Keyhole Aqueduct Syndrome.

Keyhole aqueduct syndrome is a rare progressive neurodegenerative disorder describing a unique set of neuro-ophthalmologic, neuroimaging, and histopathological findings on autopsy. A midline mesencephalic cleft communicating with the cerebral aqueduct resembling syrinx is seen on imaging and histopathology. There are 9 cases published in the literature. We encountered a patient with vertical nystagmus, internuclear ophthalmoplegia, and progressive ataxia who has a midline cleft connecting the cerebral aqueduct with the interpeduncular cistern highlighting a distinguishing feature of this syndrome.

The prepontine block and its relevance for the development and treatment of hydrocephalus.

OBJECTIVE: Pulsatile CSF flow patterns include flow through the ventricles to the subarachnoid space and cisterns and from the infra- to the supratentorial subarachnoid space. In this study, we demonstrate how an obstruction at the level of the prepontine space may lead to obstructive hydrocephalus with specific radiological characteristics, as well as the implications for treatment options. METHODS: We retrospectively collected data of patients who underwent surgery between February 2010 and December 2022 for hydrocephalus secondary to a suspected prepontine block. One additional patient diagnosed with prepontine block who did not undergo surgery was also included. We excluded patients with a background of previous unrelated neurosurgical procedures or CNS infections. RESULTS: Six children and two adults were included. Three presented with hydrocephalus on imaging, without any other underlying pathology. Five had a suprasellar arachnoid cyst, with its lower border abating the pons and occluding the spinal subarachnoid space (SAS). All cases had an open aqueduct on T2 sagittal sequences, as well as an infracerebellar or retrocerebellar CSF collection. In most cases, a horizontal web was identified in the prepontine region. Seven cases were treated with an endoscopic fenestration. One patient subsequently underwent a shunt surgery. All the operated children reached normal developmental milestones after surgery. CONCLUSIONS: This paper describes a rather small series of cases where clear obstruction was observed at the level of the prepontine subarachnoid space. We believe this anatomical subtlety adds to a better understanding of CSF pathways and the role of ETV in treating hydrocephalus, focusing on a small subgroup of patients without a clear obstruction.

Impact of aquaporin-4 and CD11c + microglia in the development of ependymal cells in the aqueduct: inferences to hydrocephalus.

AQP4 is expressed in the endfeet membranes of subpial and perivascular astrocytes and in the ependymal cells that line the ventricular system. The sporadic appearance of obstructive congenital hydrocephalus (OCHC) has been observed in the offspring of AQP4-/- mice (KO) due to stenosis of Silvio's aqueduct. Here, we explore whether the lack of AQP4 expression leads to abnormal development of ependymal cells in the aqueduct of mice. We compared periaqueductal samples from wild-type and KO mice. The microarray-based transcriptome analysis reflected a large number of genes with differential expression (809). Gene sets (GS) associated with ependymal development, ciliary function and the immune system were specially modified qPCR confirmed reduced expression in the KO mice genes: (i) coding for transcription factors for ependymal differentiation (Rfx4 and FoxJ1), (ii) involved in the constitution of the central apparatus of the axoneme (Spag16 and Hydin), (iii) associated with ciliary assembly (Cfap43, Cfap69 and Ccdc170), and (iv) involved in intercellular junction complexes of the ependyma (Cdhr4). By contrast, genes such as Spp1, Gpnmb, Itgax, and Cd68, associated with a Cd11c-positive microglial population, were overexpressed in the KO mice. Electron microscopy and Immunofluorescence of vimentin and γ-tubulin revealed a disorganized ependyma in the KO mice, with changes in the intercellular complex union, unevenly orientated cilia, and variations in the planar cell polarity of the apical membrane. These structural alterations translate into reduced cilia beat frequency, which might alter cerebrospinal fluid movement. The presence of CD11c + microglia cells in the periaqueductal zone of mice during the first postnatal week is a novel finding. In AQP4-/- mice, these cells remain present around the aqueduct for an extended period, showing peak expression at P11. We propose that these cells play an important role in the normal development of the ependyma and that their overexpression in KO mice is crucial to reduce ependyma abnormalities that could otherwise contribute to the development of obstructive hydrocephalus.

Aqueductal CSF stroke volume is associated with the burden of perivascular space enlargement in chronic adult hydrocephalus.

