Incidence, follow-up, and postnatal clinical progress of children with central nervous system anomalies on fetal MRI.

OBJECTIVE: MRI is increasingly employed to assess intrauterine fetal anomalies. Central nervous system (CNS) anomalies are common structural conditions that warrant evaluation with fetal MRI and subsequent prenatal consultation with a pediatric neurosurgeon. As the use of fetal MRI increases, there is greater impetus to understand the most common CNS structural anomalies diagnosed in utero, as well as their natural histories. METHODS: The authors performed a single-center retrospective review of fetal MRI evaluations performed between January 2012 and December 2020. Children who underwent both prenatal and postnatal neurosurgical evaluations of CNS anomalies were included. Specific CNS anomalies on fetal MRI, associated extra-CNS findings, and suspicion for genetic abnormality or syndromes were noted. Postnatal clinical status and interventions were assessed. RESULTS: Between January 2012 and December 2020, a total of 469 fetal MRI evaluations were performed; of these, 114 maternal-fetal pairs had CNS anomalies that warranted prenatal consultation and postnatal pediatric neurosurgical follow-up. This cohort included 67 male infants (59%), with a mean ± SD follow-up of 29.8 ± 25.0 months after birth. Fetal MRI was performed at 27.3 ± 5.8 weeks of gestational age. The most frequently reported CNS abnormalities were ventriculomegaly (57%), agenesis or thinning of the corpus callosum (33%), Dandy-Walker complex (DWC) (21%), neuronal migration disorders (18%), and abnormalities of the septum pellucidum (17%). Twenty-one children (18%) required neurosurgical intervention at a mean age of 2.4 ± 3.7 months. The most common surgical conditions included myelomeningocele, moderate to severe ventriculomegaly, encephalocele, and arachnoid cyst. Corpus callosum agenesis or thinning was associated with developmental delay (p = 0.02) and systemic anomalies (p = 0.05). The majority of prenatal patients referred for DWC had Dandy-Walker variants that did not require surgical intervention. CONCLUSIONS: The most common conditions for prenatal neurosurgical assessment were ventriculomegaly, corpus callosum anomaly, and DWC, whereas the most common surgical conditions were myelomeningocele, hydrocephalus, and arachnoid cyst. Only 18% of prenatal neurosurgical consultations resulted in surgical intervention during infancy. The majority of referrals for prenatal mild ventriculomegaly and DWC were not associated with developmental or surgical sequelae. Patients with corpus callosum abnormalities should be concurrently referred to a neurologist for developmental assessments.

Initial experience with magnetic resonance-guided focused ultrasound stereotactic surgery for central brain lesions in young adults.

OBJECTIVE: Magnetic resonance-guided focused ultrasound (MRgFUS) is an incisionless procedure capable of thermoablation through the focus of multiple acoustic beams. Although MRgFUS is currently approved for the treatment of tremor in adults, its safety and feasibility profile for intracranial lesions in the pediatric and young adult population remains unknown. METHODS: The long-term outcomes of a prospective single-center, single-arm trial of MRgFUS at Nicklaus Children's Hospital in Miami, Florida, are presented. Patients 15-22 years of age with centrally located lesions were recruited, clinically consistent with WHO grade I tumors that require surgical intervention. This cohort consisted of 4 patients with hypothalamic hamartoma (HH), and 1 patient with tuberous sclerosis complex harboring a subependymal giant cell astrocytoma (SEGA). RESULTS: In each case, high-intensity FUS was used to target the intracranial lesion. Real-time MRI was used to monitor the thermoablations. Primary outcomes of interest were tolerability, feasibility, and safety of FUS. The radiographic ablation volume on intra- and postoperative MRI was also assessed. All 5 patients tolerated the procedure without any complications. Successful thermoablation was achieved in 4 of the 5 cases; the calcified SEGA was undertreated due to intratumor calcification, which prevented attainment of the target ablation temperature. The HHs underwent target tissue thermoablations that led to MR signal changes at the treatment site. For the patients harboring HHs, FUS thermoablations occurred without procedure-related complications and led to improvement in seizure control or hypothalamic hyperphagia. All 5 patients were discharged home on postoperative day 1 or 2, without any readmissions. There were no cases of hemorrhage, electrolyte derangement, endocrinopathy, or new neurological deficit in this cohort. CONCLUSIONS: This experience demonstrates that FUS thermoablation of centrally located brain lesions in adolescents and young adults can be performed safely and that it provides therapeutic benefit for associated symptoms.

