Symbiotic and nonsymbiotic hemoglobin genes of Casuarina glauca

Casuarina glauca has a gene encoding hemoglobin (cashb-nonsym). This gene is expressed in a number of plant tissues. Casuarina also has a second family of hemoglobin genes (cashb-sym) expressed at a high level in the nodules that Casuarina forms in a nitrogen-fixing symbiosis with the actinomycete Frankia. Both the nonsymbiotic and symbiotic genes retained their specific patterns of expression when introduced into the legume Lotus corniculatus. We interpret this finding to mean that the controls of expression of the symbiotic gene in Casuarina must be similar to the controls of expression of the leghemoglobin genes that operate in nodules formed during the interaction between rhizobia and legumes. Deletion analyses of the promoters of the Casuarina symbiotic genes delineated a region that contains nodulin motifs identified in legumes; this region is critical for the controlled expression of the Casuarina gene. The finding that the nonsymbiotic Casuarina gene is also correctly expressed in L. corniculatus suggests to us that a comparable non-symbiotic hemoglobin gene will be found in legume species.

Differential interactions of promoter elements in stress responses of the Arabidopsis Adh gene

The Adh (alcohol dehydrogenase, EC 1.1.1.1.) gene from Arabidopsis thaliana (L.) Heynh. can be induced by dehydration and cold, as well as by hypoxia. A 1-kb promoter fragment (CADH: -964 to +53) is sufficient to confer the stress induction and tissue-specific developmental expression characteristics of the Adh gene to a beta-glucuronidase reporter gene. Deletion mapping of the 5' end and site-specific mutagenesis identified four regions of the promoter essential for expression under the three stress conditions. Some sequence elements are important for response to all three stress treatments, whereas others are stress specific. The most critical region essential for expression of the Arabidopsis Adh promoter under all three environmental stresses (region IV: -172 to -141) contains sequences homologous to the GT motif (-160 to -152) and the GC motif (-147 to -144) of the maize Adh1 anaerobic responsive element. Region III (-235 to -172) contains two regions shown by R.J. Ferl and B.H. Laughner ([1989] Plant Mol Biol 12: 357-366) to bind regulatory proteins; mutation of the G-box-1 region (5'-CCACGTGG-3', -216 to -209) does not affect expression under uninduced or hypoxic conditions, but significantly reduces induction by cold stress and, to a lesser extent, by dehydration stress. Mutation of the other G-box-like sequence (G-box-2: 5'-CCAAGTGG-3', -193 to -182) does not change hypoxic response and affects cold and dehydration stress only slightly. G-box-2 mutations also promote high levels of expression under uninduced conditions. Deletion of region I (-964 to -510) results in increased expression under uninduced and all stress conditions, suggesting that this region contains a repressor binding site. Region II (-510 to -384) contains a positive regulatory element and is necessary for high expression levels under all treatments.

Promoter elements required for developmental expression of the maize Adh1 gene in transgenic rice

To define the regions of the maize alcohol dehydrogenase 1 (Adh1) promoter that confer tissue-specific expression, a series of 5' promoter deletions and substitution mutations were linked to the Escherichia coli beta-glucuronidase A (uidA) reporter gene and introduced into rice plants. A region between -140 and -99 not only conferred anaerobically inducible expression in the roots of transgenic plants but was also required for expression in the root cap, embryo, and in endosperm under aerobic conditions. GC-rich (GC-1, GC-2, and GC-3) or GT-rich (GT-1 and GT-2) sequence motifs in this region were necessary for expression in these tissues, as they were in anaerobic expression. Expression in the root cap under aerobic conditions required all the GC- and GT-rich motifs. The GT-1, GC-1, GC-2, and GC-3 motifs, and to a lesser extent the GT-2 motif, were also required for anaerobic responsiveness in rice roots. All elements except the GC-3 motif were needed for endosperm-specific expression. The GC-2 motif and perhaps the GT-1 motif appeared to be the only elements required for high-level expression in the embryos of rice seeds. Promoter regions important for shoot-, embryo-, and pollen-specific expression were proximal to -99, and nucleotides required for shoot-specific expression occurred between positions -72 and -43. Pollen-specific expression required a sequence element outside the promoter region, between +54 and +106 of the untranslated leader, as well as a silencer element in the promoter between -72 and -43.

