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Jennifer Phung, Paul Krogstad and Gary W. Mathern

Object

The authors sought to determine if clinical epilepsy variables, maximum daily temperature (Tmax), and blood and CSF findings were associated with the risk of developing hydrocephalus after first-time resection-disconnection hemispherectomy.

Methods

Patients who underwent cerebral hemispherectomy in whom a standardized perioperative protocol was used, including the use of ventriculostomies (n = 79), were classified into those who developed and those who did not develop hydrocephalus requiring CSF shunts. The authors compared these 2 groups for clinical variables, Tmax, and blood and CSF studies through postoperative Day 12.

Results

In this cohort, 30% of the patients required CSF shunts, of which 8% developed late hydrocephalus up to 3 years posthemispherectomy. Multivariate analysis found that etiology was associated with developing posthemispherectomy hydrocephalus. Higher shunt rates were observed for patients with hemimegalencephaly (40%; n = 15) and a history of CNS infection (100%; n = 4) compared with cortical dysplasia (17%; n = 23) and Rasmussen encephalitis (17%; n = 12). In univariate analysis, other factors associated with developing hydrocephalus were elevated maximum daily temperatures, elevated white blood cell counts, decreased CSF protein, and increased CSF red blood cell counts.

Conclusions

The findings of the study indicate that etiology was the factor most strongly associated with developing posthemispherectomy hydrocephalus. These findings suggest that there are variable mechanisms for developing hydrocephalus after cerebral hemispherectomy depending on the procedure, and in resection-disconnection operations the mechanism may involve changes in CSF bulk flow that varies by histopathology.

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Gary W. Mathern, James K. Pretorius and Thomas L. Babb

✓ Quantified hippocampal mossy fiber synaptic reorganization and neuron losses were measured to determine the pathological features associated with epileptogenic fascia dentata. Twenty-five patients with temporal lobe epilepsy (TLE) were classified as having either mesial temporal sclerosis (MTS; 16 patients), with seizure genesis in the hippocampus, or temporal mass lesions (nine patients), with seizures that were probably extrahippocampal. Neo-Timm's histochemistry identified mossy fiber sprouting, and aberrant fascia dentata puncta densities were objectively measured by light microscopic analysis on an image-analysis computer. Neuron densities determined cell losses and the two seizure groups were compared to control specimens obtained from autopsies. Results showed significantly greater fascia dentata mossy fiber puncta densities and neuron losses in TLE patients compared to autopsy specimens (p < 0.026). Furthermore, there were significant differences between the two seizure groups: 1) mossy fiber puncta densities in the inner molecular layer were significantly greater in MTS compared to lesions (p < 0.02), and 2) mossy fiber puncta densities were greater in the inner molecular layer than in the stratum granulosum in 14 of 16 MTS patients (88%) compared to four of nine patients with lesions (44%, p < 0.01). Neuron densities were significantly different comparing MTS, lesion and control groups for stratum granulosum (p = 0.0001) and Ammon's horn (p = 0.0001), with each group significantly different (p < 0.05) compared to another. All patients were either seizure-free or significantly improved 1 year or more after en bloc temporal lobectomy. There were no significant correlations between fascia dentata mossy fiber puncta densities and counts of hilar neurons, CA4 pyramids, granule cells, or years of seizures. This indicates that inner molecular layer mossy fiber puncta densities and neuron losses are greater in patients with MTS than in those with lesions, and mossy fiber sprouting probably contributes to the pathophysiology of hippocampal seizures. Furthermore, these data show that some patients with extrahippocampal lesions have mossy fiber sprouting similar to MTS patients, suggesting that hippocampi in lesion patients may be capable of epileptogenesis from synaptic reorganization.

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Jennifer Phung, Paul Krogstad and Gary W. Mathern

Object

The object of this study was to determine if etiology and age at surgery were linked with fevers and altered white blood cell and CSF laboratory values after cerebral hemispherectomy.

Methods

Seizure etiologies (n = 76) were classified into hemimegalencephaly (HME), cortical dysplasia (CD), infarcts (stroke), Rasmussen encephalitis (RE), history of infections, and Sturge-Weber syndrome (SWS) and were compared with clinical variables, maximum daily temperature (Tmax), and blood and CSF studies through Day 12 posthemispherectomy.

