The Piano Man: A Case Report of Anterior Thalamic Infarct with Dementia and Preserved Music Ability

OBJECTIVE

The thalamus is the integrative hub of the brain with reciprocal connections throughout the cortex. This case report describes a right-handed 81-year-old male patient who experienced sudden onset cognitive impairment following a focal left anterior thalamic infarct.

METHODS

With consent/assent, the patient was seen for a short neuropsychological assessment 6 weeks post stroke. Neuropsychological assessment included review of medical history, collateral intake, the Toronto Cognitive Assessment, Frontal Systems Behavior Scale-Family Rating Form, the Neuropsychiatric Inventory Questionnaire, and piano performance.

RESULTS

The assessment revealed impaired performance on measures of orientation, memory, executive function, and language, as well as symptoms including hallucinations, apathy, and hypersomnolence, consistent with thalamic dementia. Remarkably, in this context, the patient maintained an ability to play piano and read music.

CONCLUSIONS

The case has implications for understanding the complex integrative functions of the thalamus, including how profound impairment can simultaneously present with cognitive strengths that may not be captured by performance on neuropsychological testing. This case also suggests that magnetic resonance imaging may be indicated in cases presenting with vascular risk factors and sudden onset cognitive impairment, given that computed tomography may not be sensitive to small subcortical infarcts.

Photochemically induced thalamus infarction impairs cognition in a mouse model

BACKGROUND

Small subcortical infarcts account for up to 25% of ischaemic strokes. Thalamus is one of the subcortical structures that commonly manifest with lacunar infarcts on MRI of the brain. Studies have shown that thalamus infarction is associated with cognitive decline. However, due to the lack of proper animal models, little is known about the mechanism. We aimed to establish a focal thalamus infarction model, characterise the infarct lesion and assess functional effects.

METHODS

Male C57BL/6J mice were anaesthetised, and Rose Bengal dye was injected through the tail vein. The right thalamus was illuminated with green laser light by stereotactic implantation of optic fibre. Characteristics of the infarct and lesion evolution were evaluated by histological analysis and 7T MRI at various times. The cognitive and neurological functions were assessed by behavioural tests. Retrograde tracing was performed to analyse neural connections.

RESULTS

An ischaemic lesion with small vessel occlusion was observed in the thalamus. It became a small circumscribed infarct with reactive astrocytes accumulated in the infarct periphery on day 21. The mice with thalamic infarction demonstrated impaired learning and memory without significant neurological deficits. Retrogradely labelled neurons in the retrosplenial granular cortex were reduced.

CONCLUSION

This study established a mouse model of thalamic lacunar infarction that exhibits cognitive impairment. Neural connection dysfunctions may play a potential role in post-stroke cognitive impairment. This model helps to clarify the pathophysiology of post-stroke cognitive impairment and to develop potential therapies.

A - 77 Case Study of Bilateral Thalamic Infarction with Persistent Cognitive and Behavioral Symptoms

OBJECTIVE

Bilateral thalamic infarction due to artery of Percheron (AOP) occlusion is rare (0.01-2% of all ischemic strokes) and neuropsychological sequelae are not well-defined. We present the case of a 50-year-old, right-handed, Caucasian woman, with 12 years of education, who presented with cognitive and behavioral symptoms following AOP stroke.

METHOD

Following AOP stroke, the patient experienced seven-day hospitalization and one-month subacute rehabilitation. Symptoms after discharge from the latter included vertical gaze palsy, mild balance difficulties, impulsivity, and amnesia (retrograde and anterograde). Compared to neuroimaging five days after stroke, follow up imaging at three months revealed bilateral thalamic encephalomalacia (Figure 1), as well as small bilateral cerebellar infarcts. Neuropsychology was consulted six months post-stroke to evaluate persistent cognitive and emotional/behavioral symptoms.

RESULTS

(Test results in Table 1). Test results demonstrated average estimated premorbid functioning, amnesia (anterograde and retrograde) and executive dysfunction (including emotional lability, stimulus bound behaviors), which interfered with performances on processing speed and verbal fluency tasks. Attention, working memory, and core language/visuospatial skills were spared. These symptoms contributed to difficulty navigating/exacerbation of psychosocial stress and necessitated external support for daily functions. Neuropsychological evaluation data were used to identify strategies to optimize patient coping and reduce caregiver burnout. At 16-months post-stroke, persistent amnesia and reduced emotional lability were reported by her family.

CONCLUSIONS

This case highlights the presence and need to characterize cognitive and behavioral deficits following bilateral thalamic infarction. Additionally, this case demonstrates the role of neuropsychology in characterization of cognitive and neuropsychiatric sequelae, including identification of relevant interventions/recommendations to inform treatment planning.

A clinical study of artery of Percheron infarction

Artery of Percheron (AOP) infarction, a rare cause of acute altered mental status (AMS), is characterized by bilateral paramedian thalamic infarction. The aim of this study was to review the clinical manifestation, radiological patterns, treatment, and prognosis of patients with AOP infarction. This retrospective case series included patients with AOP infarction from 2009 to 2020 from a medical center in Taiwan. We defined AOP infarction as acute bilateral paramedian thalamic infarction from magnetic resonance imaging, and patients were further categorized by their additional AOP territorial involvements. We determined outcomes with the modified Rankin Scale at discharge. Among the 10 included patients, AMS was the most common presentation (90%). We identified two patients with bilateral vertebral artery (VA), five with unilateral posterior cerebral artery (PCA), and one with bilateral PCA occlusion. Atherosclerosis was the most common presumed etiology (60%). Two and eight patients had favorable and unfavorable prognoses, respectively. PCA occlusion, rather than VA and BA occlusion, was common in angiography. Residual symptoms often resulted in significant disability at discharge. Basilar tip syndrome may share indistinguishable thalamic infarct patterns with AOP infarction but could be differentiated by angiography and other infarcted territories.

Artery of Percheron Occlusion in China: A Case Report and Chinese Literature Review

INTRODUCTION

The artery of Percheron (AOP) is a rare anatomical variant in which bilateral paramedian thalami are supplied by a single vascular branch arising from the P1 segment of the posterior cerebral artery. We present a case of AOP occlusion presenting as loss of consciousness and summarize the literature in Chinese to find the clinical characteristics.

CASE REPORT

An 83-year-old woman was found unconscious for 1 day at home and was sent to the hospital the next day. Cerebral magnetic resonance imaging on day 1 of the patient showed a recent bilateral paramedian thalamic infarction. Simultaneously, magnetic resonance angiography found evident artery stenosis of the right P1 segment of the posterior cerebral artery, suggesting that the patient was diagnosed with AOP occlusion. Since the patient has missed the best time for thrombolytic therapy, anticoagulant therapy was given immediately; as the patient was then found to have pulmonary infections, antibiotic therapy was also initiated. The neurological status of this patient improved very slow. In about 2 weeks, the patient becomes more conscious but still could not speak or move.