Functional imaging localization of complex organic hallucinations.

Background: fMRI of mental phenomena is quite difficult to perform because lack of patient's cooperation or because the symptoms are stable. In some exceptional cases, however, fMRI and DTI are capable to provide insights on the anatomy of organic hallucinations. Methods: In this report we describe a 14-year-old boy with a left fronto-dorsal tumor who experienced chronic complex brief, frequent and repetitive complex visual and auditory hallucinations. His clinical picture included multiple and severe social and mood problems. During a presurgical fMRI mapping the patient complained of having the visual and auditory hallucinations. A block-design FMRI paradigm was obtained from the event timecourse. Deterministic DTI of the brain was obtained seeding the lesion as ROI. The patient underwent surgery and electrocorticography of the lesional area. Results: The fMRI of the hallucinations showed activation in the left inferior frontal gyrus (IFG) and the peri-lesional area. The tractography of the tumor revealed structural aberrant connectivity to occipital and temporal areas in addition to the expected connectivity with the IFG via the aslant fasciculus and homotopic contralateral areas. Intraoperative EEG demonstrated epileptic discharges in the tumor and neighboring areas. After resection, the patient's hallucinations stopped completely. He regained his normal social life and recover his normal mood. He remained asymptomatic for 90 days. Afterwards, hallucinations reappeared but with less intensity. Conclusions: To our knowledge, this is the first reported case of combined functional and structural connectivity imaging demonstrating brain regions participating in a network involved in the generation of complex auditory and visual hallucinations.

Presurgical hyperconnectivity of the ablation volume is associated with seizure-freedom after magnetic resonance-guided laser interstitial thermal therapy.

PURPOSE: Magnetic Resonance-guided Laser Interstitial Thermal Therapy (MRgLITT) is an emerging minimally-invasive alternative to resective surgery for medically-intractable epilepsy. The precise lesioning effect produced by MRgLITT supplies opportunities to glean insights into epileptogenic regions and their interactions with functional brain networks. In this exploratory analysis, we sought to characterize associations between MRgLITT ablation zones and large-scale brain networks that portended seizure outcome using resting-state fMRI. METHODS: Presurgical fMRI and intraoperatively volumetric structural imaging were obtained, from which the ablation volume was segmented. The network properties of the ablation volume within the brain's large-scale brain networks were characterized using graph theory and compared between children who were and were not rendered seizure-free. RESULTS: Of the seventeen included children, five achieved seizure freedom following MRgLITT. Greater functional connectivity of the ablation volume to canonical resting-state networks was associated with seizure-freedom (p < 0.05, FDR-corrected). The ablated volume in children who subsequently became seizure-free following MRgLITT had significantly greater strength, and eigenvector centrality within the large-scale brain network. CONCLUSIONS: These findings provide novel insights into the interaction between epileptogenic cortex and large-scale brain networks. The association between ablation volume and resting-state networks may supply novel avenues for presurgical planning and patient stratification.

Squamosal Suture Synostosis: Incidence, Associations, and Implications for Treatment.

Squamosal suture craniosynostosis is thought to be a relatively rare entity. In the authors' experience, it is underreported in imaging examinations and the existing literature. The authors sought to determine the incidence of squamosal synostosis, whether it is increasing in frequency, and its relationship with synostosis of the major calvarial sutures.Patients undergoing computed tomography imaging for suspected craniosynostosis over a 15-year period were reviewed by a plastic surgeon and pediatric neuroradiologist. Patients with synostosis of the squamosal sutures were identified and involvement of additional sutures, gender, and the presence of a known syndromic diagnosis were recorded. Patients greater than 4 years of age or those with prior craniofacial surgery were excluded.One hundred twenty-five patients met inclusion criteria, 26 of whom had squamosal suture synostosis (26/125, 20.8%). Squamosal synostosis was found in isolation in 3 patients (3/26, 11.5%), with 1 additional major suture in 10 patients (10/26, 38.5%), and ≥2 major sutures in 13 patients (13/26, 50%). Squamosal synostosis was more common in patients with a syndromic diagnosis (11/26 syndromic, 15/99 nonsyndromic, P < 0.001). Eleven of 26 patients with squamosal synostosis were identified in the radiology report (42.3%).Craniosynostosis of the squamosal suture is much more common than previously reported and can contribute to abnormal head shape in isolation, or in combination with major sutures. Squamosal suture synostosis is underdiagnosed clinically and radiologically, although insufficient evidence exists to determine if its true incidence is increasing.

