Detection of human herpesvirus-6 in mesial temporal lobe epilepsy surgical brain resections

BACKGROUND

Human herpesvirus-6 (HHV-6), a ubiquitous beta-herpesvirus, is the causative agent of roseola infantum and has been associated with a number of neurologic disorders including seizures, encephalitis/meningitis, and multiple sclerosis. Although the role of HHV-6 in human CNS disease remains to be fully defined, a number of studies have suggested that the CNS can be a site for persistent HHV-6 infection.

OBJECTIVE

To characterize the extent and distribution of HHV-6 in human glial cells from surgical brain resections of patients with mesial temporal lobe epilepsy (MTLE).

METHOD

Brain samples from eight patients with MTLE and seven patients with neocortical epilepsy (NE) undergoing surgical resection were quantitatively analyzed for the presence of HHV-6 DNA using a virus-specific real-time PCR assay. HHV-6 expression was also characterized by western blot analysis and in situ immunohistochemistry (IHC). In addition, HHV-6-reactive cells were analyzed for expression of glial fibrillary acidic protein (GFAP) by double immunofluorescence.

RESULTS

DNA obtained from four of eight patients with MTLE had significantly elevated levels of HHV-6 as quantified by real-time PCR. HHV-6 was not amplified in any of the seven patients with NE undergoing surgery. The highest levels of HHV-6 were demonstrated in hippocampal sections (up to 23,079 copies/10(6) cells) and subtyped as HHV-6B. Expression of HHV-6 was confirmed by western blot analysis and IHC. HHV-6 was co-localized to GFAP-positive cells that morphologically appeared to be astrocytes.

CONCLUSIONS

HHV-6B is present in brain specimens from a subset of patients with MTLE and localized to astrocytes in the absence of inflammation. The amplification of HHV-6 from hippocampal and temporal lobe astrocytes of MTLE warrants further investigation into the possible role of HHV-6 in the development of MTLE.

Hypothalamic hamartoma secreting corticotropin-releasing hormone. Case report

The authors describe a unique case of a 2-year-old boy with a hypothalamic hamartoma secreting corticotropin-releasing hormone (CRH). The patient presented with a history of behavioral disturbances progressing over 12 months. His neurological status was intact. Magnetic resonance imaging demonstrated a 1.8 x 1.6 x 1.2-cm isointense, nonenhancing hypothalamic lesion. Endocrinological workup revealed elevated serum CRH and adrenocorticotropic hormone levels, nonsuppression with low-dose dexamethasone, and partial suppression with high-dose dexamethasone. He underwent tumor resection via a right frontotemporal craniotomy. Pathological examination of the tissue confirmed a hypothalamic hamartoma with CRH immunostaining. Postoperatively, his hormone levels normalized and his behavioral disturbances abated. The radiographic and clinical characteristics of hypothalamic hamartomas are reviewed and therapeutic considerations discussed.

Medulloblastoma: clinical and biologic aspects

Medulloblastoma is the most common childhood primary CNS tumor, and treatment approaches have evolved over the past three decades. The biologic underpinnings of medulloblastoma are not fully characterized, but recent work has identified new, important directions for research. Stratification of patients with medulloblastoma into risk groups is the backbone of most ongoing therapeutic studies. Patients are usually characterized as being either average risk or poor risk, although an intermediate risk group may exist. Standard treatment for older children with medulloblastoma consists of radiation and, for most, chemotherapy. Children with nondisseminated disease at the time of diagnosis have been reported to have as high as an 80% five-year disease-free survival rate after treatment with reduced dose (2340 cGy) craniospinal irradiation, local boost radiation therapy (5500 cGy), and chemotherapy, given during and after radiation therapy. Preradiation chemotherapy has yet to be shown to be of benefit for children with medulloblastoma. Children with disseminated disease are a highly problematic subgroup of patients to treat. A variety of new approaches are being studied, most of which are intensifying chemotherapy either prior to or after radiation. Long-term survivors of medulloblastoma are at significant risk for permanent endocrinologic, cognitive, and psychological sequelae. Infants and very young children with medulloblastoma remain a difficult therapeutic challenge because they have the most virulent form of the disease and are at highest risk for treatment-related sequelae.

