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PubMed1990

[A new approach to the quantitative analysis of the vascular architecture and its application to the cerebral cortex of the reeler mouse].

(1) A new method for morphometric studies on the vascular architecture of the mouse brain was developed. The method was as follows: the cerebral vascular images of the arteries, capillaries and veins, which were visualized by injection with gelatinized India-ink, were entirely entered into a personal computer system from a digitizer through light-microscopic photographs (X250). Thus the vessels were transformed into consecutive lines composed of short straight "line segments". The parameters obtained from these "line segments" were the total vascular length per unit area and volume ("length density"), the direction of the "orientation axis" and the "intensity of orientation" of the blood vessels. The three-dimensional properties of the vascular vessels were calculated from these data. The frontal and sagittal vascular patterns of the occipital cortex, thalamus, hippocampus, piriform cortex, internal capsule and corpus callosum were entered and the parameters described above were calculated. The calculated three-dimensional "length densities" of the blood vessels in the occipital cortex and thalamus were about twice as great as those of the corpus callosum and internal capsule, and those of the hippocampus and piriform cortex had intermediate values. The "orientation axis" of the occipital cortex was approximately perpendicular to the cerebral surface, while those of the corpus callosum and internal capsule were parallel to the course of the nerve fibers. The axis of the thalamus was parallel to the horizontal plane, and that of the hippocampus was perpendicular to its surface. The "intensity of orientation" of the piriform cortex, however, was very small. (2) In order to investigate the factors defining the vascular pattern in the cerebral cortex, the reeler mutant mouse, in which the lamination of the cortex is reversed and the neurons distributed more homogeneously than in normal mice, was investigated by the above-mentioned method. The vascular pattern of the reeler mutant mouse revealed a difference from that of the normal mouse in that the "length density" of the reeler mouse was apparently equal in different layers, and the degree of vascular orientation was not as intensive as that of the normal cortex, in which the blood vessels tended to be perpendicular to the pial surface.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed2002

Prenatal development of neural excitation in rat thalamocortical projections studied by optical recording.

To elucidate the formation of early thalamocortical synapses we recorded optical images with voltage-sensitive dyes from the cerebral cortex of prenatal rats by selective thalamic stimulation of thalamocortical slice preparations. At embryonic day (E) 17, thalamic stimulation elicited excitation that rapidly propagated through the internal capsule to the cortex. These responses lasted less than 15 ms, and were not affected by the application of glutamate receptor antagonists, suggesting that they might reflect presynaptic fiber responses. At E18, long-lasting (more than 300 ms) responses appeared in the internal capsule and in subplate. By E19, long-lasting responses increased in the cortical subplate. By E21, shortly before birth, the deep cortical layers were also activated in addition to the subplate. These long-lasting responses seen in the internal capsule and subplate were blocked by the antagonist perfusion, but the first spike-like responses still remained. The laminar location of the responses was confirmed in the same slices by Nissl staining and subplate cells were labeled by birthdating with bromodeoxyuridine at E13. Our results demonstrate that there is a few days delay between the arrival of thalamocortical axons at the subplate at E16 and the appearance of functional thalamocortical synaptic transmission at E19. Since thalamocortical connections are already functional within the subplate and in the deep cortical plate at embryonic ages, prenatal thalamocortical synaptic connections could influence cortical circuit formation before birth.

Action Potentials↗

PubMed1994

Late local and remote structural changes after capsulotomy for obsessive compulsive disorder.

Stereotactic subcaudate capsulotomy (SC) is used to treat medically intractable obsessive compulsive disorders (OCD). Although clinical improvement has been observed, post-SC structural correlates are lacking in this biological disorder. Our study provides imaging evidence for local and distant alterations in structures which may have an important role in the manifestations of OCD. Five OCD patients treated with SC received MR imaging for pre-SC planning, early (1-7 days) post-SC assessment, and late (5-12 months) follow-up. The volumes of the anterior limb of the internal capsules, caudate heads, third ventricle, mamillary bodies, thalami, and hippocampal formations were digitally computed. Volumes from each of the serial imaging studies were compared. At 5-12 months post-SC, all patients showed reduction in volume of the anterior limbs of the internal capsules, caudate heads, thalami, and increased volume of the third ventricle (reflecting thalamic/caudate atrophy). 2-5 patients showed reduction in hippocampal formation volume. The post-SC reduction in volume of these structures, some far distant to the stereotactic lesion, suggests that the interrelationships of the anterior limb of the internal capsule, the caudate/thalamic nuclei, and possibly the pallidal and limbic systems are necessary for the manifestations of OCD and their variants.

