Cerebrospinal fluid reconstitution via a perfusion-based cadaveric model: feasibility study demonstrating surgical simulation of neuroendoscopic procedures.

Cadaveric surgical simulation carries the advantage of realistic anatomy and haptic feedback but has been historically difficult to model for intraventricular approaches given the need for active flow of CSF. This feasibility study was designed to simulate intraventricular neuroendoscopic approaches and techniques by reconstituting natural CSF flow in a cadaveric model. In 10 fresh human cadavers, a simple cervical laminectomy and dural opening were made, and a 12-gauge arterial catheter was introduced. Saline was continuously perfused at physiological CSF pressures to reconstitute the subarachnoid space and ventricles. A neuroendoscope was subsequently inserted via a standard right frontal bur hole. In 8 of the 10 cadavers, adequate reconstitution and endoscopic access of the lateral and third ventricles were achieved. In 2 cadavers, ventricular access was not feasible, perhaps because of a small ventricle size and/or deteriorated tissue quality. In all 8 cadavers with successful CSF flow reconstitution and endoscopic access, identifying the foramen of Monro was possible, as was performing septum pellucidotomy and endoscopic third ventriculostomy. Furthermore, navigation of the cerebral aqueduct, fourth ventricle, prepontine cistern, and suprasellar cistern via the lamina terminalis was possible, providing a complementary educational paradigm for resident education that cannot typically be performed in live surgery. Surgical simulation plays a critical and increasingly prominent role in surgical education, particularly for techniques with steep learning curves including intraventricular neuroendoscopic procedures. This novel model provides feasible and realistic surgical simulation of neuroendoscopic intraventricular procedures and approaches.

An anatomic review of thalamolimbic fiber tractography: ultra-high resolution direct visualization of thalamolimbic fibers anterior thalamic radiation, superolateral and inferomedial medial forebrain bundles, and newly identified septum pellucidum tract.

BACKGROUND: Images obtained through ultra-high-field 7.0-tesla magnetic resonance imaging with track-density imaging provide clear, high-resolution tractograms that have been hitherto unavailable, especially in deep brain areas such as the limbic and thalamic regions. This study is a largely pictorial description of the deep fiber tracts in the brain using track-density images obtained with 7.0-T diffusion-weighted imaging. METHODS: To identify the fiber tracts, we selected 3 sets of tractograms and performed interaxis correlation between them. These tractograms offered an opportunity to extract new information in areas that have previously been difficult to examine using either in vivo or in vitro human brain tractography. RESULTS: With this new technique, we identified 4 fiber tracts that have not previously been directly visualized in vivo: septum pellucidum tract, anterior thalamic radiation, superolateral medial forebrain bundle, and inferomedial forebrain bundle. CONCLUSIONS: We present the high-resolution images as a tool for researchers and clinicians working with neurodegenerative and psychiatric diseases, such as Parkinson disease, Alzheimer disease, and depression, in which the accurate positioning of deep brain stimulation is essential for precise targeting of nuclei and fiber tracts.

[Morphometric characterization of median brain structures using intravital magnetic resonance tomography]. / Morfometricheskaia kharakteristika sredinnykh struktur golovnogo mozga po dannym prizhiznennoi magnito-rezonansnoi tomografii.

Linear parameters of corpus callosum and submucosal structures (transparent septum, cupula, thalamus, pineal body and the third ventricle choroid plexus) were measured using 80 MR tomograms and 40 craniograms of 20 patients aged 20-50. Linear parameters were compared with the cranium shape and statistically processed. The dependence of linear parameters of the structures mentioned upon the shape of the cranium was demonstrated. They were characterized morphometrically in dolychomeso- and brachiocephals. The data obtained are of interest in assessment of MR tomograms with pathological changes and individualization of surgical interventions in median structures of brain.

Projections of the ventral premammillary nucleus.

