"Clock dial pattern", a radiologic clue to neuro-chikungunya diagnosis: a case series.

BACKGROUND: Chikungunya is a mosquito-borne disease caused by the chikungunya virus (CHIKV) and can lead to neurological complications in severe cases. OBJECTIVE: This study examined neuroimaging patterns in chikungunya cases during two outbreaks in Brazil to identify specific patterns for diagnosis and treatment of neuro-chikungunya. METHODS: Eight patients with confirmed chikungunya and neurological involvement were included. Clinical examinations and MRI scans were performed, and findings were analyzed by neuroradiologists. Data on age, sex, neurological symptoms, diagnostic tests, MRI findings, and clinical outcomes were recorded. RESULTS: Patients showed different neuroimaging patterns. Six patients exhibited a "clock dial pattern" with hyperintense dotted lesions in the spinal cord periphery. One patient had thickening and enhancement of anterior nerve roots. Brain MRI revealed multiple hyperintense lesions in the white matter, particularly in the medulla oblongata, in six patients. One patient had a normal brain MRI. CONCLUSION: The "clock dial pattern" observed in spinal cord MRI may be indicative of chikungunya-related nervous system lesions. Isolated involvement of spinal cord white matter in chikungunya can help differentiate it from other viral infections. Additionally, distinct brainstem involvement in chikungunya-associated encephalitis, particularly in the rostral region, sets it apart from other arboviral infections. Recognizing these neuroimaging patterns can contribute to early diagnosis and appropriate management of neuro-chikungunya.

ANTECEDENTES: A chikungunya é uma doença transmitida por mosquitos causada pelo vírus chikungunya (CHIKV) e pode levar a complicações neurológicas em casos graves. OBJETIVO: Este estudo examinou padrões de neuroimagem em casos de chikungunya durante dois surtos no Brasil para identificar padrões específicos para o diagnóstico e tratamento de neurochikungunya. MéTODOS: Oito pacientes com chikungunya confirmada e envolvimento neurológico foram incluídos. Exames clínicos e ressonâncias magnéticas (RM) foram realizados, e os achados foram analisados por neurorradiologistas. Dados sobre idade, sexo, sintomas neurológicos, testes diagnósticos, achados de RM e desfechos clínicos foram registrados. RESULTADOS: Os pacientes apresentaram diferentes padrões de neuroimagem. Seis pacientes apresentaram um "padrão de mostrador de relógio" com lesões pontilhadas hiperintensas na periferia da medula espinhal. Um paciente apresentou espessamento e realce das raízes nervosas anteriores. A RM do cérebro revelou múltiplas lesões hiperintensas na substância branca, especialmente no bulbo em seis pacientes. Um paciente apresentou uma RM cerebral normal. CONCLUSãO: O "padrão de mostrador de relógio" observado na RM da medula espinhal pode ser indicativo de lesões do sistema nervoso relacionadas à chikungunya. O envolvimento isolado da substância branca da medula espinhal na chikungunya pode ajudar a diferenciá-la de outras infecções virais. Além disso, o envolvimento distinto do tronco cerebral na encefalite associada à chikungunya, especialmente na região rostral, a distingue de outras infecções por arbovírus. O reconhecimento desses padrões de neuroimagem pode contribuir para o diagnóstico precoce e manejo adequado da neurochikungunya.

"Clock dial pattern", a radiologic clue to neuro-chikungunya diagnosis: a case series / "Padrão em ponteiro de relógio", uma dica radiológica para o diagnóstico de neurochikungunya: série de casos

Abstract Background Chikungunya is a mosquito-borne disease caused by the chikungunya virus (CHIKV) and can lead to neurological complications in severe cases. Objective This study examined neuroimaging patterns in chikungunya cases during two outbreaks in Brazil to identify specific patterns for diagnosis and treatment of neuro-chikungunya. Methods Eight patients with confirmed chikungunya and neurological involvement were included. Clinical examinations and MRI scans were performed, and findings were analyzed by neuroradiologists. Data on age, sex, neurological symptoms, diagnostic tests, MRI findings, and clinical outcomes were recorded. Results Patients showed different neuroimaging patterns. Six patients exhibited a "clock dial pattern" with hyperintense dotted lesions in the spinal cord periphery. One patient had thickening and enhancement of anterior nerve roots. Brain MRI revealed multiple hyperintense lesions in the white matter, particularly in the medulla oblongata, in six patients. One patient had a normal brain MRI. Conclusion The "clock dial pattern" observed in spinal cord MRI may be indicative of chikungunya-related nervous system lesions. Isolated involvement of spinal cord white matter in chikungunya can help differentiate it from other viral infections. Additionally, distinct brainstem involvement in chikungunya-associated encephalitis, particularly in the rostral region, sets it apart from other arboviral infections. Recognizing these neuroimaging patterns can contribute to early diagnosis and appropriate management of neuro-chikungunya.

