The Healthy and Diseased Retina Seen through Neuron-Glia Interactions

The retina is the sensory tissue responsible for the first stages of visual processing, with a conserved anatomy and functional architecture among vertebrates. To date, retinal eye diseases, such as diabetic retinopathy, age-related macular degeneration, retinitis pigmentosa, glaucoma, and others, affect nearly 170 million people worldwide, resulting in vision loss and blindness. To tackle retinal disorders, the developing retina has been explored as a versatile model to study intercellular signaling, as it presents a broad neurochemical repertoire that has been approached in the last decades in terms of signaling and diseases. Retina, dissociated and arranged as typical cultures, as mixed or neuron- and glia-enriched, and/or organized as neurospheres and/or as organoids, are valuable to understand both neuronal and glial compartments, which have contributed to revealing roles and mechanisms between transmitter systems as well as antioxidants, trophic factors, and extracellular matrix proteins. Overall, contributions in understanding neurogenesis, tissue development, differentiation, connectivity, plasticity, and cell death are widely described. A complete access to the genome of several vertebrates, as well as the recent transcriptome at the single cell level at different stages of development, also anticipates future advances in providing cues to target blinding diseases or retinal dysfunctions.

Calcium pyruvate in the attenuation of the water deficit on the agro-industrial quality of ratoon sugarcane

Sugarcane is one of the largest agricultural commodities when considering the export volume and the number of jobs generated. Sugarcane production in the Brazilian Northeast region is generally low due to several factors, including the irregular rainfall distribution, which highlights the importance of studies aimed at mitigating the deleterious effects of water stress. In this scenario, this study aimed to evaluate calcium pyruvate as a water deficit attenuator on the agro-industrial quality of sugarcane in the second cycle of cultivation. The experiment was conducted out under greenhouse conditions of the Federal University of Campina Grande, where five sugarcane commercial genotypes tested (G1- RB863129, G2- RB92579, G3- RB962962, G4- RB021754, and G5- RB041443) and three irrigation management strategies (E1- full irrigation, E2- water deficit with application of 30 mM of calcium pyruvate, and E3- water deficit without calcium pyruvate application), distributed in randomized blocks in 5 × 3 factorial arrangement with three replications. The RB021754 genotype under water deficit and without foliar application of calcium pyruvate increased the fiber content (13.2%) and the sugarcane moist cake weight (143.5 g). The effects of water deficit in sugarcane genotypes are attenuated by the exogenous application of 30 mM of calcium pyruvate, with benefits on the polarized sucrose content, apparent sucrose content of the juice, soluble solids content, purity, corrected cane POL, total recoverable sugars, and stem mass in relation to plants under water deficit without calcium pyruvate application.

Mineral composition and production of guava under salt stress and salicylic acid

The limitation in the quality of water sources for irrigation in the semi-arid region of northeastern Brazil is increasingly present, so it is necessary to use water with high concentrations of salts for agricultural production, which makes the use of elicitors essential to mitigate the harmful effects of salinity on plants. Given the above, the objective of this study was to evaluate the effects of foliar application of salicylic acid on the mineral composition and production of guava plants under salt stress conditions in the post-grafting phase. The experiment was carried out under greenhouse conditions, in a randomized block design, in a 2 × 4 factorial scheme, with two levels of electrical conductivity of irrigation water (0.6 and 3.2 dS m-1) and four concentrations of salicylic acid (0, 1.2, 2.4, and 3.6 mM), with three replicates. During the flowering stage of guava, N, P, and K contents accumulated in the leaves according to the following order of concentration: N > K > P. Foliar application of 1.2 mM of salicylic acid increases the leaf contents of N, P, and K in guava plants grown under irrigation with water of 0.6 dS m-1. Water salinity of 3.2 dS m-1 reduces the growth and production components of guava plants.

Pyruvic acid as attenuator of water deficit in cotton plants varying the phenological stage

The lack of water during crop growth causes damage to any production system, especially when it occurs during the initial establishment or beginning of the reproductive stage. Although cotton can be properly managed in regions with water limitation, its yield is affected at different levels according to the genetics of the cultivar adopted. Exogenous application of some organic components has shown a stress-mitigating effect and can be a valuable procedure to enhance the yield of water stress-sensitive cultivars. The objective of this work was to evaluate the benefits of exogenous application of pyruvic acid (100 µM) in cotton plants under water deficit varying the phenological stage of the crop. The experiment was conducted in a greenhouse, where the plants were grown in pots and subjected to seven days of water suspension, initiated individually in stages V2 and B1. Each pot contained two plants. The treatments adopted were: T1 - control, T2 - water suppression; and T3 - water suppression + pyruvate application. The design was randomized blocks in a factorial scheme (3 × 3) with three replicates. The reductions in gas exchange and growth of the cultivars BRS Seridó, CNPA 7MH and FM 966 were more significant in the reproductive stage, especially for FM 966, which was more sensitive. Pyruvate application reduced the effects of water suppression on boll production by 31% in BRS Seridó and 34% in CNPA 7MH and FM 966.

The Role of Axonal Transport in Glaucoma

Glaucoma is a neurodegenerative disease that affects the retinal ganglion cells (RGCs) and leads to progressive vision loss. The first pathological signs can be seen at the optic nerve head (ONH), the structure where RGC axons leave the retina to compose the optic nerve. Besides damage of the axonal cytoskeleton, axonal transport deficits at the ONH have been described as an important feature of glaucoma. Axonal transport is essential for proper neuronal function, including transport of organelles, synaptic components, vesicles, and neurotrophic factors. Impairment of axonal transport has been related to several neurodegenerative conditions. Studies on axonal transport in glaucoma include analysis in different animal models and in humans, and indicate that its failure happens mainly in the ONH and early in disease progression, preceding axonal and somal degeneration. Thus, a better understanding of the role of axonal transport in glaucoma is not only pivotal to decipher disease mechanisms but could also enable early therapies that might prevent irreversible neuronal damage at an early time point. In this review we present the current evidence of axonal transport impairment in glaucomatous neurodegeneration and summarize the methods employed to evaluate transport in this disease.