Results

The Tmax on Days 2–4 and 9–12 postsurgery were higher for HME and RE cases than for stroke cases. Patients with RE showed positive correlations, whereas those with SWS had negative correlations between Tmax and age at surgery. Blood WBC counts on postsurgery Days 3, 6, and 9–12 were higher in the HME and CD cases than in the stroke and RE cases. The percentage of blood polymorphonuclear cells (%bloodPMNs) was higher in the RE cases than in the HME, CD, and SWS cases. The RE, HME, and CD cases showed positive correlations between %bloodPMNs and age at surgery. The percentage of blood monocytes (%bloodMono) was higher in the patients with HME than in those with stroke or RE. The HME and CD cases showed negative correlations between %bloodMono and age at surgery. The CSF red blood cell counts were higher in the RE than in the CD and stroke cases. The percentage of CSF monocytes was higher in patients with CD than in those with stroke and RE. The percentage of CSF lymphocytes positively correlated with age at surgery.

Conclusions

Seizure etiology and age at surgery were associated with developing fevers and altered blood and CSF values after pediatric cerebral hemispherectomy. These findings indicate that besides infections, other clinical variables have an impact on developing fevers and abnormal laboratory values posthemispherectomy. Cultures appear to be the most reliable predictor of infections.

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Gary W. Mathern, James K. Pretorius and Thomas L. Babb

✓ The type of initial precipitating injury and the age at which it occurred in 20 patients with nonlesional temporal lobe epilepsy (TLE) were related to clinical features, presurgical neuroimaging, quantified hippocampal pathologies, and seizure outcomes. Clinical data, neuroimaging records, and seizure outcomes were abstracted from medical records and confirmed with patient and family contacts. Hippocampal neuron losses and mossy fiber reactive synaptogenesis were quantified independently. Results showed that the type of initial precipitating injury and the patient's age at which it occurred were related to the clinicopathological features of TLE. An initial precipitating injury occurred in 18 patients (90%), all of whom had mesial temporal sclerosis (MTS). Patients with a prolonged initial seizure or a nonseizure initial precipitating injury before age 5 years were significantly more likely to have unilateral hippocampal atrophy (p < 0.05) shown on magnetic resonance (MR) imaging, and had significantly greater inner molecular layer mossy fiber puncta densities (p < 0.001) than patients with nonprolonged childhood initial precipitating injuries and/or seizures after age 5 years. Furthermore, nonseizure injuries in patients before age 5 years had significantly longer latent periods (p < 0.05), and the patients did not respond to surgical treatment as well as other MTS patients. Those with an initial precipitating injury after age 5 years had MTS but showed significantly less inner molecular layer mossy fiber sprouting (p < 0.05) than patients whose injuries appeared before age 5 years. Patients without an initial precipitating injury (idiopathic TLE) had significantly fewer neuron losses (p < 0.05) and inner molecular layer mossy fiber puncta densities (p < 0.05) and had worse outcomes following en bloc temporal lobectomy compared to patients with MTS who had experienced initial precipitating injuries. Patients with unilateral hippocampal abnormalities on MR imaging did not show significant differences in neuron losses or aberrant mossy fiber puncta densities compared to patients without asymmetry. These results support the hypothesis that the type of initial precipitating injury and the age at which the injury occurred initiates and influences the pathophysiological process that eventually develops into MTS. These data support the notion that the pathophysiology of hippocampal damage and mossy fiber sprouting after an initial precipitating injury may be a progressive process.

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Gary W. Mathern, James K. Pretorius, Thomas L. Babb and Bruce Quinn

✓ Rarely are both sides of the hippocampus available for pathological study in a patient with intractable temporal lobe epilepsy (TLE). The authors report a patient with TLE investigated with bilateral depth electrodes who had an episode of postictal psychosis. The patient died 4 weeks after temporal lobectomy of unknown reasons, despite complete postmortem examination and clinical evidence of postsurgery seizure control. Pathological examination of surgical and autopsy hippocampal specimens found bilateral asymmetric neuron losses. However, only the resected epileptogenic hippocampus showed the profile of neuron loss typical of mesial temporal sclerosis (MTS) and abnormal mossy fiber synaptic reorganization. Quantitative depth electroencephalographic (EEG) analysis of the postictal psychotic event showed that it was not associated with a cluster of seizures, increased postictal depth EEG spike activity, or insufficient antiepileptic medication. These results support the hypothesis that ipsilateral hippocampal epileptogenesis is associated with MTS and mossy fiber sprouting. The results also suggest that the etiology of postictal psychosis in this patient was initiated by an ictal event and the behavior apparently depended on seizure propagation outside the hippocampus. The relevance of these two findings to the literature is discussed.