Brain↗

PubMed1989

Three variant forms of subcortical aphasia in Chinese stroke patients.

Five right-handed patients with subcortical aphasia that involved the left hemisphere subcortical lesion sites were subjected to CT scans. Given their etiology, two cases were infarctions and the other three were hemorrhages. Two of the patients presented an involvement of the anterior limb of the internal capsule and of the basal ganglia and an anterior superior white-matter lesion extension. In both cases slow scanty dysarthric speech was noted; one had markedly impaired auditory comprehension, and the others were only partially impaired. The third patient presented an involvement of the posterior limb of the internal capsule and of the thalamus and a posterior paraventricular white-matter lesion extension. He had poor auditory comprehension, echolalia, and fluent speech. The last two patients presented an involvement of the internal capsule, the basal ganglia, and the thalamus and an anterior posterior paraventricular white-matter lesion extension. The latter two showed poor auditory comprehension with nonfluent and scanty spontaneous speech. The speech sounds were nonsensical monosyllabic words with a pattern similar to that of global aphasia. All patients had lasting right hemiplegia.

Aged↗

PubMed1990

Fetal striatal neurons grafted into the ibotenate lesioned adult striatum: efferent projections and synaptic contacts in the host globus pallidus.

The efferent projections to the host brain from intrastriatal grafts have been examined at the ultrastructural level. Cell suspensions of E14 rat fetal striatal tissue were implanted into the ibotenic acid lesioned caudate-putamen of adult rats. After survival times of at least five months, the anterograde neuronal tracer Phaseolus vulgaris leucoagglutinin was injected into the grafts. Consistent with our previous light microscopical analysis, anterogradely labelled fibres could be followed from the grafts into the host globus pallidus along the normal trajectory of the striatopallidal pathway in the internal capsule, and a few fibres also reached the entopeduncular nucleus and the substantia nigra. In the electron microscope, the graft-derived efferents were seen to be myelinated as they projected caudally along the fibre bundles of the internal capsule, and they were thus similar to the neostriatal projection in normal control animals. In the host globus pallidus, the graft-derived fibres ramified into a terminal network forming morphologically normal synaptic contacts with neuronal elements in the host globus pallidus. A total of 118 synaptic contacts were identified, all of them formed symmetric membrane specializations. The major postsynaptic targets were dendritic shafts (90%), with only a few contacts with spines or small shafts (8%) and perikarya (2%). The morphology of the synaptic contacts and their distribution on different postsynaptic targets were similar to that which was found in the globus pallidus after tracer-injections into the caudate-putamen of normal control animals. The results show that grafted fetal striatal neurons can grow along the myelinated territory of the internal capsule to reinstate a seemingly normal synaptic input to the previously denervated neurons in the host globus pallidus.

Animals↗

PubMed1986

[Evaluation of computerized tomography-guided stereotactic evacuation of putaminal hematomas by somatosensory evoked potentials].

Computerized tomography (CT) guided stereotactic evacuation of intracerebral hematomas is effective and little invasive treatment at subacute or chronic stage. Somatosensory evoked potentials (SEPs) of 23 patients with putaminal hemorrhage whose stereotactic evacuations were performed from day 4 to day 24 are studied about surgical result and CT findings. As for SEP, N20 which is thought to be generated in the thalamus or in the primary parietal area receiving direct projections from the thalamus is used for comparison with functional recovery. Among 12 patients whose N20s before the evacuation showed normal, 9 had good recovery of their hemiplegia. Motor recovery tended to begin quickly after the evacuation and the evacuation of hematomas were thought to make better result than conservative treatment. CT findings of 9 patients with good recovery revealed that the hematomas didn't invade to the internal capsule or invaded to the posterior part of the posterior limb alone. Among 3 patients whose N20s before the evacuation were not distinct and those after the evacuation were normal, 2 had good recovery of their hemiplegia. As those hematomas were relatively large but located laterally, the internal capsule was seem to be not invaded but only compressed. Among 8 patients whose N20s were not distinct both before and after the evacuation, 7 could not get the recovery of their hemiplegia. CT findings of them revealed that the hematomas were large or invaded toward the internal capsule and thalamus. From this study N20s of SEPs are thought to be useful to the decision of indication and the prediction of the functional prognosis about stereotactic evacuation of putaminal hemorrhage.