Neuroprotective Gene Therapy by Overexpression of the Transcription Factor MAX in Rat Models of Glaucomatous Neurodegeneration

Purpose

Based on our preview evidence that reduced nuclear content of the transcription factor Myc-associated protein X (MAX) is an early event associated with degeneration of retinal ganglion cells (RGCs), in the present study, our purpose was to test whether the overexpression of human MAX had a neuroprotective effect against RGC injury.

Methods

Overexpression of either MAX or green fluorescent protein (GFP) in the retina was achieved by intravitreal injections of recombinant adenovirus-associated viruses (rAAVs). Lister Hooded rats were used in three models of RGC degeneration: (1) cultures of retinal explants for 30 hours ex vivo from the eyes of 14-day-old rats that had received intravitreal injections of rAAV2-MAX or the control vector rAAV2-GFP at birth; (2) an optic nerve crush model, in which 1-month-old rats received intravitreal injection of either rAAV2-MAX or rAAV2-GFP and, 4 weeks later, were operated on; and (3) an ocular hypertension (OHT) glaucoma model, in which 1-month-old rats received intravitreal injection of either rAAV2-MAX or rAAV2-GFP and, 4 weeks later, were subject to cauterization of the limbal plexus. Cell death was estimated by detection of pyknotic nuclei and TUNEL technique and correlated with MAX immunocontent in an ex vivo model of retinal explants. MAX expression was detected by quantitative RT-PCR. In the OHT model, survival of RGCs was quantified by retrograde labeling with DiI or immunostaining for BRN3a at 14 days after in vivo injury. Functional integrity of RGCs was analyzed through pattern electroretinography, and damage to the optic nerve was examined in semithin sections.

Results

In all three models of RGC insult, gene therapy by overexpression of MAX prevented RGC death. Also, ON degeneration and electrophysiologic deficits were prevented in the OHT model.

Conclusions

Our experiments offer proof of concept for a novel neuroprotective gene therapy for glaucomatous neurodegeneration based on overexpression of MAX.

Gene Therapy Strategies for Glaucomatous Neurodegeneration

Glaucoma leads to irreversible vision loss and current therapeutic strategies are often insufficient to prevent the progression of the disease and consequent blindness. Elevated intraocular pressure is an important risk factor, but not required for the progression of glaucomatous neurodegeneration. The demise of retinal ganglion cells represents the final common pathway of glaucomatous vision loss. Still, lifelong control of intraocular pressure is the only current treatment to prevent severe vision loss, although it frequently fails despite best practices. This scenario calls for the development of neuroprotective and pro-regenerative therapies targeting the retinal ganglion cells as well as the optic nerve. Several experimental studies have shown the potential of gene modulation as a tool for neuroprotection and regeneration. In this context, gene therapy represents an attractive approach as persistent treatment for glaucoma. Viral vectors engineered to promote overexpression of a broad range of cellular factors have been shown to protect retinal ganglion cells and/or promote axonal regeneration in experimental models. Here, we review the mechanisms involved in glaucomatous neurodegeneration and regeneration in the central nervous system. Then, we point out current limitations of gene therapy platforms and review a myriad of studies that use viral vectors to manipulate genes in retinal ganglion cells, as a strategy to promote neuroprotection and regeneration. Finally, we address the potential of combining neuroprotective and regenerative gene therapies as an approach to glaucomatous neurodegeneration.

Primary standardization and determination of gamma ray emission intensities of Ho-166

The procedure followed by the Nuclear Metrology Laboratory (LMN) at the IPEN-CNEN/SP, in São Paulo, for the primary standardization of ¹⁶⁶Ho is described. The activity of ¹⁶⁶Ho was determined by the efficiency extrapolation technique applied to a 4πβ(PC)-γ coincidence system using a gas flow proportional counter in 4π geometry coupled to a 76 × 76 mm NaI(Tl) crystal. The results for the γ-rays intensities at 80.57 and 1379.45 keV were 0.0651(11) and 0.00904(11), respectively.

Consistency test of coincidence-summing calculation methods for extended sources

An internal consistency test of the calculation of coincidence-summing correction factors F_C for volume sources is presented. The test is based on exact equations relating the values of F_C calculated for three ideal measurement configurations. The test is applied to a number of 33 sets of F_C values sent by 21 teams. Most sets passed the test, but not the results obtained using the quasi-point source approximation; in the latter case the test qualitatively indicated the magnitude of the bias of F_C.

Disintegration rate and gamma-ray emission probability per decay measurement of Cu-64

The procedure followed by the Nuclear Metrology Laboratory (LMN) at the IPEN for the standardization of activity of ⁶⁴Cu is described. The measurement was carried out in a 4π (PC) β-γ coincidence system. The activity per unit mass of the solution was determined by the extrapolation technique. The events were registered using a Time to Amplitude Converter (TAC) associated with a Multi-channel Analyzer. The gamma-ray emission probability per decay of the 1345.7keV transition of ⁶⁴Cu determined with a calibrated REGe gamma-ray spectrometer was (0.472 ± 0.010) %, in agreement with the literature.

SUMCOR: Cascade summing correction for volumetric sources applying MCNP6

The main features of code SUMCOR developed for cascade summing correction for volumetric sources are described. MCNP6 is used to track histories starting from individual points inside the volumetric source, for each set of cascade transitions from the radionuclide. Total and FEP efficiencies are calculated for all gamma-rays and X-rays involved in the cascade. Cascade summing correction is based on the matrix formalism developed by Semkow et al. (1990). Results are presented applying the experimental data sent to the participants of two intercomparisons organized by the ICRM-GSWG and coordinated by Dr. Marie-Cristine Lépy from the Laboratoire National Henri Becquerel (LNE-LNHB), CEA, in 2008 and 2010, respectively and compared to the other participants in the intercomparisons.