The inflow of CSF into perivascular spaces (PVS) in the brain is crucial for clearing waste molecules. Inefficiency in PVS flow leads to neurodegeneration. Failure of PVS flushing is associated with CSF flow impairment in the intracranial hydrodynamic condition of CSF hypo-pulsatility. However, enlarged PVS (ePVS), a finding indicative of PVS flow dysfunction, is also present in patients with derangement of CSF dynamics characterized by CSF hyper-pulsatility, which increases CSF flow. Intriguingly, two opposite intracranial hydrodynamic conditions would lead to the same result of impairing the PVS flushing. To investigate this issue, we assessed the subsistence of a dysfunctional interplay between CSF and PVS flows and, if the case, the mechanisms preventing a hyper-pulsatile brain from providing an effective PVS flushing. We analyzed the association between phase contrast MRI aqueductal CSF stroke volume (aqSV), a proxy of CSF pulsatility, and the burden of ePVS in chronic adult hydrocephalus, a disease involving a broad spectrum of intracranial hydrodynamics disturbances. In the 147 (85 males, 62 females) patients, the age at diagnosis ranged between 28 and 88 years (median 73 years). Ninety-seven patients had tri-ventriculomegaly and 50 tetra-ventriculomegaly. According to the extent of ePVS, 113 patients had a high ePVS burden, while 34 had a low ePVS burden. aqSV, which ranged between 0 and 562 µL (median 86 µL), was increased with respect to healthy subjects. Patients presenting with less ePVS burden had higher aqSV (p < 0.002, corrected for the multiple comparisons) than those with higher ePVS burden. The present study confirmed the association between CSF dynamics and PVS flow disturbances and demonstrated this association in intracranial hyper-pulsatility. Further studies should investigate the association between PVS flow failure and CSF hypo- and hyper-pulsatility as responsible/co-responsible for glymphatic failure in other neurodegenerative diseases, particularly in diseases in which CSF disturbances can be corrected, as in chronic adult hydrocephalus.

Expanding the phenotypic spectrum of LIG4 pathogenic variations: neuro-histopathological description of 4 fetuses with stenosis of the aqueduct.

Severe ventriculomegaly is a rare congenital brain defect, usually detected in utero, of poor neurodevelopmental prognosis. This ventricular enlargement can be the consequence of different mechanisms: either by a disruption of the cerebrospinal fluid circulation or abnormalities of its production/absorption. The aqueduct stenosis is one of the most frequent causes of obstructive ventriculomegaly, however, fewer than 10 genes have been linked to this condition and molecular bases remain often unknown. We report here 4 fetuses from 2 unrelated families presenting with ventriculomegaly at prenatal ultra-sonography as well as an aqueduct stenosis and skeletal abnormalities as revealed by fetal autopsy. Genome sequencing identified biallelic pathogenic variations in LIG4, a DNA-repair gene responsible for the LIG4 syndrome which associates a wide range of clinical manifestations including developmental delay, microcephaly, short stature, radiation hypersensitivity and immunodeficiency. Thus, not only this report expands the phenotype spectrum of LIG4-related disorders, adding ventriculomegaly due to aqueduct stenosis, but we also provide the first neuropathological description of fetuses carrying LIG4 pathogenic biallelic variations.

A cell junction pathology of neural stem cells leads to abnormal neurogenesis and hydrocephalus

Most cells of the developing mammalian brain derive from the ventricular (VZ) and the subventricular (SVZ) zones. The VZ is formed by the multipotent radial glia/neural stem cells (NSCs) while the SVZ harbors the rapidly proliferative neural precursor cells (NPCs). Evidence from human and animal models indicates that the common history of hydrocephalus and brain maldevelopment starts early in embryonic life with disruption of the VZ and SVZ. We propose that a "cell junction pathology" involving adherent and gap junctions is a final common outcome of a wide range of gene mutations resulting in proteins abnormally expressed by the VZ cells undergoing disruption. Disruption of the VZ during fetal development implies the loss of NSCs whereas VZ disruption during the perinatal period implies the loss of ependyma. The process of disruption occurs in specific regions of the ventricular system and at specific stages of brain development. This explains why only certain brain structures have an abnormal development, which in turn results in a specific neurological impairment of the newborn. Disruption of the VZ of the Sylvian aqueduct (SA) leads to aqueductal stenosis and hydrocephalus, while disruption of the VZ of telencephalon impairs neurogenesis. We are currently investigating whether grafting of NSCs/neurospheres from normal rats into the CSF of hydrocephalic mutants helps to diminish/repair the outcomes of VZ disruption.