CONCLUSION

Our report suggests that unusual mood disorder and language disorder of aged patients might indicate the AOP occlusion, and cerebral imaging of magnetic resonance imaging (better with magnetic resonance angiography) should be performed to establish the diagnosis of AOP occlusion. The fast and accurate diagnosis of stroke because of AOP occlusion could best benefit the patients.

Isolated unilateral thalamic venous infarct in a toddler

Isolated deep cerebral venous thrombosis (CVT), especially involving only the right thalamus, is one of the rarest forms of intracranial venous thrombosis in a child. The anatomy and flow patterns of the deep cerebral venous system are complex and usually, the thrombosis of the internal cerebral veins (ICV) results in thalamic infarction bilaterally. The focal infections, thalamic tumours and vascular malformations may have overlapping clinicoradiological patterns. The treating team should be able to recognise the atypical phenotypes of the deep CVT at the earliest, which can facilitate apt treatment and obviate the need for unnecessary investigations and interventions. We present a rare case of an isolated right thalamic acute venous infarct secondary to bilateral ICV thrombosis in a toddler who was successfully managed by timely diagnosis and with only conservative therapy.

[Bilateral paramedian thalamic infraction due artery of Percheron occlusion]

INTRODUCTION

Artery of Percheron (AOP) is an anatomical variant responsible for the bilateral irrigation of both the medial thalami and rostral sector of the brainstem. Its obstruction causes infarcts in these areas.

OBJECTIVE

To describe a clinical case of AOP infarction, highlighting the clinical and imaging fin dings to consider this pathology in the pediatric population with acute altered state of consciousness.

CLINICAL CASE

A healthy 17-year-old adolescent presented with altered state of consciousness and diplopia, which was resolved in a few hours. Brain MRI showed a bilateral medial thalamic infarction, diagnosing an occlusion of the AOP. The only presumed etiological element was the presence of a patent foramen ovale. Surgical correction of the cardiac defect and anticoagulation were performed, with complete recovery.

CONCLUSION

It is essential to know the clinical-radiological pattern of this condition, which is very characteristic, but infrequent in the pediatric age.

Outcome after acute ischemic stroke is linked to sex-specific lesion patterns

Acute ischemic stroke affects men and women differently. In particular, women are often reported to experience higher acute stroke severity than men. We derived a low-dimensional representation of anatomical stroke lesions and designed a Bayesian hierarchical modeling framework tailored to estimate possible sex differences in lesion patterns linked to acute stroke severity (National Institute of Health Stroke Scale). This framework was developed in 555 patients (38% female). Findings were validated in an independent cohort (n = 503, 41% female). Here, we show brain lesions in regions subserving motor and language functions help explain stroke severity in both men and women, however more widespread lesion patterns are relevant in female patients. Higher stroke severity in women, but not men, is associated with left hemisphere lesions in the vicinity of the posterior circulation. Our results suggest there are sex-specific functional cerebral asymmetries that may be important for future investigations of sex-stratified approaches to management of acute ischemic stroke.

Effects of acetate on cerebral blood flow, systemic inflammation, and behavior in alcohol use disorder

BACKGROUND

Alcohol use disorders (AUDs) are associated with altered regulation of physiological processes in the brain. Acetate, a metabolite of ethanol, has been implicated in several processes that are disrupted in AUDs including transcriptional regulation, metabolism, inflammation, and neurotransmission. To further understand the effects of acetate on brain function in AUDs, we investigated the effects of acetate on cerebral blood flow (CBF), systemic inflammatory cytokines, and behavior in AUD.

METHODS

Sixteen participants with AUD were recruited from a nonmedical, clinically managed detoxification center. Each participant received acetate and placebo in a randomly assigned order of infusion and underwent 3T MR scanning using quantitative pseudo-continuous arterial spin labeling. Participants and the study team were blinded to the infusion. CBF values (ml/100 g/min) extracted from thalamus were compared between placebo and acetate using a mixed effect linear regression model accounting for infusion order. Voxel-wise CBF comparisons were set at threshold of p < 0.05 cluster-corrected for multiple comparisons, voxel-level p < 0.0001. Plasma cytokine levels and behavior were also assessed between infusions.

RESULTS

Fifteen men and 1 woman were enrolled with Alcohol Use Disorders Identification Test (AUDIT) scores between 13 and 38 with a mean of 28.3 ± 9.1. Compared to placebo, acetate administration increased CBF in the thalamus bilaterally (Left: 51.2 vs. 68.8, p < 0.001; Right: 53.7 vs. 69.6, p = 0.001), as well as the cerebellum, brainstem, and cortex. Older age and higher AUDIT scores were associated with increases in acetate-induced thalamic blood flow. Cytokine levels and behavioral measures did not differ between placebo and acetate infusions.

CONCLUSIONS

This pilot study in AUD suggests that during the first week of abstinence from alcohol, the brain's response to acetate differs by brain region and this response may be associated with the severity of alcohol dependence.

Isolated acute pseudobulbar palsy with infarction of artery of percheron: case report and literature review

Introduction

Pseudobulbar palsy (PBP) is characterized by supranuclear lesions in the corticobulbar pathway. Neoplasia, inflammatory, demyelinating, and stroke are possible etiologies of this disorder.

Case report

We report an elderly female who presented with dysarthria. She was dysarthric with a hypernasal voice, no apraxia or aphasia was observed. Tongue movements were slow with limited amplitude. Her soft palate dropped bilaterally; gag reflex was present. Also, she reported swallowing difficulty and choking with her saliva. Bilateral vertical and horizontal gaze were intact to either voluntary or oculocephalic movements. A cranial CT scan was suggestive of artery of Percheron (AOP) infarction. Brain magnetic resonance imaging showed hypersignal on diffusion-weighted and T2-weighted images and hyposignal on apparent diffusion coefficient in both thalami. CT angiography scan revealed an AOP originating from the left posterior cerebral artery. The swallowing study with a videofluoroscopic demonstrated oral and pharyngeal phases with severe dysfunction.

Conclusion

To the authors' knowledge, there are two cases of individuals with artery of Percheron infarction who developed PBP associated with other clinical syndromes. Still, isolated PBP following infarction of Percheron's artery was not reported. We hypothesized that the PBP may have occurred because of the existence of vascular territory variations in the perforating arteries that arise from the AOP.

