G-quadruplex dynamics contribute to regulation of mitochondrial gene expression.

Single-stranded DNA or RNA sequences rich in guanine (G) can adopt non-canonical structures known as G-quadruplexes (G4). Mitochondrial DNA (mtDNA) sequences that are predicted to form G4 are enriched on the heavy-strand and have been associated with formation of deletion breakpoints. Increasing evidence supports the ability of mtDNA to form G4 in cancer cells; however, the functional roles of G4 structures in regulating mitochondrial nucleic acid homeostasis in non-cancerous cells remain unclear. Here, we demonstrate by live cell imaging that the G4-ligand RHPS4 localizes primarily to mitochondria at low doses. We find that low doses of RHPS4 do not induce a nuclear DNA damage response but do cause an acute inhibition of mitochondrial transcript elongation, leading to respiratory complex depletion. We also observe that RHPS4 interferes with mtDNA levels or synthesis both in cells and isolated mitochondria. Importantly, a mtDNA variant that increases G4 stability and anti-parallel G4-forming character shows a stronger respiratory defect in response to RHPS4, supporting the conclusion that mitochondrial sensitivity to RHPS4 is G4-mediated. Taken together, our results indicate a direct role for G4 perturbation in mitochondrial genome replication, transcription processivity, and respiratory function in normal cells.

An unusual cystic appearance of disseminated low-grade gliomas.

We report five cases of pediatric disseminated low-grade gliomas of the brainstem or spinal cord that exhibited an unusual, cystic pattern. Leptomeningeal disease was present in three of these at diagnosis, and was detected shortly afterwards in the other two. Four patients are alive up to 5 years later, following minimal to no intervention, while one is dead.

Large cell/anaplastic medulloblastomas and medullomyoblastomas: clinicopathological and genetic features.

OBJECT: Medulloblastoma is the most common malignant central nervous system neoplasm found in children. A distinct variant designated large cell/anaplastic (LC/A) medulloblastoma is characterized by frequent dissemination of cerebrospinal fluid (CSF) at presentation and a more aggressive clinical course. The authors report on their examination of the clinicopathological and genetic features of seven such cases encountered at their institution. METHODS: Eighty cases of medulloblastomas were reviewed and seven (8.8%) of these were believed to fit the histological and immunohistochemical criteria for LC/A medulloblastoma. In three cases (43%) either desmoplastic or classic medulloblastoma was the underlying subtype, and in two cases (28%) the LC/A tumor was found within the setting of medullomyoblastoma. Fluorescence in situ hybridization was used in six of the seven cases to characterize the presence of isochromosome 17q, deletion of chromosome 22q (a deletion characteristically found in atypical teratoid/rhabdoid tumors), and c-myc amplification. The patients' clinical histories revealed CSF dissemination in all cases and lymph node metastasis in one case. Isochromosome 17q was found in five (83%) of six cases. Evidence of chromosomal gains indicated aneuploidy in three tumors (50%), and amplification of c-myc was found in three tumors (50%). No 22q deletions were encountered. CONCLUSIONS: A high percentage of LC/A medulloblastomas arise within a background of typical medulloblastomas or medullomyoblastomas. As is the case in conventional medulloblastomas, the presence of 17q is a common early tumorigenic event; however, in a significant percentage of specimens there is also evidence of aneuploidy and/or amplification of c-myc. These findings indicate that LC/A morphological characteristics reflect a more advanced tumor stage than that found in pure medulloblastomas or in typical medullomyoblastomas.

Evaluating pediatric brain tumor cellularity with diffusion-tensor imaging.