The projections of the ventral premammillary nucleus (PMv) have been examined with the Phaseolus vulgaris leucoagglutinin (PHAL) method in adult male rats. The results indicate that the nucleus gives rise to two major ascending pathways and a smaller descending pathway. One large ascending pathway terminates densely in most regions of the periventricular zone of the hypothalamus, with the notable exception of the suprachiasmatic, suprachiasmatic preoptic, and median preoptic nuclei. This pathway is in a position to influence directly many cell groups known to regulate anterior pituitary function. The second large pathway ascends through the medial zone of the hypothalamus and densely innervates the ventrolateral part of the ventromedial nucleus and adjacent basal parts of the lateral hypothalamic area, medial preoptic nucleus, principal nucleus of the bed nuclei of the stria terminalis, ventral lateral septal nucleus, posterodorsal part of the medial nucleus of the amygdala, posterior nucleus, and immediately adjacent regions of the posterior cortical nucleus of the amygdala. It is already known that these regions are major components of the sexually dimorphic circuit, and, interestingly, that they provide the major neural inputs to the PMv. The smaller descending projection from the PMv seems to innervate preferentially the posterior hypothalamic nucleus, although a small number of fibers appear to end in the tuberomammillary nucleus, supramammillary nucleus, specific regions of the medial mammillary nucleus, interfascicular nucleus, interpeduncular nucleus, periaqueductal gray, dorsal nucleus of the raphe, laterodorsal tegmental nucleus, Barrington's nucleus, and locus coeruleus. Relatively sparse terminal fields associated with ascending fibers were also observed in the dorsomedial nucleus of the hypothalamus; in the nucleus reuniens, parataenial nucleus, paraventricular nucleus of the thalamus, and mediodorsal nucleus; in the central nucleus of the amygdala, anterodorsal part of the medial nucleus of the amygdala, posterior part of the basomedial nucleus of the amygdala; and in the ventral subiculum and adjacent parts of hippocampal field CA1, and the infralimbic and prelimbic areas of the medial prefrontal cortex. Taken as a whole, the evidence suggests that the PMv receives two major inputs--one from the sexually dimorphic circuit, and the other from the blood in the form of gonadal steroid hormones--and gives rise to two major outputs: one (perhaps feed-forward) to the neuroendocrine (periventricular) zone of the hypothalamus, and the other (perhaps feed-back) to the sexually dimorphic circuit.

Projections of the ventral subiculum to the amygdala, septum, and hypothalamus: a PHAL anterograde tract-tracing study in the rat.

The projections of the ventral subiculum are organized differentially along the dorsoventral (or septotemporal) axis of this cortical field, with more ventral regions playing a particularly important role in hippocampal communication with the amygdala, bed nuclei of the stria terminalis (BST), and rostral hypothalamus. In the present study we re-examined the projection of the ventral subiculum to these regions with the Phaseolus vulgaris leucoagglutinin (PHAL) method in the rat. The results confirm and extend earlier conclusions based primarily on the autoradiographic method. Projections from the ventral subiculum course either obliquely through the angular bundle to innervate the amygdala and adjacent parts of the temporal lobe, or follow the alveus and fimbria to the precommissural fornix and medial corticohypothalamic tract. The major amygdalar terminal field is centered in the posterior basomedial nucleus, while other structures that appear to be innervated include the piriformamygdaloid area, the posterior basolateral, posterior cortical, posterior, central, medial, and intercalated nuclei, and the nucleus of the lateral olfactory tract. Projections from the ventral subiculum reach the BST mainly by way of the precommissural fornix, and provide rather dense inputs to the anterodorsal area as well as the transverse and interfascicular nuclei. The medial corticohypothalamic tract is the main route taken by fibers from the ventral subiculum to the hypothalamus, where they innervate the medial preoptic area, "shell" of the ventromedial nucleus, dorsomedial nucleus, ventral premammillary nucleus, and cell-poor zone around the medial mammillary nucleus. We also observed a rather dense terminal field just dorsal to the suprachiasmatic nucleus that extends dorsally and caudally to fill the subparaventricular zone along the medial border of the anterior hypothalamic nucleus and ventrolateral border of the paraventricular nucleus. The general pattern of outputs to the hypothalamus and septum is strikingly similar for the ventral subiculum and suprachiasmatic nucleus, the endogenous circadian rhythm generator.

Efferent connections of the dorsal cortex of the lizard Gekko gecko studied with Phaseolus vulgaris-leucoagglutinin.