Children with severe epilepsy: evidence of hippocampal neuron losses and aberrant mossy fiber sprouting during postnatal granule cell migration and differentiation

Surgically resected hippocampi from children with extrahippocampal seizures and structurally non-atrophic brains were examined to determine the relationship of neuron losses and aberrant mossy fiber (MF) sprouting to the postnatal migration and differentiation of the fascia dentata (FD) granule cells (GC). Percent neuron loss compared to age-matched autopsy controls was determined by quantitative cell densities, and aberrant MF sprouting by neo-Timm histochemistry. Postnatal immature GC migration and differentiation was demonstrated by the transient but GC-specific expression of the immature form of neural cell adhesion molecule (NCAM-H). Results showed that the hippocampi from children with seizures appeared microanatomically intact without focal areas of damage. However, significant neuron losses were found by neuron counts in the fascia dentata (P < 0.01), CA4 (P < 0.01), and CA2 (P < 0.05). Aberrant supragranular inner molecular layer MF sprouting was found in hippocampi of children with seizures, and the MFs showed smaller puncta in specimens resected under 2 years of age (n = 3) compared to the larger puncta in older children (n = 5). Hippocampi from children under 2 years of age also demonstrated NCAM-H positive primitive cells in the infragranular and stratum granulosum of the fascia dentata consistent with the postnatal migration and differentiation of GCs, the parent neurons of the MFs. These results indicate that seizures in the immature but structurally intact human hippocampus are associated with decreased neuron densities and aberrant MF sprouting very early in postnatal development. The data also show that aberrant MF sprouting is found during postnatal migration, differentiation and axogenesis of GCs.(ABSTRACT TRUNCATED AT 250 WORDS)

Properties and synaptic mechanisms of bicuculline-induced epileptiform bursts in neocortical slices from children with intractable epilepsy

1. Bicuculline-induced epileptiform bursts in slices of neocortical tissue resected from children (3 mo to 14 yr) undergoing neurosurgical treatment for intractable epilepsy were studied with conventional intracellular recording techniques. The purposes of this study were to characterize the bursts evoked in immature human neocortical slices, to gain further insight to how N-methyl-D-aspartate (NMDA) and non-NMDA receptors contribute to the genesis of the bursts, and to determine whether the characteristics of the bursts were related to patient age or clinically defined abnormality of the tissue. 2. Epileptiform bursts evoked by focal stimulation of the underlying white or gray matter in bicuculline (10 microM) were all-or-none events. Once evoked, the bursts in a given neuron appeared very similar to one another, regardless of stimulus intensity. Stronger stimuli only decreased the onset latency of the bursts. The bursts evoked with relatively weak stimuli (< 2-3 times the threshold), particularly those from stimulation of a distant site (4-5 mm), were variable in onset latency. The bursts from stimulation of a close site (0.5-2 mm) with stronger stimuli (> 3 times the threshold) were invariable in onset latency. 3. Across different cells, particularly across the cells in different slices, the bursts were quite variable in terms of their morphology and duration. When measured at one-half of the amplitude of the underlying depolarization (approximately 20-50 mV), the duration of the bursts ranged from 20 to 775 ms (n = 80 cells). In 23% of the cases (18 of 80 cells), afterdischarges lasting for tens of milliseconds to a few seconds followed the bursts.(ABSTRACT TRUNCATED AT 250 WORDS)

Does the ocs-element occur as a functional component of the promoters of plant genes?

The structural requirements of the ocs-element, a promoter element in several genes transferred to the host plant nucleus by Agrobacterium tumefaciens and certain DNA viruses, have been further characterized both in vitro and in vivo. Two adjacent and functionally identical protein-binding sites separated by an exact number of nucleotides are required for in vivo activity of the ocs-element. Plant pathogens have presumably recruited cellular transcription factors that interact with these binding sites to drive the high-level expression of their essential genes. Our functional analyses of the ocs-elements from two pathogen promoters define the structure of a sequence motif that might also be expected to occur in plant nuclear genes, and a search of the plant gene database has identified a number of plant gene promoters that contain sequences that resemble the ocs-element. These sequences were analysed for their ability both to bind the maize nuclear protein OCSTF and to activate transcription of an inactive promoter. A functional ocs-element was identified in only one of the plant genes, the soybean heat-shock gene, Gmhsp26-A. The apparent rarity of the ocs-element in plant genes contrasts with its frequent use by pathogens that transform the plant nucleus. Sequences resembling half of an ocs-element, on the other hand, are common in plant promoters and may form part of multi-element control motifs with a variety of regulatory functions. Plant pathogens may, therefore, have evolved to circumvent tight regulatory control of their promoters by the host by duplicating the half ocs-element promoter motifs to take advantage of the ubiquitous ocs-element-binding transcription factors in plants.

