Pediatric neuroblastoma with intraspinal extension: the role of surgical management.

OBJECTIVE: Neuroblastoma with spinal involvement accounts for up to 30% of pediatric spinal tumors and can cause profound neurological deficits. Chemotherapy is the preferred treatment option, but in select patients resection may be indicated. The goal of this study was to identify preoperative factors that led to early surgical intervention, with a specific emphasis on identifying differences on long-term neurological function and spinal deformity in the recent treatment era. METHODS: A retrospective chart review was performed on all children diagnosed with neuroblastoma at a single institution from 2007 to 2020. Patient demographics, symptoms (motor deficit and sphincter dysfunction), and tumor characteristics (e.g., 123I metaiodobenzylguanidine [MIBG] avidity, MYCN amplification, chromosomal abnormality, pathology, catecholamine secretion, and stage) were recorded. Spine involvement included neural or vertebral extension, spinal cord compression, and/or T2 signal change on MRI. Survival, neurological status (motor deficit, sphincter dysfunction), and spine deformity at last follow-up were compared using univariate and multivariate analyses. The variables that contributed to neurological and deformity outcome were assessed with binomial logistic and linear regression models using R software. RESULTS: Seventy-seven of the 160 patients with neuroblastoma had spinal neuroblastoma, meaning either bone metastases alone (n = 43) or intraspinal extension with or without neurological deficit (n= 34). Most patients with spinal neuroblastoma were treated with chemotherapy and/or radiation therapy (97% and 57%, respectively). Resection of the spinal tumor was performed in 14 (18%) patients, all of whom also received chemotherapy. Between the surgical and nonsurgical patients, no baseline demographic differences were found. However, surgical patients were more likely to present with either motor deficits (50% vs 5%, p = 0.0011) or bladder/bowel dysfunction (14% vs 0%, p 0.035), and a shorter median time to onset of neurological symptoms (33 vs 80 days, p = 0.0096). Surgical patients also had a significantly shorter median overall survival (33.0 vs 54 months, p = 0.014). Of the 14 patients who underwent spine surgery, 2 patients underwent surgery at the time of diagnosis while the remaining 12 underwent initial chemotherapy followed later by resection. The 2 patients who underwent initial surgery had excellent outcomes, with neither long-term motor or bowel/bladder deficits nor spinal deformity. CONCLUSIONS: Surgical patients had shorter overall survival. However, the 2 patients with radiographic evidence of cord compression and acute neurological symptom onset who underwent initial, immediate surgery within 3 days of diagnosis had fewer long-term neurological deficits than surgical patients who underwent initial trials of chemotherapy. Thus, acute decompression may provide benefit in carefully selected patients with acute neurological deficits and cord compression on imaging.

Responsive Neurostimulation in Drug-Resistant Pediatric Epilepsy: Findings From the Epilepsy Surgery Subgroup of the Pediatric Epilepsy Research Consortium.

BACKGROUND: Responsive neurostimulation (RNS), a closed-loop intracranial electrical stimulation system, is a palliative surgical option for patients with drug-resistant epilepsy (DRE). RNS is approved by the US Food and Drug Administration for patients aged ≥18 years with pharmacoresistant partial seizures. The published experience of RNS in children is limited. METHODS: This is a combined prospective and retrospective study of patients aged ≤18 years undergoing RNS placement. Patients were identified from the multicenter Pediatric Epilepsy Research Consortium Surgery Registry from January 2018 to December 2021, and additional data relevant to this study were retrospectively collected and analyzed. RESULTS: Fifty-six patients received RNS during the study period. The mean age at implantation was 14.9 years; the mean duration of epilepsy, 8.1 years; and the mean number of previously trialed antiseizure medications, 4.2. Five patients (9%) previously trialed dietary therapy, and 19 patients (34%) underwent prior surgery. Most patients (70%) underwent invasive electroencephalography evaluation before RNS implantation. Complications occurred in three patients (5.3%) including malpositioned leads or transient weakness. Follow-up (mean 11.7 months) was available for 55 patients (one lost), and four were seizure-free with RNS off. Outcome analysis of stimulation efficacy was available for 51 patients: 33 patients (65%) were responders (≥50% reduction in seizure frequency), including five patients (10%) who were seizure free at follow-up. CONCLUSIONS: For young patients with focal DRE who are not candidates for surgical resection, neuromodulation should be considered. Although RNS is off-label for patients aged <18 years, this multicenter study suggests that it is a safe and effective palliative option for children with focal DRE.

