Hippocampus shapes cortical sensory output and novelty coding through a direct feedback circuit.

To extract behaviorally relevant information from our surroundings, our brains constantly integrate and compare incoming sensory information with those stored as memories. Cortico-hippocampal interactions could mediate such interplay between sensory processing and memory recall1-4 but this remains to be demonstrated. Recent work parsing entorhinal cortex-to-hippocampus circuitry show its role in episodic memory formation5-7 and spatial navigation8. However, the organization and function of the hippocampus-to-cortex back-projection circuit remains uncharted. We combined circuit mapping, physiology and behavior with optogenetic manipulations, and computational modeling to reveal how hippocampal feedback modulates cortical sensory activity and behavioral output. Here we show a new direct hippocampal projection to entorhinal cortex layer 2/3, the very layer that projects multisensory input to the hippocampus. Our finding challenges the canonical cortico-hippocampal circuit model where hippocampal feedback only reaches entorhinal cortex layer 2/3 indirectly via layer 5. This direct hippocampal input integrates with cortical sensory inputs in layer 2/3 neurons to drive their plasticity and spike output, and provides an important novelty signal during behavior for coding objects and their locations. Through the sensory-memory feedback loop, hippocampus can update real-time cortical sensory processing, efficiently and iteratively, thereby imparting the salient context for adaptive learned behaviors with new experiences.

Advanced multiparametric magnetic resonance imaging of multinodular and vacuolating neuronal tumor.

BACKGROUND AND PURPOSE: Multinodular and vacuolating neuronal tumor (MVNT) of the cerebrum is a rare brain lesion with suggestive imaging features. The aim of our study was to report the largest series of MVNTs so far and to evaluate the utility of advanced multiparametric magnetic resonance (MR) techniques. METHODS: This multicenter retrospective study was approved by our institutional research ethics board. From July 2014 to May 2019, two radiologists read in consensus the MR examinations of patients presenting with a lesion suggestive of an MVNT. They analyzed the lesions' MR characteristics on structural images and advanced multiparametric MR imaging. RESULTS: A total of 64 patients (29 women and 35 men, mean age 44.2 ± 15.1 years) from 25 centers were included. Lesions were all hyperintense on fluid-attenuated inversion recovery and T2-weighted imaging without post-contrast enhancement. The median relative apparent diffusion coefficient on diffusion-weighted imaging was 1.13 [interquartile range (IQR), 0.2]. Perfusion-weighted imaging showed no increase in perfusion, with a relative cerebral blood volume of 1.02 (IQR, 0.05) and a relative cerebral blood flow of 1.01 (IQR, 0.08). MR spectroscopy showed no abnormal peaks. Median follow-up was 2 (IQR, 1.2) years, without any changes in size. CONCLUSIONS: A comprehensive characterization protocol including advanced multiparametric magnetic resonance imaging sequences showed no imaging patterns suggestive of malignancy in MVNTs. It might be useful to better characterize MVNTs.

Multinodular and Vacuolating Posterior Fossa Lesions of Unknown Significance.

Multinodular and vacuolating neuronal tumor of the cerebrum is a rare supratentorial brain tumor described for the first time in 2013. Here, we report 11 cases of infratentorial lesions showing similar striking imaging features consisting of a cluster of low T1-weighted imaging and high T2-FLAIR signal intensity nodules, which we referred to as multinodular and vacuolating posterior fossa lesions of unknown significance. No relationship was found between the location of the lesion and clinical symptoms. A T2-FLAIR hypointense central dot sign was present in images of 9/11 (82%) patients. Cortical involvement was present in 2/11 (18%) of patients. Only 1 nodule of 1 multinodular and vacuolating posterior fossa lesion of unknown significance showed enhancement on postcontrast T1WI. DWI, SWI, MRS, and PWI showed no malignant pattern. Lesions did not change in size or signal during a median follow-up of 3 years, suggesting that multinodular and vacuolating posterior fossa lesions of unknown significance are benign malformative lesions that do not require surgical intervention or removal.

Diffusion-weighted magnetic resonance imaging of the fetal brain in intrauterine growth restriction.

