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PubMed2004

Impaired volitional closure of the left eyelid after right anterior cerebral artery infarction: apraxia due to interhemispheric disconnection?

BACKGROUND: The inability of volitional unilateral eyelid closure is an uncommon symptom of a central nervous system disorder. When it occurs as the result of a localized brain lesion, it is debated to be a form of supranuclear facial palsy or an apraxic phenomenon. OBJECTIVES: To report and discuss a unilateral (left-sided) higher-order movement disorder of the facial periocular musculature bearing apraxic features. SETTING: University neurology department. PATIENT: A 78-year-old right-handed man was admitted to the hospital with a left-sided brachiofacial hemiparesis of sudden onset. After thrombolysis with intravenous recombinant tissue-type plasminogen activator, the hemiparesis, including the left-sided facial weakness, disappeared. Serial computed tomographic scans showed that the patient was left with a stroke in the right anterior cerebral artery territory, affecting the frontal commissural fibers of the corpus callosum. There were no signs of upper motor neuron facial paresis on the left side when gesturing in a natural context. Eyelid closure was complete during sleep. However, left eyelid closure and elevation of the left eyebrow were not possible on verbal command. In contrast, voluntary innervation of the perioral facial musculature was performed properly. CONCLUSIONS: The voluntary-automatic dissociation of our patient's eyelid closure was suggestive of an apraxic disorder. Disconnection from a praxis center caused by callosal damage may be assumed to be the underlying cause. The unilaterality of the symptom might imply that in a bilaterally organized corticonuclear system such as upper face innervation, it is the crossing fibers that are primarily involved in praxis tasks.

Aged↗
PubMed1985

Agenesis of the corpus callosum. Clinical features in 40 children.

Forty children with partial agenesis of the corpus callosum have been prospectively identified and followed up for up to 15 years. Additional physical anomalies and diagnoses were frequent. At the time of diagnosis, the majority of children were developmentally delayed or retarded. If callosal agenesis was diagnosed during infancy, most children had or subsequently developed seizures. Older patients had a more favorable outcome and were less likely to develop epilepsy.

Adolescent↗
PubMed1976

Plantar pressure measurements. Rational shoe-wear in patients with rheumatoid arthritis.

Objective measurements of forefoot plantar pressures were taken on 25 patients with rheumatoid arthritis. The Harris mat footprint test and the Brand slipper sock test were used to assess both compressive shearing forces. The Harris mat footprint test is a static used when the patient is unshod. The Brand slipper sock test is a dynamic test used while the shoe is worn. An experimental sandal was designed and used for the treatment of symptomatic forefoot callosities. The Harris mat footprint test results improved dramatically after the patients had worn an experimental sandal for six months. The Brand slipper sock test results showed marked diminution in the pressure profile while the patients wore the experimental sandal. All of the patients improved in their functional abilities while wearing the experimental sandal.

Arthritis, Rheumatoid↗
PubMed1997

Opitz C trigonocephaly syndrome and midline brain anomalies.

We describe a child with trigonocephaly, strabismus, upslanting palpebral fissures, nasal bridge hypoplasia, hypertrophic alveolar ridges and large gingivo-labial frenula, short neck, hip "dysplasia," equinovarus deformities, cryptorchidism, atrial septal defect ostium secundum, and severe mental retardation, findings consistent with C syndrome. The patient also had a Dandy-Walker malformation, complete callosal agenesis, and occipital meningocele. These structural defects are independent of the premature closure of the metopic suture, and confirm that midline brain anomalies are part of C syndrome. The hypothesis that the basic developmental defect in this syndrome primarily affects the midline field is supported by the concomitance of other anomalies, such as conotruncal heart defects, omphalocele, and genital anomalies.

Agenesis of Corpus Callosum↗
PubMed1999

New syndrome of growth and mental retardation, structural anomalies of the central nervous system, and first branchial arch, anophthalmia, heminasal a/hypoplasia, and atypical clefting: report on four Brazilian patients.

