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PubMed2003

Nonmalignant pediatric brain tumors.

Brain tumors are the most common solid neoplasms in the pediatric population. Each year in the United States, approximately 1500 to 2000 children are affected by one of these tumors. About 50% of pediatric brain tumors are malignant. Nonmalignant pediatric brain tumors comprise an eclectic group of pathologic entities that have fascinating clinical features. Many of these tumors demonstrate a favorable prognosis. In this report, we review the epidemiology, histopathology, genetics, clinical presentation, neuroimaging, and treatment of the common nonmalignant pediatric brain tumors, including low grade astrocytomas (such as cerebellar astrocytoma and optic pathway glioma), subependymal giant cell astrocytomas, central neurocytomas, dysembryoplastic neuroepithelial tumor, choroid plexus papilloma, and craniopharyngioma. Advances in the therapeutic management of patients with these tumors have considerably improved their prognosis.

Adolescent↗

PubMed1991

Effect of eye removal on N-acetylaspartylglutamate immunoreactivity in retinal targets of the cat.

The endogenous brain dipeptide N-acetylaspartylglutamate (NAAG) has previously been demonstrated in the somata of retinal ganglion cells and the neuropil of retinal targets. In this paper we report that the NAAG immunoreactivity of the neuropil in the retinal targets is dependent on an intact optic pathway. Removal of one eye produced a marked decrease in the staining of the neuropil in layer A of the contralateral geniculate nucleus (LGN) and layer A1 of the ipsilateral LGN. There was also decreased staining in the superficial layers of the superior colliculus contralateral to the removal. These results suggest that NAAG is present in the terminals of retinal ganglion cells and is consistent with a role for NAAG in visual synaptic transmission.

Animals↗

PubMed1991

The cause of increased pupillary light reflex latencies in diabetic patients: the relationship between pupillary light reflex and visual evoked potential latencies.

In 42 diabetic patients the relationship between the latency of the pupillary light reflex and the pattern reversal visual evoked potential (P100) was examined. Fifty-five percent of diabetic patients had pupillary light reflex latencies above the normal range. In 19% the visual evoked potentials were prolonged when compared to the normal range. Latencies of pupillary light reflexes and VEPs showed no correlation. There was a minimal correlation between the presence of retinopathy and prolongation of both the pupillary light reflex and the visual evoked response latency (kappa coefficients respectively: 0.31, P less than 0.01 and 0.36, P less than 0.02). The presence of an increased pupillary light reflex latency was positively correlated with a reduced respiratory sinus arrhythmia (kappa coefficient: 0.58, P less than 0.0001). Increased VEP latencies showed no correlation with signs of cardiovascular autonomic neuropathy. We conclude that the afferent optic pathway can be affected in diabetic patients. However, prolongation of pupillary light reflex latency in diabetic patients is primarily due to an efferent pupillary defect and represents parasympathetic dysfunction.

Adult↗

PubMed1988

Anomalous retrograde labeling of brain cells from the eye in the goldfish: evidence for long distance growth of sprouted neurites.

We have used retrograde labeling with horseradish peroxidase (HRP) and a wheat germ agglutinin conjugate of HRP (WGA:HRP) to investigate the projections of the nucleus postglomerulosus (nPg) both in normal goldfish and in animals which had undergone retinal removal. In normal animals, our evidence indicates that nPg projects only to the optic tectum. Using small HRP and WGA:HRP application sites in the tectum, we have shown that nPg cells have broadly spread terminals in the tectal neuropil and that there is no obvious correspondence between the rostrocaudal axis of the nPg and the deployment of the terminal arbors of its cells along the rostrocaudal axis of the tectum. In addition, we found no evidence for an nPg projection to the eye in normal animals. After retinal removal we found that nPg cells were more readily backfilled from small tectal applications of HRP. However, our most interesting observation was that at 4-6 weeks and more after ocular surgery, we could retrogradely label the cells of the nPg with intraocular or retroocular injections of WGA:HRP. At the same postoperative times, we were also able to label neurites in the atrophied optic nerve by microinjecting WGA:HRP into the contralateral midbrain tegmentum. Finally, we found that the cells of the nPg undergo a hypertrophic response, similar to that seen in other neurons after axotomy, following retinal removal or section of the dorsomedial brachium of the optic tract. Thus, these cells respond to retinal denervation of the tectum with a response characteristic of axotomized cells although their axons have not been cut. Similar changes were also seen in the nucleus isthmi on both sides of the brain following retinal removal. We interpret our data to indicate that cells of the nPg can respond to optic (and thus heterotypic) denervation of their terminal field by sprouting processes which grow away from the terminal field, through denervated optic pathways, to the retinaless eye. This interpretation requires that the sprouted processes grow for several millimeters.