A comparison of incidental and symptomatic unruptured brain arteriovenous malformations in children.

OBJECTIVE: Patients with unruptured brain arteriovenous malformations (AVMs) may present with headaches, seizures, and/or neurological deficits. A smaller number of cases may be discovered incidentally. These lesions remain incompletely understood due to their sparse reporting. Herein, the authors describe the largest series to date comparing the presentation, angioarchitecture, and management of incidental versus symptomatic unruptured AVMs in children. METHODS: The authors performed a retrospective analysis of patients who presented with brain AVMs from 1998 to 2022 at the University of California, San Francisco. Inclusion criteria were age ≤ 18 years at the time of presentation and an angiographically proven unruptured AVM that had been diagnosed postnatally. RESULTS: Of 76 children with unruptured AVMs, 66 (86.8%) presented with headaches, seizures, and/or neurological deficit. Ten AVMs (13.1%) were incidentally discovered through unrelated disease workup (50%), cranial trauma (40%), or research study participation (10%). Compared with patients with symptomatic unruptured AVMs, patients with incidental unruptured AVMs had a smaller mean ± SD maximum nidus diameter (2.82 ± 1.1 vs 3.98 ± 1.52 cm, p = 0.025) and fewer had deep venous drainage (20% of patients vs 61%, p = 0.036). They also presented at an earlier age (10 ± 5.2 vs 13.5 ± 4 years, p = 0.043) and with longer duration to first treatment (541 ± 922 vs 196 ± 448 days, p = 0.005). During the observation period, 1 patient developed recurring headaches and demonstrated AVM nidus growth. Four AVMs greater than 3 cm in size or in a deep location were treated with radiosurgery. Six other AVMs were treated with resection, with 2 receiving preoperative embolization. Eight AVMs (80%) were obliterated on last follow-up. Postprocedural complications included 2 transient neurological deficits after resection and 1 case of delayed seizure development after radiosurgery. The mean follow-up period was 5.7 ± 5.7 years without any hemorrhage episodes. CONCLUSIONS: A substantial proportion of pediatric patients with unruptured AVMs are discovered incidentally. With earlier presentation and more elementary angioarchitecture than symptomatic unruptured AVMs, these incidental lesions provide a snapshot into the natural history of AVM before symptom development or rupture.

TRAF7 somatic mosaicism in a patient with bilateral optic nerve sheath meningiomas: illustrative case.

BACKGROUND: In the past decade, next-generation sequencing has spurred significant progress in the understanding of cytogenetic alterations that occur in meningiomas. Eighty percent of adult meningiomas harbor pathogenic somatic variants involving NF2, TRAF7, SMARCB1, KLF4, PI3K, or POLR2A. Somatic variants in TRAF7 associated with meningiomas usually localize to the gene's WD40 domains but are mutually exclusive to germline mutations, which cause a distinctive autosomal dominant syndrome. OBSERVATIONS: This case involved a 15-year-old girl with bilateral optic nerve sheath meningiomas, diffuse meningiomatosis, and syndromic features, including craniosynostosis, brain anomalies, syndactyly, brachydactyly, epicanthus, and patent ductus arteriosus. Genetic testing of the meningioma specimen 7 years after biopsy showed a pathogenic p.R641C variant within the WD40 domain of the TRAF7 gene. Additional testing of unaffected tissues identified the same variant at lower allele frequencies, consistent with postzygotic somatic mosaicism. LESSONS: The authors report postzygotic somatic mosaicism for a p.R641C variant in the TRAF7 gene in a patient with bilateral optic nerve sheath meningiomas, diffuse meningiomatosis and a constellation of systemic findings previously recognized in patients with germline mutations of this gene. This is the first report of optic nerve sheath meningioma in a patient with mutation in the TRAF7 gene.

The Hybrid Operative Suite with Intraoperative Biplane Rotational Angiography in Pediatric Cerebrovascular Neurosurgery: Utility and Lessons Learned.