We report on four unrelated Brazilian patients with growth and mental retardation, structural anomalies of the central nervous system (CNS), mainly callosal agenesis, prominent forehead, facial asymmetry, anophthalmia, heminasal a/hypoplasia, preauricular skin tags, structural anomalies of the external ears, and atypical clefting. This combination of anomalies is unique and, to our knowledge, is a previously undescribed syndrome of unknown etiology, although one of the patients was born to a consanguineous couple, suggesting the possibility of autosomal recessive inheritance. Clinical, genetic, and differential diagnosis aspects are discussed.

Abnormalities, Multiple↗
PubMed2000

Chudley-McCullough syndrome: bilateral sensorineural deafness, hydrocephalus, and other structural brain abnormalities.

The Chudley-McCullough syndrome, an autosomal recessive condition first reported by Chudley et al. [1997], comprises profound sensorineural hearing loss and hydrocephalus secondary to an obstruction of the foramen of Munro. We describe two more sibs with this condition. One girl had sensorineural hearing loss and hydrocephalus due to obstruction of the foramen of Munro. Incidentally she was also found to carry a full mutation in the FMR1 gene. The older sister had profound sensorineural hearing loss and hydrocephalus not due to obstruction of the foramen of Munro; she also had callosal dysgenesis, gray matter heterotopia, cortical dysplasia, and cerebellar dysgenesis. Thus, the Chudley-McCullough syndrome may include hydrocephalus not necessarily related to obstruction of the foramen of Munro and other structural brain abnormalities.

Adolescent↗
PubMed1996

Role of directed growth and target selection in the formation of cortical pathways: prenatal development of the projection of area V2 to area V4 in the monkey.

In experiments combining retrograde tracers and histochemistry, we have looked at the prenatal development of the cortical pathway linking areas V2 and V4. Transient expression of acetylcholinesterase in fetal area V2 reveals the separate compartments that project to V4 (temporal directed pathway) and V5 (parietal directed pathway). During early stages of pathway formation, V2 neurons projecting to area V4 are clustered in the appropriate compartments. During the phase of rapid axonal growth, there is a selective increase of connections originating from the appropriate compartments leading to a strongly clustered organization at the peak of connectivity. During this phase, injections involving the white matter also showed clustering, but this was somewhat reduced in comparison to that of gray matter injections. The growth phase is followed by an elimination phase during which there is a tendency for a preferential loss of intercluster connections, which may sharpen the early formed pattern. These results demonstrate the primary role of axonal guidance and target recognition mechanisms followed by a limited extent of selective elimination during the formation of functional cortical pathways in the primate isocortex. Compared to previous findings, these results suggest that the developmental restriction of callosal connections is not a universal model of cortical development. In the present report, the directed growth and early specification of feed-forward connections contrast with the prolonged remodelling of monkey feedback projections, suggesting two distinct developmental strategies of pathway formation in the monkey.

Acetylcholinesterase↗
PubMed1996

Differential distribution of AMPA receptors and glutamate during pre- and postnatal development in the visual cortex of ferrets.

Immunohistochemical methods were used to study the distribution and time-course of appearance of cells expressing glutamate and alpha-amino-3-hydroxy-5-methyl-4-isoaxazole propionic acid (AMPA)-type glutamate receptors (GluR1 and GluR2/3) during development of the ferret visual cortex. Glutamate is present in many neurons in the ventricular zone, intermediate zone, developing cortical plate, and marginal zone as early as embryonic day (E) 34 (birth is at E41 in ferrets). Glutamate attains its adult distribution coincident with the completion of cellular migration. By contrast, GluR1 immunoreactivity emerges more slowly. By birth, GluR1 immunoreactivity is present only in a few neurons in the marginal zone and ventricular zone but is abundant in the marginal zone and subplate, where synaptogenesis commences. The number and staining intensity of GluR1-positive cells increases dramatically during the first two postnatal weeks and is maximal between the second and third week, before slowly declining to adult levels. Cortical cells immunopositive for GluR2/3 follow a similar pattern, although their distribution differs: GluR2/3-positive cells are mainly pyramidal cells. During the first postnatal week, GluR2/3 is also transiently present in fibers in the intermediate zone, which at this stage contains many thalamocortical and callosal and corticofugal axons. The abundance of glutamate at fetal stages, especially in the ventricular zone, is consistent with the previously proposed role of glutamate in mediating trophic effects in vivo, as previously demonstrated in vitro. The expression of AMPA receptors, as well as their transient overexpression, confirms the results of in situ hybridization studies and may imply a developmental role in neuronal differentiation for these receptors, in addition to their mature role in mediating cortical transmission.