Animals↗

PubMed1987

Distribution of Theiler's virus in the CNS of athymic nude mice: effect of varying the route of inoculation.

Immunohistochemical and ultrastructural techniques were used to map the distribution of Theiler's virus in the central nervous system (CNS) of the nude mouse, after intracerebral (i.c.), intravenous (i.v.) or intraocular (i.o.) inoculation. Expression of viral antigen was largely restricted to the subthalamus, substantia nigra, ventral tegmental tract and the grey and white matter of the spinal cord. Electron microscopy showed paracrystalline arrays of viral particles within neurons in the substantia nigra and spinal cord. Inoculation of virus i.v. or i.o. rather than i.c. delayed the onset of neurological signs but did not affect the distribution of virus within the CNS. In particular, there was no evidence of spread along the optic pathways after i.o. inoculation. The localization of Theiler's virus within certain regions of the CNS seems to depend on differential susceptibility to infection or differential restriction of replication rather than on the route of inoculation.

Animals↗

PubMed1990

Ventriculoperitoneal shunt in cryptococcal meningitis with hydrocephalus.

Fourteen patients with cryptococcal meningitis were reviewed. All patients had a ventriculoperitoneal shunt for hydrocephalus. Early recognitions and prompt relief of hydrocephalus were useful for eight patients who showed rapid deterioration of consciousness or signs of cerebral herniation. There was no surgical response in four patients who had had weeks of confusion or mental change. It seems, therefore, that the duration of disturbance of consciousness or change of mentality before shunting is critical in determination of the outcome of the treatment. Ventricular shunting was effective in relieving papilledema in five patients. However, the surgery did not prevent the development of papilledema to optic atrophy and subsequent blindness in two patients. Hence, in addition to hydrocephalus with increased intracranial pressure, conditions such as direct invasion of the optic pathways by Cryptococcus neoformans or optochiasmatic arachnoiditis may be responsible for the visual failure. Ventricular shunting was also helpful in restoring paraparesis in one patient. Of the cerebrospinal fluid determinations, low protein concentration was a favorable indicator for surgery. Of the seven patients who received the surgical procedure before the start of antifungal therapy, four showed a significant improvement despite active infection of the central nervous system. None of the seven patients deteriorated because of the surgical operation. Thus, active stage of cryptococcal meningitis does not contraindicate the necessity of shunting, and premedication with antifungal drugs is unnecessary. Also, no shunt-related morbidity and mortality was seen in this study.

Adolescent↗

PubMed1989

Postnatal development of the ipsilaterally projecting retinal ganglion cells in normal rats and rats with neonatal lesions.