Expression profiling of medulloblastoma: PDGFRA and the RAS/MAPK pathway as therapeutic targets for metastatic disease

Little is known about the genetic regulation of medulloblastoma dissemination, but metastatic medulloblastoma is highly associated with poor outcome. We obtained expression profiles of 23 primary medulloblastomas clinically designated as either metastatic (M+) or non-metastatic (M0) and identified 85 genes whose expression differed significantly between classes. Using a class prediction algorithm based on these genes and a leave-one-out approach, we assigned sample class to these tumors (M+ or M0) with 72% accuracy and to four additional independent tumors with 100% accuracy. We also assigned the metastatic medulloblastoma cell line Daoy to the metastatic class. Notably, platelet-derived growth factor receptor alpha (PDGFRA) and members of the downstream RAS/mitogen-activated protein kinase (MAPK) signal transduction pathway are upregulated in M+ tumors. Immunohistochemical validation on an independent set of tumors shows significant overexpression of PDGFRA in M+ tumors compared to M0 tumors. Using in vitro assays, we show that platelet-derived growth factor alpha (PDGFA) enhances medulloblastoma migration and increases downstream MAP2K1 (MEK1), MAP2K2 (MEK2), MAPK1 (p42 MAPK) and MAPK3 (p44 MAPK) phosphorylation in a dose-dependent manner. Neutralizing antibodies to PDGFRA blocks MAP2K1, MAP2K2 and MAPK1/3 phosphorylation, whereas U0126, a highly specific inhibitor of MAP2K1 and MAP2K2, also blocks MAPK1/3. Both inhibit migration and prevent PDGFA-stimulated migration. These results provide the first insight into the genetic regulation of medulloblastoma metastasis and are the first to suggest a role for PDGFRA and the RAS/MAPK signaling pathway in medulloblastoma metastasis. Inhibitors of PDGFRA and RAS proteins should therefore be considered for investigation as possible novel therapeutic strategies against medulloblastoma.

Analysis of PTCH/SMO/SHH pathway genes in medulloblastoma

Inactivation of the PTCH tumor suppressor gene occurs in a subset of sporadic medulloblastomas, suggesting that alterations in the PTCH pathway may be important in the development of this tumor. In order to address the frequency of genetic alterations affecting genes in this pathway, we used a combination of loss of heterozygosity (LOH) analysis, single-stranded conformational polymorphism (SSCP) analysis, and direct sequencing of DNA samples from sporadic primitive neuroectodermal tumors (PNETs). To identify alterations in the PTCH gene, we performed LOH analysis on 37 tumor DNA samples. Of those with matched constitutional DNA samples, one demonstrated LOH. Of those without matched constitutional DNA, six were homozygous with all markers. All exons of the PTCH gene were sequenced in these seven tumors, and three mutations were found. To identify alterations in the SHH and SMO genes, we analyzed all exons of both genes in 24 tumors with SSCP and sequenced any exons that showed aberrant band patterns. No mutations were found in either SHH or SMO in any tumor. We also identified the following genes as candidate tumor suppressors based on their roles in controlling hh/ptc signaling in Drosophila: EN-1 and EN-2, deletion of which results in a lack of cerebellar development in mice; SMAD family members 1-7, and protein kinase A subunits RIalpha, RIbeta, RIIbeta, Calpha, and Cbeta. Each of these genes was investigated in a panel of 24 matched constitutional and tumor DNA samples. Our search revealed no mutations in any of these genes. Thus, PTCH is the only gene in this complex pathway that is mutated with notable frequency in PNET. Genes Chromosomes Cancer 27:44-51, 2000.

Medulloblastoma: clinical and biologic aspects

Medulloblastoma is the most common childhood primary CNS tumor, and treatment approaches have evolved over the past three decades. The biologic underpinnings of medulloblastoma are not fully characterized, but recent work has identified new, important directions for research. Stratification of patients with medulloblastoma into risk groups is the backbone of most ongoing therapeutic studies. Patients are usually characterized as being either average risk or poor risk, although an intermediate risk group may exist. Standard treatment for older children with medulloblastoma consists of radiation and, for most, chemotherapy. Children with nondisseminated disease at the time of diagnosis have been reported to have as high as an 80% five-year disease-free survival rate after treatment with reduced dose (2340 cGy) craniospinal irradiation, local boost radiation therapy (5500 cGy), and chemotherapy, given during and after radiation therapy. Preradiation chemotherapy has yet to be shown to be of benefit for children with medulloblastoma. Children with disseminated disease are a highly problematic subgroup of patients to treat. A variety of new approaches are being studied, most of which are intensifying chemotherapy either prior to or after radiation. Long-term survivors of medulloblastoma are at significant risk for permanent endocrinologic, cognitive, and psychological sequelae. Infants and very young children with medulloblastoma remain a difficult therapeutic challenge because they have the most virulent form of the disease and are at highest risk for treatment-related sequelae.