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Nikhil Bellamkonda, H. Westley Phillips, Jia-Shu Chen, Alexander M. Tucker, Cassia Maniquis, Gary W. Mathern and Aria Fallah

OBJECTIVE

Rasmussen encephalitis (RE) is a rare inflammatory neurological disorder typically involving one hemisphere and resulting in drug-resistant epilepsy and progressive neurological decline. Here, the authors present seizure outcomes in children who underwent epilepsy surgery for RE at a single institution.

METHODS

The records of consecutive patients who had undergone epilepsy surgery for RE at the UCLA Mattel Children’s Hospital between 1982 and 2018 were retrospectively reviewed. Basic demographic information, seizure history, procedural notes, and postoperative seizure and functional outcome data were analyzed.

RESULTS

The cohort included 44 patients, 41 of whom had sufficient data for analysis. Seizure freedom was achieved in 68%, 48%, and 22% of the patients at 1, 5, and 10 years, respectively. The median time to the first seizure for those who experienced seizure recurrence after surgery was 39 weeks (IQR 11–355 weeks). Anatomical hemispherectomy, as compared to functional hemispherectomy, was independently associated with a longer time to postoperative seizure recurrence (HR 0.078, p = 0.03). There was no statistically significant difference in postoperative seizure recurrence between patients with complete hemispherectomy and those who had less-than-hemispheric surgery. Following surgery, 68% of the patients could ambulate and 84% could speak regardless of operative intervention.

CONCLUSIONS

A large proportion of RE patients will have seizure relapse after surgery, though patients with anatomical hemispherectomies may have a longer time to postoperative seizure recurrence. Overall, the long-term data in this study suggest that hemispheric surgery can be seen as palliative treatment for seizures rather than a cure for RE.

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Shon W. Cook, Snow T. Nguyen, Bin Hu, Sue Yudovin, W. Donald Shields, Harry V. Vinters, Barbara M. Van de Wiele, Rick E. Harrison and Gary W. Mathern

Object. Cerebral hemispherectomy for intractable seizures has evolved over the past 50 years, and current operations focus less on brain resection and more on disconnection. In addition, cases involving cortical dysplasia and Rasmussen encephalitis are being identified and surgically treated in younger individuals. Few studies have been conducted to compare whether there are perioperative differences based on hemispherectomy technique and/or pathological substrate in pediatric patients with epilepsy.

Methods. In this study the authors compared, stratified by disease, anatomical (37 cases) and Rasmussen functional hemispherectomy (32 cases) with a new modified lateral hemispherotomy (46 cases). Pathological processes included cortical dysplasia (55 cases), Rasmussen encephalitis (21 cases), infarction/ischemia (27 cases), and other/miscellaneous (12 cases). The authors found differences in perioperative clinical factors based on operative technique and/or pathological substrate. In terms of technique, the lateral hemispherotomy was associated with the least intraoperative blood loss, shortest intensive care unit stay, and lowest complication rate. The anatomical hemispherectomy was associated with the longest hospital stay, delayed oral food intake, highest postsurgery fevers, and the highest incidence of shunt requirement. The functional hemispherectomy was associated with the highest reoperation rate for recurrent seizures (25%). In terms of pathology, patients with cortical dysplasia were the youngest at surgery, suffered the greatest amount of blood loss, and required the longest operative/anesthesia times compared with the other pathologically defined groups. Postoperative seizure control (range 0.5–2 years) was not statistically different according to technique or disease process and was similar to that in cases of pediatric temporal lobe epilepsy.

Conclusions. The authors found differences in perioperative risks and hospital course but not postsurgery seizure control, which vary by hemispherectomy technique and/or disease process. The modified lateral hemispherotomy approach offers various advantages related to operative blood loss and reoperation compared with anatomical and functional hemispherectomies that are especially relevant in younger patients with cortical dysplasia and Rasmussen encephalitis with small and/or malformed ventricles.

