from the hippocampus at the anterior end of the temporal choroid fissure and holding it dorsally, the suction/incision through the dorsomedial amygdala was connected with the frontobasal incision in the axis of the optic tract. The transsection was confirmed with the anterior choroid artery and eventually the posterior cerebral artery as well as the basal vein visualized in a subpial plane. An ultrasonic aspirator was used only in patients with a firm brain parenchyma.

After completed disconnection, the entire ventricular system was irrigated with synthetic liquor until the cerebrospinal fluid (CSF) was perfectly clean. No ventricular drain was left in space. The corticotomy tunnel that served as the access to the lateral ventricle was closed with Lyostypt (Braun) and fibrin glue (Baxter) to minimize the risk of subdural hygroma formation.

All operations were performed by the same neurosurgeon (T.C.).

After surgery, patients remained at the pediatric intensive care unit (PICU) for at least 24 h and then approximately 10 days at the pediatric intermediate care unit (IMC). An MRI control examination was performed before discharge.

Postsurgical follow-up

Postsurgical outcome was assessed on an inpatient basis 3 months after surgery, and then once per year for 5 years and every 2 years from then on if stable. Patients were seen more frequently if necessary.

Postoperative follow-up examinations included thorough neurologic, neuropsychological, ophthalmologic, and psychiatric assessment as well as 48-h video-EEG monitoring. MRI was performed 3 and 12 months, and 5 and 10 years after surgery (or, in case of brain tumor, according to oncologic protocols).

Seizure outcome was classified according to the International League Against Epilepsy (ILAE) proposal (Wieser et al., 2001) based on patient and family reporting. The “Wieser classification” was chosen, because it uses multiple yearly outcome data points and overcomes several disadvantages of the widely used Engel seizure outcome classification (Engel et al., 1993).

Withdrawal of AEDs was recommended 2 years after surgery, provided that the patient was completely seizure-free and that EEG control examinations did not show epileptic activity in the contralateral hemisphere.

Data analysis

Approval from the Medical University of Vienna Clinical Research Ethics Board was obtained. This is a retrospective analysis of prospectively collected data. Data analysis was descriptive (median, range), using SSPS 18.0 (IBM, Armonk, New York, U.S.A.).


Presurgical details

Between October 1998 and May 2013, 249 children with drug-resistant epilepsies underwent surgery at our center; 40 (16.1%) of them had hemispherotomy. No patients were lost to follow-up.

Table 1 summarizes patients' clinical characteristics.

Table 1. Patients' characteristics
NoSexAge at onset (years)Age at operation (years)SideEtiologyHistopathologyaIntra-/peri-/postoperative complicationsFollow-up time (years)Seizure outcomeb
  1. CSF, cerebrospinal fluid; FCD, focal cortical dysplasia; MCD, malformation of cortical development; PNET, primitive neuroectodermal tumor; MMCD, mild malformation of cortical development.

  2. a

    FCD classification according to Blümcke, MMCD classification according to Palmini et al.

  3. b

    Seizure outcome according to Wieser.

1M6.318.3LeftPre-/perinatal strokeNANone5.01a
2F5.88.4RightPre-/perinatal strokeFCD IIIDNone2.61a
3F0.111.7RightPre-/perinatal strokeNANone1.21a
4M0.0011.4LeftPre-/perinatal strokeFCD IIInosNone1.01a
5F1.32.2LeftPre-/perinatal strokeNATemporary CSF drainage2.21a
6M2.45.5LeftPre-/perinatal strokeFCD IIInosTemporary CSF drainage3.11a
7M1.310.8LeftPre-/perinatal strokeNANone3.71a
8M1.517.7LeftPre-/perinatal strokeNANone3.61a
9M7.28.7RightPre-/perinatal strokeNANone2.31a
10M6.217.9RightPre-/perinatal strokeFCD IIIDNone2.81a
11F11.620.1RightPre-/perinatal strokeNANone2.31a
12M6.118.8LeftPre-/perinatal strokeNANone6.51a
13F1.02.1RightPre-/perinatal strokeNANone1.81a
14M0.27.3LeftPre-/perinatal strokeNANone8.41a
15F0.44.9LeftPre-/perinatal strokeFCD IIInosNone4.71a
16F0.63.5LeftPre-/perinatal strokeFCD IIIDNone4.81a
17F0.75.0LeftPre-/perinatal strokeNANone13.21a
18M0.43.7LeftPre-/perinatal strokeNANone9.61a
19F6.110.3LeftPre-/perinatal strokeNANone3.51a
22F0.11.8LeftMCDFCD IBNone5.61a
24F0.0020.4RightHemimegalencephalyFCD IIBBlood replacement (90 ml)8.21a
25M3.64.8RightMCDPolymicrogyriaHyponatremic brain edemaDeath on day 4th after surgery 
26F1.50.9LeftMCDMMCD IINone4.31a
27M0.26.1LeftHemimegalencephalyPolymicrogyria FCD IIB,None14.81a
28F00.7LeftMCDFCD IIAVP-Shunt7.05