Standardization of (59)Fe by 4π(PC)β-γ software coincidence system

The procedure for the standardization of (59)Fe using a 4π(PC)β-γ software coincidence system is described. The standardization was performed with an experimental setup consisting of a thin window gas-flow proportional counter (PC) in 4π geometry coupled to a NaI(Tl) scintillator and to a HPGe detector. The data acquisition was carried out by means of a Software Coincidence System (SCS). The beta efficiency was changed by using Collodion films and aluminum foils as external absorbers.

Combination of nonlinear function and mixing method for fitting HPGe efficiency curve in the 59–2754kev energy range

A nonlinear function in combination with the method of mixing activity-calibrated and uncalibrated gamma-ray sources is applied for fitting the experimental peak efficiency of HPGe spectrometers in the 59-2754 keV energy range. In addition, a step function was developed for fitting the gamma-ray background under the peak. Calibrated 241Am, 133Ba, 137Cs, 152Eu, 60Co and 88Y sources, as well as one 24Na source (treated as uncalibrated) were used for obtaining the experimental peak efficiency curve. The results were compared to the conventional linear polynomial fitting. From the fitted parameters, the 24Na activity was determined and compared with the result obtained from absolute measurements in a 4pibeta-gamma coincidence system.

Methodology for monitoring the residual activity in silicon rods irradiated with thermal neutrons

A calibrated detection system developed for monitoring the residual activity in silicon rods irradiated for neutron transmutation doping is described. This residual activity is mainly due to 31Si and 32P, produced by thermal neutron capture reactions. The set-up consists of a scanning device, developed for positioning the rods, coupled to a GM detector for measuring beta-rays coming from the rod. The set-up has been calibrated using a 32P aqueous solution standardised in a 4pibeta gas-flow proportional counter system. The validity of the experimental procedure has been checked by Monte Carlo calculations. An additional check has been made by measuring the residual activity of a silicon rod irradiated in a well-known neutron fluence and the formalism used for calculating the activity on the basis of irradiation parameters is given. The results are compared to the radiological limit imposed by IAEA regulations in order to consider the material as exempt before it could be released for industrial applications.

[Developing the care proposed by Leininger with a person in dialysis treatment]

Study of a ethnographic approach, type case study. Describing a person's bearer of chronic renal inadequacy accompaniment, with adhesion deficit to the treatment. The theoretical presupposition had the model SUNRISE proposed by Leininger. It's presented the Mr. Light and the involved sceneries. Described. Influences economical, social, cultural, technological and educational in the process of taking care. After the identification of the systems of health, were decided the actions of taking care through the maintenance, accommodation and restoration. The study possibilited effective interventions for the behaviors of non adherence. The referencial in continuous and lingering processes of care, favoured by the proximity between nurse and attended person.

Cranial birth injuries in term newborn infants

While cranial birth injuries in term infants are well recognized, to date, only small case series have been described. In an attempt to further define the spectrum of cranial birth injuries, we analyzed 41 consecutive cranial birth injuries at our institution over the period 1991-1998. The most common clinical presentations were apnea (39%) and seizures (37%). Average Apgar scores were 5.7 at 1 min and 7.3 at 5 min; 54% of infants had abnormally low Apgar scores at 1 min and 31% had abnormally low scores at 5 min. The most common intracranial lesion was subdural hemorrhage, present in 73% of infants; most had either a tentorial (57%) and/or interhemispheric (50%) location. Operative treatment was required in 5 infants (12%). Two of the 41 infants (4.8%) died. The study group was compared with a control group of 63 randomly selected births without cranial injury. Using a stepwise logistic regression model, independently significant variables included neonatal birth weight, Apgar scores at 1 and 5 min and mode of delivery. Compared with the controls, the study group had a significantly higher incidence of forceps and/or vacuum deliveries. Combining vacuum, forceps and urgent cesarean section deliveries together as 'urgent' and elective cesarean and spontaneous vaginal deliveries as 'nonurgent', we could find no significant differences between these two groups. Our data conflict with those of Towner et al. [N Engl J Med 1999;341:1709-1714], and suggest that the method of assisted delivery, rather than the urgency of the delivery or dysfunctional labor per se, is a more important variable in cranial birth injuries.

Measurement of the gamma-ray probability per decay of 42K

In the present work, the gamma-ray emission probabilities per decay of 42K transitions have been measured. The activity measurement was carried out in a 4pi (PC)beta-gamma coincidence system. The gamma-ray measurements were performed in a HPGe system. All the uncertainties involved were treated rigorously, by means of covariance analysis. The value of the 1524 keV gamma-ray intensity per decay of 42K obtained in the present work was (0.1813+/-0.0014). This result is compared to the data from other authors.

Disintegration rate measurement of a 192Ir solution

The disintegration rate of 192Ir has been measured using the 4pibeta-gamma coincidence technique. This radionuclide decays by electron capture (EC) and beta-emission. Since the EC contribution is low (4.5%), it has been corrected using decay scheme data taken from the literature. This measurement has been performed in collaboration with the Laboratório Nacional de Metrologia das Radiações Ionizantes (IRDDM), in Rio de Janeiro. The results, which were obtained independently and employed different techniques, are compared with the Systéme International Reference (SIR) maintained at the Bureau International des Poids et Mesures.

Double vision in a child

A 10-year-old boy presented with a complete left oculomotor cranial nerve palsy. Diagnostic evaluation, including neuroimaging and cerebral angiography revealed a small intracranial aneurysm compressing the third nerve. Neurosurgical clipping of the aneurysm produced resolution of the third nerve palsy. The rarity of this presentation in a young patient is discussed, along with the importance of rapid diagnosis and treatment.

The results of a practice survey on the management of patients with shunted hydrocephalus

The care of patients with shunted hydrocephalus is one of the most common clinical problems facing a pediatric neurosurgeon. Despite the prevalence of this clinical entity, it is our impression that the management strategies for these patients vary significantly amongst pediatric neurosurgeons. In an effort to better understand how varied these practices are, we surveyed 261 neurosurgeons with an expressed interest in pediatric neurosurgery, of whom 149 (57%) responded. The survey contained questions pertaining to preoperative and intraoperative management, choice of shunt valve, treatment philosophies with respect to shunt revision, evaluation process for potential shunt malfunction, treatment strategies for shunt infections and routine follow-up care. The answers to the questions confirmed our expectations that there are a variety of ways to manage these patients.