Animals↗
PubMed2000

Architectonic analysis of the human retrosplenial cortex.

The architecture of the macaque retrosplenial cortex, including its posteroventral extension around and below the splenium of the corpus callosum, was recently characterized (Morris et al. [1999a] Eur. J. Neurosci. 11:2506-2518.). This analysis was made possible by sectioning the posterior cingulate gyrus radially, i.e., in planes that were orthogonal to its line of curvature and that, therefore, preserved the laminar organization of this region. The aim of the present study was to examine the architecture and the limits of the human retrosplenial cortex. Cross sections through the entire posterior cingulate gyrus were obtained by applying the sectioning technique developed in the monkey, so that an explicit comparison could be made between the architecture of the human and the monkey retrosplenial cortex. The present analysis revealed that, as is the case in the macaque brain, the human retrosplenial cortex is composed of granular areas 29a-c and d, and dysgranular/agranular area 30. The human retrosplenial cortex, like that of the macaque monkey, runs, as an arch, around the splenium of the corpus callosum. In the macaque brain, the retrosplenial cortex remains buried within the callosal sulcus throughout its entire course around the splenium. In the human brain, however, the posteroventral segment of the retrosplenial cortex extends on the medial wall of the cerebral hemisphere to encompass most of the cortical region commonly referred to as the "isthmus of the cingulate gyrus."

Adult↗
PubMed2000

Thoughts on the cerebellum as a model for cerebral cortical development and evolution.

This chapter explores the prospect of using the cerebellar cortex as a model for the development and evolution of the cerebral neocortex. At first, this would seem a nearly fruitless task given the readily apparent structural and functional differences between the two cortices. Cerebellum and cerebrum perform different associative tasks, the cellular 'circuit diagram' of the two structures is different, even the developmental sequences that give rise to the two structures differ markedly. Yet there are similarities between the structures at the conceptual level that are difficult to ignore. Both structures have a relatively simple modular circuitry and achieve their complexity by an increase in either the size or number of the modules. Both have massive commisures connecting the left and right halves of the structure. For the cortex this commisure is the obvious corpus callosum; the cerebellar commisure is made up of parallel fibres of the granule cells that pass freely across the midline. As they are thin and unmyelinated, the number of these crossing fibres may well exceed the number of the callosal axons by a significant amount. By far the most obvious similarity between cortex and cerebellum, however, is that they are both topologically sheet-like in structure. They are broad and wide in the two-dimensional plane of the pial membrane with a relatively modest thickness in the radial dimension. The question for this chapter then is whether these similarities, in particular the sheet-like organization are coincidental or indicative of larger themes that play deeper roles in the development and function of these two seemingly disparate brain regions.

Animals↗
PubMed2000

Variability in the phenotypic expression of fryns syndrome: A report of two sibships.

We report on two sibships with four fetuses of 12, 15, 17, and 20 weeks of gestation, respectively, and 1 preterm baby of 31 weeks of gestation affected by a multiple congenital disorder with manifestation suggestive of Fryns syndrome. In addition to the characteristic malformation pattern in Fryns syndrome, they presented with fetal hydrops, cystic hygroma, and multiple pterygias, allowing prenatal ultrasound diagnosis as early as in the 11th week of gestation. The two affected fetuses of family 1 showed severe craniofacial anomalies with bilateral cleft lip and palate, acral hypoplasia, postaxial oligodactyly, persistent truncus arteriosus, and interrupted aortic arch, asplenia sequence, and complex central nervous system midline malformations. In family 2 with three affected sibs, ear anomalies with atresia of the auditory canals, postaxial hexadactyly, intestinal atresias, callosal defects, and eye colobomas were the most outstanding features. On the basis of the present findings and former reports, the inter- and intrafamiliar phenotypic variability in Fryns syndrome, possible pathogenetic mechanisms, and the value of prenatal diagnosis are discussed. In the pathogenetic discussion, a special emphasis is put on the neural crest cell developmental field.