Adult↗

PubMed1992

Long distance directed axonal growth from human dopaminergic mesencephalic neuroblasts implanted along the nigrostriatal pathway in 6-hydroxydopamine lesioned adult rats.

Dissociated ventral mesencephalon of 6 to 8-week-old human embryos were implanted by stereotaxic injection at different sites along the nigrostriatal pathway in adult rats, previously subjected to a 6-hydroxydopamine lesion of the intrinsic mesotelencephalic dopamine pathways. The recipients were immunosuppressed by daily injections of cyclosporin A to prevent rejection. At 13-20 weeks after transplantation, the implanted human neurons and their associated fiber outgrowths were visualized with a species-specific antibody recognizing human, but not rat, intermediary neurofilaments (HNF). From implants placed in the host rostral mesencephalic region, HNF-positive axonal projections were seen to extend in large numbers rostrally along the medial forebrain bundle and the internal capsule, and ramify within the caudate putamen, the ventral striatum and the amygdaloid nuclei (a distance of about 5-6 mm), and more sparsely in the frontal cortex and the olfactory bulb (a distance of about 10 mm). From implants placed in the internal capsule, abundant HNF-positive axons extended in the rostral, but not caudal, direction along the myelinated fiber bundles into the caudate putamen and the ventral striatum. Tyrosine hydroxylase (TH) immunohistochemistry revealed that the vast majority of the rostrally projecting HNF-positive axons were also TH-positive, and that the graft-derived axons gave rise to dense TH-positive terminal networks, above all in large areas of the previously denervated caudate putamen. From control implants of cortical neuroblasts, axonal projections were seen along the medial forebrain bundle and the internal capsule, but the axons were TH-negative and showed only sparse projections to the striatal areas. Instead, dense projections were seen, e.g., in the frontal cortex. The results demonstrate a remarkable ability of human mesencephalic neuroblasts to extend axons along the trajectories of the nigrostriatal and mesolimbocortical pathways to reach and innervate the principal striatal and limbic target areas in the forebrain. This shows that the basic requirements for the formation of long axonal pathways may be present in the adult mammalian central nervous system (CNS) at least for certain types of projection neurons. Furthermore, it implies that the developing human neuroblasts can escape the inhibitory features known to be present along myelinated growth trajectories in the adult mammalian brain. In addition, the present approach may offer new possibilities for functional neural grafting in the rat Parkinson model, since transplanted nigral neurons placed in their natural position within the rostral mesencephalon could provide an anatomically and functionally more integrated system than the standard model with ectopically placed intrastriatal nigral grafts.

Animals↗

PubMed1998

[Effect of somatosensory disturbance to outcomes of motor function in thalamic hemorrhage: evaluation with short-latency somatosensory evoked potential (SSEP)].

We investigated the effect of the somatosensory functions to the outcomes of motor functions in 28 patients with thalamic hemorrhage. The disturbance of the pyramidal tracts was assessed by the destruction of the internal capsule found in computed tomography (CT). The disturbance of the somatosensory function was analyzed by the N20 component of short-latency somatosensory evoked potentials (SSEP). The outcomes of motor function was evaluated after 3 months of ictus. Correlations between the outcomes of motor function, disturbance of the pyramidal tract, and disturbance of the somatosensory function were discussed. The result indicated that functional outcomes statistically correlated with neither disturbance of the internal capsule alone nor disturbance of N20 alone. But, there was statistically significant between functional outcomes and the combination of disturbance of the internal capsule with disturbance of N20 (p < 0.05, Wilcoxon signed-rank). There was not statistical difference in hematoma volume or consciousness. The implications of these results suggest that somatosensory function may affect the recovery of motor functions.

Aged↗

PubMed1996

A quantitative analysis of rat central nervous system myelination using the immunohistochemical method for MBP.