OBJECTIVE: Diffusion-weighted magnetic resonance imaging (DWI) is a sensitive method for assessing brain maturation and detecting brain lesions, providing apparent diffusion coefficient (ADC) values as a measure of water diffusion. Abnormal ADC values are seen in ischemic brain lesions, such as those associated with acute or chronic hypoxia. The aim of this study was to assess whether ADC values in the fetal brain were different in fetuses with severe intrauterine growth restriction (IUGR) compared with normal controls. METHODS: Brain magnetic resonance imaging (MRI) with single-shot axial DWI (b = 0 and b = 700 s/mm2 ) was performed in 30 fetuses with severe IUGR (estimated fetal weight < 3rd centile with absent or reversed umbilical artery Doppler flow) and in 24 normal controls of similar gestational age. Brain morphology and biometry were analyzed. ADC values were measured in frontal and occipital white matter, centrum semiovale, thalami, cerebellar hemisphere and pons. Frontal-occipital and frontal-cerebellar ADC ratios were calculated, and values were compared between IUGR fetuses and controls. RESULTS: There was no difference in gestational age at MRI between IUGR and control fetuses (IUGR, 30.2 ± 1.6 weeks vs controls, 30.7 ± 1.4 weeks). Fetal brain morphology and signals were normal in all fetuses. Brain dimensions (supratentorial ± infratentorial) were decreased (Z-score, < -2) in 20 (66.7%) IUGR fetuses. Compared with controls, IUGR fetuses had significantly lower ADC values in frontal white matter (1.97 ± 0.23 vs 2.17 ± 0.22 × 10-3 mm2 /s; P < 0.0001), thalami (1.04 ± 0.15 vs 1.13 ± 0.10 ×10-3 mm2 /s; P = 0.0002), centrum semiovale (1.86 ± 0.22 vs 1.97 ± 0.23 ×10-3 mm2 /s; P = 0.01) and pons (0.85 ± 0.19 vs 0.94 ± 0.12 ×10-3 mm2 /s; P = 0.043). IUGR fetuses had a lower frontal-occipital ADC ratio than did normal fetuses (1.00 ± 0.11 vs 1.08 ± 0.05; P = 0.003). CONCLUSIONS: ADC values in IUGR fetuses were significantly lower than in normal controls in the frontal white matter, thalami, centrum semiovale and pons, suggesting abnormal maturation in these regions. However, the prognostic value of these ADC changes is still unknown. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

[Cerebellar injury in premature infants less than 30 weeks of gestation]. / Lésions acquises du cervelet chez le grand prématuré : prévalence, facteurs de risque et conséquences fonctionnelles.

UNLABELLED: Traditionally, the cerebellum has been regarded as a central component of the motor system. Recent studies suggest an important role played by the cerebellum in the development of cognitive and social functions. The objective of this study was to evaluate the incidence of cerebellar injury and to define the obstetrical, neonatal, and radiologic characteristics, as well as the functional outcomes in a population of very preterm infants. METHODS: This retrospective study included neonates born before 30 weeks of gestational age between March 2004 and July 2007. Infants underwent MRI studies at a term-adjusted age; for each preterm infant with cerebellar injury, we identified two infants for the control group with normal MRI, matched on the basis of gestational age. We collected pertinent demographic, prenatal, and acute postnatal data for all infants. Follow-up assessment was performed at 2 years, using the Brunet-Lezine scale. RESULTS: A total of 148 ex-preterm infants were studied. Cerebellar injury was present in 14 (9 %) cases and associated with supratentorial parenchymal injury in 90 %. Duration of ventilation was longer in children with cerebellar injury, compared to controls (19.5 days vs 16.5 days; P=0.03). The other neonatal criteria analyzed were comparable between the two groups. Global developmental, functional, and social-behavioral deficits were more common and profound in preterm infants with cerebellar injury, with no significant difference. CONCLUSION: This study confirms the high incidence of cerebellar injury in very preterm infants and the importance of a specific neurobehavioral follow-up.

[Fetal ocular anomalies: the advantages of prenatal magnetic resonance imaging]. / Anomalies oculaires foetales : apport de l'imagerie anténatale en résonance magnétique.