30M0.36.6LeftMCDMMCD IINone4.91a
31M0.31.0LeftSturge WeberFCD IIICBlood replacement (130 ml)1.71a
32M0.11.0LeftSturge-WeberFCD IIICNone1.11a
33F1.93.5RightRasmussen EncephalitisRasmussenNone3.61a
34F8.811.0RightTumor relatedPilocytic AstrocytomaNone2.51a
35M0.35.5LeftTumor relatedPNETNone4.25
36M6.612.3LeftEncephaliticFCD IIInosNone1.81a
37M0.66.4LeftEncephaliticNANone0.3<12 months
39F0.51.0RightPosthemorrhagicFCD IIICNone0.1<12 months
40F9.417.4RightCavernomaFCD IIICNone3.21a

There were 22 boys and 18 girls. The median age at seizure onset was 1.2 years (range 1 day to 11.6 years). Twenty children had seizure onset at <1 year of age. The median duration of epilepsy before surgery was 3.8 years (range 4.4 months to 15.8 years).

Etiology was ischemic vascular in 19 children, MCD in 11, Sturge-Weber syndrome in 2, gliosis after tumor resection in 2, posthemorrhagic in 2, postencephalitic in 2, and Rasmussen encephalitis and cavernoma in one each.

Seizure frequency before surgery was high in all cases, and on a daily basis in 77.5%. Thirteen children had infantile spasms.

Eight patients had previous brain surgery with resection of a temporoparietal membrane (n = 1), implantation of a ventriculoperitoneal (VP) shunt system (n = 3), biopsy to document Rasmussen encephalitis (n = 1), tumor resection (n = 2); (one optic pathway glioma, one congenital parietooccipital primitive neuroectodermal tumor [PNET]), and cavernoma resection followed by unsuccessful extended resection and partial disconnection (n = 1).

Neurologic examination documented hemiparesis without useful hand function in all children (16 left-handed with a right-sided hemiparesis). In six patients, homonymous hemianopia was also present. No visual field abnormalities were identified in the rest, although young age and/or mental retardation made clinical assessment less reliable. One patient with an optic pathway glioma showed bilateral amaurosis.

All patients were developmentally delayed. In addition, 11 patients were diagnosed with atypical autism, and three with attention deficit/hyperactivity disorder (ADHD).

Perisurgical details

Median age at the time of hemispherotomy was 5.5 years (range 4.4 months to 20.1 years). Eighteen children were younger than 5 years, eight of them <2 years, and six <12 months.

Hemispherotomy was left in 26 and right in 14 patients.

We encountered no serious intraoperative complications. Only two patients (5.0%), aged 5 and 13 months (cases 24 and 31) needed intraoperative blood replacement (90 and 130 mL). The underlying pathology in these cases was hemimegalencephaly (case 24) and Sturge-Weber syndrome (case 31).

One patient (case 25) died on day 4 after surgery because of refractory hyponatremic brain edema developing on day 3 after an initially uneventful course.

Three patients developed CSF disturbances that needed temporary placement of external ventricular drainage, but a VP shunt had to be placed in only one. None of the three preexisting shunt systems had to be revised after hemispherotomy.

Postsurgical outcome

After surgery, all patients had—as expected—both hemiparesis (with no useful hand function) and homonymous hemianopia. Four patients had slight worsening of their presurgical motor skills. However, all patients are ambulatory and have useful proximal upper limb function.