The temporal order of the myelination of the nervous pathways in 0-42-day-old Wistar rats was quantitatively analyzed using immunohistochemistry with anti-myelin basic protein (MBP) antibody. Immunohistochemistry was performed on paraffin-embedded tissue according to the standard ABC technique. For the objective evaluation of myelination, we converted the level stained with the immunohistochemical method into continuous numbers of 0-256 giving the intensity of myelination, using an image analyzing system. We analyzed nine nervous pathways: corpus callosum, optic tract, internal capsule, spinal tract of trigeminal nerve, inferior cerebellar peduncle, cerebellar white matter, pyramidal tract, medial longitudinal fasciculus, and cuneate fasciculus. The onset of the myelination of the spinal tract of the trigeminal nerve, inferior cerebellar peduncle, medial longitudinal fasciculus and cuneate fasciculus was day 7 (postnatal). That of the corpus callosum, optic tract, internal capsule and cerebellar white matter was day 14, and that of the pyramidal tract was day 21. The time required to reach the level of myelination of day 42 was day 21 for the spinal tract of the trigeminal nerve and the inferior cerebellar peduncle, day 28 for the internal capsule, day 35 for the corpus callosum, optic tract, cerebellar white matter and pyramidal tract, and day 42 for the medial longitudinal fasciculus. Our method using immunohistochemistry with anti-MBP antibody provided a highly sensitive and objective criterion for judging precisely the time and the progress of myelination in each nervous pathway and compare one nervous pathway with another.

Age Factors↗

PubMed2005

Prediction of outcome in new-born infants with arterial ischaemic stroke using diffusion-weighted magnetic resonance imaging.

OBJECTIVE: The aim of this study was to assess the additional value of diffusion-weighted magnetic resonance imaging (DW-MRI) compared to conventional magnetic resonance imaging (MRI) in new-born infants with arterial ischaemic stroke, with regard to the prediction of neurodevelopmental outcome. METHODS: Neonatal DW-MRI data were available in 15 infants with a gestational age of > or = 35 weeks and repeat MRI data were obtained in 12 of the 14 survivors. T(1)- and T(2)-weighted transverse images were obtained as well as 4-mm DWI slices. ADC maps were calculated in manually selected regions on the basis of the DWI scans. All 14 survivors were seen in the follow-up clinic and 12 were > 18 months when last seen. RESULTS: T (2) hyperintensity was detected in the descending white matter tracts at the level of the internal capsule in 7 infants and in only one of these also at the level of the cerebral peduncles. Increased signal intensity (SI) was seen on DW-MRI in 8 infants in the descending white matter tract ipsilateral to the territorial infarct at the level of the internal capsule and in 5 of these also at the level of the cerebral peduncles. ADC maps were available in 12 infants. ADC values were calculated at the level of the cerebral peduncles, using the contralateral side as a reference value. A significantly reduced value was found in 3 of the 5 infants who showed an increased SI on DW-MRI. ADC maps were not available in the other two. Five of the seven infants with abnormalities on DW-MRI/ADC of the corticospinal tracts developed a mild to moderate hemiplegia, one showed an asymmetry of tone and one with only involvement of the anterior part of the internal capsule was normal at follow-up. Wallerian degeneration, seen at the level of the cerebral peduncles and/or the PLIC on the repeat MRI, was seen in the 5 infants who had shown acute changes of the corticospinal tracts in the neonatal period and who went on to develop motor sequelae. CONCLUSIONS: Compared to MRI, DW-MRI and ADC maps provided additional, quantitative data of acute corticospinal tract injury at an early time point after the insult, especially at the level of the cerebral peduncles. The presence of increased SI on DW-MRI at the level of the PLIC and the cerebral peduncles in new-born infants with arterial ischaemic stroke is followed by Wallerian degeneration and subsequent development of hemiplegia.

Brain Ischemia↗

PubMed2004

Corticospinal tract degeneration and possible pathogenesis in ALS evaluated by MR diffusion tensor imaging.