Identification of the sensory/motor area and pathologic regions using ECoG coherence

An electrophysiologic mapping technique which enables identification of the central sulcus and pathologic cortical regions is described. Electrocorticographic recordings of 1 min duration were recorded from 25 patients who were undergoing resection of tumors in the sensory-motor region or being evaluated for temporal lobectomy for epilepsy. Analysis of the patterns of subdural inter-electrode coherence revealed low coherence across the central sulcus for 11/12 cases where its location could be verified with direct cortical stimulation and/or somatosensory evoked potential mapping. Regions of high coherence identified the location of tumors in the sensory-motor region for 10/10 cases. Over the temporal lobe, localized areas of high coherence were evident in 8/9 epilepsy patients, but were not indicative of the location of mesial temporal lobe tumors or inter-ictal spiking, when present. We conclude that analysis of cortical coherence patterns may be helpful for revealing the location of pathologic processes relative to critical cortical areas.

Detection of medulloblastoma and astrocytoma-associated ganglioside GD3 in cerebrospinal fluid

Shedding of gangliosides by tumor cells may enhance tumor development. We recently showed that cells of the human brain tumor, medulloblastoma, shed gangliosides in vitro and have therefore examined ganglioside shedding by pediatric brain tumors into the cerebrospinal fluid (CSF). GD3, a major ganglioside in medulloblastoma and astrocytoma, was the target for detection in the CSF by immunostaining using the monoclonal antibody R24 and enhanced chemiluminescence detection. Mean CSF GD3 levels in patients with medulloblastomas (n = 9) and astrocytomas (n = 10) were significantly higher than those of controls (mean +/- SD 44.7 +/- 8.4 versus 18.2 +/- 1.9 pmol/ml, n = 20, P < 0.0002). Mass spectrometric analysis showed that tumor-derived ganglioside GD3 contained heterogeneous ceramide structures and, interestingly, the ceramide subspecies with shorter fatty acyl chains were selectively shed. The elevated CSF GD3 concentrations in patients with medulloblastoma and astrocytoma support the concept that ganglioside shedding, which may have significant biological consequences, is characteristic of human brain tumors.

Displaying electrocorticographic findings on gyral anatomy

Human electrocorticographic findings recorded from subdural arrays of electrodes were topographically mapped directly onto magnetic resonance images of gyral anatomy. With this technique gyri involved in generating somatosensory evoked potentials and epileptic phenomena are easily identified. Regions of the cortex which exhibit local spectral changes associated with cognitive tasks can also be visualized. These composite images of structure and function can provide insight regarding the functional organization of human cortex in relation to gyral anatomy and localized pathologic rhythms.

[T-cell receptor repertoire in tumor infiltrating lymphocytes within malignant brain tumors]

Expression of T cell receptor (TCR) V alpha and V beta genes in tumor infiltrating lymphocytes (TILs) within human malignant brain tumor was examined. Primers for 18 different human TCR V alpha and 21 V beta families were used to analyze TCRV-(D)-J-C gene rearrangements in TILs in 8 human malignant glioma specimens obtained at surgery. Using the polymerase chain reaction (PCR) method, we detected limited TCR variable region, V alpha gene expression in malignant glial tumors and also V alpha 7 and V alpha 12 TCR genes were preferentially expressed. Usage of TCR V beta gene was not as restricted as in TCR V alpha. These TILs expressing a limited repertoire of TCRs might be isolated, expanded, and used therapeutically for treatment of malignant brain tumors.