Congenital ocular malformations are uncommon and require prenatal diagnosis. Severe anomalies are more often detected by trained teams and minor anomalies are more difficult to identify and must be systematically sought, particularly when multiple malformations or a family and maternal history is known. The prenatal diagnosis-imaging tool most commonly used is ultrasound but it can be completed by magnetic resonance imaging (MRI), which contributes crucial information. Fetal dysmorphism can occur in various types of dysfunction and prenatal diagnosis must recognize fetal ocular anomalies. After systematic morphologic ultrasound imaging, different abnormalities detected by MRI are studied. Classical parameters such as binocular and interorbital measurements are used to detect hypotelorism and hypertelorism. Prenatal ocular anomalies such as cataract microphthalmia, anophthalmia, and coloboma have been described. Fetal MRI added to prenatal sonography is essential in detecting cerebral and general anomalies and can give more information on the size and morphology of the eyeball. Fetal abnormality detection includes a detailed family and maternal history, an amniotic fluid sample for karyotype, and other analyses for a better understanding of the images. Each pregnancy must be discussed with all specialists for genetic counseling. With severe malformations, termination of pregnancy is proposed because of risk of blindness and associated cerebral or systemic anomalies. Early prenatal diagnosis of ocular malformations can also detect associated abnormalities, taking congenital cataracts that need surgical treatment into account as early as possible. Finally, various associated syndromes need a pediatric check-up that could lead to emergency treatment.

Expanding the clinical and neuroradiologic phenotype of primary microcephaly due to ASPM mutations.

OBJECTIVE: To determine the spectrum of clinical, neuropsychological, and neuroradiologic features in patients with autosomal recessive primary microcephaly (MCPH) due to ASPM gene mutations. METHODS: ASPM was sequenced in 52 unrelated MCPH probands. In patients with ASPM mutations, we evaluated the clinical phenotype, cognition, behavior, brain MRI, and family. RESULTS: We found homozygous or compound heterozygous ASPM loss-of-function mutations in 11 (22%) probands and 5 siblings. The probands harbored 18 different mutations, of which 16 were new. Microcephaly was severe after 1 year of age in all 16 patients, although in 4 patients the occipital-frontal circumference (OFC) at birth was decreased by only 2 SD. The OFC Z score consistently decreased after birth. Late-onset seizures occurred in 3 patients and significant pyramidal tract involvement in 1 patient. Intellectual quotients ranged from borderline-normal to severe mental retardation. Mild motor delay was noted in 7/16 patients. Language development was delayed in all patients older than 3 years. Brain MRI (n = 12) showed a simplified gyral pattern in 9 patients and several malformations including ventricle enlargement (n = 7), partial corpus callosum agenesis (n = 3), mild cerebellar hypoplasia (n = 1), focal cortical dysplasia (n = 1), and unilateral polymicrogyria (n = 1). Non-neurologic abnormalities consisted of short stature (n = 1), idiopathic premature puberty (n = 1), and renal dysplasia (n = 1). CONCLUSIONS: We provide a detailed description of features associated with ASPM mutations. Borderline microcephaly at birth, borderline-normal intellectual efficiency, and brain malformations can occur in ASPM-related primary hereditary microcephaly.

[Genetic and clinical aspects of lissencephaly]. / Lissencéphalies: aspects cliniques et génétiques.