Resumo Antecedentes A chikungunya é uma doença transmitida por mosquitos causada pelo vírus chikungunya (CHIKV) e pode levar a complicações neurológicas em casos graves. Objetivo Este estudo examinou padrões de neuroimagem em casos de chikungunya durante dois surtos no Brasil para identificar padrões específicos para o diagnóstico e tratamento de neurochikungunya. Métodos Oito pacientes com chikungunya confirmada e envolvimento neurológico foram incluídos. Exames clínicos e ressonâncias magnéticas (RM) foram realizados, e os achados foram analisados por neurorradiologistas. Dados sobre idade, sexo, sintomas neurológicos, testes diagnósticos, achados de RM e desfechos clínicos foram registrados. Resultados Os pacientes apresentaram diferentes padrões de neuroimagem. Seis pacientes apresentaram um "padrão de mostrador de relógio" com lesões pontilhadas hiperintensas na periferia da medula espinhal. Um paciente apresentou espessamento e realce das raízes nervosas anteriores. A RM do cérebro revelou múltiplas lesões hiperintensas na substância branca, especialmente no bulbo em seis pacientes. Um paciente apresentou uma RM cerebral normal. Conclusão O "padrão de mostrador de relógio" observado na RM da medula espinhal pode ser indicativo de lesões do sistema nervoso relacionadas à chikungunya. O envolvimento isolado da substância branca da medula espinhal na chikungunya pode ajudar a diferenciá-la de outras infecções virais. Além disso, o envolvimento distinto do tronco cerebral na encefalite associada à chikungunya, especialmente na região rostral, a distingue de outras infecções por arbovírus. O reconhecimento desses padrões de neuroimagem pode contribuir para o diagnóstico precoce e manejo adequado da neurochikungunya.

Zika virus infection histories in brain development.

An outbreak of births of microcephalic patients in Brazil motivated multiple studies on this incident. The data left no doubt that infection by Zika virus (ZIKV) was the cause, and that this virus promotes reduction in neuron numbers and neuronal death. Analysis of patients' characteristics revealed additional aspects of the pathology alongside the decrease in neuronal number. Here, we review the data from human, molecular, cell and animal model studies attempting to build the natural history of ZIKV in the embryonic central nervous system (CNS). We discuss how identifying the timing of infection and the pathways through which ZIKV may infect and spread through the CNS can help explain the diversity of phenotypes found in congenital ZIKV syndrome (CZVS). We suggest that intraneuronal viral transport is the primary mechanism of ZIKV spread in the embryonic brain and is responsible for most cases of CZVS. According to this hypothesis, the viral transport through the blood-brain barrier and cerebrospinal fluid is responsible for more severe pathologies in which ZIKV-induced malformations occur along the entire anteroposterior CNS axis.

Nootropic effects of LSD: Behavioral, molecular and computational evidence.

The therapeutic use of classical psychedelic substances such as d-lysergic acid diethylamide (LSD) surged in recent years. Studies in rodents suggest that these effects are produced by increased neural plasticity, including stimulation of the mTOR pathway, a key regulator of metabolism, plasticity, and aging. Could psychedelic-induced neural plasticity be harnessed to enhance cognition? Here we show that LSD treatment enhanced performance in a novel object recognition task in rats, and in a visuo-spatial memory task in humans. A proteomic analysis of human brain organoids showed that LSD affected metabolic pathways associated with neural plasticity, including mTOR. To gain insight into the relation of neural plasticity, aging and LSD-induced cognitive gains, we emulated the experiments in rats and humans with a neural network model of a cortico-hippocampal circuit. Using the baseline strength of plasticity as a proxy for age and assuming an increase in plasticity strength related to LSD dose, the simulations provided a good fit for the experimental data. Altogether, the results suggest that LSD has nootropic effects.

Cyclic alternation of quiet and active sleep states in the octopus.