For outcome analysis we included 37 of the 40 patients with a follow-up of at least 12 months.

Thirty-four (91.9%) of 37 children were seizure-free (Wieser class 1a) at last follow-up, after a median follow-up time of 3.7 years (range 12 months to 14.8 years).

Three patients (8.1%) were classified class 5 (<50% reduction of baseline seizure days). The underlying etiology of these children was gliosis after multimodal treatment of a congenital PNET, malformation of cortical development, and posthemorrhagic defect:

  1. Patient 35 diagnosed with a congenital left parietooccipital PNET had had multimodal treatment, including resection and chemotherapy according to the HIT 2000 protocol. Because of ongoing intractable epilepsy despite successful treatment of the tumor, hemispherotomy was performed at the age of 5.5 years. Histopathology showed unspecific gliosis.
  2. Patient 28 was diagnosed with MCD. Epilepsy surgery was performed at the age of 9 months. Presurgical evaluation did not reveal involvement of the contralateral hemisphere. There was no suspicion of incomplete disconnection, neither due to the surgeon′s impression nor due to postoperative MRI. Histopathology showed focal cortical dysplasia type IIA. VP shunt placement was necessary 2 years after hemispherotomy because of slowly progressing ipsilateral hydrocephalus. There was no effect on seizure frequency.
  3. Patient 38 diagnosed with a cystic posthemorrhagic defect and drug-resistant epilepsy since the age of 3 months, was operated at age 16 years. Presurgical evaluation did not reveal involvement of the contralateral hemisphere. In this patient the neurosurgeon suspected incomplete disconnection of the splenium with MRI supporting his impression. However, despite ongoing seizure activity, the patient′s family did not agree to perform a second operation.

Increase of baseline seizure days (as described in Wieser classes 5 and 6) was not seen (Wieser et al., 2001). Reoperation for ongoing seizures was not performed in any patient.

Seizure outcome according to etiology showed no significant differences between groups: 19 (100%) of 19 patients with a vascular ischemic etiology and 10 (91.1%) of 11 patients with MCD (including two patients with hemimegalencephaly) were completely seizure-free at last follow-up (4.2 years, range 12 months to 14.4 years). Furthermore, the patients with Sturge-Weber syndrome and Rasmussen encephalitis have been free of seizures since hemispherotomy.

In 16 (47.1%) of 34 seizure-free children, AEDs were completely stopped, and in a further four AEDs are currently gradually withdrawn.

Histopathologic findings

Histopathologic evaluation was performed in 25 (62.5%) of 40 patients by one of the authors (A.M.) with central review by Ingmar Blümcke/Department of Neuropathology, University Hospital Erlangen, in 9 patients.

In 11 patients with neuroradiologic (MRI) evidence of MCD, histology revealed polymicrogyria in 6, focal cortical dysplasia (FCD) in 3 (type IB n = 1; type IIB n = 1, type IIA n = 1; Blümcke & Spreafico, 2011), and mild malformation of cortical development (MMCD) type II in two (Palmini et al., 2004).

Histopathologic evaluation was performed in 6 of 19 patients with pre/perinatal stroke (FCD IIID n = 3, FCD IIInot otherwise specified n = 3). The two Sturge-Weber patients had associated FCD IIIC. The remaining histologies were FCD IIInos in one associated with encephalitis, FCD IIIC associated with cavernoma, posthemorrhagic defect, and Rasmussen encephalitis, PNET, and pilocytic astrocytoma in one each.


We report our experience with a single disconnective technique. Results from single-center studies comparing different techniques by using historical controls support the evolution toward less resective and more disconnective techniques (Cook et al., 2004; Kwan et al., 2010).

Vertical perithalamic hemispherotomy was implemented at our center in 1998. After thorough study of the techniques described at that time including the historical French experience with regard to the disconnection plane at the level of the basal ganglia, we adopted the technique developed by Delalande (Laine & Gros, 1956; Rasmussen, 1973; Delalande et al., 1992; Schramm et al., 1995; Villemure & Mascott, 1995; Kanev et al., 1997). We thought the perithalamic incision would help to disconnect any dysplastic gray matter between the cortex and the ventricular wall. Insular cortex and any adjacent dysplasia are disconnected with no need to dissect between the middle cerebral artery (MCA) branches. In addition, the main axis of the surgical approach being sagittal should reduce the risk of inadvertently damage to the contralateral hemisphere. Our experience led us to use this technique independent of the underlying pathology.

