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Sandeep Sood, Eishi Asano and Harry T. Chugani

Object

Preservation of the vein of Labbé is recommended to prevent temporal lobe infarction after skull base surgery. However, the importance of preserving the vein in epilepsy surgery involving resection of the temporal lobe is unclear.

Methods

Retrospective analysis was performed in 47 cases, in which patients underwent temporal lobe resection, out of 148 cases in which patients underwent surgery for intractable seizures over a 5-year period. Standard temporal lobe resection anterior to the vein of Labbé was performed in 11 patients. In 24 patients, the temporal lobe resection extended posterior to the vein of Labbé; the vein was preserved in eight patients, who underwent surgery prior to 2002, and resected in the other 16 patients, who underwent surgery after 2002. Twelve patients underwent a temporopari-etooccipital resection.

There was no significant difference in the pattern of venous anatomy (based on analysis of the relative size of veins [chi-square test, p = 0.1] and the number of superficial veins draining the temporal lobe [p = 1]) in patients in whom the vein was resected compared with those in whom it was preserved. No patient experienced postoperative infarction.

Conclusions

The authors conclude that the vein of Labbé may be safely resected in epilepsy surgery involving temporal lobe resection. The decision whether to resect the vein need not be based on the surface venous drainage pattern or number of veins draining the temporal lobe.

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Sandeep Sood, Eishi Asano, Deniz Altinok and Aimee Luat

Traditionally corpus callosotomy is done through a craniotomy centered at the coronal suture, with the aid of a microscope. This involves dissecting through the interhemispheric fissure below the falx to reach the corpus callosum. The authors describe a posterior interhemispheric approach to complete corpus callosotomy with an endoscope, which bypasses the need to perform interhemispheric dissection because the falx is generally close to the corpus callosum in this region.

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Sandeep Sood, Eishi Asano and Harry T. Chugani

Object

Fever is a common occurrence after cerebral hemispherectomy in children and prolongs the hospital stay. The authors determined whether an external ventriculostomy might reduce the incidence of fever following a hemispherectomy.

Methods

The postoperative courses of 27 patients who had undergone cerebral hemispherectomy for intractable seizures were retrospectively analyzed.

Results

Thirteen children underwent an external ventriculostomy, and only 1 had an elevated axillary body temperature of ≥ 39°C during the postoperative period. Among 14 patients who did not undergo an external ventriculostomy, 7 had a posthemispherectomy fever of ≥ 39°C. Patients who underwent an external ventriculostomy had a lower risk of postoperative fever compared with those who did not undergo the procedure (8 vs 50%, respectively; p = 0.03, Fisher exact test). None of the patients had an infection accounting for the cause of the fever. The hospital stay for patients who had undergone postoperative external ventriculostomy was significantly shorter than for those who had not (7.2 ± 2 vs 11.3 ± 5 days, respectively; p = 0.01, Student t-test).

Conclusions

The use of external ventriculostomy following hemispherectomy for intractable epilepsy in children reduces the incidence of postoperative fever due to infection.

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Sandeep Sood, Neena I. Marupudi, Eishi Asano, Abilash Haridas and Steven D. Ham

OBJECT

Corpus callosotomy and hemispherotomy are conventionally performed via a large craniotomy with the aid of a microscope for children with intractable epilepsy. Primary technical considerations include completeness of disconnection and blood loss. The authors describe an endoscopic technique performed through a microcraniotomy for these procedures.

METHODS

Four patients with drop attacks and 2 with intractable seizures related to a neonatal stroke underwent endoscopic complete corpus callosotomy and hemispherotomy, respectively. The surgeries were performed through a 2- to 3-cm precoronal microcraniotomy. Interhemispheric dissection to the corpus callosum was done using the standard technique. Subsequently, the bimanual technique with a suction device mounted on an endoscope was used to perform a complete corpus callosotomy, including interforniceal and anterior commissure disconnection. In patients who had hemispherotomy, the fornix was resected posteriorly and lateral disconnection was done by unroofing the temporal horn. Anteriorly, endoscopic corticectomy was done along the ipsilateral anterior cerebral artery to reach the bifurcation of the internal carotid artery to complete the anterior disconnection. Postoperative MRI and diffusion tensor imaging (DTI) of the brain were performed to confirm complete disconnection.

RESULTS

The procedure was accomplished successfully in all patients, with excellent visualization secured. None of the patients required a blood transfusion. Postoperative MRI and DTI confirmed completeness of the disconnection. Patients who underwent corpus callosotomy had complete resolution of drop attacks at a mean follow-up of 6 months, and patients who underwent hemispherotomy became seizure free.

CONCLUSIONS

Endoscopic corpus callosotomy and hemispherotomy are surgically feasible procedures associated with minimal blood loss, minimal risk, and excellent visualization.

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Taylor J. Abel, Emma Losito, George M. Ibrahim, Eishi Asano and James T. Rutka

Epileptic spasms (ES) are a common manifestation of intractable epilepsy in early life and can lead to devastating neurodevelopmental consequences. Epilepsy surgery for ES is challenging because of inherent difficulties in localizing the epileptogenic zone in affected infants and children. However, recent clinical series of resective neurosurgery for ES suggest that not only is surgery a viable option for appropriately selected patients, but postoperative seizure outcomes can be similar to those achieved in other types of focal epilepsy. Increased awareness of ES as a potentially focal epilepsy, along with advances in neuroimaging and invasive monitoring technologies, have led to the ability to surgically treat many patients with ES who were previously not considered surgical candidates. In this study, the authors review the current state of epilepsy surgery for ES. Specifically, they address how advances in neuroimaging and invasive monitoring have facilitated patient selection, presurgical evaluation, and ultimately, resection planning.