The postnatal development of normal and anomalous uncrossed retinofugal projections in albino rats was studied using horseradish peroxidase and lectin-conjugated horseradish peroxidase as retrograde neuronal tracers. In normal rats, the number of ipsilaterally projecting retinal ganglion cells (IPRGCs) decreased continuously from more than 3000 cells on the day of birth (day 0) to slightly more than 1000 on postnatal day 5. In contrast, the number of IPRGCs in rats which received either unilateral eye enucleation or thalamectomy at birth increased abruptly to more than 4000 after 24 h on postnatal day 1, thereafter the number decreased rapidly reaching an adult level of slightly more than 2000 on postnatal day 5. The overall pattern of changes of the number, density and distribution of the IPRGCs was similar in rats which received eye enucleation or thalamectomy, although minor differences regarding the number of cells labelled in the temporal and nasal parts of retinas in rats with different lesions were detected. These findings imply that a neonatal lesion such as monocular enucleation or unilateral thalamectomy may not only result in retention of normally transient IPRGCs but also cause an increased number of IPRGCs by misrouting, rerouting or collateral sprouting of optic axons at the optic chiasma that could significantly affect the developing optic pathway. Furthermore, the differential effects of the two types of neonatal lesions upon the IPRGCs provide further evidence to previous findings that different mechanisms might be involved in generating the anomalously enlarged uncrossed retinofugal projections in rodents.

Aging↗

PubMed1992

Carcinomas of the nasal cavity.

Between 1969 and 1985, 45 patients with carcinomas of the nasal cavity proper received curative treatment. Thirty patients had squamous cell carcinoma, one had undifferentiated carcinoma, 9 had adenocarcinoma, and 5 had adenoid cystic carcinoma. Eighteen patients were treated with definitive radiotherapy (interstitial brachytherapy in 5 and external beam therapy in 13 patients), and 27 received surgery and radiotherapy. The median length of follow-up was 11 years (range: 2.8-16.8 years). Thirty-six patients had no evidence of disease at the last follow-up visit. All 14 patients with carcinoma of the nasal septum had the disease controlled. Nine of 31 patients with lesions of the lateral wall and floor died of the disease, 5 of uncontrolled local disease, 2 of distant metastases, and 2 of both. The disease-specific survival rates at 5 and 10 years were 83 and 80%, respectively, and the corresponding overall survival rates were 75 and 60%, respectively. Blindness occurred in 4 patients, 2 due to orbital exenteration and 2 to radiation injury to the cornea and optic pathway. Other infrequent side effects were bone necrosis, dental decay, nasal stenosis, and septal perforation. This study indicated that the prognosis of patients with nasal cavity carcinoma was better than that of patients with maxillary sinus cancer treated during the same era. In addition, the study showed that carcinomas of the nasal septum were smaller than those of lateral wall and floor at diagnosis, so that excellent control could be achieved by definitive radiotherapy; when accessible, interstitial brachytherapy might be the treatment of choice in such patients.

Adenocarcinoma↗

PubMedDate not supplied

Visual and somatosensory evoked potentials in vitamin E deficiency with cystic fibrosis.

Patients with cystic fibrosis (CF) and pancreatic malabsorption frequently have vitamin E deficiency. Affected patients may develop spinocerebellar degeneration with dysarthria, ataxia, proximal weakness, proprioceptive loss and areflexia. Of a highly selected group of 10 patients with vitamin E levels below 5 micrograms/ml (normal 5-20 micrograms/ml), 7 had abnormal neurological examinations, predominantly affecting vibration and joint position perception with some severely affected patients manifesting diminished visual acuity, tremor, ataxia and diffuse weakness. Evoked potential studies showed marked abnormalities in 3 patients, demonstrating deficits in the optic pathways and in the cervical cord dorsal column pathways. Evoked potential studies may supplement careful neurological examination in patients with CF before and after supplementation with vitamin E to evaluate their progression and response to treatment.

Adolescent↗

PubMed1985

Identification of the principal receptor responsible for adsorptive endocytosis of a fucose-specific lectin from Aleuria aurantia in the rabbit retina.

The retinal uptake of the fucose-specific lectin from Aleuria aurantia was investigated in rabbit. Following intraocular injections of Aleuria lectin, the probe was taken up by retinal ganglion cells and rapidly transported at two distinct rates in the optic pathway, to reach the nerve terminals in the lateral geniculate body and superior colliculus [3]. In this study, it was found that adsorptive endocytosis of Aleuria lectin was mediated mainly by a glycoprotein of Mr 275,000.

Adsorption↗

PubMed1991

Presence of estrogen receptor immunoreactivity in the oxytocin-containing magnocellular neurons projecting to the neurohypophysis in the guinea-pig.