Holmes Tremor due to Artery of Percheron Infarct: Clinical Case and Treatment Using Deep Brain Stimulation of the Vim and ZI Targets

BACKGROUND

Holmes tremor (HT) arises from disruption of the cerebellothalamocortical pathways. A lesion can interrupt the projection at any point, resulting in this tremor. We describe a case of HT due to the rare artery of Percheron infarct and its successful treatment using deep brain stimulation.

CASE REPORT

A 62-year-old woman with a right medial cerebral peduncle and bilateral thalamic stroke developed HT. Ventral intermediate nucleus (Vim) zona incerta (ZI) deep brain stimulation (DBS) surgery was performed, with improvement in her tremor.

DISCUSSION

Our case supports the theory that the more caudal ZI target in combination with Vim is beneficial in treating poorly DBS-responsive tremors such as HT.

Effects of Alcohol and Acetate on Cerebral Blood Flow: A Pilot Study

BACKGROUND

Acute alcohol produces effects on cerebral metabolism and blood flow. Alcohol is converted to acetate, which serves as a source of energy for the brain and is an agonist at G protein-coupled receptors distributed in different cell types in the body including neurons. Acetate has been hypothesized to play a role in the cerebral blood flow (CBF) response after alcohol ingestion. We tested whether administration of acetate would alter CBF in a pattern similar to or different from that of alcohol ingestion in healthy individuals.

METHODS

Twenty-four healthy participants were assigned by convenience to receive either 0.6 g/kg alcohol orally (n = 12) or acetate intravenously (n = 12). For each participant, CBF maps were acquired using an arterial spin labeling sequence on a 3T magnetic resonance scanner after placebo and after drug administration. Whole-brain CBF maps were compared between placebo and drug using a paired t-test, and set at a threshold of p < 0.05 corrected for multiple comparisons (k ≥ 142 voxels, ≥3.78 cm3 ), voxel-level p < 0.005. Intoxication was measured after placebo and drug administration with a Subjective High Assessment Scale (SHAS-7).

RESULTS

Compared to placebo, alcohol and acetate were associated with increased CBF in the medial thalamus. Alcohol, but not acetate, was associated with increased CBF in the right orbitofrontal, medial prefrontal and cingulate cortex, and hippocampus. Plasma acetate levels increased following administration of alcohol and acetate and did not differ between the 2 arms. Alcohol, but not acetate, was associated with an increase in SHAS-7 scores (p < 0.001).

CONCLUSIONS

Increased thalamic CBF associated with either alcohol or acetate administration suggests that the thalamic CBF response after alcohol could be mediated by acetate. Compared to other brain regions, thalamus may differ in its ability to metabolize acetate or expression of receptors responsive to acetate. Increased prefrontal and limbic CBF associated with alcohol may be linked to alcohol's behavioral effects.

Alterations in patients with major depressive disorder before and after electroconvulsive therapy measured by fractional amplitude of low-frequency fluctuations (fALFF)

BACKGROUND

Electroconvulsive therapy (ECT) is an important treatment option for patients with major depressive disorder (MDD). However, the mechanisms of ECT in MDD are still unclear.

METHODS

Twenty-four patients with severe MDD and 14 healthy controls were enrolled in this study. Eight ECT sessions were conducted for MDD patients using brief-pulse square-wave signal at bitemporal locations. To investigate the regional cerebral blood flow in MDD patients before and after ECT treatments by resting-state functional magnetic resonance imaging (rs-fMRI), the patients were scanned twice (before the first ECT and after the eighth ECT) for data acquisition. Afterward, we adopted fractional amplitude of low-frequency fluctuations (fALFF) to assess the alterations of regional brain activity.

RESULTS

Compared with healthy controls, the fALFF in the cerebellum lobe, parahippocampal gyrus, fusiform gyrus, anterior cingulate gyrus, and thalamus in MDD patients before ECT (pre-ECT) was significantly increased. In another comparison, the fALFF in the cerebellum anterior lobe, fusiform gyrus, insula, parahippocampal gyrus, middle frontal gyrus, and inferior frontal gyrus in pre-ECT patients was significantly greater than the post-ECT fALFF.

LIMITATIONS

Only two rs-fMRI scans were conducted at predefined times: before the first and after the eighth ECT treatment. More scans during the ECT sessions would yield more information. In addition, the sample size in this study was limited. The number of control subjects was relatively small. A larger number of subjects would produce more robust findings.

CONCLUSIONS

The fALFF of both healthy controls and post-ECT patients in cerebellum anterior lobe, fusiform gyrus, and parahippocampal gyrus is significantly lower than the fALFF of pre-ECT patients. This finding demonstrates that ECT treatment is effective on these brain areas in MDD patients.

Laser speckle contrast imaging of blood flow in the deep brain using microendoscopy

Poor blood flow circulation can occur in the subcortical regions of the brain in many brain diseases. However, the limitations of light penetration imaging techniques hinder the detection of blood flow in deep brain tissues in vivo. Hence, in this Letter, we present a gradient index lens-based laser speckle contrast imaging system for time-lapse blood flow detection in subcortical regions of the brain. We monitored the hemodynamic changes in the thalamus of mouse models of acute hypoxia and transient middle cerebral artery occlusion as a proof of concept for practical applications.

Disrupting interaction of PSD-95 with nNOS attenuates hemorrhage-induced thalamic pain

Hemorrhages occurring within the thalamus lead to a pain syndrome. Clinical treatment of thalamic pain is ineffective, at least in part, due to the elusive mechanisms that underlie the induction and maintenance of thalamic pain. The present study investigated the possible contribution of a protein-protein interaction between postsynaptic density protein 95 (PSD-95) and neuronal nitric oxide synthase (nNOS) to thalamic pain in mice. Thalamic hemorrhage was induced by microinjection of type IV collagenase into unilateral ventral posterior medial/lateral nuclei of the thalamus. Pain hypersensitivities, including mechanical allodynia, heat hyperalgesia, and cold allodynia, appeared at day 1 post-microinjection, reached a peak 5-7 days post-microinjection, and persisted for at least 28 days post-microinjection on the contralateral side. Systemic pre-treatment (but not post-treatment) of ZL006, a small molecule that disrupts PSD-95-nNOS interaction, alleviated these pain hypersensitivities. This effect is dose-dependent. Mechanistically, ZL006 blocked the hemorrhage-induced increase of binding of PSD-95 with nNOS and membrane translocation of nNOS in thalamic neurons. Our findings suggest that the protein-protein interaction between PSD-95 and nNOS in the thalamus plays a significant role in the induction of thalamic pain. This interaction may be a promising therapeutic target in the clinical management of hemorrhage-induced thalamic pain.

Artery of Percheron Infarct - a diagnostic and prognostic conundrum!