BACKGROUND: MR diffusion tensor imaging (DTI) appears to be a powerful method to investigate the neuronal and axonal fibre distribution in the human brain. Changes in diffusion characteristics of water molecules in the white matter can be estimated as the apparent diffusion coefficient (ADC) and the fractional anisotropy index (FA). OBJECTIVES: To characterize DTI changes at three different levels in the corticospinal tract (CST) (corona radiata, internal capsule and pons) in order to elucidate if pathogenesis of ALS is due to an anterograde or retrograde axonal degeneration. METHODS: We studied eight ALS patients with clinical signs of upper motor neuron involvement. The patients were compared with 11 healthy age-matched controls. RESULTS: ADC was significantly increased in the CST in ALS patients at the level of the internal capsule and also increased in the pons, but without statistical significance. ADC was unchanged at the level of the corona radiata. FA was significantly reduced at the lowest level (pons), only tended to be reduced in the internal capsule, but was also unchanged in the corona radiata. CONCLUSIONS: Segmentation of the CST into three regions supports the hypothesis of a 'dying back' mechanism in ALS and suggests that ADC is a more sensitive measure than FA to detect pathological changes in ALS.

Adult↗

PubMed1985

[Role of the lemniscal system in pain modulation--a consideration based on clinical experience].

Ten patients with intractable pain of central origin were operated on for pain relief by implanting the chronic stimulating electrode (Medtronic Co.) in the posterior limb of the internal capsule, thalamic sensory nuclei or mesencephalic lemniscus medialis, and the results were briefly described. Localization of the lesion demonstrated by CT was projected on the Schaltenbrand & Bailey's atlas in each of these patients and the deep brain structure involved was identified. The lesions were located mainly in the posterolateral thalamus including posteromedial part of the internal capsule (thalamic pain), however, they were located outside of the thalamus in some cases (suprathalamic pain). Two particular patients were described in detail because clinical courses, especially operative results were esteemed to be suggestive of an important role of lemniscal system in pain modulation. A 48-year-old man (Case 7) developed severe spontaneous burning pain on the right half of the body after extensive putaminal hemorrhage. Stimulation of the posterior limb of the internal capsule or of the thalamic sensory relay nuclei elicited no pain relief. Consequently a lesion was stereotaxically made in the most medial portion of the lemniscus medialis of the rostral mesencephalon. This operative procedure provoked previously unrecognized significant dysesthesia and hyperpathia predominantly of the extremities as well as aggravation of hypesthesia and hypalgesia. The second patient (Case 8) was a 44-year-old man who developed dysesthesia, hyperpathia and spontaneous pain of the left hand and face after hemorrhage in the right sensory cortex. Stimulation of the mesencephalic lemniscus medialis of the right side elicited comfortable warm sensation in contralateral upper half of the body including hand, fingers and face with simultaneous diminution of pain. These two cases were suggestive of the role of lemniscus medialis in pain modulation. Blockade of the lemniscus medialis elicited, and its facilitation inhibited the pain. Lemniscal and extralemniscal (spinothalamic) system have been proven to be intermingled in the thalamic and suprathalamic levels. Though both of the systems might be involved in the manifestation of central pain including our present ten cases, it was discussed and postulated that the facilitation of the lemniscal system might inhibit the activity of spinothalamic system, thus resulting in pain relief.

Adult↗

PubMed1998

A quantitative study of the progress of myelination in the rat central nervous system, using the immunohistochemical method for proteolipid protein.

The temporal changes in intensity of myelination of the nervous pathways in 0 to 42-day-old Wistar rats were quantitatively analyzed by immunohistochemistry with anti-proteolipid protein and compared with that obtained by immunohistochemistry with anti-myelin basic protein. Immunohistochemistry was performed on paraffin-embedded tissue according to the standard ABC technique. Intensity of myelination was examined by an image analyzing system. We analyzed nine nervous pathways: corpus callosum, optic tract, internal capsule, spinal tract of the trigeminal nerve, inferior cerebellar peduncle, cerebellar white matter, pyramidal tract, medial longitudinal fasciculus, and cuneate fasciculus. The presence of immunoreactive fibers for proteolipid protein (PLP) in the spinal tract of the trigeminal nerve, medial longitudinal fasciculus and cuneate fasciculus was noted on postnatal day 0. Those of the corpus callosum, inferior cerebellar peduncle, cerebellar white matter, pyramidal tract and internal capsule were noted on day 7, and that of optic tract on day 14. The time required to reach the intensity of myelination of day 42 was day 14 for the cuneate fasciculus, day 21 for the spinal tract of the trigeminal nerve, inferior cerebellar peduncle and medial longitudinal fasciculus, day 28 for the optic and pyramidal tracts, day 35 for the corpus callosum and day 42 for the internal capsule and cerebellar white matter. The appearance of immunoreactive fibers for PLP was usually earlier than that for myelin basic protein (MBP) and the pattern of difference between PLP and MBP can be classified into three groups: (1) their time of appearance and progress are almost the same, as in the optic tract; (2) the appearance and progress of PLP occurs earlier than those of MBP, as in the pyramidal tract; (3) the appearance of PLP occurs earlier than that of MBP, but their progress is the same. Our findings revealed that the time of appearance and progress of myelination as measured by PLP are different among the nervous pathways, and that there is also a difference between PLP and MBP. This difference between PLP and MBP may indicate a functional difference between them.