INTRODUCTION: The benefits of performing open and endovascular procedures in a hybrid neuroangiography surgical suite include confirmation of treatment results and reduction in number of procedures, leading to improved efficiency of care. Combined procedural suites are infrequently used in pediatric facilities due to technical and logistical limitations. We report the safety, utility, and lessons learned from a single-institution experience using a hybrid suite equipped with biplane rotational digital subtraction angiography and pan-surgical capabilities. METHODS: We conducted a retrospective review of consecutive cases performed at our institution that utilized the hybrid neuroangiography surgical suite from February 2020 to August 2021. Demographics, surgical metrics, and imaging results were collected from the electronic medical record. Outcomes, interventions, and nuances for optimizing preoperative/intraoperative setup and postoperative care were presented. RESULTS: Eighteen procedures were performed in 17 patients (mean age 13.4 years, range 6-19). Cases included 14 arteriovenous malformations (AVM; 85.7% ruptured), one dural arteriovenous fistula, one mycotic aneurysm, and one hemangioblastoma. The average operative time was 416 min (range 321-745). There were no intraoperative or postoperative complications. All patients were alive at follow-up (range 0.1-14.7 months). Five patients had anticipated postoperative deficits arising from their hemorrhage, and 12 returned to baseline neurological status. Four illustrative cases demonstrating specific, unique applications of the hybrid angiography suite are presented. CONCLUSION: The hybrid neuroangiography surgical suite is a safe option for pediatric cerebrovascular pathologies requiring combined surgical and endovascular intervention. Hybrid cases can be completed within the same anesthesia session and reduce the need for return to the operating room for resection or surveillance angiography. High-quality intraoperative angiography enables diagnostic confirmation under a single procedure, mitigating risk of morbidity and accelerating recovery. Effective multidisciplinary planning enables preoperative angiograms to be completed to inform the operative plan immediately prior to definitive resection.

Repetitive transcranial magnetic stimulation (rTMS) as therapy in an infant with epilepsia partialis continua.

Introduction: We present a case of a 10-month-old girl undergoing repetitive TMS (rTMS) for the treatment of drug-resistant epilepsy. Case report: A 10-month-old girl, later diagnosed with pathogenic POLG1 mutations, presented to our institution with chronic progressive EPC (epilepsia partialis continua) manifesting as a frequent, left-sided, synchronous continuous jerking of the arms and legs. The seizures were drug-resistant to multiple antiseizure medications and epilepsy surgery, responding only to continuous anesthesia. rTMS therapy was attempted to interrupt seizures. Results: rTMS therapy, using an activating protocol to introduce a temporary lesion effect, was used to interrupt persistent, ongoing seizures. Conclusion: rTMS can be safely used to abort seizures in patients as young as 10 months old.

Superior Long-term Appearance of Strip Craniectomy Compared with Cranial Vault Reconstruction in Metopic Craniosynostosis.

BACKGROUND: Strip craniectomy with orthotic helmet therapy (SCOT) is an increasingly supported treatment for metopic craniosynostosis, although the long-term efficacy of deformity correction remains poorly defined. We compared the longterm outcomes of SCOT versus open cranial vault reconstruction (OCVR). METHODS: Patients who underwent OCVR or SCOT for isolated metopic synostosis with at least 3 years of follow-up were identified at our institution. Anthropometric measurements were used to assess baseline severity and postoperative skull morphology. Independent laypersons and craniofacial surgeons rated the appearance of each patient's 3D photographs, compared to normal controls. RESULTS: Thirty-five patients were included (15 SCOT and 20 OCVR), with similar follow-up between groups (SCOT 7.9 ± 3.2 years, OCVR 9.2 ± 4.1 years). Baseline severity and postoperative anthropometric measurements were equivalent. Independent adolescent raters reported that the forehead, eye, and overall appearance of SCOT patients was better than OCVR patients (P < 0.05, all comparisons). Craniofacial surgeons assigned Whitaker class I to a greater proportion of SCOT patients with moderate-to-severe synostosis (72.2 ± 5.6%) compared with OCVR patients with the same severity (33.3 ± 9.2%, P = 0.02). Parents of children who underwent SCOT reported equivalent satisfaction with the results of surgery (100% versus 95%, P > 0.99), and were no more likely to report bullying (7% versus 15%, P = 0.82). CONCLUSIONS: SCOT was associated with superior long-term appearance and perioperative outcomes compared with OCVR. These findings suggest that SCOT should be the treatment of choice for patients with a timely diagnosis of metopic craniosynostosis.