A 39 year old male was found unconscious at home. On arrival to the hospital the patient was profoundly somnolent but easily rousable, with no focal neurological deficits. Imaging confirmed bilateral thalamic infarcts from the occlusion of Artery of Percheron, a rare anatomic variant which is a single arterial trunk supplying the thalamus and midbrain bilaterally. Anti-platelet therapy was initiated as soon as the diagnosis was established and the patient showed a rapid remarkable recovery over the next 48 hours. He continued to improve subsequently and was at baseline functional status at 6 months. Extensive investigations for etiologies were mostly unrevealing. In such patients presenting with drowsiness/somnolence, a posterior circulation stroke should be considered if no evidence of other more common causes are found. A CT head must be followed by an MRI to confirm the diagnosis and subsequent focus should be on eliciting risk factors and careful evaluation for etiologies.

Degeneration of paramedian nuclei in the thalamus induces Holmes tremor in a case of artery of Percheron infarction

RATIONALE

Holmes' tremor is an uncommon neurologic disorder following brain insults, and its pathogenesis is undefined. The interruption of the dento-rubro-thalamic tract and secondary deterioration of the nigrostriatal pathway are both required to initiate Holmes' tremor. We used nuclear medicine imaging tools to analyze a patient with concurrent infarction in different zones of each side of the thalamus. Finding whether the paramedian nuclear groups of the thalamus were injured was a decisive element for developing Holmes' tremor.

PATIENT CONCERNS

A 36-year-old woman was admitted to our department due to a bilateral paramedian thalamic infarction. Seven months after the stroke, a unilaterally involuntary trembling with irregularly wavering motions occurring in both her left hand and forearm.

DIAGNOSIS

Based on the distinct features of the unilateral coarse tremor and the locations of the lesions on the magnetic resonance imaging (MRI), the patient was diagnosed with bilateral paramedian thalamic infarction complicated with a unilateral Holmes' tremor.

INTERVENTIONS

The patient refused our recommendation of pharmacological treatment with levodopa and other dopamine agonists based on personal reasons and was only willing to accept physical and occupational training programs at our outpatient clinic.

OUTCOMES

We utilized serial anatomic and functional neuroimaging of the brain to survey the neurologic deficit. A brain magnetic resonance imaging showed unequal recovery on each side of the thalamus. The residual lesion appeared larger in the right-side thalamus and had gathered in the paramedian area. A brain perfusion single-photon emission computed tomography (SPECT) revealed that the post-stroke hypometabolic changes were not only in the right-side thalamus but also in the right basal ganglion, which was anatomically intact. Furthermore, the brain Technetium-99m-labeled tropanes as a dopamine transporter imaging agents scan ( Tc-TRODAT-1) displayed a secondary reduction of dopamine transporters in the right nigrostriatal pathway which had resulted from the damage on the paramedian nuclear groups of the right-side thalamus.

LESSONS

Based on the functional images, we illustrated that a retrograde degeneration originating from the thalamic paramedian nuclear groups, and extending forward along the direct innervating fibers of the mesothalamic pathway, played an essential role towards initiating Holmes' tremor.

Unilateral Thalamic Infarct Presenting as a Convulsive Seizure

Lesions of the thalamus and those extending into midbrain can cause various types of movement disorders such as dystonia, asterixis and ballism-chorea. Seizures are rare manifestation of thalamic disorder. Occurrence of seizures in bilateral thalamic infarct has been reported; but seizures in unilateral thalamic infarct have been reported very rarely. Literature review showed only single case of perinatal unilateral thalamic infarct presenting with seizures. We are reporting a unique case of convulsive seizure at the onset of unilateral thalamic infarct in an adult male, which has never been reported to the best of our knowledge.

Artery of Percheron Infarct: ARarity Not to be Missed

Artery of Percheron (AOP) is a rare vascular variant of posterior cerebral circulation and it supplies blood to the bilateral paramedian thalami and the rostral midbrain. Artery of Percheron infarct requires a comprehensive clinical and radiological examination. It can be easily overlooked due to normal CTfindings and wide range of differential diagnosis. Classic triad of presentation is altered mental status, memory impairment and the vertical gaze palsy. We report a case of a 66-year female who had sudden onset of severe vertigo, diplopia and ataxia. Anon-contrast CTBrain was performed which was normal. Her MRI brain with diffusion weighted images (DWI) confirmed bilateral thalamic infarcts which were initially thought to be calcifications, as usually happens with diagnosing artery of Percheron infarcts. However, by reviewing and ruling out all other possible causes of such symptoms and further review of neuroimaging, lead us to the correct diagnosis.

[Cryptogenic stroke in a young patient with heart disease and kidney failure]

INTRODUCTION

Fabry's disease is an infrequent metabolic pathology linked to the X chromosome which causes a wide variety of signs and symptoms.

CASE REPORT

A 39-year-old male who was admitted to our stroke unit with right-side hemiparesis (1 + 0) and dysarthria (1). The score on the National Institute of Health Stroke Scale was 2. The patient presented angiokeratomas in both thighs. A computerised axial tomography scan of the head showed left thalamic acute infarction. The duplex scan of the supra-aortic trunks was normal, and the transcranial Doppler reflected a generalised increase in the pulsatility indices. Transthoracic echocardiography showed left ventricular hypertrophy and left atrial dilatation. He was discharged five days later, with antiaggregating medication but asymptomatic. The prolonged Holter-electrocardiogram recording showed paroxysmal atrial fibrillation. One notable value in the urine analysis was microalbuminuria of 281 mg/L. In view of the multi-organic involvement and the family history, a study for Fabry's disease was performed. Activity of the enzyme alpha-galactosidase A was diminished, and the presence of a mutation in the GLA gene was found. The patient's brother, who suffered from kidney failure and atrial fibrillation, was positive for this mutation. The patient is on treatment with agalsidase beta.

CONCLUSIONS

Fabry's disease must be suspected in young males with heart disease, stroke or peripheral neuropathy, skin lesions, kidney failure and a history of cases in the family. Hormone replacement therapy must be established at an early stage, as it can improve the prognosis.

Enduring disturbances in regional cerebral blood flow and brain oxygenation at 24 h after asphyxial cardiac arrest in developing rats

BACKGROUND

Disturbances in cerebral blood flow (CBF) and brain oxygenation (PbO2) are present early after pediatric cardiac arrest (CA). CBF-targeted therapies improved neurological outcome in our CA model. To assess the therapeutic window for CBF- and PbO2-targeted therapies, we propose to determine if CBF and PbO2 disturbances persist at 24 h after experimental pediatric CA.

METHODS

Regional CBF and PbO2 were measured at 24 h after asphyxial CA in immature rats (n = 26, 6-8/group) using arterial spin label MRI and tissue electrodes, respectively.