Abnormalities, Multiple↗
PubMed2000

Macaque monkey retrosplenial cortex: I. three-dimensional and cytoarchitectonic organization.

This is the first in a series of reports on the neuroanatomic organization and connectivity of the macaque monkey retrosplenial cortex, i.e., areas 29 and 30. To elucidate the topographic configuration of the retrosplenial cortex and adjacent structures, we have made three-dimensional computer reconstructions of the posterior cingulate region that includes the retrosplenial cortex. The largest portion of the posterior cingulate gyrus is located dorsal to the corpus callosum. At the caudal limit of the corpus callosum, the gyrus curves around the splenium, turns laterally and forms a region called the isthmus that links the cingulate and parahippocampal gyri. The isthmus contains the caudomedial lobule, which is a rostrally oriented bulge that is made up, in part, of portions of the retrosplenial cortex. To delineate the subdivisions of the retrosplenial and adjacent cortices, we conducted a cytoarchitectonic analysis by using cerebral hemispheres that were cut at oblique angles and stained with a variety of techniques, including immunohistochemistry for nonphosphorylated neurofilament protein. The dorsal bank of the callosal sulcus and the rostral surface of the isthmus are covered by the retrosplenial cortical areas 29l, 29m, and 30, whereas most of the medial surface of the posterior cingulate gyrus and the ventral bank of the posterior cingulate sulcus consist of areas 23i and 23e. The most caudoventral portion of the cingulate gyrus is composed of an area (area 23v) that resembles the retrosplenial and posterior cingulate cortices but has a much more prominent layer IV. On the dorsal bank of the calcarine sulcus, we also defined a transitional zone, area 30v, located between the retrosplenial cortex and the prestriate visual cortex.

Animals↗
PubMed1982

The neuropsychology of development hemispheric laterality, limbic language, and the origin of thought.

Discussed evidence and assumptions that concern hemispheric laterality and asymmetrical functional representation. It is hypothesized that the asymmetrical linguistic-motor vs. sensory-spatial-affective representation of function may be a result of differential rates of cortical, subcortical and spinal motor-sensory maturation. Evidence with regard to embryological and early postnatal neurological development is reviewed. It is argued that motor areas mature before sensory and that the left hemisphere develops prior to the right, such that the left hemisphere gains a competitive advantage in the acquisition of motor representation, whereas the later maturing right has an advantage in the establishment of sensory-affective synaptic representation, including that of limbic mediation. The influences of these differing maturational events on cognitive and psychic functioning are examined, particularly with regard to limbic influences on the development of language, thought, and mental imagery, and the effects of early emotional experience on later behavior. Thinking is viewed in part as a left hemisphere internalization of egocentric language, the internalization of which corresponds to the increasing maturation of intra-cortical and subcortical structures and fiber pathways, and the myelination of the callosal connections that subserve information transfer between the hemispheres. It is argued that thought is a means of organizing, interpreting, and explaining impulses that arise in the non-linguistic portions of the nervous system so that the language dependent regions may achieve understanding. In addition, the neurodynamics and mechanisms involved in the mislabeling, misinterpretation, and inhibition of impulses, desires, and emotional expression are discussed in relation to disturbances in psychic functioning.

Adolescent↗
PubMed1987

Remodelling of early axonal projections through the selective elimination of neurons and long axon collaterals.

Studies using neuroanatomical techniques have shown that the connections characteristic of the mature vertebrate brain are brought about by a considerable refinement of the projections initially established during development. The selective loss of neurons and long axon collaterals plays a major role in this remodeling process as illustrated in the development of the retina and cortex of the rat. In the retina, two-thirds of the initial population of ganglion cells (RGCs) die early. This loss serves to remove selectively RGCs that make erroneous axonal projections, including those which project to an incorrect target, to an inappropriate part of a correct target, or to the wrong side of the brain. Studies using the sodium channel blocker, tetrodotoxin, suggest that in rats the selective elimination of erroneously projecting RGCs is based, in part, on patterns of impulse activity. In the cortex a different mechanism is illustrated. All neocortical areas initially give rise to callosal and pyramidal tract axons but through a process of selective collateral elimination not involving cell death these projections assume the limited distributions seen in adult rats. Manipulations resulting in the maintenance of such long collaterals suggest that their removal is functionally and locally determined. In contrast to error elimination, this phenomenon of collateral elimination may be a developmental strategy for generating connectional diversity while limiting the amount of information required for the regional specification of the cortex.

