Dysphagia Post Subcortical and Supratentorial Stroke.

BACKGROUND: Studies have recognized that the damage in the subcortical and supratentorial regions may affect voluntary and involuntary aspects of the swallowing function. The current study attempted to explore the dysphagia characteristics in patients with subcortical and supratentorial stroke. METHODS: Twelve post first or second subcortical and supratentorial stroke patients were included in the study. The location of the stroke was ascertained by computed tomography and magnetic resonance imaging. The characteristics of swallowing disorder were assessed by video fluoroscopic swallowing assessment/fiberoptic endoscopic evaluation of swallowing. The following main parameters were analyzed: oral transit time, pharyngeal delay time, presence of cricopharyngeal muscle achalasia (CMA), distance of laryngeal elevation, the amounts of vallecular residue and pyriform sinus residue (PSR), and the extent of pharyngeal contraction. RESULTS: Eighty-three percent of the 12 patients were found suffering from pharyngeal dysphagia, with 50% having 50%-100% PSRs, 50% having pharyngeal delay, and 41.6% cases demonstrating CMA. Simple regression analysis showed PSRs were most strongly associated with CMA. Pharyngeal delay in the study can be caused by infarcts of basal ganglia/thalamus, infarcts of sensory tract, infarcts of swallowing motor pathways in the centrum semiovale, or a combination of the three. CONCLUSION: Subcortical and supratentorial stroke may result in pharyngeal dysphagia such as PSR and pharyngeal delay. PSR was mainly caused by CMA.

Tau pathology spread in PS19 tau transgenic mice following locus coeruleus (LC) injections of synthetic tau fibrils is determined by the LC's afferent and efferent connections.

Filamentous tau inclusions are hallmarks of Alzheimer's disease (AD) and other neurodegenerative tauopathies. An increasing number of studies implicate the cell-to-cell propagation of tau pathology in the progression of tauopathies. We recently showed (Iba et al., J Neurosci 33:1024-1037, 2013) that inoculation of preformed synthetic tau fibrils (tau PFFs) into the hippocampus of young transgenic (Tg) mice (PS19) overexpressing human P301S mutant tau induced robust tau pathology in anatomically connected brain regions including the locus coeruleus (LC). Since Braak and colleagues hypothesized that the LC is the first brain structure to develop tau lesions and since LC has widespread connections throughout the CNS, LC neurons could be the critical initiators of the stereotypical spreading of tau pathology through connectome-dependent transmission of pathological tau in AD. Here, we report that injections of tau PFFs into the LC of PS19 mice induced propagation of tau pathology to major afferents and efferents of the LC. Notably, tau pathology propagated along LC efferent projections was localized not only to axon terminals but also to neuronal perikarya, suggesting transneuronal transfer of templated tau pathology to neurons receiving LC projections. Further, brainstem neurons giving rise to major LC afferents also developed perikaryal tau pathology. Surprisingly, while tangle-bearing neurons degenerated in the LC ipsilateral to the injection site starting 6 months post-injection, no neuron loss was seen in the contralateral LC wherein tangle-bearing neurons gradually cleared tau pathology by 6-12 months post-injection. However, the spreading pattern of tau pathology observed in our LC-injected mice is different from that in AD brains since hippocampus and entorhinal cortex, which are affected in early stages of AD, were largely spared of tau inclusions in our model. Thus, while our study tested critical aspects of the Braak hypothesis of tau pathology spread, this novel mouse model provides unique opportunities to elucidate mechanisms underlying the selective vulnerability of neurons to acquire tau pathology and succumb to or resist tau-mediated neurodegeneration.

Ataxia and tremor due to lesions involving cerebellar projection pathways: a DTI tractographic study in six patients.