OBJECTIVE: MR imaging of central nervous system (CNS) malignancies falls short of a definitive evaluation. Tissue diagnosis remains the gold standard. Diffusion-tensor MR imaging measures the apparent diffusion coefficient and diffusion anisotropy of water in tissue. The purpose of this study was to test the hypothesis that the apparent diffusion coefficient may improve the MR imaging evaluation of newly diagnosed CNS neoplasms. We examined the relationship between the apparent diffusion coefficient, anisotropy, and tumor cellularity in 12 pediatric patients. MATERIALS AND METHODS: On the basis of histopathologic evaluation, tumors in this case series were segregated into three types: low-grade gliomas, embryonal tumors, and nonembryonal high-grade tumors. Mean apparent diffusion coefficient and anisotropy values obtained from the solid components of each tumor were compared with cellularity, total cellular area, and total nuclear area derived from biopsy material. RESULTS: The apparent diffusion coefficient ratio (tumor to normal brain) correlated well with tumor classification (p = 0.001). Anisotropy was decreased similarly in all tumor classifications. The absolute apparent diffusion coefficient correlated well with cellularity (p = 0.014) and total nuclear area (p = 0.005) per high-power field. The correlation between apparent diffusion coefficient and total cellular area per high-power field was not statistically significant. CONCLUSION: The apparent diffusion coefficient may be predictive of tumor classification and may be a useful tool in characterizing tumor cellularity and total nuclear area. These parameters are not available in standard MR imaging. Therefore, diffusion-tensor imaging may enhance the diagnostic process in pediatric CNS malignancies.

Prepontine lesions with chiari II malformation. Report of two cases.

In 2 cases of infants with the Chiari II malformation, a prepontine cyst presented in association with the hindbrain abnormalities characteristic of the Chiari II syndrome. Both infants presented with bulbar dysfunction and had poor outcome despite decompression of the cerebellar tonsillar herniation and drainage of the prepontine cysts. No such association between prepontine lesions and Chiari II has been described previously.

In organello formaldehyde crosslinking of proteins to mtDNA: identification of bifunctional proteins.

The segregating unit of mtDNA is a protein-DNA complex called the nucleoid. In an effort to understand how nucleoid proteins contribute to mtDNA organization and inheritance, we have developed an in organello formaldehyde crosslinking procedure to identify proteins associated with mtDNA. Using highly purified mitochondria, we observed a time-dependent crosslinking of protein to mtDNA as determined by sedimentation through isopycnic cesium chloride gradients. We detected approximately 20 proteins crosslinked to mtDNA and identified 11, mostly by mass spectrometry. Among them is Abf2p, an abundant, high-mobility group protein that is known to function in nucleoid morphology, and in mtDNA transactions. In addition to several other proteins with known DNA binding properties or that function in mtDNA maintenance, we identified other mtDNA-associated proteins that were not anticipated, such as the molecular chaperone Hsp60p and a Krebs cycle protein, Kgd2p. Genetic experiments indicate that hsp60-ts mutants have a petite-inducing phenotype at the permissive temperature and that a kgd2Delta mutation increases the petite-inducing phenotype of an abf2Delta mutation. Crosslinking and DNA gel shift experiments show that Hsp60p binds to single-stranded DNA with high specificity for the template strand of a putative origin of mtDNA replication. These data identify bifunctional proteins that participate in the stability of rho(+) mtDNA.

Ventricular anatomy and shunt catheters.

A functioning shunt must have a patent proximal catheter within the cerebrospinal fluid space. Occlusion with choroid plexus or ependymal tissue might be expected if these tissues are in contact with the proximal inlets. This study was undertaken to define the intraventricular distances available for a standard-placement shunt cather and to compare the available distances with actual ventricular catheter inlets. In 52 normal subjects (age range from 1 month to 20 years; median 7.7 years) magnetic resonance imaging was used to measure the dimensions of the anterior horn in planes typically used for cather placement. For anterior placements, the intraventricular length (ventricle entry to the foramen of Monro) was measured for a standardized catheter route ('As') and for a route yielding a maximum lenght ('Amax'). For posterior placements, the length (ventricle tip to foramen of Monro) was obtained for a standardized catheter placement to the ipsilateral ('Pi') and the contralateral ventricle ('Pc') as well as measuring a maximum length in a curved trajectory ('Pmax'). The average length (and range) in centimeters for the various trajectories was: As = 1.5 (1.1-1.9), Amax = 1.7 (1.2-2.2), Pi = 1.6 (1.2-2.1), Pc = 2.0 (1.4-2.9), and Pmax = 2.8/3.1 (2.1-3.6). Minor variations from a standard shunt insertion site did not affect the length of catheter within the ventricle. Current ventricular catheters have proximal inlets extending 1.6-2.4 cm from the catheter tip. Variations in standard ventricular catheter placement should have no measurable effect on how much ventricle is available for the proximal catheter. It may not be possible to place a standard ventricular catheter and keep the inlets within the ventricle and placed consistently away from choroid plexus and ependyma, regardless of approach. This may contribute to the similar proximal occlusion rates reported for the differing placements. Subsequent studies of shunt placement should correlate proximal occlusion rates with ventricular size. To prevent ventricular size from directly affecting proximal conclusion, consideration should be given to altering the design of ventricular catheters by placing inlets over a shorter distance (1.0 cm) from the tip.