Navigated transcranial magnetic stimulation mapping of the motor cortex for preoperative diagnostics in pediatric epilepsy.

OBJECTIVE: Navigated transcranial magnetic stimulation (nTMS) is a noninvasive technique often used for localization of the functional motor cortex via induction of motor evoked potentials (MEPs) in neurosurgical patients. There has, however, been no published record of its application in pediatric epilepsy surgery. In this study, the authors aimed to investigate the feasibility of nTMS-based motor mapping in the preoperative diagnostic workup within a population of children with medically refractory epilepsy. METHODS: A single-institution database was screened for preoperative nTMS motor mappings obtained in pediatric patients (aged 0 to 18 years, 2012 to present) with medically refractory epilepsy. Patient clinical data, demographic information, and mapping results were extracted and used in statistical analyses. RESULTS: Sixteen patients met the inclusion criteria, 15 of whom underwent resection. The median age was 9 years (range 0-17 years). No adverse effects were recorded during mapping. Specifically, no epileptic seizures were provoked via nTMS. Recordings of valid MEPs induced by nTMS were obtained in 10 patients. In the remaining patients, no MEPs could be elicited. Failure to generate MEPs was associated significantly with younger patient age (r = 0.8020, p = 0.0001863). The most frequent seizure control outcome was Engel Epilepsy Surgery Outcome Scale class I (9 patients). CONCLUSIONS: Navigated TMS is a feasible, effective, and well-tolerated method for mapping the motor cortex of the upper and lower extremities in pediatric patients with epilepsy. Patient age modulates elicitability of MEPs, potentially reflecting various stages of myelination. Successful motor mapping has the potential to add to the existing presurgical diagnostic workup in this population, and further research is warranted.

Direct brain recordings reveal occipital cortex involvement in memory development.

Processing of low-level visual information shows robust developmental gains through childhood and adolescence. However, it is unknown whether low-level visual processing in the occipital cortex supports age-related gains in memory for complex visual stimuli. Here, we examined occipital alpha activity during visual scene encoding in 24 children and adolescents, aged 6.2-20.5 years, who performed a subsequent memory task while undergoing electrocorticographic recording. Scenes were classified as high- or low-complexity by the number of unique object categories depicted. We found that recognition of high-complexity, but not low-complexity, scenes increased with age. Age was associated with decreased alpha power and increased instantaneous alpha frequency during the encoding of subsequently recognized high- compared to low-complexity scenes. Critically, decreased alpha power predicted improved recognition of high-complexity scenes in adolescents. These findings demonstrate how the functional maturation of the occipital cortex supports the development of memory for complex visual scenes.

Comprehensive analysis of diverse low-grade neuroepithelial tumors with FGFR1 alterations reveals a distinct molecular signature of rosette-forming glioneuronal tumor.

The FGFR1 gene encoding fibroblast growth factor receptor 1 has emerged as a frequently altered oncogene in the pathogenesis of multiple low-grade neuroepithelial tumor (LGNET) subtypes including pilocytic astrocytoma, dysembryoplastic neuroepithelial tumor (DNT), rosette-forming glioneuronal tumor (RGNT), and extraventricular neurocytoma (EVN). These activating FGFR1 alterations in LGNET can include tandem duplication of the exons encoding the intracellular tyrosine kinase domain, in-frame gene fusions most often with TACC1 as the partner, or hotspot missense mutations within the tyrosine kinase domain (either at p.N546 or p.K656). However, the specificity of these different FGFR1 events for the various LGNET subtypes and accompanying genetic alterations are not well defined. Here we performed comprehensive genomic and epigenomic characterization on a diverse cohort of 30 LGNET with FGFR1 alterations. We identified that RGNT harbors a distinct epigenetic signature compared to other LGNET with FGFR1 alterations, and is uniquely characterized by FGFR1 kinase domain hotspot missense mutations in combination with either PIK3CA or PIK3R1 mutation, often with accompanying NF1 or PTPN11 mutation. In contrast, EVN harbors its own distinct epigenetic signature and is characterized by FGFR1-TACC1 fusion as the solitary pathogenic alteration. Additionally, DNT and pilocytic astrocytoma are characterized by either kinase domain tandem duplication or hotspot missense mutations, occasionally with accompanying NF1 or PTPN11 mutation, but lacking the accompanying PIK3CA or PIK3R1 mutation that characterizes RGNT. The glial component of LGNET with FGFR1 alterations typically has a predominantly oligodendroglial morphology, and many of the pilocytic astrocytomas with FGFR1 alterations lack the biphasic pattern, piloid processes, and Rosenthal fibers that characterize pilocytic astrocytomas with BRAF mutation or fusion. Together, this analysis improves the classification and histopathologic stratification of LGNET with FGFR1 alterations.