Age Factors↗

PubMed2006

White matter damage of patients with Alzheimer's disease correlated with the decreased cognitive function.

Increasing evidence demonstrates that there is marked damage and dysfunction in the white matter in Alzheimer's disease (AD). The present study investigates the nature of white matter damage of patients with Alzheimer's disease with diffusion tensor magnetic resonance imaging (DTI) and analyses the relationship between the white matter damage and the cognition function. DTI, as well as T1 fluid attenuated inversion recovery (FLAIR) and T2-FLAIR, was performed on probable patients of Alzheimer's disease, and sex and age matched healthy volunteers to measure the fractional anisotropy (FA) and mean diffusivity (MD) in the genu and splenium of the corpus callosum, anterior and posterior limbs of the internal capsule, and the white matter of frontal, temporal, parietal, and occipital lobes. FA was lower in the splenium of corpus callosum, as well as in the white matter of the frontal, temporal, and parietal lobes from patients with Alzheimer's disease than in the corresponding region from healthy controls and was strongly positive correlated with MMSE scores, whereas FA appeared no different in the anterior and posterior limbs of internal capsule, occipital lobes white matter, and the genu of corpus callosum between the patients and healthy controls. MD was significantly higher in the splenium of corpus callosum and parietal lobes white matter from patients than in that those from healthy controls and was strongly negative correlated with MMSE scores, whereas MD in the anterior and posterior limbs of internal capsule, as well as in frontal, temporal, occipital lobes white matter and the genu of corpus callosum, was not different between the patients and healthy controls. The most prominent alteration of FA and MD was in the splenium of corpus callosum. Our results suggested that white matter of patients with Alzheimer's disease was selectively impaired and the extent of damage had a strong correlation with the cognitive function, and that selective impairment reflected the cortico-cortical and cortico-subcortical disconnections in the pathomechanism of Alzheimer's disease. The values of FA and MD in white matter, especially in the splenium of corpus callosum in AD patients, might be a more appropriate surrogate marker for monitoring the disease progression.

Aged↗

PubMed2003

Quantitative T1 mapping of hepatic encephalopathy using magnetic resonance imaging.

Changes are shown in the spin-lattice (T1) relaxation time caused by the putative deposition of manganese in various brain regions of hepatic encephalopathy (HE) patients using a novel and fast magnetic resonance imaging (MRI) method for quantitative relaxation time mapping. A new method, T1 mapping with partial inversion recovery (TAPIR), was used to obtain a series of T1-weighted images to produce T1 maps. Imaging of 15 control subjects and 11 patients was performed on a 1.5T MRI scanner. The measurement time per patient with this technique, including adjustments, was approximately 5 minutes. Regions of interest in the globus pallidus, the caudate nucleus, the posterior and anterior limbs of the internal capsule, the putamen, the frontal and occipital white matter, the white matter of the corona radiata, the occipital visual and frontal cortices, and the thalamus were interactively defined in the left hemisphere and analyzed with respect to their T1 values. T1 changes in the brains of HE patients can be determined quantitatively with TAPIR in short, clinically relevant measurement times. Significant correlations between the change in T1 and HE severity have been shown in the globus pallidus, the caudate nucleus, and the posterior limb of the internal capsule. No significant correlation of T1 with grade of HE was found in the putamen, frontal white matter, white matter of the corona radiata, white matter in the occipital lobe, the anterior limb of the internal capsule, visual cortex, thalamus, or frontal cortex. In conclusion, these measurements show that T1 mapping is feasible in short, clinically relevant acquisition times.

Adult↗

PubMedDate not supplied

[Hemiplegia in posterior cerebral artery infarctions: analysis of various responsible mechanisms].