The term lissencephaly covers a group of rare malformations sharing the common feature of anomalies in the appearance of brain convolutions (characterised by simplification or absence of folding) associated with abnormal organisation of the cortical layers as a result of neuronal migration defects during embryogenesis. Children with lissencephaly have feeding and swallowing problems, muscle tone anomalies (early hypotonia and subsequently limb hypertonia), seizures (in particular, infantile spasms) and severe psychomotor retardation. Multiple forms of lissencephaly have been described and their current classification is based on the associated malformations and underlying aetiology. Two large groups can be distinguished: classical lissencephaly (and its variants) and cobblestone lissencephaly. In classical lissencephaly (or type I), the cortex appears thickened, with four more or less disorganised layers rather than six normal layers. In the variants of classical lissencephaly, extra-cortical anomalies are also present (total or subtotal agenesis of the corpus callosum and/or cerebellar hypoplasia). The classical lissencephalies and the variant forms can be further divided into several subgroups. Four forms can be distinguished on the basis of their genetic aetiology: anomalies in the LIS1 gene (isolated lissencephaly and Miller-Dieker syndrome), anomalies in the TUBA3 and DCX genes, and lissencephalies caused by mutations in the ARX gene (XLAG syndrome, X-linked lissencephaly with agenesis of the corpus callosum). The incidence of all forms of type I lissencephaly is around 1 in 100,000 births. In addition to these four entities, isolated lissencephalies without a known genetic defect, lissencephalies with severe microcephaly (microlissencephaly) and lissencephalies associated with polymalformative syndromes are also included in the group of classical lissencephalies. Cobblestone lissencephaly (formally referred to as type II) is present in three entities: the Walker-Warburg, Fukuyama and MEB (Muscle-Eye-Brain) syndromes. It is characterised by global disorganisation of cerebral organogenesis with an uneven cortical surface (with a pebbled or cobblestone appearance). Microscopic examination reveals total disorganisation of the cortex and the absence of any distinguishable layers. Management is symptomatic only (swallowing problems require adapted feeding to prevent food aspiration, articular and respiratory physiotherapy to prevent orthopaedic problems resulting from hyptonia and treatment of gastrooesophageal reflux). The epilepsy is often resistant to treatment. The encephalopathy associated with lissencephaly is often very severe and affected children are completely dependent on the carer.

Prenatal isolated mild ventriculomegaly: outcome in 167 cases.

OBJECTIVE: To define the contribution of prenatal investigation and evaluate the prognosis of isolated mild ventriculomegaly (IMV). DESIGN: Retrospective study. SETTING: University hospital between January 1992 and December 2002. POPULATION: One hundred and sixty-seven cases of prenatal unilateral or bilateral IMV without any associated anomaly at the time of initial diagnosis. METHODS: Complementary investigations were performed: amniocentesis with karyotyping, screening for viruses and acetylcholinesterase electrophoresis, magnetic resonance imaging (MRI), and ultrasonography every 3-4 weeks. MAIN OUTCOME MEASURES: Results of prenatal investigations, pregnancy outcome, and postnatal psychomotor development. RESULTS: IMV was diagnosed around 26.5 weeks. Amniocentesis revealed four chromosomal anomalies and two cytomegalovirus infections. MRI diagnosed brain-associated anomalies in 15 cases and ultrasonographic monitoring highlighted malformations not initially diagnosed in 28 cases. Termination of pregnancy (TOP) was considered in 21 pregnancies (12.6%). Indications were aneuploidy, fetal infectious disease or associated malformations. In women for whom a TOP was considered, consanguinity, fetus of female sex and frontal horn enlargement were statistically more frequent, ventriculomegaly was more often bilateral and asymmetrical, atrial width, and the rate of progressive ventricular enlargement were significantly higher. One hundred and one children with prenatal IMV were assessed between 19 and 127 months (mean age 54.68 +/- 2.87 months). Twelve children had neurological disease or psychomotor delay and 89 children had a normal psychomotor development. Poor neurological outcome was more often associated with atrial width greater than or equal to 12 mm, asymmetrical bilateral enlargement, and progression of the ventriculomegaly. CONCLUSION: The detection of IMV raises the question of the child's psychomotor development and justifies meticulous prenatal investigation. In addition to associated anomalies, three criteria are often associated with an unfavourable outcome: atrial width greater than 12 mm, progression of the enlargement, and asymmetrical and bilateral ventriculomegaly.

[Bilateral jugular thrombosis in Lemierre syndrome]. / Un cas de syndrome de Lemierre avec thrombose veineuse jugulaire bilatérale.

An adolescent presented with a rhinosinusitis complicated with bilateral jugular veins and left superior ophthalmic vein thrombosis and respiratory distress with pulmonary hypertension. Blood culture was positive for Haemophilus influenzae and sinus puncture for Streptococcus constellatus. Evolution was under control after 1 week of appropriate antibiotherapy, antithrombotic and anti-inflammatory treatment. He had no neurologic, respiratory or ophthalmologic sequelae 6 months later. Despite lack of pharyngitis or isolation of anaerobic species on blood cultures, the picture was considered compatible with Lemierre syndrome. The risk for such a complication should be considered in cases of severe otorhinolaryngologic infection in young adults.

Bronchial trifurcation in a congenital pulmonary venolobar syndrome.