Extradural thoracic meningeal cyst without spinal dysraphism causing adulthood myelopathy: Case illustration and review of the literature.

Extradural spinal meningeal cysts are rare lesions in the adult spine and are an uncommon cause of neurologic deficits. We present the case of an adult who presented with myelopathic symptoms related to a dorsally based extradural thoracic meningeal cyst in the absence of any defect in the posterior spinal elements and no history of spinal dysraphism or trauma. We also performed a review of the literature to evaluate the surgical techniques for extradural meningeal cysts. Most thoracic cysts are intradural arachnoid cysts, yet this lesion is an extradural meningeal cyst, not an intradural arachnoid cyst. Because of the rarity of this lesion, its anatomic characterization can be difficult to conceptualize. An artist's illustration helps illustrate the anatomic characteristics of this cyst and our surgical management.

Single-center series of boys with recurrent strokes and rotational vertebral arteriopathy.

OBJECTIVE: To describe a pediatric stroke syndrome with chronic focal vertebral arteriopathy adjacent to cervical abnormalities. METHODS: At a single pediatric stroke center, we identified consecutive children with stroke and vertebral arteriopathy of the V3 segment with adjacent cervical bony or soft tissue abnormalities. We abstracted clinical presentation, treatment, and follow-up data from medical charts. RESULTS: From 2005 to 2019, 10 children (all boys, ages 6-16 years) presented with posterior circulation strokes and vertebral arteriopathy with adjacent cervical pathology. Two children had bony abnormalities: one had a congenital arcuate foramen and one had os odontoideum with cervical instability. In children without bony pathology, vertebral artery narrowing during contralateral head rotation was visualized by digital subtraction angiography. Eight boys had recurrent ischemic events despite anti-thrombotic treatment (including 5 with multiple recurrences) and were treated surgically to prevent additional stroke. Procedures included vertebral artery decompression (n = 6), endovascular stent and spinal fusion (n = 1), and vertebral artery endovascular occlusion (n = 1). In boys treated with decompression, cervical soft tissue abnormalities (ruptured atlantoaxial bursa, ruptured joint capsule, or connective tissue scarring) were directly visualized during open surgery. No other etiology for stroke or dissection was found in any of the cases. Two boys without recurrent stroke were treated with activity restriction and antithrombotics. At a median follow-up of 51 months (range 17-84), there have been no additional recurrences. CONCLUSIONS: Children with V3 segmental vertebral arteriopathy frequently have stroke recurrence despite antithrombotics. Cervical bone imaging and angiography with neck rotation can identify underlying pathology.

Meningiomas in children.

Meningiomas in children are poorly understood because they are rare. Recent reports have provided a more complete description of their incidence, genetics, imaging features, and outcome. In general, meningiomas in children are more likely to be higher grade, present in atypical locations, and have a higher risk of recurrence. The challenges encountered in children with respect to surgical and postoperative management are unique. Improved understanding of pediatric meningiomas, as well as the availability of new surgical, medical, and radiation therapies, creates opportunities to improve outcomes in this unique population.

Responsive neurostimulation for treatment of pediatric drug-resistant epilepsy.