Complex cervical spine neoplastic disease: reconstruction after surgery by using a vascularized fibular strut graft. Case report.

The authors report a case of an aggressive chordoma in the cervical spine of a 15-year-old girl who underwent radical resection followed by reconstruction using an anterior vascularized fibular strut graft and posterior arthrodesis prior to receiving immediate postoperative radiation therapy. The patient had successful graft incorporation 4 months postoperatively. The authors review the advantages of using vascularized fibular strut grafts for the treatment of multilevel cervical spine neoplastic disease and discuss the theoretical advantages of using vascularized grafts that tolerate therapeutic levels of radiation.

Management of uncomplicated skull fractures in children: is hospital admission necessary?

OBJECTIVE: This study was undertaken to determine the necessity for routine hospital admission of children with skull fractures, a normal neurological exam, a normal head CT, and no other injuries ('uncomplicated skull fracture'). METHODS: A prospective study of closed-head injuries in children was done over a 2-year period at St. Louis Children's Hospital. All patients with closed head injuries underwent skull radiographs and a head CT scan. From this cohort, children with uncomplicated skull fractures were identified and studied. For comparison, a retrospective analysis was also performed of the hospital admission records of children admitted over a 5-year period (1990-1994) with the diagnosis of epidural hematoma (EDH) to identify the typical time intervals between injury and documentation of the lesion in these cases. RESULTS: Forty-four patients with uncomplicated skull fractures were identified; all had been admitted for observation. Mean age was 1.8 years. Average time between injury and hospital admission was 6.35 h with half of this time being spent in the emergency room. Average LOS was 35 h, but 50% of patients were hospitalized less than 24 h. No patient in this study group suffered a complication related to their inury. Twenty-three patients with EDH had been admitted during the 5-year review period. Slightly more than one-half of patients had their EDH detected within 6 h of injury. The others were diagnosed more than 6 h after injury due to a delay in medical evaluation or a delay in obtaining a computed tomographic (CT) scan after an initial medical evaluation. CONCLUSIONS: Patients with uncomplicated skull fractures, in the absence of recurrent emesis and/or evidence of child abuse, can be considered for discharge home. The definition of an uncomplicated skull fracture requires that a head CT be performed on these patients.

Posterior vermal split syndrome.

We have studied a battery of movements in 5 children (age, 6-15 years) after transection of the posterior inferior cerebellar vermis. In each case, the surgery destroyed the midline vermis only (ranging from lobules VI-X). Tandem gait was badly impaired in all subjects. No subjects had impairments of kicking, reaching, pinching, or speech. Regular gait, standing, and hopping on one leg were relatively unimpaired. Cutting the parallel fibers that cross the midline may be the critical variable causing incoordination in tandem gait.

Intracranial tumor in children: MR imaging findings within 24 hours of craniotomy.

PURPOSE: To evaluate whether very early magnetic resonance (MR) imaging enables distinction of residual tumor from benign postoperative change in children. MATERIALS AND METHODS: Forty-six postoperative MR examinations were performed in 43 children with intracranial tumors within 24 hours of the completion of surgery during a 2-year period. These examinations were categorized according to whether residual tumor could be definitely identified or excluded, or whether the diagnosis was uncertain. RESULTS: Contrast enhancement occurred in 33 of 46 MR examinations performed within 24 hours of surgery. In 18 instances, this was associated with obvious residual tumor. In 15 patients, only small amounts of linear or patchy enhancement were seen. Of these, seven patients (46%) were disease-free for an average of 4.5 years. Assessment for postoperative enhancement was hampered in seven patients because of the presence of methemoglobin in the tumor bed. Contrast enhancement was not observed in two patients before surgery. CONCLUSION: Surgically induced, MR-detectable contrast enhancement and extracellular methemoglobin formation occurs within 24 hours of the completion of intracranial surgery. This can interfere with the detection of small amounts of residual tumor.