Congenital malformations of the tracheobronchal tree and the related arterial blood supply are a complex group of lesions in which there are abnormalities of the venous drainage and lung parenchyma. These malformations are examples of congenital pulmonary venolobar syndrome (CPVS). Tracheal trifurcation is an extremely rare anomaly associated with CPVS. We report on an unusual case of lower right extralobar sequestration connected to the trachea, plus a type I posterior laryngeal cleft, an aberrant systemic artery, and an anomalous route of the phrenic nerve. This paper discusses the place of this unusual abnormality in the spectrum of congenital bronchopulmonary vascular malformations.

Fetal cerebral cortex: normal gestational landmarks identified using prenatal MR imaging.

BACKGROUND AND PURPOSE: Few investigators have analyzed the MR imaging patterns of fetal gyration. Our purpose was to establish, with a large prospective series, the normal sulcation landmarks according to gestational age by using in utero MR imaging and to correlate our findings with established neuroanatomic timetables. METHODS: A standardized fetal cerebral MR examination was performed in 173 normal fetuses at 22 to 38 weeks' gestation. Eight T1- and T2-weighted coronal, axial, and sagittal slices were obtained for each fetus and systematically analyzed. The sequential development of the different fissures and sulci of the cerebral cortex with respect to gestational age were tabulated. RESULTS: Sulcation of the medial, lateral, and inferior surfaces of the brain was depicted, and a timetable for the MR depiction of the primary and secondary sulci was established for the 22- to 38-week gestational period. This timetable was in good agreement with the neuroanatomic standards of reference, with a mean lag time of 1 week. CONCLUSION: This analysis of fetal brain sulcation in a large series of fetuses contributes to a better understanding of the maturation of the fetal cortex on MR imaging studies. It furthermore provides a standard of reference that can be used to assess the normality of fetal sulcation and to diagnose gyrational abnormalities with prenatal MR imaging.

[Direct foreign body footplate trauma: 3 cases]. / Traumatisme direct de la platine par corps étranger, à propos de 3 cas.

3 cases of direct foreign body footplate trauma are described in children. A surgical exploration was decided on history, cochleovestibular signs and/or CT abnormalities. Hearing improved in all cases after surgery.

Rhombencephalosynapsis diagnosed in childhood: clinical and MRI findings.

Rhombencephalosynapsis is an unfrequent malformation of the posterior fossa essentially characterized by vermian agenesis or hypogenesis, fusion of the cerebellar hemispheres and fusion of the dentate nuclei. Supratentorial abnormalities are usually associated. No specific clinical syndrome can be described in relation with this disorder. We report a case diagnosed by MRI in a living patient.

Contribution of single-photon emission computed tomography in the diagnosis and follow-up of CNS toxicity of a cytarabine-containing regimen in pediatric leukemia.

PURPOSE: Cytarabine (ara-C) is one of the most effective chemotherapeutic agents in patients with acute leukemia (AL), with a clear dose effect. Use of high-dose ara-C is hampered, however, by a noticeable toxicity, particularly to the CNS. We investigated the usefulness of CNS perfusion imaging with technetium-99m ((99m)Tc)-hexamethyl-propylene-amine oxime (HMPAO) single-photon emission computed tomography (SPECT) concurrent to magnetic resonance imaging (MRI) to specifically assess the effects of standard- and high-dose ara-C in children with AL. PATIENTS AND METHODS: Twenty-six perfusion studies using (99m)Tc-HMPAO SPECT were performed in 12 children (age range, 4 to 15 years) with AL after induction therapy, which consisted of a standard-dose ara-C, immediately after consolidation with high-dose ara-C, and later during follow-up (range, 6 to 44 months). The chemotherapy-related adverse events were monitored and correlated to SPECT and MRI. RESULTS: After the induction phase, all children were neurologically normal on MRI. On SPECT imaging, four children displayed a slightly heterogeneous perfusion. After high-dose ara-C (4 to 36 g/m(2)), five children had regressive neurologic signs of potential toxic origin. Of these five children, only one had an abnormal MRI scan, whereas all patients showed evidence of diffuse cerebral and/or cerebellar heterogeneous perfusion on SPECT. The seven other patients without any neurologic symptoms had normal MRI scans; SPECT was normal for three patients and abnormal for four patients. On follow-up, for four children who had presented with clinical neurologic toxicity, SPECT improved in three patients and remained unchanged in one patients. In two of these four children, delayed abnormalities (T2 white matter hypersignal and cerebellar atrophy) appeared on MRI scans. CONCLUSION: In our series, diffuse heterogeneous brain hypoperfusion is often the sole early objective imaging feature identified by SPECT of high-dose ara-C neurotoxicity, where MRI still demonstrates normal pictures.