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Jason S. Hauptman, Andrew Dadour, Taemin Oh, Christine B. Baca, Barbara G. Vickrey, Stefanie D. Vassar, Raman Sankar, Noriko Salamon, Harry V. Vinters and Gary W. Mathern

Object

Low income, government insurance, and minority status are associated with delayed treatment for neurosurgery patients. Less is known about the influence of referral location and how socioeconomic factors and referral patterns evolve over time. For pediatric epilepsy surgery patients at the University of California, Los Angeles (UCLA), this study determined how referral location and sociodemographic features have evolved over 25 years.

Methods

Children undergoing epilepsy neurosurgery at UCLA (453 patients) were classified by location of residence and compared with clinical epilepsy and sociodemographic factors.

Results

From 1986 to 2010, referrals from Southern California increased (+33%) and referrals from outside of California decreased (−19%). Over the same period, the number of patients with preferred provider organization (PPO) and health maintenance organization (HMO) insurance increased (+148% and +69%, respectively) and indemnity insurance decreased (−96%). Likewise, the number of Hispanics (+117%) and Asians (100%) increased and Caucasians/whites decreased (−24%). The number of insurance companies decreased from 52 carriers per 100 surgical patients in 1986–1990 to 19 per 100 in 2006–2010. Patients living in the Eastern US had a younger age at surgery (−46%), shorter intervals from seizure onset to referral for evaluation (−28%) and from presurgical evaluation to surgery (−61%) compared with patients from Southern California. The interval from seizure onset to evaluation was shorter (−33%) for patients from Los Angeles County compared with those living in non-California Western US states.

Conclusions

Referral locations evolved over 25 years at UCLA, with more cases coming from local regions; the percentage of minority patients also increased. The interval from seizures onset to surgery was shortest for patients living farthest from UCLA but still within the US. Geographic location and race/ethnicity was not associated with differences in becoming seizure free after epilepsy surgery in children.

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Anthony C. Wang, George M. Ibrahim, Andrew V. Poliakov, Page I. Wang, Aria Fallah, Gary W. Mathern, Robert T. Buckley, Kelly Collins, Alexander G. Weil, Hillary A. Shurtleff, Molly H. Warner, Francisco A. Perez, Dennis W. Shaw, Jason N. Wright, Russell P. Saneto, Edward J. Novotny, Amy Lee, Samuel R. Browd and Jeffrey G. Ojemann

OBJECTIVE

The potential loss of motor function after cerebral hemispherectomy is a common cause of anguish for patients, their families, and their physicians. The deficits these patients face are individually unique, but as a whole they provide a framework to understand the mechanisms underlying cortical reorganization of motor function. This study investigated whether preoperative functional MRI (fMRI) and diffusion tensor imaging (DTI) could predict the postoperative preservation of hand motor function.

METHODS

Thirteen independent reviewers analyzed sensorimotor fMRI and colored fractional anisotropy (CoFA)–DTI maps in 25 patients undergoing functional hemispherectomy for treatment of intractable seizures. Pre- and postoperative gross hand motor function were categorized and correlated with fMRI and DTI findings, specifically, abnormally located motor activation on fMRI and corticospinal tract atrophy on DTI.

RESULTS

Normal sensorimotor cortical activation on preoperative fMRI was significantly associated with severe decline in postoperative motor function, demonstrating 92.9% sensitivity (95% CI 0.661–0.998) and 100% specificity (95% CI 0.715–1.00). Bilaterally robust, symmetric corticospinal tracts on CoFA-DTI maps were significantly associated with severe postoperative motor decline, demonstrating 85.7% sensitivity (95% CI 0.572–0.982) and 100% specificity (95% CI 0.715–1.00). Interpreting the fMR images, the reviewers achieved a Fleiss’ kappa coefficient (κ) for interrater agreement of κ = 0.69, indicating good agreement (p < 0.01). When interpreting the CoFA-DTI maps, the reviewers achieved κ = 0.64, again indicating good agreement (p < 0.01).

CONCLUSIONS

Functional hemispherectomy offers a high potential for seizure freedom without debilitating functional deficits in certain instances. Patients likely to retain preoperative motor function can be identified prior to hemispherectomy, where fMRI or DTI suggests that cortical reorganization of motor function has occurred prior to the operation.