Surgery for intractable infantile spasms: neuroimaging perspectives

Twenty-three infants and children underwent cortical resection (n = 15) or hemispherectomy (n = 8) for intractable infantile spasms. Infantile spasms were present at the time of surgery in 17 of the 23 patients; in six, spasms had evolved to other seizure types during surgical evaluation. Children with a remote history of infantile spasms were excluded from this study. Focal or hemispheric lesions were identified by magnetic resonance imaging in seven children; an additional two showed focal atrophy without a discrete lesion. Positron emission tomography (PET) showed lateralized or localized abnormalities of cerebral glucose utilization in all patients; in 14, PET was the only neuroimaging modality to identify the epileptogenic cortex. When this occurred, neuropathological examination of resected brain tissue typically showed malformative and dysplastic cortical lesions. Focal interictal and/or ictal electrographic abnormalities were present in all patients, and corresponded well with localization from neuroimaging. None of the patients were subjected to chronic invasive electrographic monitoring with intracranial electrodes. At follow-up (range 4-67 months; mean 28.3 months), 15 children were seizure-free, three had 90% seizure control, one had 75% seizure control, and four failed to benefit from surgery with respect to seizure frequency.

Communication deficits in children undergoing temporal lobectomy

OBJECTIVE

To examine formal thought disorder and discourse (cohesive) devices that make speech coherent prospectively in seven children, aged 5.7 to 16.7 years, before and after temporal lobectomy for intractable cut points determined from sensitivity and specificity analyses of formal thought disorder and discourse measures in 22 children with complex partial seizure disorder and 45 normal children.

RESULTS

Before surgery, the mean illogical thinking and discourse scores of the surgical candidates were in the pathological range. After a mean postoperative follow-up period of 15.1 months, their illogical thinking (but not their discourse scores) decreased significantly to the normal range.

CONCLUSIONS

These preliminary findings are discussed in terms of the possible role of postsurgical changes in seizure control, behavior, antiepileptic drugs, cognition, and prefrontal function.

Isolation of a maize bZIP protein subfamily: candidates for the ocs-element transcription factor

Ocs-elements, a family of 20 bp DNA sequences, are components of a number of promoters active in plants. In the maize BMS cell line the dominant ocs-element binding activity is the ocs-element transcription factor complex called OTF. The isolation of cDNA clones from a BMS cDNA expression library for two bZIP (basic region-leucine zipper) proteins that bind the ocs-element sequence and are good candidates for forming at least part of OTF is described. The two ocs-element binding proteins, called OBF3.1 and OBF3.2, are closely related, with the OBF3.1 protein sharing 95.8% amino acid homology with part of the OBF3.2 protein although there were significant differences in the 3' untranslated regions. Genomic Southern blot analysis revealed a small gene family with a minimum of two OBF3 loci mapping to chromosomes 3L105 and 8L075. The OBF3.1 protein shared considerable homology with the wheat HBP1b protein (80% amino acid identity) and to a lesser extent with the tobacco TGA1aa protein. OBF3.1 like HBP1b was able to bind well to the Hex sequence but poorly to G-box/ABRE sequences. Interestingly, OBF3.1 bound eightfold more efficiently to an ocs-element sequence than TGA1a, raising the possibility that OBF3.1 and TGA1a may be distinct members of an OBF3/TGA subfamily.

Isolation of a maize bZIP protein subfamily: candidates for the ocs-element transcription factor

Ocs-elements, a family of 20 bp DNA sequences, are components of a number of promoters active in plants. In the maize BMS cell line the dominant ocs-element binding activity is the ocs-element transcription factor complex called OTF. The isolation of cDNA clones from a BMS cDNA expression library for two bZIP (basic region-leucine zipper) proteins that bind the ocs-element sequence and are good candidates for forming at least part of OTF is described. The two ocs-element binding proteins, called OBF3.1 and OBF3.2, are closely related, with the OBF3.1 protein sharing 95.8% amino acid homology with part of the OBF3.2 protein although there were significant differences in the 3' untranslated regions. Genomic Southern blot analysis revealed a small gene family with a minimum of two OBF3 loci mapping to chromosomes 3L105 and 8L075. The OBF3.1 protein shared considerable homology with the wheat HBP1b protein (80% amino acid identity) and to a lesser extent with the tobacco TGA1aa protein. OBF3.1 like HBP1b was able to bind well to the Hex sequence but poorly to G-box/ABRE sequences. Interestingly, OBF3.1 bound eightfold more efficiently to an ocs-element sequence than TGA1a, raising the possibility that OBF3.1 and TGA1a may be distinct members of an OBF3/TGA subfamily.