[The value of orbital ultrasonography in ethmoid sinusitis in children]. / Intérêt de l'échographie orbitaire dans les ethmoïdites de l'enfant.

PURPOSE: To assess the value of orbital sonography (US) compared to CT in the management of children with ethmoid sinusitis. MATERIAL AND METHODS: A total of 13 consecutive patients admitted for non-complicated ethmoid sinusitis (absence of visual or neurological symptoms) were prospectively evaluated at US and CT. RESULTS: Three patients had no evidence of postseptal involvement at US. Ten patients had variable degree of postseptal involvement at US: hypoechoic area or fluid collection in the extraconal fat along the medial orbital wall. Results were confirmed at CT in all patients. CONCLUSION: US is useful to confirm the presence of postseptal involvement in patients with ethmoid sinusitis. Contrary to CT, findings at US remain non-specific as to the nature of involvement. Nonetheless, US is helpful for patient management.

Transnasal endoscopic repair of congenital defects of the skull base in children.

OBJECTIVE: To examine imaging findings and methods of endoscopic treatment of congenital skull base defects in children. DESIGN: Retrospective study and case series. SETTING: Academic tertiary care center. PATIENTS: Four patients (aged 12 and 14 months and 8 and 13 years) were included from 1995 to 1997. Three presented with a nasal glioma, which was recurrent in 1 case. The fourth patient presented with bacterial meningitis due to a spontaneous cerebrospinal fluid leak. Computed tomography and magnetic resonance imaging were used to locate the defect of the skull base. INTERVENTION: Transnasal endoscopic resection of the glioma or the meningocele, with immediate repair of the skull base defects using free mucosal flaps and/or pediculized mucosal flaps and/or conchal cartilage together with fibrin glue and nasal packing during a 3-week period. RESULTS: None of the 4 patients has experienced recurrent cerebrospinal fluid leaks or postoperative meningitis. CONCLUSIONS: The transnasal endoscopic repair of congenital meningoceles is a reliable technique in select pediatric patients. Computed tomography and magnetic resonance imaging provide information that can be used to help the surgical procedure.

[Prenatal MRI of corpus callosum agenesis. Study of 20 cases with neuropathological correlations]. / IRM anténatale des agénésies calleuses. Etude de 20 cas avec corrélations neuropathologiques.

Twenty prenatal MR studies of corpus callosum agenesis were retrospectively studied and compared with neuropathologic examinations (18) or postnatal imaging (2). Corpus callosum agenesis were either complete (14) or partial (6). Positive diagnosis was made in 19 cases/20. The diagnosis of "isolated" or "associated" corpus callosum agenesis was assessed in 11 cases/15. MR depicted 15 of the 33 associated neurologic abnormalities. Prenatal MR is a valuable complementary technique for the diagnosis of corpus callosum agenesis when sonography is doubtful. MR could improve prognosis evaluation, since it enables depiction of associated abnormalities, notably gyral abnormalities, posterior fossa malformations, and intra-cranial cysts. MR images prove to be useful before neuropathologic examinations.

Magnetic resonance imaging of the fetus.

Fetal magnetic resonance imaging (FMRI) has gained considerable interest during the last decade, especially in its intracranial applications. Due to its high soft-tissue contrast and presumed safety, FMRI should be accepted as a complementary technique in prenatal diagnosis, useful either to elucidate equivocal findings on routine US studies or to further delineate some pathological entities. Normal patterns of fetal brain maturation, as shown by FMRI, are described because they are of paramount importance to accurately evaluate intracranial diseases. To date, however, FMRI requires specialised facilities and should be considered as an evolving clinical research modality and performed within precise guidelines in a multidisciplinary approach to prenatal pathology.