RESULTS

In all regions but the thalamus, CBF recovered to sham values by 24 h; thalamic CBF was >32% higher after CA vs. sham. PbO2 values at 24 h after CA in the cortex and thalamus were similar to shams in rats who received supplemental oxygen, however, on room air, cortical PbO2 was lower after CA vs. shams.

CONCLUSION

CBF remains increased in the thalamus at 24 h after CA and PbO2 is decreased to hypoxic levels in cortex at 24 h after CA in rats who do not receive supplemental oxygen. Given the enduring disturbances in this model and the lack of routine CBF or PbO2 monitoring in patients, our data suggest the need for clinical correlation.

The age-dependent effects of a single-dose methylphenidate challenge on cerebral perfusion in patients with attention-deficit/hyperactivity disorder

Methylphenidate (MPH) is a stimulant drug and an effective treatment for attention-deficit/hyperactivity disorder (ADHD) in both children and adults. Pre-clinical studies suggest that the response to stimulants is dependent on age, which may reflect the ontogeny of the dopamine (DA) system, which continues to develop throughout childhood and adolescence. Therefore, the aim of this study was to investigate the modulating effect of age on the cerebral blood flow (CBF) response to MPH in stimulant treatment-naive children and adults with ADHD. Ninety-eight stimulant treatment-naive male pediatric (10-12 years) and adult (23-40 years) patients with ADHD were included in this study. The CBF response to an acute challenge with MPH (0.5 mg/kg) was measured using arterial spin labeling (ASL) pharmacological magnetic resonance imaging, as a proxy for DA function. Region-of-interest (ROI) analyses were carried out for the striatum, thalamus and medial prefrontal cortex and in addition voxel-wise analyses were conducted. An acute challenge with MPH decreased CBF in both children and adults in cortical areas, although to a greater extent in adults. In contrast, ROI analyses showed that MPH decreased thalamic CBF only in children, but not adults. Our findings highlight the importance of taking the developmental perspective into account when studying the effects of stimulants in ADHD patients.

Artery of Percheron infarction after endoscopic pituitary surgery

Infarction in the artery of Percheron territory is a rare phenomenon in which occlusion of an unpaired perforating artery arising from the P1 segment on one side results in infarcts in the bilateral paramedian thalami with or without midbrain infarcts. We describe the case of a 40-year-old male who developed this complication following re-exploratory trans-sphenoidal surgery for a pituitary adenoma. In this first report of its kind in endoscopic pituitary surgery, the pathogenesis and clinico-radiological features of this rare vascular event are discussed.

Bloodletting at Jing-well points decreases interstitial fluid flow in the thalamus of rats

OBJECTIVE

To investigate the changes in the neuronal microenvironment of the middle cerebral artery (MCA) territory induced by Jing-well points bloodletting acupuncture (WPBA) and to explore the neuroprotective mechanism of WPBA in stroke.

METHODS

Adult male Sprague Dawley (n = 32) rats were randomly divided into four groups of eight animals each: WPBA-thalamus group (WT), WPBA-caudate nucleus group (WC), sham-control thalamus group (ST) and sham-control caudate nucleus group (SC). Animals in the WT and WC groups received 2 µL of the extracellular tracer gadolinium-diethylene triamine pentaacetic acid (Gd-DTPA) injected into the thalamus or caudate nucleus, respectively, and 12 Jing-well points in the distal ends of the rats' digits were used for WPBA. Although 2 µL of Gd-DTPA was injected into the thalamus or caudate nucleus, respectively, for animals in the two sham groups (ST and SC), no acupuncture or bloodletting was performed. Brain extracellular space and interstitial fluid flow parameters were measured using Gd-DTPA-enhanced magnetic resonance imaging.

RESULTS

The brain interstitial fluid flow speed was decreased in the thalamus after WPBA, with a significantly lower Gd-DTPA clearance rate and longer half-life of Gd-DTPA in the thalamus of treated rats than those in sham-control rats [WPBA-treated rats' clearance rate, (7.47 ± 3.15) x 10(-5)/s (P.= 0.009); half-life, (1.52 ± 0.13) h, P = 0.000]. By contrast, no significant changes in brain extracellular space and interstitial fluid flow parameters were detected in the caudate nucleus after WPBA (P = 0.649). In addition, no differences in the morphology of the brain extracellular space or the final distribution of the traced brain interstitial fluid were demonstrated between the WT and WC groups (P = 0.631, P = 0.970, respectively).

CONCLUSION

The WPBA decreased the speed of the local thalamic ISF flow in rats, which is assumed to be a beneficial protection by down-modulated the metabolic rate of the attacked neurons under stroke.

Lesson of the month 1: Artery of Percheron occlusion - an -uncommon cause of coma in a middle-aged man

Bilateral paramedian thalamic infarction resulting from artery of Percheron occlusion presents with a distinct clinical syndrome comprising impaired consciousness, often with vertical gaze palsy and memory impairment. This uncommon anatomical variant arises as a single artery supplying both paramedian thalami. Early recognition can be challenging in the obtunded patient, where the differential diagnosis is broad. The acute physician should consider this diagnosis in a patient presenting with unexplained coma so that emergent treatments such as thrombolysis can be employed. Early imaging with computerised tomography can often be normal; therefore the use of magnetic resonance imaging is essential in confirming the diagnosis.

CORRELATION INDICES OF CEREBRAL HEMODYNAMICS AND ELECTRICAL ACTIVITY IN CHILDREN WITH IMPAIRED MOTOR SKILLS

The correlations between the indicators of cerebral hemodynamics and electrical activity in children with impaired motor skills of central origin (children with cerebral palsy) were investigated. There is established a high number of links between indicators of rheoencephalogram (REG) and electroencephalogram (EEG) in the left cerebral hemisphere than in the right. In frontomastoidal allocation 19 correlations and in occipitomastoidal - 59 links. We suppose that poor circulation in vertebroplasty-basilar system leads to the defeat of the brain stem, which, with afferent pathways of the reticular formation, connects the thalamus with the cortex. In the reticular formation there is an inhibition of ascending activators influences, which eland to decreasing of the cortex is tonus. You can talk about the functional immaturity of the system of nonspecific activation by the reticular formation of the brain stem. Children with violation of motor activity had significantly more negative and positive significant and high correlation among the existing indicators of electric brain activity and cerebral hemodynamics, in our opinion, is due to the development of interconnection compensation that is carried out by adjustment of the functional systems and the formation of new forms of adaptive responses in conditions of disontogenetik. Feature correlation pattern of the EEG, of children with disorders of motor activity, is associated with a significantly great number of high and significant correlations between measures of electrical brain activity in the δ- and q- rhythms, especially in the temporal areas of the cerebral cortex. According to visual analysis of EEG there is revealed a common manifestation of changes of bioelectric brain activity in children with disorders of motor activity. This is manifested in the development of paroxysmal activity of action potentials of θ- and δ-rhythms with the focus of activity in the anterior areas of the cerebral cortex; the formation of a mosaic representation of the θ-rhythms in temporal areas; the presence of hypersynchronous a-paroxysms in the posterior areas of the cerebral cortex. The given facts testify to activation of mechanisms of limbic-neocortical systems and synchronizing influences of the reticular formation of the stem and diencephalic structures. There is also detected greater number of correlations when occipitomastoidal registration was lone it reflects compensatory redistribution of cerebral blood flow over the affected structures of brain stem structures that are associated with the provision of cortical functions.