The efferent connections from the dorsal cortex of the lizard Gekko gecko have been studied with the anterograde tracer Phaseolus vulgaris-leucoagglutinin. It appeared that the dorsal cortex is not a homogeneous structure as far as the efferent connections are concerned. All parts of the dorsal cortex project to the septum. All parts except the most medial project to the dorsal ventricular ridge, amygdala, nucleus periventricularis hypothalami, area lateralis hypothalami, and the anterior olfactory nucleus. The most medial part, in addition to the septal projections, is connected with the medial cortex and the contralateral medial and dorsal cortices. From the rostral part additional projections could be traced to the nucleus dorsolateralis hypothalami, nucleus ventromedialis thalami, nucleus dorsolateralis thalami, striatum, pallial thickening, medial cortex, nucleus olfactorius anterior, and the main and accessory olfactory bulbs. From the caudal part additional projections exist to the nucleus dorsomedialis thalami, nucleus accumbens, and the contralateral dorsal cortex. A system of intrinsic connections exists that can be subdivided into four subsystems, each of which subserves the interconnections within four subdivisions of the cortex: 1) the superficial medial part, 2) the deep medial part, 3) the caudal lateral and caudal intermediate parts, and 4) the rostral lateral and rostral intermediate parts. Connections between these four areas are scarce. From the present results the conclusion is drawn that the dorsal cortex of the lizard Gekko gecko has many hodological aspects in common with the ventral subiculum of mammals. The present results do not support the hypothesis that the dorsal cortex is the reptilian equivalent of the mammalian neocortex.

[Afferent connections of the basolateral division of the amygdaloid complex of the cat brain]. / Afferentnye sviazi bazolateral'nogo otdela mindalevidnogo kompleksa mozga koshki.

Injection of horseradish peroxidase into the basal macrocellular and lateral nuclei of the amygdaloid complex (BLAC) in the cat brain has revealed their rich thalamic afferentation. On the BLAC there are massive projections of: a) nuclei of the middle line of the precommissural pole of the dorsal thalamus (anterior parts of the paratenial, interanteromedial and reunial nuclei), as well as the whole anterior paraventricular nucleus, medial part of the ventral posteromedial nucleus; b) postcommissural nuclei of the dorsal thalamus; some "nonacustical" nuclei of the internal geniculate body (ventrolateral nucleus, medial and macrocellular parts and the most caudal end of the internal geniculate body). Rather essential are projections of the "posterior group nuclei", those of the suprageniculate nucleus, of some parts of the ventral thalamus (subparafascicular nucleus, marginal and peripeduncular nuclei) and parabrachial nucleus. Scattered single projections are obtained from all hypothalamic parts (most of all the ventromedial nucleus), reticular nuclei of the septum, substantia innominata, substantia nigra, truncal nuclei of the raphe. Variety of the dorsal thalamic nuclei, sending their fibers to the BLAC reflects variety of sensory information, that gets here, according to its modality, degree of its differentiation and integrity. A number of the dorsal thalamus nuclei, owing to abundance of labelled neurons, can be considered as special relay thalamic nuclei for the BLAC resembling corresponding relay nuclei for the new cortex.

Efferent projections of the interpeduncular complex in the rat, with special reference to its subnuclei: a retrograde horseradish peroxidase study.

Projections of the subnuclei of the interpeduncular complex were studied by the retrograde horseradish peroxidase technique in the rat. The pars caudalis and pars dorsalis magnocellularis project to the septum, hippocampus and entorhinal cortex; a part of the pars medialis and the pars paramediana, to the dorsal thalamus; all subnuclei, to the midbrain raphe; and the pars lateralis, to the dorsal tegmental nucleus.

Cells of origin of the ventral cholinergic septohippocampal pathway undergoing compensatory collateral sprouting following fimbria-fornix transection.

The axons of the septohippocampal pathway reach the hippocampal formation via the fimbria, dorsal fornix and supracallosal striae. Complete lesions of these pathways denervate most of the hippocampal formation but a small, residual innervation occurs via a different ventral route. The cells of origin for this additional route for cholinergic innervation of the hippocampal formation have been identified in the present study with a combined technique using a fluorescent retrograde tracer and acetylcholinesterase histochemistry. These cells were localized to the diagonal band of Broca. In a subsequent experiment it was demonstrated, by destroying these cells unilaterally, that they were responsible to a large extent for the cholinergic compensatory collateral sprouting in the hippocampus that has previously been shown to develop following complete fimbria-fornix transection.