Polymorphous low-grade neuroepithelial tumor of the young (PLNTY): an epileptogenic neoplasm with oligodendroglioma-like components, aberrant CD34 expression, and genetic alterations involving the MAP kinase pathway.

Epileptogenic tumors affecting children and young adults are a morphologically diverse collection of neuroepithelial neoplasms that, as a group, exhibit varying levels of glial and/or neuronal differentiation. Recent advances in molecular profiling technology, including comprehensive DNA sequencing and methylation analysis, have enabled the application of more precise and biologically relevant classification schemes to these tumors. In this report, we describe a morphologically and molecularly distinct epileptogenic neoplasm, the polymorphous low-grade neuroepithelial tumor of the young (PLNTY), which likely accounts for a sizable portion of oligodendroglioma-like tumors affecting the pediatric population. Characteristic microscopic findings most notably include infiltrative growth, the invariable presence of oligodendroglioma-like cellular components, and intense immunolabeling for cluster of differentiation 34 (CD34). Moreover, integrative molecular profiling reveals a distinct DNA methylation signature for PLNTYs, along with frequent genetic abnormalities involving either B-Raf proto-oncogene (BRAF) or fibroblast growth factor receptors 2 and 3 (FGFR2, FGFR3). These findings suggest that PLNTY represents a distinct biological entity within the larger spectrum of pediatric, low-grade neuroepithelial tumors.

Pediatric applications of functional magnetic resonance imaging.

Pediatric functional MRI has been used for the last 2 decades but is now gaining wide acceptance in the preoperative workup of children with brain tumors and medically refractory epilepsy. This review covers pediatrics-specific difficulties such as sedation and task paradigm selection according to the child's age and cognitive level. We also illustrate the increasing uses of functional MRI in the depiction of cognitive function, neuropsychiatric disorders and response to pharmacological agents. Finally, we review the uses of resting-state fMRI in the evaluation of children and in the detection of epileptogenic regions.

Conventional and advanced MRI features of pediatric intracranial tumors: posterior fossa and suprasellar tumors.

OBJECTIVE: In this article, we review the most common posterior fossa and suprasellar intracranial neoplasms in the pediatric population. We briefly discuss basic MRI concepts used in the initial evaluation of a pediatric brain tumor and then discuss sophisticated MRI techniques that give insight into the physiology and chemical makeup of these tumors to help the radiologist make a more specific diagnosis. CONCLUSION: Diagnosis and treatment of pediatric CNS tumors necessitate a multi-disciplinary approach and require expertise and diligence of all parties involved. Imaging is an essential component has evolved greatly over the past decade. We are becoming better at making a preoperative diagnosis of that tumor type, detecting recurrence, and guiding surgical management to avoid injury to vital brain structures.

Conventional and advanced MRI features of pediatric intracranial tumors: supratentorial tumors.

OBJECTIVE. Our objective is to review the imaging characteristics and applications of conventional and advanced neuroimaging techniques of supratentorial intracranial masses in the pediatric population. Specifically, we review astrocytomas, oligodendrogliomas, primary neuroectodermal tumors, dysembryoplastic neuroepithelial tumors, gangliogliomas, arachnoid cysts, and choroid plexus and pineal region masses. CONCLUSION. Advanced imaging methods, such as MR spectroscopy, perfusion MRI, functional MRI, diffusion-tensor imaging, and tractography, help develop a more accurate differential diagnosis and aid in planning tumor treatment.

FMRI under sedation: what is the best choice in children?

BACKGROUND: Pediatric fMRI may require sedation. The aim of this study is to compare different sedation schemes to determine which medication yields least failures and the best activation. METHODS: A total of 100 children who had fMRI performed as part of the work up for epilepsy surgery, were divided into different medication groups (Pentobarbital, Propofol, Dexmedetomidine, Sevoflurane). Comparison was performed among the groups for number of failures, rank of activation, adverse effects, anesthesia time, and recovery time. The study was approved by the IRB and followed all HIPAA guidelines. BOLD sequences were utilized to perform two block-design paradigms (auditory and visual). The activation was ranked into 5 categories according to the presence and localization of the activation. Descriptive and parametric statistics (ANOVA) were utilized to look for significant differences. RESULTS: Pentobarbital yielded the least amount of failures, for the auditory task, followed by propofol, while sevoflurane yielded the highest number of failures for both tasks. In the visual task, propofol administered after dexmedetomidine resulted in the least number of failures. Brain activations were not statistical different (auditory: ANOVA, P = 0.42; F = 1.01; visual: ANOVA, P = 0.077; F = 2.1). The shortest recovery time was obtained with sevoflurane, followed by propofol. Agitation and cardiac complications were seen in 28% of cases in the pentobarbital group. CONCLUSION: No statistically significant difference in brain activation was found utilizing different sedative medications in children with intractable epilepsy. A trend toward less failures was obtained with pentobarbital and propofol; however pentobarbital was more frequently associated with undesirable side effects.