Naltrexone for treatment of impaired awareness of hypoglycemia in type 1 diabetes: A randomized clinical trial

AIMS

Impaired awareness of hypoglycemia (IAH) is a limiting factor in the treatment of type 1 diabetes (T1D) and is a challenging condition to reverse. The objective of this study was to test the hypothesis that naltrexone therapy in subjects with T1D and IAH will improve counterregulatory hormone response and recognition of hypoglycemia symptoms during hypoglycemia.

METHODS

We performed a pilot randomized double blind trial of 4weeks of naltrexone therapy (n=10) or placebo (n=12) given orally in subjects with T1D and IAH. Outcome measures included hypoglycemia symptom scores, counterregulatory hormone levels and thalamic activation as measured by cerebral blood flow using MRI during experimental hypoglycemia in all subjects before and after 4weeks of intervention.

RESULTS

After 4weeks of therapy with naltrexone or placebo, no significant differences in response to hypoglycemia were seen in any outcomes of interest within each group.

CONCLUSIONS

In this small study, short-term treatment with naltrexone did not improve recognition of hypoglycemia symptoms or counterregulatory hormone response during experimental hypoglycemia in subjects with T1D and IAH. Whether this lack of effect is related to the small sample size or due to the dose, the advanced stage of study population or the drug itself should be the subject of future investigation.

Distribution of temperature changes and neurovascular coupling in rat brain following 3,4-methylenedioxymethamphetamine (MDMA, "ecstasy") exposure

(+/-)3,4-methylenedioxymethamphetamine (MDMA, "ecstasy") is an abused psychostimulant that produces strong monoaminergic stimulation and whole-body hyperthermia. MDMA-induced thermogenesis involves activation of uncoupling proteins (UCPs), primarily a type specific to skeletal muscle (UCP-3) and absent from the brain, although other UCP types are expressed in the brain (e.g. thalamus) and might contribute to thermogenesis. Since neuroimaging of brain temperature could provide insights into MDMA action, we measured spatial distributions of systemically administered MDMA-induced temperature changes and dynamics in rat cortex and subcortex using a novel magnetic resonance method, Biosensor Imaging of Redundant Deviation in Shifts (BIRDS), with an exogenous temperature-sensitive probe (thulium ion and macrocyclic chelate 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetramethyl-1,4,7,10-tetraacetate (DOTMA(4-))). The MDMA-induced temperature rise was greater in the cortex than in the subcortex (1.6 ± 0.4 °C versus 1.3 ± 0.4 °C) and occurred more rapidly (2.0 ± 0.2 °C/h versus 1.5 ± 0.2 °C/h). MDMA-induced temperature changes and dynamics in the cortex and body were correlated, although the body temperature exceeded the cortex temperature before and after MDMA. Temperature, neuronal activity, and blood flow (CBF) were measured simultaneously in the cortex and subcortex (i.e. thalamus) to investigate possible differences of MDMA-induced warming across brain regions. MDMA-induced warming correlated with increases in neuronal activity and blood flow in the cortex, suggesting that the normal neurovascular response to increased neural activity was maintained. In contrast to the cortex, a biphasic relationship was seen in the subcortex (i.e. thalamus), with a decline in CBF as temperature and neural activity rose, transitioning to a rise in CBF for temperature above 37 °C, suggesting that MDMA affected CBF and neurovascular coupling differently in subcortical regions. Considering that MDMA effects on CBF and heat dissipation (as well as potential heat generation) may vary regionally, neuroprotection may require different cooling strategies.

Relating Alpha Power and Phase to Population Firing and Hemodynamic Activity Using a Thalamo-cortical Neural Mass Model

Oscillations are ubiquitous phenomena in the animal and human brain. Among them, the alpha rhythm in human EEG is one of the most prominent examples. However, its precise mechanisms of generation are still poorly understood. It was mainly this lack of knowledge that motivated a number of simultaneous electroencephalography (EEG) - functional magnetic resonance imaging (fMRI) studies. This approach revealed how oscillatory neuronal signatures such as the alpha rhythm are paralleled by changes of the blood oxygenation level dependent (BOLD) signal. Several such studies revealed a negative correlation between the alpha rhythm and the hemodynamic BOLD signal in visual cortex and a positive correlation in the thalamus. In this study we explore the potential generative mechanisms that lead to those observations. We use a bursting capable Stefanescu-Jirsa 3D (SJ3D) neural-mass model that reproduces a wide repertoire of prominent features of local neuronal-population dynamics. We construct a thalamo-cortical network of coupled SJ3D nodes considering excitatory and inhibitory directed connections. The model suggests that an inverse correlation between cortical multi-unit activity, i.e. the firing of neuronal populations, and narrow band local field potential oscillations in the alpha band underlies the empirically observed negative correlation between alpha-rhythm power and fMRI signal in visual cortex. Furthermore the model suggests that the interplay between tonic and bursting mode in thalamus and cortex is critical for this relation. This demonstrates how biophysically meaningful modelling can generate precise and testable hypotheses about the underpinnings of large-scale neuroimaging signals.

DISC1 Ser704Cys impacts thalamic-prefrontal connectivity

The Disrupted-in-Schizophrenia 1 (DISC1) gene has been thought as a putative susceptibility gene for various psychiatric disorders, and DISC1 Ser704Cys is associated with variations of brain morphology and function. Moreover, our recent diffusion magnetic resonance imaging (dMRI) study reported that DISC1 Ser704Cys was associated with information transfer efficiency in the brain anatomical network. However, the effects of the DISC1 gene on functional brain connectivity and networks, especially for thalamic-prefrontal circuit, which are disrupted in various psychiatric disorders, are largely unknown. Using a functional connectivity density (FCD) mapping method based on functional magnetic resonance imaging data in a large sample of healthy Han Chinese subjects, we first investigated the association between DISC1 Ser704Cys and short- and long-range FCD hubs. Compared with Ser homozygotes, Cys-allele individuals had increased long-range FCD hubs in the bilateral thalami. The functional and anatomical connectivity of the thalamus to the prefrontal cortex was further analyzed. Significantly increased thalamic-prefrontal functional connectivity and decreased thalamic-prefrontal anatomical connectivity were found in DISC1 Cys-allele carriers. Our findings provide consistent evidence that the DISC1 Ser704Cys polymorphism influences the thalamic-prefrontal circuits in humans and may provide new insights into the neural mechanisms that link DISC1 and the risk for psychiatric disorders.