Focal lesions of brainstem, thalamus, and subcortical white matter may cause movement disorders that are clinically indistinguishable from cerebellar symptoms. It is suspected that ataxia in these cases is due to damage of efferent or afferent pathways of the cerebellum. However, the precise anatomical correlate often remains undefined. We used deterministic diffusion tensor magnetic resonance imaging (DTI) tractography to study the anatomical relationship between lesions causing ataxia and efferent cerebellar pathways. Study subjects were six male patients with focal lesions of different etiology (demyelination, hemorrhage, ischemia, neoplasm) outside the cerebellum. Five patients had cerebellar-like ataxia with prominent contralateral upper limb involvement. One patient with an almost midline mesencephalic lesion had a symmetrical ataxic syndrome. We used 3T MRI (Intera, Philips Medical Systems, Best, Netherlands) and DTI tractography (32 directions, StealthViz DTI, Medtronic Navigation, Louisville, USA) to delineate the dentato-rubro-thalamo-cortical tract (DRT). In all patients, tractography demonstrated focal lesions affecting the DRT in different locations. We conclude that in vivo mapping of cerebral pathways using DTI tractography in patients with focal extracerebellar brain lesions may provide direct evidence of circumscribed damage to the DRT, causing unilateral cerebellar-like ataxia. Also, a unilateral mesencephalic lesion at the level of the crossing of the DRT may cause bilateral ataxia.

MR imaging evaluation of inferior olivary nuclei: comparison of postoperative subjects with and without posterior fossa syndrome.

BACKGROUND AND PURPOSE: Posterior fossa syndrome is a severe postoperative complication occurring in up to 29% of children undergoing posterior fossa tumor resection; it is most likely caused by bilateral damage to the proximal efferent cerebellar pathways, whose fibers contribute to the Guillain-Mollaret triangle. When the triangle is disrupted, hypertrophic olivary degeneration develops. We hypothesized that MR imaging patterns of inferior olivary nucleus changes reflect patterns of damage to the proximal efferent cerebellar pathways and show association with clinical findings, in particular the presence or absence of posterior fossa syndrome. MATERIALS AND METHODS: We performed blinded, randomized longitudinal MR imaging analyses of the inferior olivary nuclei of 12 children with and 12 without posterior fossa syndrome after surgery for midline intraventricular tumor in the posterior fossa. The Fisher exact test was performed to investigate the association between posterior fossa syndrome and hypertrophic olivary degeneration on MR imaging. The sensitivity and specificity of MR imaging findings of bilateral hypertrophic olivary degeneration for posterior fossa syndrome were measured. RESULTS: Of the 12 patients with posterior fossa syndrome, 9 had bilateral inferior olivary nucleus abnormalities. The 12 patients without posterior fossa syndrome had either unilateral or no inferior olivary nucleus abnormalities. The association of posterior fossa syndrome and hypertrophic olivary degeneration was statistically significant (P < .0001). CONCLUSIONS: Hypertrophic olivary degeneration may be a surrogate imaging indicator for damage to the contralateral proximal efferent cerebellar pathway. In the appropriate clinical setting, bilateral hypertrophic olivary degeneration may be a sensitive and specific indicator of posterior fossa syndrome.

Neonatal hypoxia-ischaemia disrupts descending neural inputs to dorsal raphé nuclei.

Neuronal losses have been shown to occur in the brainstem following a neonatal hypoxic-ischaemic (HI) insult. In particular serotonergic neurons, situated in the dorsal raphé nuclei, appear to be vulnerable to HI injury. Nonetheless the mechanisms contributing to losses of serotonergic neurons in the brainstem remain to be elucidated. One possible mechanism is that disruption of neural projections from damaged forebrain areas to dorsal raphé nuclei may play a role in the demise of serotonergic neurons. To test this, postnatal day 3 (P3) rat pups underwent unilateral common carotid artery ligation followed by hypoxia (6% O2 for 30 min). On P38 a retrograde tracer, fluorescent-coupled choleratoxin b, was deposited in the dorsal raphé dorsal (DR dorsal) nucleus or the dorsal raphé ventral (DR ventral) nucleus. Compared to control animals, P3 HI animals had significant losses of retrogradely labelled neurons in the medial prefrontal cortex, preoptic area and lateral habenula after tracer deposit in the DR dorsal nucleus. On the other hand, after tracer deposit in the DR ventral nucleus, we found significant reductions in numbers of retrogradely labelled neurons in the hypothalamus, preoptic area and medial amygdala in P3 HI animals compared to controls. Since losses of descending inputs are associated with decreases in serotonergic neurons in the brainstem raphé nuclei, we propose that disruption of certain descending neural inputs from the forebrain to the DR dorsal and the DR ventral nuclei may contribute to losses of serotonergic neurons after P3 HI. It is important to delineate the phenotypes of different neuronal networks affected by neonatal HI, and the mechanisms underpinning this damage, so that interventions can be devised to target and protect axons from the harmful effects of neonatal HI.