The immunoperoxidase technique was used on adjacent sections of guinea-pig brain to compare precisely the distribution of estrogen receptor-immunoreactive cells and progesterone receptor-immunoreactive cells in the supraoptic nucleus and the paraventricular nucleus. Only estrogen receptor-immunoreactive neurons were found in the supraoptic nucleus. A large number of estrogen receptor-positive cells were observed in the periventricular magnocellular groups throughout the rostrocaudal extent of the paraventricular nucleus, whereas only a few progesterone receptor-immunoreactive cells were scattered in the anterior portion of this region. We used a combination of axonal tracing with double immunocytochemical detection to determine whether estradiol acts directly on the oxytocin-immunoreactive neurons which project to the neurohypophysis. Oxytocin-immunoreactive cells were found in the supraoptic nucleus, ventrally to the optic pathways, in subchiasmatic and retrochiasmatic areas, and in the anterior hypothalamic area. These cells were also retrogradely labeled by Granular Blue when this tracer was injected intravenously. In the paraventricular nucleus, the Granular Blue/oxytocin-positive cells were observed in the periventricular magnocellular groups whereas Granular Blue labeled neurons were found in both parvocellular and magnocellular components. We found that almost all the oxytocin-immunoreactive cells revealed estrogen receptor immunoreactivity. In conclusion, the comparative study of distribution of estrogen receptors and progesterone receptors in the guinea-pig supraoptic and paraventricular nuclei indicates that, in the supraoptic nucleus, only estrogen receptors are present and that, in the paraventricular nucleus, they are far more numerous than progesterone receptors. The present findings demonstrate that the magnocellular cells which contain estrogen receptors are oxytocinergic. In addition, these cells are retrogradely labeled pointing to a neurohypophysial projection. It is likely that estradiol controls the hypothalamo-neurohypophysial oxytocin system by direct action on the magnocellular neurons.

Animals↗

PubMed1994

Radiation therapy for pituitary adenoma: treatment outcome and prognostic factors.

PURPOSE: Radiation therapy is often an integral part of postoperative treatment in patients with nonfunctional pituitary adenomas. The Princess Margaret Hospital (PMH) experience was reviewed and analyzed to establish the role of radiation therapy in local control relative to its complications, and to see if subgroups of patients with a greater or lesser risk of recurrence postsurgery can be defined. METHODS AND MATERIALS: Records of 160 patients with nonfunctional pituitary adenoma treated between 1972 and 1986 were reviewed retrospectively. The review focused on 128 patients treated with surgery and postoperative radiation as initial therapy. The median total dose was 45 Gy. Local tumor control was defined as lack of progression or recurrence of adenoma as assessed clinically and by imaging studies. The following factors were analyzed for prognostic significance in local tumor control: age, sex, direction of tumor extension, radiation dose, and preoperative tumor size as reflected by the radiation field size. Complications including hypopituitarism and second tumors were analyzed. Hypopituitarism was defined as requirement for permanent hormone replacement therapy. RESULTS: With a median follow-up duration of 8.3 years, the 10-year actuarial local control rate was 87% for the entire 160 patients and 91% for the 128 patients given postoperative radiation as initial treatment. For the 29 patients referred for treatment of recurrent tumor, the 10-year local control rate was 78%. Prognostic factors for local control identified in univariate analysis included age (p = 0.005) and radiation field size (p = 0.0001). Older patients and those with larger tumors requiring large radiation portals were less likely to achieve durable local control. These two factors remained significant in a multivariate analysis (p < 0.005). The major complication, hypopituitarism requiring hormonal replacement with thyroxine, glucocorticoid, and sex hormone was observed to date in 65% (100 out of 155), 68% (105 out of 154), and 67% (85 out of 127) of evaluable patients, respectively. Radiation was the contributing cause of the hypopituitarism in only 23%, 16%, and 13%, respectively. There were no cases of brain necrosis or radiation damage to the optic pathways. Two patients developed a fatal in-field glioma of the brain stem at 10 and 15 years following radiation. CONCLUSION: Postoperative external beam radiation therapy is highly effective in preventing recurrence of hormonally inactive pituitary adenomas. Hypopituitarism is commonly observed, but radiation can only be incriminated as the contributing cause in approximately one-fifth of the cases. Treatment of patients at the time of recurrence gave comparable local control rates to those irradiated initially. Favorable patients (age < or = 50, with small tumors removed totally) probably can be safely observed postoperatively with radiation reserved for recurrence.