Arterial spin-labelling perfusion MRI and outcome in neonates with hypoxic-ischemic encephalopathy

PURPOSE

Hyperperfusion may be related to outcome in neonates with hypoxic-ischemic encephalopathy (HIE). The purpose of this study was to evaluate whether arterial spin labelling (ASL) perfusion is associated with outcome in neonates with HIE and to compare the predictive value of ASL MRI to known MRI predictive markers.

METHODS

Twenty-eight neonates diagnosed with HIE and assessed with MR imaging (conventional MRI, diffusion-weighted MRI, MR spectroscopy [MRS], and ASL MRI) were included. Perfusion in the basal ganglia and thalami was measured. Outcome at 9 or 18 months of age was scored as either adverse (death or cerebral palsy) or favourable.

RESULTS

The median (range) perfusion in the basal ganglia and thalami (BGT) was 63 (28-108) ml/100 g/min in the neonates with adverse outcome and 28 (12-51) ml/100 g/min in the infants with favourable outcome (p < 0.01). The area-under-the-curve was 0.92 for ASL MRI, 0.97 for MRI score, 0.96 for Lac/NAA and 0.92 for ADC in the BGT. The combination of Lac/NAA and ASL MRI results was the best predictor of outcome (r(2) = 0.86, p < 0.001).

CONCLUSION

Higher ASL perfusion values in neonates with HIE are associated with a worse neurodevelopmental outcome. A combination of the MRS and ASL MRI information is the best predictor of outcome.

KEY POINTS

• Arterial spin labelling MRI can predict outcome in neonates with hypoxic-ischemic encephalopathy • Basal ganglia and thalami perfusion is higher in neonates with adverse outcome • Arterial spin labelling complements known MRI parameters in the prediction of outcome • The combined information of ASL and MRS measurements is the best predictor of outcome.

A preliminary study of functional connectivity of medication naïve children with obsessive-compulsive disorder

BACKGROUND

Evidence suggests that obsessive-compulsive disorder (OCD) is associated with a dysfunction in the cortico-striatal-thalamic-cortical (CSTC) circuitry. Resting state functional connectivity magnetic resonance imaging (rs-fcMRI) allows measurements of resting state networks (RSNs), brain networks that are present at 'rest'. However, although OCD has a typical onset during childhood or adolescence, only two other studies have performed rs-fcMRI comparisons of RSNs in children and adolescents with OCD against healthy controls.

METHODS

In the present study, we performed resting state functional magnetic resonance imaging using a 3 Tesla MRI, in 11 medication-naïve children and adolescents with OCD and 9 healthy controls. In contrast to previous studies that relied on a priori determination of RSNs, we determined resting state functional connectivity with a data-driven independent component analysis (ICA).

RESULTS

Consistent with previous reports in healthy adults, we identified 13 RSNs. Case-control un-adjusted statistical significance (p<0.05) was found for two networks. Firstly, increased connectivity (OCD>control) in the right section of Brodmann area 43 of the auditory network; Secondly, decreased connectivity in the right section of Brodmann area 8 and Brodmann area 40 in the cingulate network.

CONCLUSIONS

Our preliminary findings of case-control differences in RSNs lend further support to the CSTC hypothesis of OCD, as well as implicating other regions of the brain outside of the CSTC.

[The clinical and imaging study of thalamic venous infarction]

OBJECTIVE

To explore the clinical and radiological features of bilateral thalamus venous infarction.

METHODS

The cases definitely diagnosed as thalamus venous infarction were collected and the corresponding clinical and radiological data were retrospectively analyzed.

RESULTS

Four cases confirmed as thalamus venous infarction by digital substraction angiography (DSA) were collected. Bilateral thalamus lesions were detected in all cases by brain MRI scans which mainly presented as thalamus edema with high T1 and T2 signals with partial enhancement. Mild hemorrage was also shown in one case. Acute or subacute onset with clinical manifestations of headache, hypomnesia and hypersomnia were reported in all cases. The neurological examination showed conscious disturbance, memory impairment and positive Babinski sign. The venous thrombi were formed mainly in the transverse and the straight sinuses in 3 cases with the deep cerebral venous involved in 2 cases. All patients were improved after the anticoagulation therapy. Dural arteriovenous fistula was found in the other case drained by the Rosenthal's vein, and the symptoms were ameliorated after the embolotherapy.

CONCLUSIONS

As the thalamus is drained by the thalamostriate vein and the lateral thalamic vein towards the internal cerebral vein with the caudate portion drained particularly by the Rosenthal's vein, venous thrombosis or fistula drainage into these veins would probably disturb the normal drainage of the thalamus and result in further edema and infarction. Thus, the venous infarction should be taken into consideration whenever bilateral thalamus lesions are encountered in clinical practice and DSA is necessary to confirm the diagnosis.

Decreased consciousness: bilateral thalamic infarction and its relation to the artery of Percheron

This case series highlights two patients seen in the same stroke centre presenting with unusual symptoms. They were later diagnosed with bilateral thalamic infarcts, probably related to an unusual anatomical variant. The difficulties in establishing the diagnoses due to their relative rarity and complexity could have impacted on patient outcomes.

Simultaneous bilateral hypertensive putaminal or thalamic hemorrhage: case report and systematic review of the literature

Simultaneous multiple hypertensive intracranial hemorrhage is rare, and its mechanism is unclear. We report a case of simultaneous hypertensive bilateral thalamic hemorrhage. A 58-year-old man presented with sudden mild right hemiparesis. Computed tomography 1 hour after the onset showed bilateral thalamic hemorrhage. Gradient-echo T2-weighted magnetic resonance imaging showed 17 microbleeds. The patient was treated with medication, discharged home, and achieved a modified Rankin scale of 1 at 3 months from the onset. Additionally, by systematically searching in PubMed, we found 41 cases of simultaneous bilateral hypertensive putaminal or thalamic hemorrhage, including our case: 18 bilateral putaminal, 12 bilateral thalamic, and 11 unilateral putaminal and contralateral thalamic hemorrhage. Symmetric hemorrhage occurred more frequently than expected ratios of hemorrhage occurring randomly in terms of location (p=0.013; Fisher's exact test). These new findings raise the hypothesis that patients may have symmetrically vulnerable vessels. Such conditions would result in coincidence or subsequent rupture of perforating arteries or micro-aneurysms by increased blood pressure and cause symmetric hemorrhages. Studies on the distribution of microbleeds may address these issues.