When cerebral infarction determines hemiplegia or hemiparesia which accompany a hemilateral sensitive deficit and hemianopsia and even neuropsychologic symptoms (aphasic alterations in the case of injury to the left hemisphere, heminegligence and anosognosy in the case of injury to the right hemisphere) the involvement of a sylvian artery syndrome is usually considered. Nonetheless, recent contributions have reported that such symptoms may appear in infarctions of the territory of the posterior cerebral artery. Two clinical-radiologic observations in this line are presented. Nuclear magnetic resonance demonstrated injury to the posterior arm of the internal capsule in one case and in the other the lesion developed over three times, in the latter of which injury to the cerebral peduncle was produced causing hemiparesia. The authors emphasize that hemiplegia or hemiparesia in some infarctions of the posterior cerebral artery may be due to 1) mesencephalic infarction in the posterior plane of the retromamillar Foix and Hillemand pediculum (or G. Lazorthes interpedunculum), 2) infarction or "ischemic penumbra" in the internal capsule by involvement of any of the perforating branches of the posterior cerebrum irrigating the thalamus, except for the medial posterior choroid artery or even of the Foix and Hillemand thalamus-tuberian pediculum (or Lazorthes inferior and anterior) which principally initiates at the posterior communicating branch with a fragment of the posterior branch of the internal capsule perhaps not always being under its control. In this case, the thrombus occupying the posterior cerebrum may extend to the cited communicating branch or a hemodynamic deficit may be produced in the territory of the same.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed1995

Experimental allergic encephalomyelitis in non-human primates: diffusion imaging of acute and chronic brain lesions.

Diffusion imaging and T2-weighted magnetic resonance imaging were performed on 16 monkeys with experimental allergic encephalomyelitis (EAE), a model of the human demyelinating disease MS. The purpose of this study was to determine whether local changes in diffusion image intensity could be correlated with the formation of acute and chronic demyelinating lesions. Diffusion image analysis was restricted to the internal capsule of the brain because of its anatomic orientation of fiber pathways. Acute inflammatory EAE lesions were large and monophasic, as visualized by T2-weighted MRI, and were accompanied by a decrease in the diffusion MR image signal with the diffusion-sensitizing gradient in all three orthogonal directions (n = 27 brain regions, P < 0.005). Chronic demyelinating lesions were preceded by multiple inflammatory attacks, as visualized by MRI, and by a decrease in diffusion MR image signal with the diffusion-sensitizing gradient in the two orthogonal directions perpendicular to the fibers of the internal capsule (n = 18 brain regions, P < 0.005). However, for the chronic group, there was no significant change in the diffusion MR image signal with diffusion-sensitizing gradient parallel to the fibers of the internal capsule at the terminal scan, suggesting little change in the water diffusion within the nerve fibers. These results suggest that diffusion imaging holds promise for measuring subtle changes in water diffusion due to different types of brain damage.

Acute Disease↗

PubMedDate not supplied

Can collagen impregnated polyester arterial prostheses be recommended as small diameter blood conduits?

A collagen impregnated graft and its parent preclotted prosthesis were implanted as thoraco-abdominal bypasses in dogs for periods ranging from 4 hr to 6 months and evaluated for their ease of handling, imperviousness, and healing behavior in terms of luminal surface thrombogenicity using labeled platelets and fibrinogen, prostacyclin (PGI2) secretion, histomorphometric determination of internal capsule thickness, and histopathologic and scanning electron microscopic studies. The collagen impregnated graft was impervious to blood and both grafts showed excellent handling characteristics. Fibrin uptake was negligible on both grafts; however, platelet uptake was higher on the collagen impregnated graft than on the control graft at 4 and 24 hr. The healing behavior of the collagen impregnated graft was also found to be different than that of the control graft between 1 and 6 months post implantation. The development of a host collagenous internal capsule at the anastomoses, and a confluent endothelial lining, was observed in both grafts at 1 month; in later implantation periods, the healing of the medial region was found to be more irregular in the collagen impregnated grafts, showing a lower mean PGI2 secretion than the preclotted control grafts. Histomorphometric analysis showed the internal capsule on the collagen impregnated grafts to be thicker than on the control grafts for most periods of implantation. The current study illustrates that the healing process of collagen impregnated grafts is delayed and that bovine collagen has a stimulating effect on tissue encapsulation. Current impregnated polyester arterial prostheses therefore cannot be recommended as small diameter blood conduits.

Animals↗