Surgery for epilepsy. Special pediatric considerations

Children with epilepsy require special consideration because the nature of their seizures is different from those in adults, the effects of intractable epilepsy may be more serious in children, and younger children may have greater potential for recovery than adults. This article reviews the unique problems and approaches to resective surgery for pediatric epilepsy.

Pathologic findings in a patient with a vein of Galen aneurysm treated by staged endovascular embolization

Vein of Galen aneurysms are uncommon malformations that can be treated with a combination of endovascular embolization and surgery. Since the relevant techniques are new and innovative, their pathologic sequelae are not yet well described. A patient treated with staged embolization over a 15-month period developed evidence of cerebral venous hypertension on angiography. At necropsy, we observed marked myointimal proliferation of the aneurysm wall, dura, and cerebral vessels in addition to severe widespread encephalomalacia, calcinosis, and rare mural thrombi. These vascular changes have not been previously described in cases of vein of Galen aneurysm, and may, in part, be a consequence of embolization therapy.

DNA methylation, vernalization, and the initiation of flowering

Late-flowering ecotypes and mutants of Arabidopsis thaliana and the related crucifer Thlaspi arvense flower early after cold treatment (vernalization). Treatment with the DNA demethylating agent 5-azacytidine induced nonvernalized plants to flower significantly earlier than untreated controls. Cytidine at similar concentrations had no effect on time to flower. In contrast, late-flowering mutants that are insensitive to vernalization did not respond to 5-azacytidine treatment. Normal flowering time was reset in the progeny of plants induced to flower early with 5-azacytidine, paralleling the lack of inheritance of the vernalized condition. Arabidopsis plants, either cold-treated or 5-azacytidine-treated, had reduced levels of 5-methylcytosine in their DNA compared to nonvernalized plants. A Nicotiana plumbaginifolia cell line also showed a marked decrease in the level of 5-methylcytosine after treatment with either 5-azacytidine or low temperature. We suggest that DNA methylation provides a developmental control preventing early flowering in Arabidopsis and Thlaspi ecotypes. Vernalization, through its general demethylating effect, releases the block to flowering initiation. We propose that demethylation of a gene critical for flowering permits its transcription. We further suggest, on the basis of Thlaspi data, that the control affects transcription of kaurenoic acid hydroxylase, a key enzyme in the gibberellic acid biosynthetic pathway.

Treatment of infantile spasms: medical or surgical?

Although infantile spasms were initially described in 1841, remarkably little progress has been made in understanding the pathophysiology of this "peculiar form of infantile convulsions." Consequently, our ability to treat infantile spasms is limited. Infantile spasms are classified as a "generalized" seizure disorder in the international classification system, which suggests that the underlying brain abnormality causing the seizures also must be diffuse or generalized. As the classification suggests, there are many diffuse, or multifocal, brain disorders related to infantile spasms, e.g., inborn errors of metabolism, hypoxic-ischemic brain injury, and developmental brain defects such as tuberous sclerosis or Aicardi's syndrome. On the other hand, infantile spasms have been reported in which a localized brain abnormality was present, e.g., tumor, stroke, and trauma. On rare occasions, removal of a tumor has resulted in cessation of the generalized infantile spasms. This finding suggests that focal cortical abnormalities can cause infantile spasms and that removing the abnormality can stop the seizures. At University of California, Los Angeles, the Pediatric Epilepsy Surgery Program has developed new approaches to the treatment of infantile spasms. The principal underlying concepts are (a) children with medically refractory infantile spasms may have an area of cortical defect (called the zone of cortical abnormality) that causes the seizures and (b) infantile spasms are usually generalized seizures. Thus, the goal of the surgical assessment is not the identification of the focus of seizure onset but rather the identification of the zone of cortical abnormality.

Non-verbal communication skills of surgically treated children with infantile spasms

The authors present preliminary findings on the effects of surgery on the development of early non-verbal social communication skills in eight children with intractable infantile spasms. After a mean follow-up of 15.2 months, there was no statistically significant change in the post-surgical non-verbal communication behavior of these children beyond the expected developmental change. Implications of these findings for the developmental impairment associated with infantile spasms are discussed.