Hemangiomas revisited: the useful, the unusual and the new. Part 2: endangering hemangiomas and treatment.

Hemangiomas, although benign tumors, can when located in particular regions threaten vital structures or in certain clinical circumstances be associated with other abnormalities, carrying significant morbidity and mortality. We review these endangering hemangiomas. We also discuss briefly the treatment with emphasis on the recent use of propranolol.

Hemangiomas revisited: the useful, the unusual and the new. Part 1: overview and clinical and imaging characteristics.

Hemangiomas are common vascular tumors occurring in children. Though most of the lesions present in infants and young children with a typical appearance, it is important to understand that they all do not behave in the same way. Rather, they are a group of vascular lesions with different clinico-pathological subtypes, with their clinical behavior varying with the stage of the tumor as well. As such, they can and do have a varied clinical, imaging and pathological appearance according to the location of the tumor and also the stage at which the patient is seen. In this pictorial essay, the classification, pathogenesis, clinical appearance, natural history and imaging characteristics of hemangiomas are reviewed and illustrated.

Agenesis of the arcuate fasciculi in congenital bilateral perisylvian syndrome: a diffusion tensor imaging and tractography study.

OBJECTIVE: To describe the absence of the arcuate fasciculi in 2 cases of congenital bilateral perisylvian syndrome (CBPS). DESIGN: Case series. SETTING: Pediatric referral hospital-based study. PATIENTS: Two patients with CBPS, referred to our institution as candidates for surgical treatment of epilepsy. Intervention Diffusion tensor imaging (1.5-T scanner; 15 encoding directions; b = 800 s/mm(2)) and deterministic tractography of the main projection and association tracts. MAIN OUTCOME MEASURES: Neuropsychology evaluation; fractional anisotropy, apparent diffusion coefficients, and anatomical aspect of the tracts. RESULTS: Absence of the arcuate fasciculus was observed in both subjects. Ancillary findings were complete absence of the superior longitudinal fasciculi in 1 case and underdevelopment in the other. Low fractional anisotropy of the left inferior occipitofrontal fasciculus was found in both cases. The same tract was maloriented in 1 of the cases. CONCLUSION: Agenesis of the arcuate fasciculus may accompany CBPS.

Atypical propositional language organization in prenatal and early-acquired temporal lobe lesions.

This study investigated differences in propositional language organization in children with developmental and acquired brain lesions. We evaluated 30 right-handed subjects with intractable epilepsy due to either focal cortical dysplasia or hippocampal sclerosis with neuropsychological testing and functional MRI prior to epilepsy surgery. Atypical activations were seen in both prenatal and early postnatal lesions, but the contribution of specific histopathological substrate was minimal. Atypical organization of both temporal and frontal language areas also correlated inversely with receptive vocabulary scores. The data demonstrated a greater propensity toward atypical activation patterns for receptive than expressive networks, particularly when lesions were located in the dominant temporal lobe. Atypical language organization was not correlated with seizure-related factors such as age at onset or duration of epilepsy. The patterns of atypical language activation support prior studies implicating proximity of pathology to eloquent cortex in the dominant hemisphere as the primary determinant of functional reorganization.

Diagnostic performance of MRI and MR myelography in infants with a brachial plexus birth injury.