Immediate posttraumatic seizures: is routine hospitalization necessary?

OBJECTIVE

A recent Internet survey of pediatric neurosurgeons showed that 86% routinely admitted children with immediate posttraumatic seizures (PTS) for a brief period of observation. We wished to determine whether certain children meeting predefined criteria could instead be safely discharged from the emergency room.

METHODS

We reviewed the records of children admitted during the past 5 years with a diagnosis of seizure and head injury. Children with a minor head injury, a PTS occurring within 24 h of injury and no intracranial abnormalities on admission CT scan were included. Children with previous neurological conditions, a history of prior seizures (other than PTS or febrile seizures), a prior history of anticonvulsant use, or intracranial abnormalities on the admission CT scan were excluded. Records were abstracted for child's age, gender, length of admission, previous history of PTS or febrile seizures, mechanism of injury, location of impact, time between impact and PTS, the number, length and type of PTS, Glasgow Coma Score (GCS) on admission, subsequent complications and hospital costs.

RESULTS

Seventy-one children met the inclusion criteria. Eleven children presented to the emergency room with prolonged seizures, transient apnea or persistently low GCS and required admission to the intensive care unit (ICU). Among the 60 remaining children with simple PTS, none had further seizures during the follow-up period, and none had significant complications. The average cost of hospitalization was known for 58 children; after excluding the costs for 5 patients who were admitted to the ICU, the average hospital cost amounted to USD 1,615 per patient.

CONCLUSIONS

Our data suggest that children with isolated minor head injuries and simple PTS who recover fully in the emergency room, whose CT scans show no intracranial abnormalities and who have no prior history of neurological disease, epilepsy or anticonvulsant use are at low risk for recurrent seizures or neurological complications, and could potentially be sent home to a reliable caretaker and a stable home situation. However, because of the limited sample size in this study, the statistical risk of a bad outcome may be as high as 9%; we therefore suggest that much larger studies are potentially needed before this becomes a standard policy.

Low-pressure shunt 'malfunction' following lumbar puncture in children with shunted obstructive hydrocephalus

Most shunt malfunctions present with signs and symptoms of high intracranial pressure, and computed tomography scans demonstrate ventricular enlargement. However, several authors have described a rare 'low-pressure' hydrocephalic state in which ventricular enlargement can occur in the face of low, or even negative, intracranial pressures. We report 2 children with obstructive hydrocephalus in whom this 'low-pressure state' followed a lumbar puncture; in both children, the shunts were functioning properly despite increased ventricular size on computed tomography scans, and all symptoms resolved (and the ventricles returned to baseline) following a period of enforced recumbency without shunt revision. We hypothesize that subarachnoid cerebrospinal fluid leakage through the puncture site in the lumbar theca decreases the intracranial pressures globally to a point below the opening pressures of the shunt valves. The ventricular cerebrospinal fluid, unable to be drained through either the subarachnoid space or the shunt, accumulates within the ventricular system under low pressure. One consistent feature in our 2 patients has been the postural nature of the headaches. We recommend enforced recumbency and, if necessary, a blood patch to seal the lumbar leakage. Shunt revision or prolonged external ventricular drainage appears to be unnecessary in these patients. Finally, neurosurgeons should be aware of this potential complication.

The embryogenesis of congenital vertebral dislocation: early embryonic buckling?

Congenital vertebral dislocation (CVD) is a rare congenital spinal malformation characterized by a translatory or rotatory vertebral displacement, or both, at a single level, that results in an abrupt angulation of the neural canal. The more caudal vertebra is dysplastic and appears at first glance to be posteriorly dislocated into the vertebral canal as a posterior hemivertebra, but is actually well aligned with the more caudal vertebral column. Unfortunately, the present classification of complex congenital vertebral anomalies is confusing, and CVD has been grouped together with other congenital vertebral malformations under the terms 'segmental spinal dysgenesis', 'medial spinal aplasia', and others. Moreover, a putative embryonic mechanism has never been proposed for CVD. Based upon our experience with 6 children and a critical review of the literature, we identify CVD as a distinct entity having characteristic anatomical features. We propose a novel putative embryonic mechanism - early embryonic 'buckling' - which likely occurs by the 6th embryonic week, prior to the period of axonal outgrowth and the beginning of vertebral chondrification.

Pediatric neurosurgical disease

The most common, primary referrals to a pediatric neurosurgeon's office are the evaluation and management of the child with a large head (to rule out hydrocephalus and other space occupying lesions) a mishappen head (to rule out various forms of craniosynostosis), or some form of congenital spinal abnormality (spinal dysraphism). The authors discuss the pathogenesis and clinical features of these disorders, provide a framework for diagnostic evaluation and referral, and discuss the various treatment options available for each.

Serial radiography in the infant shaken impact syndrome

Certain CT and/or MRI abnormalities have been used medicolegally to time intracranial injuries from the infant shaken impact syndrome (ISIS). For example, parenchymal hypodensities on CT scans are said to arise only after 6-48 h have elapsed postinjury, and the presence of chronic or mixed subdural hematomas suggests injury that occured 1-4 weeks prior. However, these statements are based largely upon inference from data obtained in other conditions such as ischemic anoxic injury and chronic subdural hemorrhage in adults. Direct evidence about the evolution of intracranial injuries in infants with ISIS is sparse, and the radiographic changes following ISIS have never been systematically studied on serial imaging studies. One hundred-seventeen serial CT and MRI scans obtained from 33 infants with ISIS were reviewed retrospectively. The exact scan dates and times were obtained directly from the scans. Acute subdural hemorrhage was the most common intracranial abnormality and was present in 27 (81%) of the 33 infants. Other intracranial abnormalities included chronic subdural collections, subarachnoid hemorrhage, epidural hematomas, parenchymal hypodensities, edema and contusions, and atrophy and encephalomalacia. In 15 of the 33 infants, the injury could be timed with reasonable certainty, and the evolution of the radiographic changes followed over time. Six of the 15 infants had evidence of prior cranial trauma such as chronic subdural collections (5 infants) or mild atrophy (1 infant). Of the remaining 9 infants, parenchymal abnormalities such as hypodensities, edema and contusion appeared in virtually all of the initial scans performed approximately 3 h following the report of injury. One 'chronic' subdural collection was absent on the first scan performed 2.75 h postinjury, but appeared on a second scan performed 17 h later, suggesting that some 'chronic' subdural fluid collections may arise much sooner than previously thought. These findings challenge some of the current dogma about the timing of radiographic changes following abuse and are important in timing the alleged abuse for legal purposes.