Origins of substance P-containing fibers in the lateral septal area of young rats: immunohistochemical analysis of experimental manipulations.

The majority of substance P-like immunoreactive (SPLI) fibers in the lateral septal area (LS) are supplied by SPLI cells in the area (BAL) between the anterior hypothalamic nucleus and the lateral hypothalamus, and by those in the nucleus latero-dorsalis tegmenti (TLD). These conclusions are based on following: (1) Unilateral destruction of the BAL resulted in an ipsilateral decrease in the septal SPLI fibers similar to that seen after the destruction of the TLD, and (2) simultaneous destruction of the BAL and TLD caused a marked reduction of SPLI fibers in the LS on the operated side. The possibility that the destruction of the BAL affected the ascending SPLI system from the TLD seems to be excluded, because (1) the destruction of the TLD resulted in a decrease in SPLI fibers in the ipsilateral medial forebrain bundle (MFB), but failed to reduce the number of SPLI fibers in the BAL, and (2) the destruction of the BAL caused a decrease in SPLI fibers in the perifornical area rostral to the lesion, but failed to reduce the number of SPLI fibers in the MFB. These facts further suggest that ascending SPLI fibers from the BAL travel in the perifornical area and those from the TLD pass through the MFB. It should be noted that a few SPLI fibers remained intact following the simultaneous destruction of the BAL and TLD. The present study suggests that these remaining SPLI fibers might be innervated by intrinsic SPLI cells. In support of this, several SPLI cells were detected in the septal area after colchicine pretreatment.

Evidence for the existence of an enkephalin-containing pathway from the area just ventrolateral to the anterior hypothalamic nucleus to the lateral septal area of the rat.

The afferent source of enkephalin-like immunoreactive (ELI) fibers in the lateral septal area of the rat was elucidated experimentally by means of an indirect immunofluorescence technique. These ELI fibers had almost completely disappeared on the operated side after the destruction of the area just ventrolateral to the anterior hypothalamic nucleus, where a number of ELI cells was detected. This fact strongly suggests that these ELI cells project ipsilaterally to the lateral septal area.

Afferent connections to the bed nucleus of the stria terminalis.

A systematic analysis of the distribution of cells containing horseradish peroxidase (HRP) end-product following HRP injections in the bed nucleus of the stria terminalis (BNST) revealed a topographic distribution of input from the amygdala. The appearance of HRP cells in the medial amygdaloid nucleus was associated with HRP injections in all parts of the amygdala except its most lateral portion. Injections of HRP confined to the anterolateral portion of the BNST resulted in extensive HRP labeling of cells in the basolateral amygdala, the central nucleus, and the amygdala hippocampal area. Labeling of the amygdala hippocampal area was also associated with HRP injections in the caudodorsal BNST or the supracommissural portion of the stria terminalis. Injections that labeled the commissural division of the stria terminalis produced labeling of cells in the anterior basolateral amygdala and in the nucleus of the lateral olfactory tract. The cortical and basomedial amygdaloid nuclei appear to project only weakly to the BNST. Several other regions that provide afferents to the BNST are described although their input is minor relative to that of the amygdala.

Efferent projections of the septum in the Tegu lizard, Tupinambis nigropunctatus.

A H3 proline or H3 leucine mixture was injected into the septal region of the Tegu lizard in order to determine its efferent projections. The brains were processed according to standard autoradiographic technique and counterstained with cresyl violet. Septal projections were limited to either telencephalic or diencephalic areas. Intratelencephalic projections consisted of efferents to medial pallium, nucleus accumbens, bed nucleus of the anterior commissure, preoptic area and septum itself. Fibers entering the diencephalon projected to medial habenular nucleus, dorsomedial thalamic nucleus, dorsolateral thalamic area, periventricular nucleus of the hypothalamus, lateral hypothalamic area and mammillary nucleus. The results are discussed in relation to the efferent projections of the septum in other vertebrates.