Animals↗
PubMed1990

Compounds from plants that regulate or participate in disease resistance.

Disease resistance is multifactorial. The response phase includes: synthesis of phytoalexins, i.e. low molecular weight antimicrobial compounds which accumulate at sites of infection; systemically produced enzymes which degrade pathogens, e.g. chitinases, beta-1,3-glucanases and proteases; systemically produced enzymes which generate antimicrobial compounds and protective biopolymers, e.g. peroxidases and phenoloxidases; biopolymers which restrict the spread of pathogens, e.g. hydroxyproline-rich glycoproteins, lignin, callose; and compounds which regulate the induction and/or activity of the defence compounds, e.g. elicitors of plant and microbial origin, immunity signals from immunized plants and compounds which release immunity signals. Disease resistance in plants is not determined by the presence or absence of genes for resistance mechanisms, it is determined by the speed and degree of gene expression and the activity of the gene products. It is likely, therefore, that all plants have the genetic potential for resistance. This potential can be expressed systemically (immunization) after restricted inoculation with pathogens, attenuated pathogens or selected non-pathogens, or treatment with chemical substances that are produced by immunized plants or chemicals which release such signals. Immunization is effective against diseases caused by fungi, bacteria and viruses, and it has been successfully tested in the laboratory and field. Advances in science have provided information and technology to enhance resistance to plant pests. Pesticides are part of this technology, but they also contribute to a complex world problem which threatens our environment and hence our survival. The future will see the restriction of pesticide use and a greater reliance on resistant plants generated using immunization and other biological control technologies, genetic engineering and classical plant breeding. However, as with past and current technology, we will have created unique problems. The survival of our planet depends upon anticipating these problems and meeting the challenge of their solution.

Breeding↗
PubMed1984

Phytoalexins and disease resistance mechanisms from a perspective of evolution and adaptation.

Plants respond to cellular injury and infection by accumulating low molecular weight antimicrobial stress metabolites called phytoalexins. The accumulation of phytoalexins, together with lignification, suberization, callose formation and the production of agglutinins and inhibitors of extracellular microbial hydrolases, appears to be part of a multi-component response mechanism associated with disease resistance and wound repair. Compared to the antibody-antigen response in animals, the phytoalexin response in plants has low specificity for induction and activity of the phytoalexins. Plants also contain preformed antimicrobial chemical and physical barriers to infection in their external tissues. The successful pathogen has evolved to cope with preformed inhibitors and barriers and either avoids eliciting the response mechanism, or suppresses the mechanism, or detoxifies its antimicrobial components. Annual plants can be systemically immunized against diseases caused by viruses, bacteria and fungi by limited infection with any one of the respective organisms. As with animals, disease resistance in plants depends on the rate and magnitude of response rather than on the ability to respond. The genetic information for disease resistance is found in all organisms, and disease resistance is the rule in nature. The interactions of plants with microorganisms in their environment are nature's example of diplomacy--compromise, adjustment to change and avoidance of deadly conflict.

Adaptation, Biological↗
PubMed1992

CNS midline anomalies in the Opitz G/BBB syndrome: report on 12 Brazilian patients.

We report on 12 Brazilian boys with the Optiz G/BBB syndrome associated with CNS midline anomalies, namely, Dandy-Walker anomaly (two patients), enlarged cisterna magna (four patients), enlarged 4th ventricle (four patients), and callosal a/hypoplasia (two patients). These signs clearly show the involvement of the CNS midline in the Opitz G/BBB syndrome.

Abnormalities, Multiple↗
PubMed1992

Acrocallosal syndrome: report of a Brazilian girl.

We report on a Brazilian girl born to nonconsanguineous parents and presenting with frontonasal dysostosis, callosal agenesis, abnormal upper lids, cleft lip/palate, redundant skin in the neck, grooved chin, and bifid thumbs. Major diagnostic criteria present in this patient are related to the acrocallosal syndrome. The clinical and major nosologic aspects of this condition are discussed.

Agenesis of Corpus Callosum↗