Cutaneous magnetic stimulation reduces rat chronic pain via activation of the supra-spinal descending pathway.

Recent studies have demonstrated that magnetic stimulation (MS) can induce cellular responses such as Ca(2+) influx into the cultured neurons and glia, leading to increased intracellular phosphorylation. We have demonstrated previously that MS reduces rat neuropathic pain associated with the prevention of neuronal degeneration. Thus, we aimed to elucidate the actions of MS in relation to modulation of spinal neuron-glia and the descending inhibitory system in chronic pain. The male SD rats intrathecally implanted with catheters were subjected to sciatic nerve ligation (CCI). MS is a low power apparatus characterized by two different frequencies, 2 KHz and 83 MHz. Rats were given MS to the skin (injured sciatic nerve) for 10 min from the seventh day after CCI. The paw withdrawal latency (PWL) evoked by thermal stimuli was measured for 14 days after CCI. Immunohistochemistry for Iba-1 or GFAP was performed after 4% paraformaldehyde fixation (microscopic analysis). We employed microdialysis for measuring CSF 5-HIAA as a reflection of 5-HT release by MS stimulation. Following CCI, rats showed a decrease in PWL after CCI, and the decrease continued until the 14th day. With MS treatment, the decrease in PWL was reduced during the 10-14 day after CCI. Injection of JNK-1 inhibitors on the 14th day antagonized the analgesic effect of MS. MS also eliminated the CCI-induced decrease in GFAP immunoreactivity. Moreover, MS evoked spinal 5-HT release reflected by increase in spinal 5-HIAA level. Thus, we demonstrate that a novel magnetic stimulator used cutaneously can ameliorate chronic pain by not only preventing abnormal spinal neuron-glia interaction, but also through the activation of the supra-spinal descending inhibitory system.

Phrenic nerve stimulation: the Australian experience.

Phrenic nerve stimulation is a technique whereby a nerve stimulator provides electrical stimulation of the phrenic nerve to cause diaphragmatic contraction. The most common indications for this procedure are central alveolar hypoventilation and high quadriplegia. This paper reviews the available data on the 19 patients treated with phrenic nerve stimulation in Australia to date. Of the 19 patients, 14 required pacing due to quadriplegia, one had congenital central hypoventilation syndrome and one had brainstem encephalitis. Information was unavailable for the remaining three patients. Currently, 11 of the pacers are known to be actively implanted, with the total pacing duration ranging from 1 to 21 years (mean 13 years). Eight of the 19 patients had revision surgeries. Four of these were to replace the original I-107 system (which had a 3-5-year life expectancy) with the current I-110 system, which is expected to perform electrically for the patient's lifetime. Three patients had revisions due to mechanical failure. The remaining patients' notes were incomplete. These data suggest that phrenic nerve stimulation can be used instead of mechanical ventilators for long-term ongoing respiratory support.

Accurate reaching after active but not passive movements of the hand: evidence for forward modeling.

Converging behavioral findings support recent models of motor control suggesting that estimates of the future positions of a limb as well as the expected sensory consequences of a planned movement may be derived, in part, from efference copies of motor commands. These estimates are referred to as forward models. However, relatively little behavioral evidence has been obtained for proposed forward models that provide on-line estimates of current position. We report data from a patient (JD) who reached accurately to visualized targets with and without vision of her hand despite substantial proprioceptive loss. Additionally, we administered a double-start reaching test to examine the possibility that efference copy information could be used to estimate current limb position. JD reached accurately, without vision, to a final target after actively reaching to a landmark, but exhibited severely impaired reaching after passive movements to the landmark. This finding suggests that forward modeling of efference copy signals may provide relatively accurate estimates of current limb position for the purpose of motor planning. The possibility that such estimates may also contribute to the awareness of body position and to self-recognition is discussed.