Responsive neurostimulation for epilepsy involves an implanted device that delivers direct electrical brain stimulation in response to detection of incipient seizures. Responsive neurostimulation is a safe and effective treatment for adults with drug-resistant epilepsy, but although novel treatments are critically needed for younger patients, responsive neurostimulation is currently not approved for children with drug-resistant epilepsy. Here, we report a 16-year-old patient with seizures arising from eloquent cortex, who was successfully treated with responsive neurostimulation. This case highlights the potential utility of this therapy for pediatric patients and underscores the need for larger studies.

Complications following pediatric cranioplasty after decompressive craniectomy: a multicenter retrospective study.

OBJECTIVE In children, the repair of skull defects arising from decompressive craniectomy presents a unique set of challenges. Single-center studies have identified different risk factors for the common complications of cranioplasty resorption and infection. The goal of the present study was to determine the risk factors for bone resorption and infection after pediatric cranioplasty. METHODS The authors conducted a multicenter retrospective case study that included all patients who underwent cranioplasty to correct a skull defect arising from a decompressive craniectomy at 13 centers between 2000 and 2011 and were less than 19 years old at the time of cranioplasty. Prior systematic review of the literature along with expert opinion guided the selection of variables to be collected. These included: indication for craniectomy; history of abusive head trauma; method of bone storage; method of bone fixation; use of drains; size of bone graft; presence of other implants, including ventriculoperitoneal (VP) shunt; presence of fluid collections; age at craniectomy; and time between craniectomy and cranioplasty. RESULTS A total of 359 patients met the inclusion criteria. The patients' mean age was 8.4 years, and 51.5% were female. Thirty-eight cases (10.5%) were complicated by infection. In multivariate analysis, presence of a cranial implant (primarily VP shunt) (OR 2.41, 95% CI 1.17-4.98), presence of gastrostomy (OR 2.44, 95% CI 1.03-5.79), and ventilator dependence (OR 8.45, 95% CI 1.10-65.08) were significant risk factors for cranioplasty infection. No other variable was associated with infection. Of the 240 patients who underwent a cranioplasty with bone graft, 21.7% showed bone resorption significant enough to warrant repeat surgical intervention. The most important predictor of cranioplasty bone resorption was age at the time of cranioplasty. For every month of increased age the risk of bone flap resorption decreased by 1% (OR 0.99, 95% CI 0.98-0.99, p < 0.001). Other risk factors for resorption in multivariate models were the use of external ventricular drains and lumbar shunts. CONCLUSIONS This is the largest study of pediatric cranioplasty outcomes performed to date. Analysis included variables found to be significant in previous retrospective reports. Presence of a cranial implant such as VP shunt is the most significant risk factor for cranioplasty infection, whereas younger age at cranioplasty is the dominant risk factor for bone resorption.

Human hippocampal neurogenesis drops sharply in children to undetectable levels in adults.

New neurons continue to be generated in the subgranular zone of the dentate gyrus of the adult mammalian hippocampus. This process has been linked to learning and memory, stress and exercise, and is thought to be altered in neurological disease. In humans, some studies have suggested that hundreds of new neurons are added to the adult dentate gyrus every day, whereas other studies find many fewer putative new neurons. Despite these discrepancies, it is generally believed that the adult human hippocampus continues to generate new neurons. Here we show that a defined population of progenitor cells does not coalesce in the subgranular zone during human fetal or postnatal development. We also find that the number of proliferating progenitors and young neurons in the dentate gyrus declines sharply during the first year of life and only a few isolated young neurons are observed by 7 and 13 years of age. In adult patients with epilepsy and healthy adults (18-77 years; n = 17 post-mortem samples from controls; n = 12 surgical resection samples from patients with epilepsy), young neurons were not detected in the dentate gyrus. In the monkey (Macaca mulatta) hippocampus, proliferation of neurons in the subgranular zone was found in early postnatal life, but this diminished during juvenile development as neurogenesis decreased. We conclude that recruitment of young neurons to the primate hippocampus decreases rapidly during the first years of life, and that neurogenesis in the dentate gyrus does not continue, or is extremely rare, in adult humans. The early decline in hippocampal neurogenesis raises questions about how the function of the dentate gyrus differs between humans and other species in which adult hippocampal neurogenesis is preserved.