Habenular projections in the monitor lizard (Varanus benegalensis).

The efferent connections of the medial (MHb) and the lateral (LHb) habenular nuclei in the monitor lizard were studied using experimental degeneration techniques. The MHb was found to project to the interpeduncular nucleus and the parvocellular nucleus of the superior raphe via the core portion of the habenulo-peduncular tract (HPT). The LHb fibers form the mantle portion of the HPT and curve laterally to collect again in the ventral tegmentum. From here, they follow either (1) the medial forebrain bundle to terminate in hypothalamus, ventromedial thalamus, preoptic area, and septum, or (2) they continue caudally to terminate in the superior raphe and paramedian reticular formation or (3) they decussate and follow in smaller numbers the ascending and descending pathways on the other side. Some fibers enter the midline and reach the periventricular zone of the midbrain. Short range projections exist to the dorsomedial thalamic nucleus and the paramedian central gray and pretectum. The habenular projections are bilateral, however, much smaller on the contralateral side. Although distinct terminal fields were not found in the substantia nigra and the central gray of the isthmic region, the overall pattern of habenular pathways is strikingly similar to those found in mammals which confirms a long presumed phylogenetic stability of habenular connections.U

Chemoarchitectonics of the forebrain of the hagfish, Eptatretus burgeri.

The brain of the hagfish, Eptatretus burgeri, was investigated by enzyme histochemical methods to locate roughly the areas which have somatic, visceral, and correlative functions. From the results of previous investigations, it seems that, as a rule, AChE is found in the correlation areas and in a part of the visceral and somatic areas, whereas SDH and MAO are detected in the somatic and visceral areas, respectively. Therefore, the activities of these three enzymes can be used to indicate the functional areas. In addition, G6PD is used to detect areas related to the pentose cycle. Areas with remarkable AChE activity are layer 4 (neuropil), layer 3 (perikarya), layer 5 (perikarya and neuropil), the primordium hippocampi of Jansen (neuropil and a small number of perikarya), the median sagittal lamina of the habenula (neuropil and perikarya), some cells in the pars dorsalis thalami of Jansen (neuropil), the nucleus tuberculi posterior of Jansen (neuropil), and the hypophysis. Activity of SDH, MAO, and G6PD appears in the neuropil. Regions showing activity of both SDH and MAO are the olfactory nerves and glomeruli, the septal area, layer 1 and 4 including the neostriatum of Crosby and Schnitzlein, the primordium hippocampi of Jansen, the preotic area, the habenula, and the caudal part of the medial hypothalamus, this last being the circumference of the hypothalamic ventricle. Furthermore, the anterior part of the amygdala of Crosby and Schnitzlein shows SDH activity. Activity of G6PD is distributed in the same regions showing activity of SDH and MAO, with the exception of the primordium hippocampi of Jansen. Finally, (1) two groups of continuous areas of AChE activity are found conspicuously in the telencephalon; one group consists of layers 3, 4, and 5, and the other consists of the ventral part of the primordium hippocampi, the lateral part of the pars ventralis thalami, and the nucleus tuberculi posterior. These two groups may play a correlative role between the visceral and somatic areas and the cholinergic mechanisms. (2) It seems that the forebrain, especially in the hypothalamus, is poorly differentiated. Furthermore, (3) a comparison with other nonmammalian brains is made from the viewpoint of the chemoarchitectonics.

Topographic organization of the projection from the forebrain subcortical areas to the hippocampal formation of the rat.

Using the technique of iontophoretic microinjection of horseradish peroxidase, the present study disclosed the complexity and high degree of the topographic organization in the forebrain subcortical afferents to the different regions of rat hippocampus, e.g. diagonal band, posterior (PH), dorsomedial and rostral lateral hypothalamic nuclei chiefly project to the rostrodorsal part (DRA) and caudal gyrus dentatus including CA3, the supramammillary area predominantly to the rostroventral area (VRA), the area lateral to PH to the DRA and VRA, substantia innominata and some thalamic nuclei (n. reuniens, n. lateralis thalami, n. anterior ventralis and n. lateralis thalami pars posterior) to the dorsal subiculum, respectively.