Neurosurgical treatment of refractory status epilepticus

Refractory status epilepticus (RSE) is defined as status epilepticus that continues despite aggressive treatment. A 9.8-year-old boy with a past history of daily left focal motor seizures was transferred to University of California at Los Angeles (UCLA) Hospital in pentobarbital coma after 4 days in RSE. The RSE was treated with very high doses of all appropriate antiepileptic drugs (AEDs), alone and in combination. The pentobarbital was titrated to burst suppression on EEG, but whenever pentobarbital was decreased, the seizures recurred. An ictal positron tomography scan of glucose metabolism demonstrated a right frontal area of hypermetabolism corresponding to an epileptic focus on EEG and magnetic resonance lesion. Eight days after the boy was admitted to UCLA, the right frontal focus was surgically removed, with immediate control of the status epilepticus. Whereas before onset of RSE, he had daily focal seizures, the boy has been seizure-free postoperatively for greater than 1 year. Operative treatment should be considered in patients with RSE in whom a focus of seizure onset can be demonstrated and who are reasonably considered surgical candidates.

Single-electrode voltage-clamp analysis of the N-methyl-D-aspartate component of synaptic responses in neocortical slices from children with intractable epilepsy

1. Synaptic transmission mediated by the N-methyl-D-aspartate (NMDA)-receptor type was studied in neocortex from children undergoing surgical treatment for intractable epilepsy. Intracellular recordings from pyramidal cells were obtained in slices of neocortical tissue by use of microelectrodes. Synaptic responses were induced by electrical stimulation and studied with current-clamp and single-electrode voltage-clamp techniques. The NMDA-receptor-mediated component of the synaptic responses was isolated by addition of 10 microM bicuculline and 30 microM 6-cyano-2,3-dihydroxy-7-nitroquinoxaline (CNQX) in the perfusion solution. 2. In the presence of bicuculline and CNQX, electrical stimulation evoked an excitatory postsynaptic potential (EPSP) in every recorded cell. The amplitude of this EPSP increased when membrane potential was depolarized with injected current. 3. All cells studied in voltage clamp were recorded with microelectrodes containing Cs+ and QX 314. To avoid contamination of the responses from voltage-dependent Ca2+ conductances, membrane potential was held at depolarized potentials until Ca2+ spiking inactivated completely. The evoked excitatory postsynaptic currents (EPSCs) measured at resting membrane potential ranged from 100 to 400 pA. The NMDA receptor-selective antagonist DL-2-amino-5-phosphonopentanoic acid (AP-5) reversibly decreased the current amplitude by 60% for 10 microM and 80% for 30 microM. 4. The current-voltage (I-V) relation showed a region of negative slope conductance between -100 and -20 mV. The largest currents (-250 to -900 pA) were recorded in the range of -45 to -20 mV and reversed between -10 and +10 mV. Removing Mg2+ from the perfusion solution decreased the negativity of the slope, which is consistent with a reduction in the voltage-dependent Mg2+ block of the NMDA-receptor channel. 5. The I-V plots obtained from cells recorded in the most abnormal tissue were averaged and compared with those from the least abnormal tissue. No significant difference was found between these two groups. The averaged plots from the youngest patients (8 and 10 mo old) and those from the oldest (5-15 yr old) patients were also compared, and the results from these two groups were not significantly different.(ABSTRACT TRUNCATED AT 400 WORDS)

Local synaptic circuits and epileptiform activity in slices of neocortex from children with intractable epilepsy