Diaschisis after thalamic stroke: a comparison of metabolic and structural changes in a patient with amnesic syndrome.

INTRODUCTION: We present a patient with a left anteromedial thalamic lesion with an amnesic syndrome. The patient underwent neuropsychological testing, cerebrospinal fluid (CSF) analyses, magnetic resonance imaging (MRI) [T2, flair, and diffusion tensor imaging (DTI)] and [18F]-2-fluoro-deoxy-d-glucose positron emission tomography (FDG-PET) to assess indirect effects of thalamic lesions on cortical function. CASE REPORT: A 67-year-old right-handed woman was admitted to a university-based memory unit because of memory and concentration problems. Neuropsychological testing revealed dysfunction of episodic memory, semantic memory and working memory. General intellectual function and attention capacity were preserved. MRI revealed an anteromedial thalamic lesion in the left hemisphere. FDG-PET showed decreased uptake in the frontal, parietal and temporal lobes of the left hemisphere. Regions of interest (ROI) in white matter were selected and left and right hemispheres were compared. Fractional anisotropy (FA) in ROI representing thalamo-cortical connections were decreased in the left hemisphere when compared with the right. CONCLUSION: The results show the importance of a network that include the anterior and dorsomedian nuclei, which influence the activity in areas of the cortex responsible for memory processes. The imaging findings suggest that areas of cortical diaschisis after thalamic infarction correspond to areas affected by thalamo-cortical fibre loss as measured with FA.

Isolation rearing or methamphetamine traumatisation induce a "dysconnection" of prefrontal efferents in gerbils: implications for schizophrenia.

A miswiring of prefrontal efferents is generally discussed by the name of "dysconnection" as the anatomical substrate of schizophrenia. Since direct histological confirmation of this hypothesis can hardly be obtained in humans, we used an animal model of schizophrenia to trace prefrontal efferents to distal cortical fields. Mongolian gerbils were intoxicated with a single high dose of methamphetamine on postnatal day 14 and reared in isolation after weaning (day 30). Controls received a saline injection and/or were reared under enriched conditions. Upon reaching adulthood (day 90), biocytin was injected into the medial prefrontal cortex into either deep or superficial laminae. The density of passing fibres and terminal fields in the frontal, parietal and insular cortices was assessed by digital image analysis. Isolation rearing or methamphetamine treatment alone reduced the projections from lamina V/VI to the frontal and from lamina III to the insular cortex, and from both laminae to the parietal cortex. In contrast, isolation rearing of methamphetamine-intoxicated gerbils significantly increased the projections from the deep laminae to the frontal and parietal cortices, compared to isolation-reared controls, with no difference in the efferents from superficial laminae. These results are the first to demonstrate a miswiring of prefrontal efferents in response to adverse systemic influences. They might give a hint at the anatomical basis of "dysconnection" in schizophrenia.

Emx1 and Emx2 cooperate to regulate cortical size, lamination, neuronal differentiation, development of cortical efferents, and thalamocortical pathfinding.