Anatomic hemispherectomy is rarely used today owing to well-known early and delayed surgical complications (Krynauw, 1950; Oppenheimer & Griffith, 1966; Rasmussen, 1973; Vining et al., 1997; Bahuleyan et al., 2012). Several hemispherotomy techniques have been developed to minimize the extent of resection while maintaining the same seizure outcome.

We think, that—compared with vertical parasagittal hemispherotomy—all lateral techniques have in common several drawbacks:

First, a considerable although various amount of the brain has still to be removed, thus increasing the risk of intraoperative blood loss (sometimes associated with hypovolemia and death; Brian et al., 1990). Although—compared with anatomic hemispherectomy—lateral hemispherotomy techniques led to a significant decline in blood loss and requirement for blood transfusion, the reported number of patients needing blood replacement is still 10–50% (Limbrick et al., 2009; Scavarda et al., 2009; Schramm et al., 2012). In our series, only two very young children (5.0%) needed blood replacement. Similar to the vertical technique the transsylvian keyhole technique described by Schramm uses only very limited resection, but its use seems to be restricted to patients with postischemic porencephalic defects.

Second, the subarachnoid space of the Sylvian fissure needs to be opened and dissected. The major risk of functional hemispherectomy/hemispherotomy with minimal tissue resection seems to be swelling related to vascular compromise. We think that avoiding any manipulation of the insular or opercular MCA branches minimizes the risk of vasospasm and related space-occupying ischemia, especially in patients apart from those with porencephalic cysts. In addition, a wide opening and dissection of the Sylvian fissure might contribute to the development of hydrocephalus. The vertical route of disconnection has the advantage that access to the lateral ventricle is accomplished via a small corticotomy tunnel obviating the need to open and dissect the subarachnoid space of the Sylvian fissure. This is suggested to minimize the risk to develop hydrocephalus (Lew et al., 2010). Even though lateral hemispherotomy techniques have successfully reduced the hydrocephalus rate encountered in hemispherectomy (Vining et al., 1997; Shimizu & Maehara, 2000; Devlin et al., 2003; Cook et al., 2004; Villemure & Daniel, 2006; Limbrick et al., 2009; Kwan et al., 2010; Schramm et al., 2012), a recent multicenter analysis performed by the Posthemispherectomy Hydrocephalus Workgroup still found an overall hydrocephalus rate of 20% in patients operated with various lateral hemispherotomy techniques (Lew et al., 2010). However, other large series using lateral hemispherotomy techniques reported hydrocephalus rates between 2% and 20%, indicating that the individual hemispherotomy technique and/or other surgical nuances also influence the risk to develop hydrocephalus (Shimizu & Maehara, 2000; Villemure & Daniel, 2006; Cats et al., 2007; Schramm et al., 2012).

One of these surgical nuances that possibly explains different extents of impairment of CSF may be the contamination of the CSF with blood products and tissue debris. To overcome this problem of the contaminated CSF, some authors routinely leave a ventricular catheter for some days to drain the CSF (Villemure & Mascott, 1995). However, this procedure carries the potential risk of overdrainage associated with venous hemorrhage occurring topographically at a distance from the surgical site, for example, in the unaffected hemisphere (deRibaupierre et al., 2004). At our center, we extensively irrigate the ventricular system with synthetic liquor after completion of the disconnection until the CSF is perfectly clean. With this protocol, only one patient (2.5%) needed shunt placement.

In contrast to our findings, Delalande reported a shunt rate of 15.7%. Possible explanations for the better result in our patients may be the above-mentioned extensive irrigation of the ventricular system, and the closure of the corticotomy tunnel with fibrin flue and Lyostypt, which helped to restore a normal CSF circulation. This assumption is supported by reports from other centers, where postoperative subdural hygroma formation was reported to be avoided by closure of the corticotomy with fibrin glue (Blauwblomme & Harkness, 2010). Another factor might be the higher rate of MCD patients in the series of Delalande (36%) compared with our series (27.5%).