Neurofibromatosis types 1 and 2: cranial MR findings

Neurofibromatosis 1 (NF-1) (von Rekhlinghausen disease) and neurofibromatosis 2 (NF-2) (bilateral acoustic neurofibromatosis) have been recently recognized to be distinct disorders through genetic linkages. The authors compared the cranial magnetic resonance (MR) images of 53 patients with NF-1 and 11 with NF-2. In the NF-1 group, MR imaging revealed 19 patients with optic gliomas and eight with parenchymal gliomas. In 32 patients, foci of prolonged T2, similar to those reported previously as hamartomas, were identified in the cerebellar peduncles, globus pallidus, midbrain, and other locations. The frequency of these foci was related to both age and the presence of optic gliomas. In the NF-2 group, MR imaging revealed eight patients with cranial nerve schwannomas and six with meningiomas (in addition to acoustic schwannomas in all 11). These findings demonstrate that NF-1 and NF-2 are different diseases requiring different imaging protocols. NF-1 seems to be associated with tumors of astrocytes and neurons and NF-2 with tumors of meninges and Schwann cells.

CSF pulsations within nonneoplastic spinal cord cysts

Because of its sensitivity to fluid motion, MR imaging was used to investigate fluid dynamics in syringomyelia. Three major findings characterized syringomyelia: pulsatile fluid in cysts, nonpulsatile fluid in cysts, and damaged cord tissue. The fluid in preoperative syrinx cavities pulsated in a fashion similar to subarachnoid CSF. Pulsation was more prominent in large cysts but was also seen in small cysts. Nonpulsatile cysts were generally of smaller diameter, were shorter in length, and often were single; they could, however, coexist with pulsatile cysts. Nonpulsatile cysts had etiologies similar to those of pulsatile cysts: Chiari malformation, trauma, and unknown. Damaged cord, characterized by abnormal high signal on T2-weighted sequences, was seen in 15 of 16 patients and could be either focal or diffuse but was always adjacent to syrinx cavities. Postsurgical MR scans had a lower incidence of pulsatile cysts. In five patients with both pre- and postoperative MR scans, shunting of the cyst reduced the size of the pulsating cyst (two patients) or reduced the size of the cyst and eliminated pulsation altogether (three patients). Axial, T2-weighted images are recommended in the investigation of spinal cord cysts to determine the presence or absence of pulsatile fluid. The presence of pulsation indicates a nonneoplastic cyst. The absence or reduction of CSF pulsation may prove to be a valuable indicator of the success of a shunting procedure.

Spinal cord arteriovenous malformations with significant intramedullary components

Few neurosurgeons have stressed the occurrence, manifestations, and resectability of intramedullary spinal arteriovenous malformations (AVM's). In six of 17 patients in the authors' series of operable spinal AVM's, the lesions had major intramedullary components. Three of these six patients presented with subarachnoid hemorrhage, and all had catastrophic neurological deficits which gradually improved. The hemorrhages appeared to originate from large venous varices lying adjacent to the intramedullary portion of the AVM. The mechanism explaining the sudden neurological deficit in the other three patients was presumed to be thrombosis within the venous varices associated with their AVM's. The reliability of the various radiographic procedures in identifying the intramedullary components of these AVM's is discussed. These malformations may be removed totally with a high degree of safety using microsurgical techniques. The postoperative course in this series of patients was gratifying in terms of improvement of neurological deficits. Postoperative angiography was not performed on all of these patients. However, the follow-up period averaged 5 years.

Endocrine function in the Klüver-Bucy syndrome: studies in adult female rhesus monkeys

Although the behavioral abnormalities of the Klüver-Bucy syndrome are well known, an investigation of the endocrine parameters had not been undertaken previously. The authors report normal reproductive cyclicity (including preserved feedback mechanisms) and growth hormone and cortisol secretion patterns in female rhesus monkeys with the syndrome. It is concluded that the abnormal behavior seen in the Klüver-Bucy syndrome is not associated with abnormalities of the reproductive mechanisms.

Section of the pituitary stalk in the rhesus monkey. II. Morphological studies

The effects of pituitary stalk section on anterior pituitary morphology were studied in 18 female rhesus monkeys. 4 animals were studied within 1--14 days after the operation, while the others were examined later (average 17.2 months). In 3 monkeys there was no necrosis of the anterior lobe, whereas in the remaining animals, an area of infarction averaging 20% was found. Using immunocytochemical techniques, we found that corticotropes and somatotropes were still present following the procedure, and that the number of lactotropes increased markedly. In contrast, gonadotropes, although present in the pars tuberalis, were no longer demonstrable in the pars distalis 3 weeks after stalk section. These results show remarkable agreement between endocrine studies and morphological observations, and indicate a variable degree of dependency of the various pituitary cells on central nervous system influences.