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P. Sarat Chandra and Manjari Tripathi

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Min-Hee Lee, Nolan B. O’Hara, Hirotaka Motoi, Aimee F. Luat, Csaba Juhász, Sandeep Sood, Eishi Asano and Jeong-Won Jeong

OBJECTIVE

In this study the authors investigated the clinical reliability of diffusion weighted imaging maximum a posteriori probability (DWI-MAP) analysis with Kalman filter prediction in pediatric epilepsy surgery. This approach can yield a suggested resection margin as a dynamic variable based on preoperative DWI-MAP pathways. The authors sought to determine how well the suggested margin would have maximized occurrence of postoperative seizure freedom (benefit) and minimized occurrence of postoperative neurological deficits (risk).

METHODS

The study included 77 pediatric patients with drug-resistant focal epilepsy (age 10.0 ± 4.9 years) who underwent resection of their presumed epileptogenic zone. In preoperative DWI tractography from the resected hemisphere, 9 axonal pathways, Ci=1–9, were identified using DWI-MAP as follows: C1–3 supporting face, hand, and leg motor areas; C4 connecting Broca’s and Wernicke’s areas; C5–8 connecting Broca’s, Wernicke’s, parietal, and premotor areas; and C9 connecting the occipital lobe and lateral geniculate nucleus. For each Ci, the resection margin, di, was measured by the minimal Euclidean distance between the voxels of Ci and the resection boundary determined by spatially coregistered postoperative MRI. If Ci was resected, di was assumed to be negative (calculated as –1 × average Euclidean distance between every voxel inside the resected Ci volume, ri). Kalman filter prediction was then used to estimate an optimal resection margin, d*i, to balance benefit and risk by approximating the relationship between di and ri. Finally, the authors defined the preservation zone of Ci that can balance the probability of benefit and risk by expanding the cortical area of Ci up to d*i on the 3D cortical surface.

RESULTS

In the whole group (n = 77), nonresection of the preoperative preservation zone (i.e., actual resection margin d*i greater than the Kalman filter–defined d*i) accurately predicted the absence of postoperative motor (d*1–3: 0.93 at seizure-free probability of 0.80), language (d*4–8: 0.91 at seizure-free probability of 0.81), and visual deficits (d*9: 0.90 at seizure-free probability of 0.75), suggesting that the preservation of preoperative Ci within d*i supports a balance between postoperative functional deficit and seizure freedom. The subsequent subgroup analyses found that preservation of preoperative Ci =1–4,9 within d*i =1–4,9 may provide accurate deficit predictions independent of age and seizure frequency, suggesting that the DWI-based surgical margin can be effective for surgical planning even in young children and across a range of epilepsy severity.

CONCLUSIONS

Integrating DWI-MAP analysis with Kalman filter prediction may help guide epilepsy surgery by visualizing the margins of the eloquent white matter pathways to be preserved.

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Min-Hee Lee, Nolan B. O’Hara, Yasuo Nakai, Aimee F. Luat, Csaba Juhasz, Sandeep Sood, Eishi Asano and Jeong-Won Jeong

OBJECTIVE

This study is aimed at improving the clinical utility of diffusion-weighted imaging maximum a posteriori probability (DWI-MAP) analysis, which has been reported to be useful for predicting postoperative motor, language, and visual field deficits in pediatric epilepsy surgery. The authors determined the additive value of a new clustering mapping method in which average direct-flip distance (ADFD) reclassifies the outliers of original DWI-MAP streamlines by referring to their minimum distances to the exemplar streamlines (i.e., medoids).

METHODS

The authors studied 40 children with drug-resistant focal epilepsy (mean age 8.7 ± 4.8 years) who had undergone resection of the presumed epileptogenic zone and had five categories of postoperative deficits (i.e., hemiparesis involving the face, hand, and/or leg; dysphasia requiring speech therapy; and/or visual field cut). In pre- and postoperative images of the resected hemisphere, DWI-MAP identified a total of nine streamline pathways: C1 = face motor area, C2 = hand motor area, C3 = leg motor area, C4 = Broca’s area–Wernicke’s area, C5 = premotor area–Broca’s area, C6 = premotor area–Wernicke’s area, C7 = parietal area–Wernicke’s area, C8 = premotor area–parietal area, and C9 = occipital lobe–lateral geniculate nucleus. For each streamline of the identified pathway, the minimal ADFD to the nine exemplars corrected the pathway membership. Binary logistic regression analysis was employed to determine how accurately two fractional predictors, Δ1–9 (postoperative volume change of C1–9) and γ1–9 (preoperatively planned volume of C1–9 resected), predicted postoperative motor, language, and visual deficits.

RESULTS

The addition of ADFD to DWI-MAP analysis improved the sensitivity and specificity of regression models for predicting postoperative motor, language, and visual deficits by 28% for Δ1–3 (from 0.62 to 0.79), 13% for Δ4–8 (from 0.69 to 0.78), 13% for Δ9 (from 0.77 to 0.87), 7% for γ1–3 (from 0.81 to 0.87), 1% for γ4–8 (from 0.86 to 0.87), and 24% for γ9 (from 0.75 to 0.93). Preservation of the eloquent pathways defined by preoperative DWI-MAP analysis with ADFD (up to 97% of C1–4,9) prevented postoperative motor, language, and visual deficits with sensitivity and specificity ranging from 88% to 100%.

CONCLUSIONS

The present study suggests that postoperative functional outcome substantially differs according to the extent of resected white matter encompassing eloquent cortex as determined by preoperative DWI-MAP analysis. The preservation of preoperative DWI-MAP–defined pathways may be crucial to prevent postoperative deficits. The improved DWI-MAP analysis may provide a complementary noninvasive tool capable of guiding the surgical margin to minimize the risk of postoperative deficits for children.