A novel embryogenetic mechanism for Currarino's triad: inadequate dorsoventral separation of the caudal eminence from hindgut endoderm

Currarino's triad is a congenital malformation involving the combination of anorectal stenosis, a presacral mass (most often a teratoma or ventral menigocele) and an anterior sacral bony defect (scimitar sacrum). Current theories regarding its embryogenesis are difficult to reconcile with our current understanding of caudal neuraxial and hindgut development. Caudal neuraxial structures develop from the caudal eminence (or tail bud), which normally separates from the hindgut endoderm concurrent with ingrowth of the posterior notochord during late gastrulation. We describe the first reported association of Currarino's triad with a caudal split cord malformation. It has previously been proposed that split cord malformations and related 'complex dysraphic malformations' involving abnormalities of one or more of the three primary germ layers arise through disordered midline axial integration during gastrulation. The presence of a split cord malformation in a patient with Currarino's triad suggests that the two disorders share a common embryogenetic pathway. We propose that the malformations of Currarino's triad arise through a failure of dorsoventral separation of the caudal eminence from the hindgut endoderm during late gastrulation.

Publication patterns of the American Society of Pediatric Neurosurgeons. Is there support among members for peer-reviewed pediatric neurosurgical journals?

The American Society of Pediatric Neurosurgeons (ASPN) has expressed a commitment to have all of its members' qualifying research efforts published in peer-reviewed pediatric neurosurgical journals such as Pediatric Neurosurgery. To test this commitment, citations from January 1985 through December 1994 were analyzed for all 76 current members of the ASPN. The citations were divided into those of general or adult neurosurgical interest, and those of pediatric neurosurgical interest based upon title, key words, and/or abstract. Each pediatric neurosurgical citation was further classified by topic, and by the type of journal in which it appeared (pediatric neurosurgical, general or adult neurosurgical, and other pediatric or adult journal, subspecialty journal, or basic science journal). A total of 1,887 individual author citations were identified during the study period; of these, 1,586 citations (84%) were classified as pediatric neurosurgical citations. These included 1,391 citations from peer-reviewed publications and 195 citations from Concepts in Pediatric Neurosurgery. As a society, the ASPN published only one third of its citations in peer-reviewed pediatric neurosurgery journals; the remainder were cited in general neurosurgical or other journals. Even when only citations from neurosurgical journals (in which pediatric neurosurgeons were more likely to be primary authors and therefore to have more control over the journal of publication) were analyzed, less than 50% of citations appeared in peer-reviewed pediatric neurosurgery journals. Nearly three quarters of ASPN members failed to provide even a modest commitment--publishing 51% or more of their pediatric citations in peer-reviewed pediatric neurosurgical journals. When the analysis was again limited to only those citations published in neurosurgery journals, over half of the members failed this '51% rule'. These results suggest the need for a firmer commitment from ASPN members to publish in peer-reviewed pediatric neurosurgery journals.

Pathological changes in exposed neural tissue of fetal delayed splotch (Spd) mice

If meningomyelocele is indeed a progressive intrauterine process, then early delivery or possibly intrauterine repair of meningomyelocele becomes an issue. Utilizing the delayed splotch (Spd) mouse, a genetically transmitted neural tube defect model, we looked for evidence of abnormalities of neural tissue exposed to amniotic fluid. Affected embryonic and fetal mice were examined with the light microscope, and also with the transmission and scanning electron microscope. Neuronal development and programmed cell death paralleled normal fetal development. No evidence of inflammation on or within the exposed neural tissue was observed. Because the vascular supply to the alar and basilar plate are different, vascular development was also examined and no difference could be found. In conclusion, we found no evidence of deterioration of the exposed neural tube during the gestational period of a mouse, which suggests that exposure of unneurulated spinal cord to amniotic fluid is not a risk factor to the fetus with a neural tube defect.

A modified lateral decubitus position for surgical approaches to midline posterior fossa lesions: technical note

Although a number of operative positions have been described for approaching midline posterior fossa tumors, all have potential disadvantages and complications. We describe a modified lateral decubitus position for the removal of posterior fossa tumors. The position allows blood and cerebrospinal fluid to drain from the operative wound and provides a straight-on view of the posterior fossa contents. It also allows the surgeon to sit comfortably during tumor removal, thereby reducing operator fatigue. We have found this to be a reliable and valuable approach for posterior fossa pathology.

Occipital plagiocephaly: deformation or lambdoid synostosis? I. Morphometric analysis and results of unilateral lambdoid craniectomy

Between 1987 and 1992, 30 infants aged 1.4-13 months (mean 7.3 months) underwent unilateral lambdoid strip craniectomy at the Children's Hospital of Buffalo for occipital plagiocephaly. Males outnumbered females (22:8) and right-sided occipital flattening was significantly more common than left-sided flattening (25:5). The deformity was noticed at an average age of 3.2 months; 16% of the infants had an asymmetry at birth. Positional preferences (a distinct tendency to lie preferentially on the back, in most cases with the head turned to the ipsilateral side) were described in 79% of infants for whom this information was available, and torticollis was present in 10%. Pre- and post-operative CT scans were analyzed using several morphometric measurements. Asymmetries were measured between the flattened and contralateral sides, both posteriorly and anteriorly, using a translucent grid placed over the CT slice showing maximum asymmetry. The average maximum asymmetry between the flattened and contralateral sides was 24% posteriorly and 16% anteriorly. Significant improvements were seen postoperatively, with both anterior and posterior asymmetries improving by an average of one third (p < 0.05). However, when compared with CT scans from a control group of infants without synostosis, the operated group showed persistent and significant asymmetries postoperatively. The morphometric measurements described allow an objective and reproducible means of assessing the results of various treatments for this disorder. The improvements following unilateral lambdoid craniectomy are difficult to interpret in isolation; we suggest that future efforts be directed toward similarly assessing the results of both nonoperative treatments such as positional changes and molding helmets, and more aggressive surgical treatments that have been advocated for this disorder.