BACKGROUND: Detailed evaluation of a brachial plexus birth injury is important for treatment planning. OBJECTIVE: To determine the diagnostic performance of MRI and MR myelography in infants with a brachial plexus birth injury. MATERIALS AND METHODS: Included in the study were 31 children with perinatal brachial plexus injury who underwent surgical intervention. All patients had cervical and brachial plexus MRI. The standard of reference was the combination of intraoperative (1) surgical evaluation and (2) electrophysiological studies (motor evoked potentials, MEP, and somatosensory evoked potentials, SSEP), and (3) the evaluation of histopathological neuronal loss. MRI findings of cord lesion, pseudomeningocele, and post-traumatic neuroma were correlated with the standard of reference. Diagnostic performance characteristics including sensitivity and specificity were determined. RESULTS: From June 2001 to March 2004, 31 children (mean age 7.3 months, standard deviation 1.6 months, range 4.8-12.1 months; 19 male, 12 female) with a brachial plexus birth injury who underwent surgical intervention were enrolled. Sensitivity and specificity of an MRI finding of post-traumatic neuroma were 97% (30/31) and 100% (31/31), respectively, using the contralateral normal brachial plexus as the control. However, MRI could not determine the exact anatomic area (i.e. trunk or division) of the post-traumatic brachial plexus neuroma injury. Sensitivity and specificity for an MRI finding of pseudomeningocele in determining exiting nerve injury were 50% and 100%, respectively, using MEP, and 44% and 80%, respectively, using SSEP as the standard of reference. MRI in infants could not image well the exiting nerve roots to determine consistently the presence or absence of definite avulsion. CONCLUSION: In children younger than 18 months with brachial plexus injury, the MRI finding of pseudomeningocele has a low sensitivity and a high specificity for nerve root avulsion. MRI and MR myelography cannot image well the exiting nerve roots to determine consistently the presence or absence of avulsion of nerve roots. The MRI finding of post-traumatic neuroma has a high sensitivity and specificity in determining the side of the brachial plexus injury but cannot reveal the exact anatomic area (i.e. trunk or division) involved. The information obtained is, however, useful to the surgeon during intraoperative evaluation of spinal nerve integrity for reconstruction.

The "hinge-twist" technique for anomalous origin of the left coronary artery.

A murmur was heard in an asymptomatic boy (age 4), and transthoracic echocardiography revealed anomalous origin of the left main coronary artery (LMCA) from the right sinus of Valsalva (age 6). Confirmed by catheterization and computed tomographic angiography (age 10), the LMCA followed a short interarterial course between the aorta and main pulmonary artery before supplying the anterior descending and circumflex coronary arteries. An intramural segment was not clearly seen. Results of stress testing were normal. Because sudden death was a concern, the patient underwent surgery at age 11. The "hinge-twist" technique was utilized in the absence of an intramural component or ostial stenosis in an effort to avoid the long-term complications of coronary reimplantation, ostial patching, or bypass grafting.

Seizure disorders: functional MR imaging for diagnostic evaluation and surgical treatment--prospective study.

PURPOSE: To prospectively evaluate effect of functional magnetic resonance (MR) imaging on diagnostic work-up and treatment planning in patients with seizure disorders who are candidates for surgical treatment. MATERIALS AND METHODS: Institutional review board approval was obtained; informed consent was obtained either from the patient or the parent or guardian in all patients. This study was conducted with Health Insurance Portability and Accountability Act compliance. Sixty consecutively enrolled patients (33 males, 27 females; mean age, 15.8 years +/- 8.7 [standard deviation]; range, 6.8-44.2 years) were prospectively examined. Forty-five (75%) patients were right handed, nine (15%) were left handed, and six (10%) had indeterminate hand dominance. Prospective questionnaires were used to evaluate diagnostic work-up, counseling, and treatment plans of the seizure team before and after functional MR imaging. Confidence level scales were used to determine effect of functional MR imaging on diagnostic and therapeutic thinking. Paired t test and 95% confidence interval analyses were performed. RESULTS: In 53 patients, language mapping was performed; in 33, motor mapping; and in seven, visual mapping. The study revealed change in anatomic location or lateralization of language-receptive (Wernicke) (28% of patients) and language-expressive (Broca) (21% of patients) areas. Statistically significant increases were found in confidence levels after functional MR imaging in regard to motor and visual cortical function evaluation. In 35 (58%) of 60 patients, the seizure team thought that functional MR imaging results altered patient and family counseling. In 38 (63%) of 60 patients, functional MR imaging results helped to avoid further studies, including Wada test. In 31 (52%) and 25 (42%) of 60 patients, intraoperative mapping and surgical plans, respectively, were altered because of functional MR imaging results. In five (8%) patients, two-stage surgery with extra-operative direct electrical stimulation mapping was averted, and resection was accomplished in one stage. In four (7%) patients, extent of surgical resection was altered because eloquent areas were identified close to seizure focus. CONCLUSION: Functional MR imaging results influenced diagnostic and therapeutic decision making of the seizure team; results indicated language dominance changed, confidence level in identification of critical brain function areas increased, patient and family counseling were altered, and intraoperative mapping and surgical approach were altered.

Visual functional magnetic resonance imaging in patients with Sturge-Weber syndrome.