[Posterior cerebral artery infarctions with possible interaction between hypoperfusion and embolism]

Although embolism and hypoperfusion may well occur concurrently in a non-negligible proportion of cerebral infarction patients, there is currently lack of proof, especially in the posterior circulation. Here, we are reporting on a case of multiple cerebral infarctions in a patient with neurofibromatosis type 1, multiple vascular abnormalities of the posterior cerebral circulation and intracranial artery occlusion. We hypothesize that cerebral blood flow impairment may have affected the clearance and destination of embolic particles.

Bilateral thalamic infarcts due to occlusion of the Artery of Percheron and discussion of the differential diagnosis of bilateral thalamic lesions

The Artery of Percheron is a rare vascular variant in which a single dominant thalamoperforating artery arises from one P1 segment and bifurcates to supply both paramedian thalami. Occlusion of this uncommon vessel results in a characteristic pattern of bilateral paramedian thalamic infarcts with or without mesencephalic infarctions. We report a case of a 31-year-old man with acute bilateral thalamic infarcts and a truncated Artery of Percheron demonstrated on magnetic resonance angiography (MRA). Occlusion of the vessel was presumably due to embolism from a patent foramen ovale that was subsequently closed. The case presentation is followed by a discussion of bilateral paramedian thalamic infarcts including the causes and clinical presentation. The differential diagnosis of vascular and nonvascular etiologies of bilateral thalamic lesions is also discussed.

Quantitative assessment of chronic thalamic stroke

The procedure presented quantitatively assesses thalamic lesions in the chronic phase of an ischemic episode. The structural MR images of 19 patients with ischemia in the thalamus were assessed by radiologic inspection. An independent rater allocated the damage to the thalamic nuclei. The assessments showed 89% accordance with the radiologic inspection (P < .001). This procedure ranks the extent of the damage to thalamic nuclei and accounts for postacute rearrangement of the neural tissue.

The artery of Percheron revisited: a cadaveric anatomical study

BACKGROUND

The artery of Percheron (AOP) is a single thalamoperforating arterial trunk that provides bilateral supply to the paramedian thalami and the rostral midbrain. As this rare anatomical variant artery may be involved in endovascular procedures or encountered surgically during basilar terminus aneurysms, the present study was warranted.

METHOD

Thirty-four adult (20 male and 14 female) formalin-fixed cadaveric brains underwent dissection of the 68 posterior cerebral arteries. Observations were made of the presence and the variations of the thalamoperforating arteries as well as the presence of the AOP.

FINDINGS

Thalamoperforating arteries arose from the superior or posterior surfaces of the P1 segment at a mean of a 1.87 mm (range, 0.39-5.25 mm) distance from the basilar apex and entered the brain through the posterior perforated substance. The average number was 4.25 (range 1-9), and the mean diameter was 0.73 mm (range 0.46-1.16 mm). Thalamoperforating arteries were classified into four different types according to their origin at the P1 segment: type I (bilateral multiple, n = 19), 55.8 %; type II (unilateral multiple, unilateral single, n = 4), 11.7 %; type III (bilateral single, n = 7), 20.5 %; type IV [one side with a single branch, the other side with no branches (the AOP), n = 4], 11.7 %. In three separate specimens with ruptured basilar artery aneurysms, the origin of the thalamoperforating arteries was incorporated not only into the posterior aspect of the aneurysm neck but also into the fundus.

CONCLUSIONS

In about one tenth of cases the possibility of the presence of a single arterial trunk that supplies the two paramedian thalamic territories should be taken into consideration during treatment planning of basilar terminus aneurysms. Furthermore, our data show that the thalamoperforating arteries may take off from both the aneurysm neck and the fundus.

[Pulvinar]

The pulvinar is the largest nucleus of the thalamus. Its lateral and inferior areas have rich connections with the visual- and dorsolateral parietal cortices. Several cells in the medial and upper area connect the anterior cingulum and the premotor and prefrontal association areas. This neuronal network was considered to organize the saccades and visual attention. Other cells in the medial nucleus have axonal connections with paralimbic-, insular and higher order association-cortices. The medial structure integrates complex sensory information with limbic reactivity settings, transmitting these to the temporal and parieto-occipital centres. The pulvinar is supplied by the posterior chorioideal artery. Visual salience is considered to be an important function of the pulvinar. Visual selection enables subjects to choose the actually adequate behavioral act. To serve the visual salience the pulvinar may also inhibit inappropriate eye movements. The pulvinar appears to be a key structure of the EEG's alpha rhythm generator, acting together with the parietooccipital and temporal cortices. Dynamic fluctuation of BOLD signals on fMRI correlates well with the change of alpha power even in resting state. We presume that the pulvinar is part of a closed cortico-subcortical circuit, analogous with the striatum, but the output of the pulvinar initiates complex behavioral reactions, including perception, selective attention and emotions. Damage of the pulvinar may elicit contralateral visual neglect, because of the dissociation of the neuronal network integrated by the superior temporal area. Increased activity of the pulvinar was found during abrupt reaction to fearful visual signals; and also in the etiopathology of endogenous depressions through the alteration of serotonin transporters. Increased bilateral signal intensity of the pulvinar on MRI was detected in cases of the new variants of Creutzfeldt-Jakob- and Fabry diseases.

The thalamus and brainstem act as key hubs in alterations of human brain network connectivity induced by mild propofol sedation

Despite their routine use during surgical procedures, no consensus has yet been reached on the precise mechanisms by which hypnotic anesthetic agents produce their effects. Molecular, animal and human studies have suggested disruption of thalamocortical communication as a key component of anesthetic action at the brain systems level. Here, we used the anesthetic agent, propofol, to modulate consciousness and to evaluate differences in the interactions of remote neural networks during altered consciousness. We investigated the effects of propofol, at a dose that produced mild sedation without loss of consciousness, on spontaneous cerebral activity of 15 healthy volunteers using functional magnetic resonance imaging (fMRI), exploiting oscillations (<0.1 Hz) in blood oxygenation level-dependent signal across functionally connected brain regions. We considered the data as a graph, or complex network of nodes and links, and used eigenvector centrality (EC) to characterize brain network properties. The EC mapping of fMRI data in healthy humans under propofol mild sedation demonstrated a decrease of centrality of the thalamus versus an increase of centrality within the pons of the brainstem, highlighting the important role of these two structures in regulating consciousness. Specifically, the decrease of thalamus centrality results from its disconnection from a widespread set of cortical and subcortical regions, while the increase of brainstem centrality may be a consequence of its increased influence, in the mildly sedated state, over a few highly central cortical regions key to the default mode network such as the posterior and anterior cingulate cortices.