1. Single and dual intracellular recordings were performed in neocortical slices obtained from tissue samples surgically removed from children (8 mo to 15 yr) for the treatment of intractable epilepsy. Electrical stimulation and glutamate microapplication were used to study local synaptic inputs to pyramidal cells. 2. In recordings with potassium-acetate electrodes, activation of presynaptic neocortical neurons with glutamate microdrops did not elicit a clear increase in postsynaptic potentials (PSPs) but did suppress current-evoked repetitive spike firing in recorded neurons. Bicuculline (10 microM) blocked this effect, suggesting it was caused by the activation of presynaptic gamma-aminobutyric acid (GABA) cells. In recordings with KCl electrodes, glutamate microdrops elicited an increase in the frequency and amplitude of depolarizing PSPs. Bicuculline (5-10 microM) blocked the glutamate-evoked PSPs, suggesting they were reversed GABAA-receptor-mediated inhibitory postsynaptic potentials (IPSPs). In one cell recorded with a KCl electrode (total n = 8), current-evoked spike trains elicited afterdischarges of reversed IPSPs, thus revealing a recurrent inhibitory circuit. Therefore local inhibitory synaptic circuits were robust and could be observed in tissue from patients as young as 11 mo. 3. In addition to short-latency (10-25 ms), monosynaptic excitatory postsynaptic potentials (EPSPs), electrical stimulation at low intensities sometimes elicited delayed EPSPs (20-60 ms). When GABAA-receptor-mediated synaptic inhibition was partially reduced in bicuculline (5-10 microM), electrical stimulation evoked large EPSPs at long and variable latencies (100-300 ms). Glutamate microapplication caused an increase in the frequency and amplitude of EPSPs; preliminary results suggest that glutamate microdrops were less likely to evoke EPSPs in tissue from younger patients (8-12 mo) than in slices from patients greater than 4 yr. Evidence for local excitatory synaptic circuits was thus found when synaptic inhibition was partially reduced. 4. After further reduction of inhibition in bicuculline (5-50 microM), electrical stimulation elicited epileptiform bursts. In pairs of simultaneously recorded neurons, bursts were generated synchronously from long-latency EPSPs (100-300 ms) in slices from patients as young as 8 mo. Reflected EPSPs at very long and variable latencies (500-1,100 ms) and repetitive epileptiform bursts could be evoked synchronously in pairs of cells. Glutamate activation of local presynaptic neurons elicited robust epileptiform events in recorded cells. This was seen in slices from patients as young as 16 mo. 5. These data provide physiological evidence for the presence of local inhibitory and excitatory synaptic circuits in human neocortex at least as early as 11 and 8 mo, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

Morphological substrates of infantile spasms: studies based on surgically resected cerebral tissue

Extensive surgical resections of neocortical cerebral tissue (including hemispherectomies) from 13 infants and children with infantile spasms showed that 12 of 13 specimens contained either malformative and dysplastic lesions of the cortex and white matter (sometimes with associated hamartomatous proliferation of globular cells), or destructive lesions possibly acquired as a result of anoxic-ischemic injury, or a combination of the two. In brain tissue from 4 patients, coarse neuronal cytoplasmic fibrils resembling neurofibrillary tangles were seen in areas of dysplastic brain on silver-stained (Bielschowsky technique) sections. Immunohistochemical (immunoperoxidase) study of cortical lesions containing globular cells employing primary antibodies to glial fibrillary acidic protein and synaptophysin as markers of astrocytic and neuronal differentiation, respectively, revealed that many cells showed astrocytic and/or neuronal features, suggesting the local proliferation of primitive or multipotential neuroectodermal cells as one substrate for this seizure disorder. Morphological abnormalities of a severe degree and wide extent in the resected tissue (e.g., in one patient with hemimegalencephaly) often showed features to suggest that they may represent variants of tuberous sclerosis. These most likely result from abnormal movement and/or local proliferation of neuroectodermal precursors that have migrated from the germinal matrix to the cortical mantle. Cellular, molecular and neurophysiological study of these abnormalities is likely to yield information about basic molecular mechanisms of brain malformation and injury important in the pathogenesis of infantile spasms and other forms of focal or generalized epilepsy.

Neuropathologic findings in cortical resections (including hemispherectomies) performed for the treatment of intractable childhood epilepsy

Despite the use of hemispherectomy in the treatment of medically refractory seizures since the early 1950's, few studies published have documented neuropathologic findings in the resected specimens. This report describes the neuropathologic findings in 38 children who underwent either hemispherectomy or multilobar cortical resection as treatment for medically intractable epilepsy between 1986 and 1990. Examination of the resected specimens revealed a variety of abnormalities which fell into four broad categories. Malformations or hamartomatous lesions were the dominant finding in 15 patients, whereas encephalomalacic lesions were the most prominent abnormality in 16; chronic pathogen-free encephalitits (Rasmussen's encephalitis) was present in 3 and an additional 3 children had Sturge-Weber-Dimitri syndrome. There were no gross or microscopic abnormalities in 1 patient. This report provides the first comprehensive description of the pathologic findings in a series of children with refractory epilepsy of varying types treated by hemispherectomy-multilobar resection.