The purpose of this study is to report different patterns of visual cortex activation in patients with Sturge-Weber syndrome as compared with healthy control subjects. Utilizing a visual paradigm of flashing lights, three children with Sturge-Weber syndrome were studied with functional magnetic resonance imaging. The results are compared with those documented in eight normal sedated children, and six young adult awake volunteers, using the same paradigms. All adult volunteers manifested bilateral activation in primary visual cortex (Brodmann's 17 and 18 areas). Two of them also had activation in secondary visual cortex (Brodmann's 19 area). In the eight sedated normal children, seven manifested activation in primary visual areas. The last exhibited no activation. The patients with Sturge-Weber syndrome demonstrated in the affected occipital lobe increased activation in one patient (11 months old), no activation in the second (12 years of age), and abnormal distribution of the activation in the third (11 months old). This report demonstrates that the vascular malformation of Sturge-Weber syndrome does not necessarily prevent cortical activation in the expected occipital cortex and may be associated with different patterns of abnormal activation. Assessing cortical function with functional magnetic resonance imaging in patients with Sturge-Weber syndrome may be helpful in decisions of surgical management and counseling.

Vesicoureteral reflux imaging in children: comparative cost analysis.

RATIONALE AND OBJECTIVES: The purpose of this study was to compare the costs of voiding cystourethrography (VCUG) versus radionuclide cystography (RNC) for evaluation of vesicoureteral reflux in children. MATERIALS AND METHODS: The variable direct costs of performing 25 VCUG and 25 RNC examinations in age- and general health-matched patients suspected of having vesicoureteral reflux was determined by using time and motion analyses. All personnel directly involved in the cases were tracked, and the involvement times were recorded to the nearest minute. All material items used during the procedures were recorded. The cost of labor was determined from personnel reimbursement data, and the cost of materials, from vendor pricing. The fixed direct costs were assessed from hospital accounting records. Mean, standard deviation, and 95% confidence interval (CI) were determined for all direct (fixed and variable) costs. The total costs were determined for each procedure and compared by using the Student t test. RESULTS: There was a significant difference (P < .0001) between the mean total direct cost of VCUG ($112.17 +/- 10.33) and that of RNC ($64.58 +/- 1.91). VCUG examination for vesicoureteral reflux in children cost 1.74 times more than RNC examination (95% CI: 1.28, 2.36). CONCLUSION: When the technique is clinically appropriate, institutions may obtain substantial cost savings by using RNC in place of VCUG for examining children suspected of having vesicoureteral reflux.

The use of stereotactic radiosurgery to treat intractable childhood partial epilepsy.

PURPOSE: Although conventional surgery is presently used to treat seizures of temporolimbic and neocortical origin, deep-seated lesions are often associated with morbidity. Stereotactic radiosurgery is a noninvasive procedure that effectively treats patients with vascular malformations and brain tumors, but its efficacy for epileptogenic foci is limited, especially in children. METHODS: Between 1995 and 1999, four candidates who had medically uncontrolled seizures and localized seizure foci were selected for stereotactic radiosurgery, with a mean age of 9.75 years at the time of surgery (range, 4-17 years). Seizure foci were identified on the basis of ictal and interictal video-EEG. Magnetic resonance (MR) images were obtained before and after surgery. Ictal single-photon emission computed tomography (SPECT) was performed by using stabilized hexamethyl-propyleneamine oxime (HMPAO; 300 microcuries/kg) with early injection after electrographic ictal onset. The clinical features of the patients are given. All radiosurgical procedures were performed with the gamma knife unit with the Leksell stereotactic frame, stereotactic MRI imaging, and the Gamma Plan workstation. Seizure outcome was scored according to Engel's classification. RESULTS: Two patients had hypothalamic hamartoma (HH), and two had neocortical epilepsy. At mean follow-up of 39.2 months (range, 26-69 months), two patients were seizure free, one with a HH and one with a suggestive developmental tumor in the insular cortex by MRI findings. The other patient with HH had 90% reduction of seizures. One patient with a widespread seizure focus that involved the motor strip was unimproved. The two patients with HH also exhibited markedly improved neurobehavioral status after surgery. There were no significant complications of radiosurgical therapy. CONCLUSIONS: Our findings suggest that gamma knife surgery is a potentially valuable treatment modality for children with medically intractable epilepsy due to a well-localized seizure focus that is difficult to excise by conventional techniques or for whom they are deemed unsuitable. More widespread application in childhood epilepsy should be investigated in larger series.