Laser ablative therapy of sessile hypothalamic hamartomas in children using interventional MRI: report of 5 cases.

Hypothalamic hamartomas (HHs) are benign lesions that cause medically refractory seizures, behavioral disturbances, and endocrine dysfunction. Open resection of HHs does not guarantee seizure freedom and carries a relatively high risk of morbidity. Minimally invasive stereotactic laser ablation has recently been described as an effective and safe alternative for HH treatment. Prior studies have not, however, assessed HH lesion size and morphology, 2 factors that may influence treatment results and, ultimately, the generalizability of their findings. In this paper, the authors describe seizure outcomes for 5 pediatric patients who underwent laser ablation of sessile HHs. Lesions were treated using a frameless, interventional MRI-guided approach, which facilitated laser targeting to specific components of these complex lesions. The authors' experiences in these cases substantiate prior work demonstrating the effectiveness of laser therapy for HHs, while elucidating HH complexity as a potentially important factor in laser treatment planning, and in the interpretation of early studies describing this treatment method.

Spatiotemporal dynamics of word retrieval in speech production revealed by cortical high-frequency band activity.

Word retrieval is core to language production and relies on complementary processes: the rapid activation of lexical and conceptual representations and word selection, which chooses the correct word among semantically related competitors. Lexical and conceptual activation is measured by semantic priming. In contrast, word selection is indexed by semantic interference and is hampered in semantically homogeneous (HOM) contexts. We examined the spatiotemporal dynamics of these complementary processes in a picture naming task with blocks of semantically heterogeneous (HET) or HOM stimuli. We used electrocorticography data obtained from frontal and temporal cortices, permitting detailed spatiotemporal analysis of word retrieval processes. A semantic interference effect was observed with naming latencies longer in HOM versus HET blocks. Cortical response strength as indexed by high-frequency band (HFB) activity (70-150 Hz) amplitude revealed effects linked to lexical-semantic activation and word selection observed in widespread regions of the cortical mantle. Depending on the subsecond timing and cortical region, HFB indexed semantic interference (i.e., more activity in HOM than HET blocks) or semantic priming effects (i.e., more activity in HET than HOM blocks). These effects overlapped in time and space in the left posterior inferior temporal gyrus and the left prefrontal cortex. The data do not support a modular view of word retrieval in speech production but rather support substantial overlap of lexical-semantic activation and word selection mechanisms in the brain.

Surgical management of medically refractory epilepsy in patients with polymicrogyria.

OBJECTIVE: Polymicrogyria (PMG) is a malformation of cortical development characterized by formation of an excessive number of small gyri. Sixty percent to 85% of patients with PMG have epilepsy that is refractory to medication, but surgical options are usually limited. We characterize a cohort of patient with polymicrogyria who underwent epilepsy surgery and document seizure outcomes. METHODS: A retrospective study of all patients with PMG who underwent epilepsy surgery (focal seizure foci resection and/or hemispherectomy) at our center was performed by review of all clinical data related to their treatment. RESULTS: We identified 12 patients (7 males and 5 female) with mean age of 18 (ranging from 3 months to 44 years) at time of surgery. Mean age at seizure onset was 8 years, with the majority (83%) having childhood onset. Six patients had focal, five had multifocal, and one patient had diffuse PMG. Perisylvian PMG was the most common pattern seen on magnetic resonance imaging (MRI). Eight patients had other cortical malformations including hemimegalencephaly and cortical dysplasia. Scalp electroencephalography (EEG) often showed diffuse epileptic discharges that poorly lateralized but were focal on intracranial electrocorticography (ECoG). Eight patients underwent seizure foci resection and four underwent hemispherectomy. Mean follow-up was 7 years (ranging from one to 19 years). Six patients (50%) were seizure-free at last follow-up. One patient had rare seizures (Engel class II). Three patients were Engel class III, having either decreased seizure frequency or severity, and two patients were Engel class IV. Gross total resection of the PMG cortex trended toward good seizure control. SIGNIFICANCE: Our study shows that even in patients with extensive or bilateral PMG malformations, some may still be good candidates for surgery because the epileptogenic zone may involve only a portion of the malformation. Intracranial ECoG can provide additional localizing information compared to scalp EEG in guiding resection of epileptogenic foci.