Previous observations suggest the existence of 'Active sleep' in cephalopods. To investigate in detail the behavioral structure of cephalopod sleep, we video-recorded four adult specimens of Octopus insularis and quantified their distinct states and transitions. Changes in skin color and texture and movements of eyes and mantle were assessed using automated image processing tools, and arousal threshold was measured using sensory stimulation. Two distinct states unresponsive to stimulation occurred in tandem. The first was a 'Quiet sleep' state with uniformly pale skin, closed pupils, and long episode durations (median 415.2 s). The second was an 'Active sleep' state with dynamic skin patterns of color and texture, rapid eye movements, and short episode durations (median 40.8 s). 'Active sleep' was periodic (60% of recurrences between 26 and 39 min) and occurred mostly after 'Quiet sleep' (82% of transitions). These results suggest that cephalopods have an ultradian sleep cycle analogous to that of amniotes.

Association between brain morphology and electrophysiological features in Congenital Zika Virus Syndrome: A cross-sectional, observational study.

BACKGROUND: Intrauterine infection with the Zika virus (ZIKV) has been connected to severe brain malformations, microcephaly, and abnormal electrophysiological activity. METHODS: We describe the interictal electroencephalographic (EEG) recordings of 47 children born with ZIKV-derived microcephaly. EEGs were recorded in the first year of life and correlated with brain morphology. In 31 subjects, we tested the association between computed tomography (CT) findings and interictal epileptiform discharges (IED). In eighteen, CTs were used for correlating volumetric measurements of the brainstem, cerebellum, and prosencephalon with the rate of IED. FINDINGS: Twenty-nine out of 47 (62%) subjects were diagnosed as having epilepsy. Those subjects presented epileptiform discharges, including unilateral interictal spikes (26/29, 90%), bilateral synchronous and asynchronous interictal spikes (21/29, 72%), and hypsarrhythmia (12/29, 41%). Interestingly, 58% of subjects with clinical epilepsy were born with rhombencephalon malformations, while none of the subjects without epilepsy showed macroscopic abnormalities in this region. The presence of rhombencephalon malformation was associated with epilepsy (odds ratio of 34; 95% CI: 2 - 654). Also, the presence of IED was associated with smaller brain volumes. Age-corrected total brain volume was inversely correlated with the rate of IED during sleep. Finally, 11 of 44 (25%) subjects presented sleep spindles. We observed an odds ratio of 0·25 (95% CI: 0·06 - 1·04) for having sleep spindles given the IED presence. INTERPRETATION: The findings suggest that certain CT imaging features are associated with an increased likelihood of developing epilepsy, including higher rates of IED and impaired development of sleep spindles, in the first year of life of CZVS subjects. FUNDING: This work was supported by the Brazilian Federal Government through a postdoctoral fellowship for EBS (Talented Youth, Science without Borders), an undergraduate scholarship for AJR (Institutional Program of Science Initiation Scholarships, Federal University of Rio Grande do Norte, Brazil), by International Centre for Genetic Engineering and Biotechnology (CRP/BRA18-05_EC) and by CAPES (Grant number 440893/2016-0), and CNPq (Grant number 88881.130729/2016-01).

NMDA Receptor Signaling Is Important for Neural Tube Formation and for Preventing Antiepileptic Drug-Induced Neural Tube Defects.

Failure of neural tube closure leads to neural tube defects (NTDs), which can have serious neurological consequences or be lethal. Use of antiepileptic drugs (AEDs) during pregnancy increases the incidence of NTDs in offspring by unknown mechanisms. Here we show that during Xenopus laevis neural tube formation, neural plate cells exhibit spontaneous calcium dynamics that are partially mediated by glutamate signaling. We demonstrate that NMDA receptors are important for the formation of the neural tube and that the loss of their function induces an increase in neural plate cell proliferation and impairs neural cell migration, which result in NTDs. We present evidence that the AED valproic acid perturbs glutamate signaling, leading to NTDs that are rescued with varied efficacy by preventing DNA synthesis, activating NMDA receptors, or recruiting the NMDA receptor target ERK1/2. These findings may prompt mechanistic identification of AEDs that do not interfere with neural tube formation.SIGNIFICANCE STATEMENT Neural tube defects are one of the most common birth defects. Clinical investigations have determined that the use of antiepileptic drugs during pregnancy increases the incidence of these defects in the offspring by unknown mechanisms. This study discovers that glutamate signaling regulates neural plate cell proliferation and oriented migration and is necessary for neural tube formation. We demonstrate that the widely used antiepileptic drug valproic acid interferes with glutamate signaling and consequently induces neural tube defects, challenging the current hypotheses arguing that they are side effects of this antiepileptic drug that cause the increased incidence of these defects. Understanding the mechanisms of neurotransmitter signaling during neural tube formation may contribute to the identification and development of antiepileptic drugs that are safer during pregnancy.