Foramen magnum decompression for cervicomedullary encroachment in craniometaphyseal dysplasia: case report.

OBJECTIVE AND IMPORTANCE: Foramen magnum encroachment has been cited as a potential cause for the premature demise of patients afflicted with craniometaphyseal dysplasia (CMD). To our knowledge, the association of Chiari malformation and syringomyelia with CMD has not been previously reported. We describe our evaluation and surgical treatment of a patient presenting with CMD, foramen magnum stenosis, Chiari I malformation, and syringomyelia. CLINICAL PRESENTATION: A 15-year-old female patient with CMD presented with severe headaches and progressive myelopathy. Evaluation by computed tomography and magnetic resonance imaging revealed mild ventriculomegaly, cervicomedullary compression secondary to Chiari I malformation and foramen magnum stenosis, and C3-T10 syringomyelia. INTERVENTION: Foramen magnum decompression was performed via suboccipital craniectomy, C1-C2 laminectomy, and dural augmentation. Dysplastic bone was revealed to be extremely thick and mineralized. Removal required lengthy and extensive drilling. The postoperative course was complicated by prolonged intubation secondary to airway obstruction and a perforated duodenal ulcer. Airway obstruction was attributed to severe nasopharyngeal bony dysplasia and soft tissue edema. The use of steroids in the treatment of airway edema and delayed enteral feeding was thought to contribute to ulcer development. Nevertheless, neurological symptoms improved dramatically. CONCLUSION: Foramen magnum decompression can be used to treat life-threatening cervicomedullary compression in patients with CMD. However, caution should be used because surgical intervention may be associated with a higher incidence of complications because of lengthy procedures and the spectrum of craniofacial impairments in patients with CMD.

Outcome of surgically treated birth-related brachial plexus injuries in twenty cases.

Birth-related brachial plexus injury occurs in 0.19-2.5 per 1,000 live births, of which 70-92% improve with conservative management. With the advent of microsurgical techniques, patients who fail expectant treatment may benefit from brachial plexus exploration and reconstruction. From 1991 to 1996, 87 patients were referred to the multidisciplinary brachial plexus clinic at St. Louis Children's Hospital. Twenty patients were selected for surgical management. The average age at surgery was 10.5 months (range 3-35, median = 8), with an average follow-up of 23.9 months (range 7-45, median = 24). Two patients were lost to follow-up. Surgical procedures included neurolysis (n = 8), neurotization (n = 2), nerve grafting (n = 5), and a combination (n = 3) of the above. Two patients underwent exploration without repair. Intercostal nerves, pectoral nerves, and C4 roots were used for neurotizations, and the sural nerve was used for nerve grafting. Results from 18 patients were available for follow-up review. Fifteen patients (83% demonstrated clinical improvement postoperatively. Of the 3 patients without improvement, 2 underwent exploration without repair, and one underwent neurolysis of the axillary nerve. Of patients undergoing reconstruction, 93% had improved strength postoperatively. No subjects had worsening neurologic status, and there were no complications. These results suggest that surgery for birth-related brachial plexus injury may show favorable outcomes if patients are selected appropriately. Patients undergoing neurolysis and nerve grafting had more favorable outcomes than those undergoing neurotization.

Diagnostic testing for acute head injury in children: when are head computed tomography and skull radiographs indicated?

OBJECTIVE: Despite the frequent occurrence of head injury in children, there is no agreement about clinical screening criteria that indicate the need for imaging studies. This study was undertaken to provide information relevant to the choice of imaging modalities in children with acute head trauma. METHODOLOGY: A prospective cohort of 322 children seeking care consecutively in an urban pediatric emergency department for nontrivial head injury was assembled. Skull radiographs, head computed tomography, and data forms including mechanism of injury, symptoms, and physical findings were completed for each child. RESULTS: Intracranial injury occurred in 27 children (8%), whereas 50 (16%) had skull fractures. Of those with intracranial injury, 16 (59%) had normal mental status and no focal abnormalities, and 1 of those 16 required surgery for evacuation of an epidural hematoma. Six (38%) of the 16 were younger than 1 year, 5 of whom had scalp contusion or hematoma without other symptoms. Findings not significantly associated with intracranial injury were scalp contusion, laceration, hematoma, abrasion, headache, vomiting, seizure, drowsiness, amnesia, and loss of consciousness for less than 5 minutes. Findings associated with intracranial injury were skull fracture, signs of a basilar skull fracture, loss of consciousness for more than 5 minutes, altered mental status, and focal neurologic abnormality. CONCLUSIONS: Intracranial injury may occur with few or subtle signs and symptoms, especially in infants younger than 1 year. The relative risk for intracranial injury is increased almost fourfold in the presence of a skull fracture, although the absence of a skull fracture does not rule out intracranial injury. The significance of nonsurgical intracranial injury in neurologically normal children needs further study.