Occipital plagiocephaly: deformation or lambdoid synostosis? II. A unifying theory regarding pathogenesis

Occipital plagiocephaly is characterized by both unilateral occipital flattening and ipsilateral frontal prominence with anterior deviation of the ipsilateral ear, yielding a characteristic parallelogram shape to the cranium. Radiographic changes in the lambdoid suture are often evident, but the lambdoid suture is usually patent over most or all of its length on skull X-rays and/or CT scans. Both lambdoid synostosis and deformational forces have been implicated as potentially causal in the pathogenesis of this deformity. We proposed a unifying theory which incorporates a common pathogenesis for both deformational plagiocephaly and most cases of lambdoid 'synostosis'. According to this hypothesis, intrauterine and/or postnatal deformation forces are responsible for the primary calvarial deformation. These forces initially act in reversible manner to produce the typical parallelogram-shaped skull deformity. However, with continued deformation, more enduring secondary pathological changes may eventually occur in the lambdoid suture and basicranium which are more difficult to correct even if the offending deformational forces are subsequently removed or reversed.

[Neuro-brucellosis. Report of 8 cases]

Brucellosis is an endemic disease in Portugal. There was an increase in incidence in 1994. Neurobrucellosis (NB), although only occurring in 5 to 10% of cases of cases of chronic infection, has heterogeneous forms of presentation which makes differential diagnosis difficult. By reviewing four years of in-patient clinical files in the neurology Ward of St. António dos Capuchos Hospital, the authors study the clinical features, complementary tests, therapy and evolution of differential diagnosis of eight patients with neurobrucellosis.

Split cord malformations

Previous classifications of split cord malformations (SCM's), including such terms as diastematomyelia and diplomyelia, have done little to foster a true understanding of these disorders. The authors instead propose a unifying classification in which all SCM's share a common embryogenesis. SCM's are divided into two types, based upon the composition of the dural coverings and intervening mesenchymal tissue. Type I malformations are composed of two dural sacs and a bony or fibrocartilaginous spur; Type II malformations are composed of a single dural sac and intradural fibrous bands. In either case, the intervening mesenchymal elements contribute to progressive neurologic, urologic, and orthopedic deterioration from spinal cord tethering. The natural history of these lesions supports an early and aggressive operative approach to untether the spinal cord before clinical deterioration begins.

Hydrocephalus in the child with dysraphism

Hydrocephalus develops in approximately 85% of patients with myelomeningoceles and appears most frequently to result from obstruction to cerebrospinal fluid (CSF) flow within the posterior fossa subarachnoid space and at the tentorial hiatus, due to posterior fossa crowding from the Chiari malformation. The presenting features of hydrocephalus are legion; although signs and symptoms of intracranial hypertension are most common, many patients exhibit more subtle and confusing signs, such as intellectual deterioration or behavioral changes, or those that mimic brainstem compression from the Chiari malformation or spinal cord dysfunction due to tethering or syringomyelia. Prompt recognition of these signs and symptoms will direct appropriate therapy toward shunt revision and will help the clinician avoid potentially unnecessary and more dangerous procedures.

Cervical myelomeningoceles

Cervical myelomeningoceles are rare dysraphic lesions. Nine cases of cervical myelomeningoceles are reported. The external features of all nine myelomeningoceles were strikingly similar: They were sturdy, tubular protuberances from the back of the infants' necks, covered at the base by full-thickness skin and covered on the dome by thick squamous epithelium. Internally, these were tethered cord lesions in which fibroneural bands or sagittal midline fibrous septa were tightly tethering the cervical spinal cord to the adjacent dural or intrasaccular soft tissues. Six of our early cases (Group 1) were initially treated with simple subcutaneous resection of the sac and ligation of the dural fistula without release of the internal tethering structures. Five of these children subsequently deteriorated 13 months to 8 years later, all with worsening hand function and spastic legs. All five were reexplored, and the tethering bands and septa were excised; all showed improvement. The other three neonates (Group 2) treated in the last 4 years underwent initial intradural exploration of the lesions; in one case, the tethering fibrous elements were only partially eliminated and the patient deteriorated 4 years later, but improved after a second operation for resection of a missed ventral fibrous septum. The other two Group 2 infants had a thorough release of the fibroneural stalks initially, and both were neurologically stable 3 years later. We recommend that cervical myelomeningoceles should be studied preoperatively with magnetic resonance imaging and computed tomographic myelography to identify the internal structures. The minimum initial surgical treatment should be a two-level laminectomy, intradural exploration, and excision of all tethering bands and septa, in addition to resection of the sac. If a split cord is revealed by imaging studies, both the ventral and dorsal surfaces of the hemicords must be carefully inspected to locate the median septum.