Radiological Characterization of Cerebral Phenotype in Newborn Microcephaly Cases from 2015 Outbreak in Brazil.

INTRODUCTION: Brazil is facing, since October of 2015, an outbreak of microcephalic fetuses. This outbreak is correlated with the beginning of circulation of Zika virus (ZIKV) in the country. Although it is clear that the size of the head is diminished in these fetuses, the brain phenotype associated with these malformations is unknown. METHODS: We collected computed tomography images of the microcephaly cases from the region of Natal, Rio Grande do Norte, from September 2015 to February 2016. FINDINGS: The microcephalies derived from the current outbreak are associated with intracerebral calcifications, malformation of the ventricular system, migratory disorders in the telencephalon and, in a lower frequency, malformation of the cerebellum and brainstem. DISCUSSION: The characteristics described herein are not usually found in other types of microcephaly. We suggest that this work can be used as a guideline to identify microcephaly cases associated to the current outbreak.

Spatiotemporal integration of developmental cues in neural development.

Nervous system development relies on the generation of neurons, their differentiation and establishment of synaptic connections. These events exhibit remarkable plasticity and are regulated by many developmental cues. Here, we review the mechanisms of three classes of these cues: morphogenetic proteins, electrical activity, and the environment. We focus on second messenger dynamics and their role as integrators of the action of diverse cues, enabling plasticity in the process of neural development.

Dynamic regulation of neurotransmitter specification: relevance to nervous system homeostasis.

During nervous system development the neurotransmitter identity changes and coexpression of several neurotransmitters is a rather generalized feature of developing neurons. In the mature nervous system, different physiological and pathological circumstances recreate this phenomenon. The rules of neurotransmitter respecification are multiple. Among them, the goal of assuring balanced excitability appears as an important driving force for the modifications in neurotransmitter phenotype expression. The functional consequences of these dynamic revisions in neurotransmitter identity span a varied range, from fine-tuning the developing neural circuit to modifications in addictive and locomotor behaviors. Current challenges include determining the mechanisms underlying neurotransmitter phenotype respecification and how they intersect with genetic programs of neuronal specialization. This article is part of the Special Issue entitled 'Homeostatic Synaptic Plasticity'.

Subventricular zone progenitors in time and space: generating neuronal diversity.

The adult mammalian brain harbors a population of cells around their lateral ventricles capable of giving rise to new neurons throughout life. The so-called subventricular zone (SVZ) is a heterogeneous germinative niche in regard to the neuronal types it generates. SVZ progenitors give rise to different olfactory bulb (OB) interneuron types in accordance to their position along the ventricles. Here, I review data showing the difference between progenitors located along different parts of the SVZ axes and ages. I also discuss possible mechanisms for the origin of this diversity.

Adult neural stem cells: plastic or restricted neuronal fates?

During embryonic development, the telencephalon is specified along its axis through morphogenetic gradients, leading to the positional-dependent generation of multiple neuronal types. After embryogenesis, however, the fate of neuronal progenitors becomes more restricted, and they generate only a subset of neurons. Here, we review studies of postnatal and adult neurogenesis, challenging the notion that fixed genetic programs restrict neuronal fate. We hypothesize that the adult brain maintains plastic neural stem cells that are capable of responding to changes in environmental cues and generating diverse neuronal types. Thus, the limited diversity of neurons generated under normal conditions must be actively maintained by the adult milieu.

Generation of glutamatergic neurons from postnatal and adult subventricular zone with pyramidal-like morphology.

The mammalian subventricular zone (SVZ) contains progenitors derived from cerebral cortex radial glia cells, which give rise to glutamatergic pyramidal neurons during embryogenesis. However, during postnatal life, SVZ generates neurons that migrate and differentiate into olfactory bulb γ-aminobutyric acid (GABA)ergic interneurons. In this work, we tested if SVZ cells are able to produce glutamatergic neurons if confronted with the embryonic cortical ventricular zone environment. Different from typical SVZ chain migration, cells from P9-P11 SVZ explants migrate into embryonic cortical slices individually, many of which radially oriented. An average of 82.5% of green fluorescent protein-positive cells were immunolabeled for neuronal marker class III ß-tubulin. Invading cells differentiate into multiple morphologies, including a pyramidal-like morphotype. A subset of these cells are GABAergic; however, about 28% of SVZ-derived cells are immunoreactive for glutamate. Adult SVZ explants also give rise to glutamatergic neurons in these conditions. Taken together, our results indicate that SVZ can be a source of glutamatergic cortical neurons when submitted to proper environmental cues.