Adenoma↗

PubMed1986

Field potentials from the frog optic tectum in vitro.

A new method for maintaining the isolated frog optic tectum superfused in vitro at a low temperature is described. The preparation remains viable for several hours with electrophysiological responses similar to those of the in vivo tectum. This superfusion technique will allow controlled application of putative neurotransmitters and other substances in known concentrations and therefore makes the in vitro frog optic tectum a useful model system for neuropharmacological investigations into central optic pathways.

Animals↗

PubMed2005

Photostimulation alters c-Fos expression in the dorsal raphe nucleus.

Retinal afferents to the dorsal raphe nucleus (DRN) have been described in a number of species, including Mongolian gerbils, but functional correlates of this optic pathway are unknown at present. To determine whether temporally modulated photostimulation can affect c-Fos expression in the gerbil DRN, quantitative analysis of c-Fos-immunoreactive (c-Fos-ir) neurons was conducted following 60-min exposure to pulsed (2 Hz) photostimulation at selected times over the 12:12 h light/dark cycle. For comparison, c-Fos expression was also analyzed in the subnuclei of the lateral geniculate complex and in the suprachiasmatic nucleus (SCN). In the DRN, a substantial reduction was observed in the number of c-Fos immunoreactive (c-Fos-ir) neurons during the light period and early dark period in photostimulated vs. control animals. Similar results were obtained in the intergeniculate leaflet (IGL) and ventral lateral geniculate (VLG). However, no significant changes were observed in the number of c-Fos-ir neurons in the dorsal lateral geniculate nucleus or suprachiasmatic nucleus (SCN) following photostimulation, except for an increase in the middle of the dark period. These findings indicate that photic stimulation can lead to a suppression or down-regulation of c-Fos expression in the DRN that is probably mediated via the direct retinal pathway to the DRN in this species. The similarity between c-Fos expression profiles in the DRN and IGL/VGL suggest that efferent projections from the DRN may modulate c-Fos expression to visual stimulation in these subnuclei of the lateral geniculate complex.

Animals↗

PubMed2006

Radiation-induced moyamoya syndrome.

PURPOSE: The moyamoya syndrome is an uncommon late complication after radiotherapy (RT). METHODS AND MATERIALS: A PubMed search of English-language articles, with radiation, radiotherapy, and moyamoya syndrome used as search key words, yielded 33 articles from 1967 to 2002. RESULTS: The series included 54 patients with a median age at initial RT of 3.8 years (range, 0.4 to 47). Age at RT was less than 5 years in 56.3%, 5 to 10 years in 22.9%, 11 to 20 years in 8.3%, 21 to 30 years in 6.3%, 31 to 40 years in 2.1%, and 41 to 50 years in 4.2%. Fourteen of 54 patients (25.9%) were diagnosed with neurofibromatosis type 1 (NF-1). The most common tumor treated with RT was low-grade glioma in 37 tumors (68.5%) of which 29 were optic-pathway glioma. The average RT dose was 46.5 Gy (range, 22-120 Gy). For NF-1-positive patients, the average RT dose was 46.5 Gy, and for NF-1-negative patients, it was 58.1 Gy. The median latent period for development of moyamoya syndrome was 40 months after RT (range, 4-240). Radiation-induced moyamoya syndrome occurred in 27.7% of patients by 2 years, 53.2% of patients by 4 years, 74.5% of patients by 6 years, and 95.7% of patients by 12 years after RT. CONCLUSIONS: Patients who received RT to the parasellar region at a young age (<5 years) are the most susceptible to moyamoya syndrome. The incidence for moyamoya syndrome continues to increase with time, with half of cases occurring within 4 years of RT and 95% of cases occurring within 12 years. Patients with NF-1 have a lower radiation-dose threshold for development of moyamoya syndrome.