Split cord malformation: Part I: A unified theory of embryogenesis for double spinal cord malformations

Much confusion still exists concerning the pathological definitions and clinical significance of double spinal cord malformations. Traditional terms used to describe the two main forms of these rare malformations, diastematomyelia and diplomyelia, add to the confusion by their inconsistent usage, ambiguities, and implications of their dissimilar embryogenesis. Based on the detailed radiographic and surgical findings of 39 cases of double cord malformations and the autopsy data on two other cases, this study endorses a new classification for double cord malformations and proposes a unified theory of embryogenesis for all their variant forms and features. The new classification recommends the term split cord malformation (SCM) for all double spinal cords. A Type I SCM consists of two hemicords, each contained within its own dural tube and separated by a dura-sheathed rigid osseocartilaginous median septum. A Type II SCM consists of two hemicords housed in a single dural tube separated by a nonrigid, fibrous median septum. These two essential features necessary for typing, the state of the dural tube and the nature of the median septum, do not ever overlap between the two main forms and can always be demonstrated by imaging studies so that accurate preoperative typing is always possible. All other associated structures in SCM such as paramedian nerve roots, myelomeningoceles manqué, and centromedian vascular structures frequently do overlap between types and are not reliable typing criteria. The unified theory of embryogenesis proposes that all variant types of SCMs have a common embryogenetic mechanism. Basic to this mechanism is the formation of adhesions between ecto- and endoderm, leading to an accessory neurenteric canal around which condenses an endomesenchymal tract that bisects the developing notochord and causes formation of two hemineural plates. The altered state of the emerging split neural tube and the subsequent ontogenetic fates of the constituent components of the endomesenchymal tract ultimately determine the configuration and orientation of the hemicords, the nature of the median septum, the coexistence of various vascular, lipomatous, neural, and fibrous oddities within the median cleft, the high association with open myelodysplastic and cutaneous lesions, and the seemingly unlikely relationship with fore and midgut anomalies. The multiple facets of this theory are presented in increasing complexity against the background of known embryological facts and theories; the validity of each facet is tested by comparing structures and phenomena predicted by the facet with actual radiographic, surgical, and histopathological findings of these 41 cases of SCM.

Mesoderm movement and fate during avian gastrulation and neurulation

Quail/chick transplantation chimeras were constructed during stages of gastrulation and neurulation to follow the subsequent movement and fate of cells of the primitive streak. All grafts were placed solely within the confines of the primitive streak to prevent confusion between cells that had not yet ingressed and those that had already ingressed, and transplanted cells were distinguished from host cells on the basis of a naturally occurring cell marker. Pathways of movement of ingressing cells corresponded to their level of residence within the primitive streak. Cells residing within Hensen's node (the cranial end of the primitive streak) initially migrated mainly cranially, remaining on or near the midline, and then extended caudally along the midline as regression of Hensen's node occurred. Cells residing within the nodus posterior (the caudal end of the primitive streak) migrated caudally. Cells residing at levels of the primitive streak between Hensen's node and the nodus posterior typically migrated bilaterally, confirming that such cells had not already ingressed prior to their transplantation (in which case, they would have migrated unilaterally). Subsets of these cells residing at progressively more caudal levels of the primitive streak migrated incrementally more laterally. Hensen's node contributed cells to the gut endoderm, head mesenchyme, notochord, and median hinge-point (MHP) cells of the neural tube (future floor plate). At younger stages (i.e., stages 3a, 3b) Hensen's node contributed cells to principally the foregut endoderm and head mesenchyme, whereas at older stages (i.e., stages 3c, 3d, 4), it contributed cells to principally the notochord and MHP region. The remaining segments of the cranial half of the primitive streak contributed cells to the various mesodermal subdivisions of the embryo, and the lengths of the segments forming these subdivisions were estimated. The most cranial level of the streak (directly behind Hensen's node) contributed cells to the most medial mesodermal subdivisions (head mesenchyme, somites) and consecutively more caudal levels of the streak contributed cells to sequentially more lateral mesodermal subdivisions (intermediate mesoderm, lateral plate mesoderm). The caudal half of the primitive streak contributed cells to the extraembryonic mesoderm, with the nodus posterior contributing to the most caudal extraembryonic mesoderm, including the blood islands. Our results confirm and extend the previous avian prospective fate maps, increasing our understanding of the movement and fate of cells of the gastrula and neurula stages.

Neurenteric cysts of the posterior fossa: recognition, management, and embryogenesis

Neurenteric cysts are endothelium-lined structures most commonly encountered in the lower cervical or upper thoracic spinal cord. The occurrence of neurenteric cysts within the cranial vault is unusual. We present three patients with neurenteric cysts located within the posterior fossa: one near the jugular foramen deforming the 4th ventricle, a second in the cerebellopontine angle, and a third in the prepontine cistern. Several different theories have been advanced to explain the embryogenesis of neurenteric cysts. We review these theories and conclude that cranial neurenteric cysts may arise from a disturbance of early gastrulation, shortly after the onset of primitive streak regression.

Neurenteric cysts of the posterior fossa: recognition, management, and embryogenesis

Neurenteric cysts are endothelium-lined structures most commonly encountered in the lower cervical or upper thoracic spinal cord. The occurrence of neurenteric cysts within the cranial vault is unusual. We present three patients with neurenteric cysts located within the posterior fossa: one near the jugular foramen deforming the 4th ventricle, a second in the cerebellopontine angle, and a third in the prepontine cistern. Several different theories have been advanced to explain the embryogenesis of neurenteric cysts. We review these theories and conclude that cranial neurenteric cysts may arise from a disturbance of early gastrulation, shortly after the onset of primitive streak regression.

Complications of myelomeningocele closure

Closure of a myelomeningocele is a deceptively simple operation; however, attention to several subtle details can significantly reduce operative complications. Important preoperative concerns include social issues of dealing with a distraught and often overwhelmed family, the timing of surgery, and assessment of associated severe or life-threatening malformations. Operative intervention should be directed toward preserving neurological function and optimizing the subsequent repair of a tethered spine should this become necessary. Careful attention to the vascular supply to the placode, precise separation of neural from cutaneous tissues, a diligent search for associated tethering anomalies such as diastematomyelia and a thickened filum terminale, careful pia to pia reconstruction of the placode, and simple but meticulous wound closure all help in achieving these aims. The timely management of associated hydrocephalus will help to avoid cerebrospinal fluid leakage and wound breakdown. Close attention to these details will ameliorate many of the immediate and delayed complications of myelomeningocele closure.