The homeobox transcription factors Emx1 and Emx2 are expressed in overlapping patterns that include cortical progenitors in the dorsal telencephalic neuroepithelium. We have addressed cooperation of Emx1 and Emx2 in cortical development by comparing phenotypes in Emx1; Emx2 double mutant mice with wild-type and Emx1 and Emx2 single mutants. Emx double mutant cortex is greatly reduced compared with wild types and Emx single mutants; the hippocampus and dentate gyrus are absent, and growth and lamination of the olfactory bulbs are defective. Cell proliferation and death are relatively normal early in cortical neurogenesis, suggesting that hypoplasia of the double mutant cortex is primarily due to earlier patterning defects. Expression of cortical markers persists in the reduced double mutant neocortex, but the laminar patterns exhibited are less sharp than normal, consistent with deficient cytoarchitecture, probably due in part to reduced numbers of preplate and Reelin-positive Cajal-Retzius neurons. Subplate neurons also exhibit abnormal differentiation in double mutants. Cortical efferent axons fail to exit the double mutant cortex, and TCAs pass through the striatum and approach the cortex but do not enter it. This TCA pathfinding defect appears to be non-cell autonomous and supports the hypothesis that cortical efferents are required scaffolds to guide TCAs into cortex. In double mutants, some TCAs fail to turn into ventral telencephalon and take an aberrant ventral trajectory; this pathfinding defect correlates with an Emx2 expression domain in ventral telencephalon. The more severe phenotypes in Emx double mutants suggest that Emx1 and Emx2 cooperate to regulate multiple features of cortical development.

A hypothalamic stroke producing recurrent hemihyperhidrosis.

A 40-year-old man awoke with exuberant sustained sweating of the entire left side of the body, which became intermittent over the next few days. MRI indicated a single linear hyperintensity in the right posterior hypothalamus, diminishing on a repeat scan. He continues to have episodes of left unilateral sweating precipitated by exercise or minor infection.

The cerebellar and thalamic degeneration in Fukuyama-type congenital muscular dystrophy.

We report a male autopsy case of Fukuyama-type congenital muscular dystrophy (FCMD), with unusual neuropathological findings. The patient was a Japanese man aged 26 years at the time of death. He had shown severe psychomotor retardation and muscular dystrophy since early infancy, and was diagnosed as having FCMD at the age of 5 years. He died of respiratory failure. The main neuropathological finding was extensive cerebral and cerebellar cortical dysplasia, characteristic of this disorder. In addition, degeneration of the cerebellar efferent pathway, including the dentate nucleus, superior cerebellar peduncle, and red nucleus, and that of the lateral thalamic nucleus were observed. These findings suggest the possibility that the long survival can clarify the latent neurodegeneration in the cerebellum and thalamus in FCMD, in addition to congenital malformations. The system degeneration should be carefully evaluated in the pathological examination of this disorder.

Experimental tremor produced by ventromedial tegmental lesion in monkeys. Neuroanatomical study.

Destruction of the ventromedial tegmentum (VMT) of the midbrain in the monkey has been known to produce tremor similar to that seen in Parkinson's disease. A neuroanatomical study by a silver impregnation method was conducted on 5 monkeys, demonstrating the characteristic flexed posture with hypokinesia of the contralateral upper limb (reliable premonitory sign of tremor) following destruction of VMT with a histologically proven lesion site. The results are summarized as follows: (1) the tractus nigrostriatus, (2) tractus tegmentalis centralis, (3) ascending fiber bundles going to the thalamus (particularly VL.X and VPLo) and (4) descending fibers leading to the bilateral substantia nigra constitute the bulk, if not all, of those neural tracts which pass through the VMT. This, along with the proven existence of fibers projecting to the thalamic nuclei, is thought to account for the rhythmic burst discharges recorded from the VL or Vim nucleus in the monkey and in Parkinson's disease patients. The present experimental study also seems to provide an additional anatomical basis for the concept that the tractus tectonigralis is involved in the mechanism of development of kinésie paradoxale.

Tracing neural connections of human brain with selective silver impregnation. Observations on geniculocalcarine, spinothalamic, and entorhinal pathways.

In selected human brains, it is possible to study the efferent connections of a damaged site with the suppressive silver impregnation techniques described by Nauta and Gygax. Autopsy specimens with circumscribed lesions of recent origin ( one to five weeks before death) are suitable. However, the large size of the human brain and the lack of perfusion with fixative necessitates modifications in the methodology used on experimental animals. With these modifications, it has been possible to trace details of the spinothalamic tract, the geniculocalcarine pathway, and a projection into the entorhinal area in autopsied human brains. More frequent use of this methodology may substantially increase the information that is currently available on the neuronal connections of the human brain.