Analysis of Variance↗

PubMed2006

Diffusion tensor imaging in acquired blind humans.

Retinal implants as a future possible therapy of blindness rely on an intact neural transmission from the retina to the primary visual cortex. By now it remains unknown, in how far the absence of afferent input in blindness affects also the organization of the optic radiation. Using diffusion tensor imaging (DTI), the non-invasive evaluation of large fiber tracts including the optic radiation has become possible. This method is sensitive to changes of the axonal state such as wallerian degeneration. We have compared DTI data from 6 acquired blind patients with those of a group of 11 healthy control subjects. Neither the relative anisotropy quotient of the visual fiber tract and the pyramidal tract showed a statistically significant difference between the blind patients and the control group nor did the absolute values of the relative anisotropy in the pyramidal tract and the visual fiber tract. There was no axonal degeneration of the optic radiation in late onset acquired blindness. With the optic pathways remaining intact, transmitting electric signals of retinal implants to the visual regions of the human brain seems to be possible even after decades of acquired blindness.

Adult↗

PubMed2005

Orbital and ocular imaging using 3- and 1.5-T MR imaging systems.

The goal of this article is to familiarize general radiologists and clinicians (particularly ophthalmologists, neuro-ophthalmologists, neurologists, and neurosurgeons) with the recent introduction of clinical MR imaging scanners operating at a magnetic field strength of 3-T and to compare them with the more common standard scanners operating at 1.5-T. In this study, MR imaging at 3-T was found to offer superior depiction of orbital and intracranial anatomy and pathologic findings. Spin echo, high spatial resolution, T2-weighted, thin-section MR imaging sequences are especially useful and sensitive at 3-T for the evaluation of orbital, ocular, and intracranial anatomy and pathologic findings. The authors din that time-of-flight (TOF) MR angiography at 3-T surpasses the best MR angiography at 1.5-T and that two-dimensional TOF venography and three-dimensional contrast MR venography at 3-T offer superior visualization of intracranial and facial veins as compared with MR venography at 1.5-T. We believe that with further quality image production and efficient coil design, 3-T MR imaging should hold the promise of playing an important role in the diagnostic imaging evaluation of ocular, orbital, and optic pathway pathologic findings.

Artifacts↗

PubMed2006

Positive visual phenomena in space: A scientific case and a safety issue in space travel.

Most astronauts on Apollo, Skylab, and MIR reported 'flashes of light' occurring in different shapes and apparently moving across the visual field, in the absence of auditory, somatosensory, or olfactory abnormal percepts. A temporal correlation with heavy nuclei or protons has been documented in space and comparable phosphenes were observed by volunteers whose eyes were exposed to accelerated heavy ions at intensities below the threshold for Cerenkov visible radiation. An interaction between heavy ions and the retina was suggested. However, the biophysics of heavy ions or protons action remains undefined, the effects on photoreceptors and neuroretina have not been differentiated, and some direct action on the visual cortex never ruled out. Phosphenes are common in migraine and are known to occur also in response to the electrical stimulation of ganglion cells (in retinas without photoreceptors), optic pathways or visual cortex, with mechanisms that bypass the chemically gated channels. Intrinsic photosensitive ganglion cells exist in the retina of teleost fish and mammals. In the hypothesis of a peculiar sensitivity to subatomic particles of the visual system, phosphenes due to the activation of processes by-passing the photoreceptors would raise questions about human safety in space. The issue is particularly relevant with experiments of increasing duration being now operative in the International Space Station (ISS) and with plans of space travel outside the geomagnetic shield. Research is in progress both in the ISS and on animal models, in the framework of the NASA/ESA actions to improve the astronauts' health in space.

Cosmic Radiation↗