Juvenile intervertebral disc calcification: recognition, management, and pathogenesis

Juvenile intervertebral disc calcification is an uncommon disorder of childhood, characterized by calcification of the nucleus pulposus of one or more intervertebral discs. Calcification may remain dormant or subsequently become symptomatic. The symptoms include fever, malaise, and neck pain and are associated with an elevated erythrocyte sedimentation rate and, occasionally, leukocytosis. Although disc protrusion occurs in 38% of patients, neurological signs are distinctly uncommon. We report the case of a patient with a herniated T2-T3 calcified intervertebral disc and compressive myelopathy. Juvenile intervertebral disc calcification is generally a self-limiting disease that seldom requires an operation. The symptoms are transient, and resorption of the disc calcification is the rule once symptoms occur. Neither the cause of the disc calcification nor the trigger for the onset of symptoms is known. An inflammatory response within the disc appears to give rise to clinical symptoms and is associated with eventual resorption of the disc calcification.

Formation of ectopic neurepithelium in chick blastoderms: age-related capacities for induction and self-differentiation following transplantation of quail Hensen's nodes

Hensen's node, regarded as the avian and mammalian homologue of Spemann's neural inducer (i.e., the amphibian dorsal blastoporal lip), has been transplanted in many previous studies to the germinal crescent of avian blastoderms to examine ectopic neural induction. All these studies have suffered from one or more major shortcomings, the most significant of which has been the lack of a reliable cell marker to determine the contributions of graft cells to ectopic embryos. In the absence of such marker, induced (i.e., derived from the host) and self-differentiated (i.e., derived from the graft) neurepithelium cannot be distinguished from one another with certainty. We have transplanted quail Hensen's nodes to chick host blastoderms and have subsequently used the quail nucleolar heterochromatin marker to identify graft cells unequivocally. We systematically varied both donor and host ages (i.e., stages 3-8 and 3-5, respectively) to examine the effects of age on ectopic neural induction and self-differentiation. Our results demonstrate that the age of the donor is more critical than that of the host over the stages examined. With advancing donor age, the frequency of host induction decreases, while the frequency of graft self-differentiation increases. Previous studies not using cell markers have concluded that the craniocaudal level of the induced neuraxis is determined by the age of the donor, that is, young donors induce cranial neuraxial levels, whereas old donors induce caudal levels. By contrast, we found that with grafts from older donors, neurepithelium was more commonly self-differentiated rather than induced and that progressively more caudal levels of the neuraxis self-differentiated with advancing donor age. Induction of caudal neuraxial levels never occurred in the absence of induced cranial levels. The frequency of neural induction was inversely correlated with the age of the donor and directly correlated with the quantity of graft endodermal cells contributed to the ectopic embryo, supporting a previous assertion that in avian embryos, the earliest and principal source of neural inducer lies within the endoderm rather than mesoderm. From our results, we propose that the role of neural induction is to produce neurepithelium of unspecified regional character, and that the formation of regional character depends on subsequent morphogenetic events.

Intracranial hemorrhage from aneurysms and arteriovenous malformations during pregnancy and the puerperium

Intracranial hemorrhage (ICH) from an intracranial aneurysm or arteriovenous malformation is a grave complication of pregnancy and is responsible for 5 to 12% of all maternal deaths. We critically analyzed 154 cases of verified ICH during pregnancy from an identified intracranial lesion, including 2 patients treated at our institution and 152 cases previously reported in the literature in English. Aneurysms were responsible for ICH in 77% of patients, and arteriovenous malformations in 23%. Hemorrhage occurred antepartum in 92% of patients and postpartum in 8%. Women with angiomatous hemorrhage were younger than those with aneurysmal hemorrhage; however, in contrast to previous reports, we found no differences between angiomatous and aneurysmal hemorrhage with respect to parity or gestational age at the time of the initial hemorrhage. Hypertension and/or albuminuria were present at some time during the pregnancy in 34% of patients with documentation, which sometimes made it difficult to differentiate angiomatous or aneurysmal ICH from that associated with eclampsia. In a logistic regression analysis, surgical management of aneurysms, but not arteriovenous malformations, was associated with significantly lower maternal and fetal mortality, independent of other covariants. For those patients with a lesion not operated on, cesarean delivery afforded no better maternal or fetal outcome than did vaginal delivery. We conclude that the decision to operate after ICH during pregnancy should be based upon neurosurgical principles, whereas the method of delivery should be based upon obstetrical considerations. The perioperative and anesthetic management of the pregnant patient with a neurosurgical complication is discussed.

Management of hydrocephalus complicating childhood posterior fossa tumors

We examined the treatment of hydrocephalus in children with posterior fossa tumors to (1) compare the use of external ventricular drainage (EVD) with ventriculoperitoneal shunts (VPS), (2) determine the frequency of postoperative hydrocephalus requiring permanent shunts, and (3) determine which factors predict the need for a permanent shunt. The records of 58 children with posterior fossa tumors and associated hydrocephalus treated at our institution from 1979 to 1987 were retrospectively reviewed. Initial management of hydrocephalus included VPS in 25 patients, EVD in 17, and no treatment in 16. Patients in the 'VPS', 'EVD', and 'no treatment' groups differed only in the severity of hydrocephalus (less severe in the no treatment group than in the VPS and EVD groups) and in the method of dural closure following tumor resection (dura was left open more often in the EVD and no treatment groups). Of the 33 patients not initially shunted, only 9 (27%) subsequently required a shunt. These patients were compared with the remaining 24 patients who did not require a shunt. Two features predicted the need for a subsequent shunt: (1) resection of only a small volume of tumor and (2) the dura open following tumor resection. Complications of EVD were few; no patient deteriorated neurologically during or after ventricular catheter removal. We conclude that between two thirds and three quarters of patients with childhood posterior fossa tumors and associated hydrocephalus may be managed with perioperative EVD and will not require shunts. Patients in whom only a minimal tumor resection is performed and those in whom the dura is left open are more likely to need permanent VPS.