MR imaging surface display of the cerebral cortex in children.

The purpose of this study was to introduce the use of three-dimensional (3D) surface MR imaging display for clinical use. Surface display was created using images acquired with T1 magnetization prepared rapid acquisition gradient echo (MPRAGE) in 24 cases of migrational defects, cortical dysplasia and prenatal asphyxia. Schizencephaly and cortical dysplasia were pathologically confirmed. The precise configurations of cortical abnormalities, and their relation to the adjacent gyri and sulci were demonstrated. The topography of schizencephalic clefts was clearly defined. The appearance of ulegyria was characteristic and it was sometimes possible to differentiate polymicrogyria from pachygyria.

Lack of specificity in electrophysiological identification of lower sacral roots during selective dorsal rhizotomy.

The authors investigated the efficacy of anal sphincter electromyography (EMG) in identifying the lower sacral roots during selective dorsal rhizotomy. In nine children undergoing selective dorsal rhizotomy for cerebral palsy (CP) spasticity, direct electrical stimulation of the L1-S5 dorsal and ventral roots was performed while monitoring EMG responses from the anal sphincter and lower-extremity muscles. Anal sphincter activation was seen with stimulation of lumbosacral roots at many levels. Stimulation of dorsal and ventral roots gave anal sphincter EMG responses in 100% of the dorsal and ventral roots from L-4 and caudally. Only at the L-1 level did a minority of nerve roots have anal sphincter response to stimulation. Patterns of extremity muscle and sphincter activation specific to the S3-5 roots, namely anal sphincter activation without activation of other muscle groups, were found in only five (22%) of 23 roots stimulated. The pattern of stimulation responses in the majority of S3-5 roots indicated that the pathophysiology of lower-extremity spasticity in CP may involve the anal sphincter and does not spare the lower sacral roots. Thus, this study indicates that electrophysiological mapping alone, without anatomical identification, cannot be used to identify the lower sacral roots during selective dorsal rhizotomy for CP spasticity, and it proposes a model for investigation of associated bowel and bladder symptoms.

Selective dorsal rhizotomy and rates of orthopedic surgery in children with spastic cerebral palsy.

If the spasticity of cerebral palsy (CP) is reduced in children at a young age by selective dorsal rhizotomy, the incidence of lower-extremity deformities requiring orthopedic surgery may be reduced; however, this has never been investigated in detail. The authors examined the effects of selective dorsal rhizotomy on rates of lower-extremity orthopedic surgery in 178 children with CP. Age at selective dorsal rhizotomy ranged from 2 to 19.3 years (mean 5.5 years) with follow-up intervals ranging from 24 to 70 months (mean 44 months). Spastic CP was classified as quadriplegia (33%), diplegia (65%), and hemiplegia (2%). To assess the effects of early versus late rhizotomy on rates of orthopedic surgery, patients were grouped as follows: Group I underwent rhizotomy between 2 and 4 years of age (54 patients), and Group II underwent rhizotomy between 5 and 19 years of age (124 patients). Comparison of Kaplan-Meier plots of lifetime orthopedic surgery rates revealed that Group II underwent orthopedic surgery at a higher rate than Group I (p = 0.037). Analysis by procedure type revealed higher orthopedic surgery rates in Group II than Group I for heel cord releases (p = 0.0025), adductor releases (p = 0.018), and hamstring releases (p = 0.02). Orthopedic surgery rates were no higher for Group II compared to Group I for ankle/foot operations (p = 0.023), femoral osteotomy (p = 0.25), iliopsoas releases (p = 0.35), and "other" operations (p = 0.013). The data indicate that early rhizotomy reduces the need for orthopedic surgery for heel cord, hamstring, and adductor releases.