Finally, the insular cortex and/or its subcortical structures remain in place or have to be resected in lateral techniques (Cook et al., 2004; Villemure & Daniel, 2006; Schramm et al., 2012). The role of the insula in epilepsy has received increased interest over the last decades, and several studies demonstrated ictal onset within the insula mimicking frontal, temporal, and parietal epilepsy (Nguyen et al., 2009). Insular contribution was also demonstrated in hemispheric epilepsy. Recent reports from hemispherotomy series evaluating seizure outcome with respect to the extent of insular resection demonstrated that residual insular cortex was associated with lower rates of seizure-free patients (Cats et al., 2007). This could be particularly important in MCDs, as dysplastic neurons were also identified in the striatum subserving a potential contributor in epileptogenesis and seizure spread (Kaido et al., 2012), and increased rates of seizure control were found when the insular cortex and its subcortical structures were removed (Cook et al., 2004). This may in part be responsible for less favorable seizure outcomes reported in patients with MCDs after hemispherotomy (31–70%) as compared to 71–90% in patients with acquired pathologies (Devlin et al., 2003; Kossoff et al., 2003; Schramm et al., 2012). The vertical parasagittal hemispherotomy proposed by Delalande currently is the only technique that allows complete disconnection at the level of the thalamus. Thereby, the insular cortex as well as possible dysplastic epileptogenic neurons within subcortical structures can be disconnected parallel to the axis of the perforating vessels. In lateral approaches these structures need eventually to be resected (Cook et al., 2004). This perithalamic disconnection might be one explanation for the higher percentage of MCD patients with a favorable seizure outcome in the series of Delalande (75%) and our own series (91%).

In summary, the data from Delalande and our long-term follow-up data compare favorably with the published literature of lateral techniques (Cook et al., 2004; Di Rocco et al., 2006; Villemure & Daniel, 2006; Limbrick et al., 2009; Kwan et al., 2010; Schramm et al., 2012; Wiebe & Berg, 2013).


Our study is limited by a relatively small sample size. However, no children were lost to follow-up (as seen in many other studies). Even though we present long follow-up data for at least 1 year in 92.5%, 2 years in 75.0%, and 5 years and beyond in 27.5% of the patients, we have to state that outcome may be worse with longer follow-up.

However, data were collected prospectively on an inpatient basis and not via telephone interviews or via email questionnaires.

The aim of this study was to evaluate safety and efficacy with respect to seizure outcome of a specific neurosurgical technique. The relation between surgical and developmental outcome is more complex and multifactorial (i.e., also depending on age at seizure onset and duration of the disease before surgery, AEDs used, underlying pathology, and time of AED withdrawal). Therefore, detailed developmental data were not included in this analysis. However, developmental progress was noticed in all seizure-free patients, and there was no deterioration after surgery in any of our patients.


We confirm vertical perithalamic hemispherotomy to be safe and effective in terms of seizure outcome. From a surgical point of view when compared with functional hemispherectomy and lateral hemispherotomy techniques, the procedure described by Delalande combines the advantages of a small surgical window and yet clear anatomic orientation relatively independent of the underlying pathology.


T Czech is grateful to Olivier Delalande for introducing him to this technique during an on-site visit in Paris. We thank Ingmar Bluemcke/Department of Neuropathology, University Hospital Erlangen, for central histopathologic review in 9 of 26 cases (cases 10, 21, 22, 24, 26, 27, 28, 30, and 33). We thank Daniela Prayer/Department of Radiology for her collaboration in presurgical work-up. The work of Angelika Muehlebner and Gudrun Groeppel was supported by the Anniversary Fund of the Central Bank of the Republic of Austria (ÖNB-12036 dedicated to M Feucht: “Predictors for Seizure and developmental outcome after epilepsy surgery in children”).


None of the authors has any conflict of interest to disclose. We confirm that we have read the Journal's position on issues involved in ethical publication and affirm that this report is consistent with those guidelines.


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    Christian Dorfer Christian Dorfer, M.D. Department of Neurosurgery, Medical University of Vienna