Estenosis del acueducto de Silvio / Aqueductal stenosis

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Central neurocytomas of uncommon locations: report of two cases / Localizações incomuns do neurocitoma central: relato de dois casos

We report two patients with central neurocytomas at an uncommon location in the brain. The first, a 58-year-old man presenting with signs and symptoms of increased intracranial pressure, had a tumor located at the pineal region. The second, a 21-year-old woman with tumor in the aqueductal region had worsening migraine-like headaches and diplopia. Both patients had obstructive hydrocephalus treated by neuroendoscopic third ventriculostomy and biopsy of the tumors. No additional treatment was done. We conclude that neurocytomas should be considered in the differential diagnosis of tumors located in the pineal and aqueductal regions.

Relatamos dois pacientes com neurocitoma central com localização incomum no sistema nervoso central. O primeiro, 58 anos, masculino, apresentava sinais e sintomas de hipertensão intracraniana, tinha um tumor na região da pineal. O segundo, feminino, 21 anos, tinha um tumor na região do aqueduto de Sylvius e apresentava cefaléia migranosa progressiva e diplopia. Ambos apresentavam hidrocefalia obstrutiva tratada com terceiroventriculostomia endoscópica e biópsia da lesão. Não foi feito tratamento adicional. Concluimos que os neurocitomas devem ser considerados no diagnóstico diferencial de tumores localizados na região da pineal e do aqueduto.

Estenosis acueductal en acondroplasia: a propósito de un caso / Aqueductal stenosis in achondroplasia: report of a case

Achondroplasia is the most frequent cause of disproportionate short stature. Characterized by abnormal growth of long bones, it renders a short-limbed individual of normal intelligence. A serious potential complication is spinal compression, which can happen at any level but is particularly common at the craniocervical junction. It can cause important morbility during the first few years of life, including sudden death. We present a 22-month-old patient diagnosed with achondroplasia, who developed aqueductal stenosis with symptomatic spinal cord compression, diagnosed during a routine consultation, requiring decompressive surgery with excellent results.

La acondroplasia es la condición asociada a talla baja desproporcionada más frecuente, caracterizada por un crecimiento óseo anormal, que resulta en talla baja con extremidades cortas e inteligencia normal. Una de las complicaciones más habituales es la compresión medular, que puede ocurrir a cualquier nivel, siendo más frecuente en la unión cráneo cervical, generando alta morbimortalidad en los primeros años de vida, principalmente por muerte súbita. Presentamos una paciente de 1 año 10 meses con diagnóstico precoz de acondroplasia, que presentó en su evolución estenosis acueductal con compresión medular, sintomática, pesquisada en control rutinario, que requirió cirugía descompresiva con buena evolución posterior.

Tumores de tronco cerebral asociados con neurofibromatosis tipo 1. Presentación de 20 pacientes infantiles / Brain stem tumors associated with neurofibromatosis type 1. Presentation of 20 infantile patients

Objetivo. Describir los hallazgos clínicos y de imagen de 20 pacientes (12 mujeres y 8 varones) con tumores del tronco cerebral asociados con neurofibromatosis tipo 1 (NF1). Pacientes y métodos. Todos los pacientes fueron estudiados por primera vez antes de los 11 años desde el punto de vista clínico y de imagen por resonancia magnética (RM) en los 20 pacientes y RM espectroscópica (RME) en 7. Trece de los 20 pacientes (65%) presentaban también tumor de vías ópticas. El diagnóstico del tumor del tronco cerebral se realizó al mismo tiempo que el de la NF1 en los pacientes estudiados desde el principio con RM. Resultados. El tumor se localizaba de forma difusa o focalizada en el bulbo en 13 pacientes (65%) y se extendía por todo el tronco cerebral en 6 pacientes (30 %). En este último grupo uno afectaba al tronco cerebral y al cerebelo, en otro se extendía a lo largo del acueducto y de la zona periacueductal y otro mostraba signos de agresividad en el estudio de RME. El paciente restante presentaba un tumor agresivo que afectaba al nervio óptico izquierdo, quiasma, mesencéfalo y protuberancia. El estudio histológico del tejido tumoral biópsico de los últimos 2 pacientes mostró astrocitoma grado 1 (tumor benigno). Los dos tumores de carácter agresivo fueron tratados con radioterapia y quimioterapia, estando todavía vivos tras 4 y 7 años, respectivamente, del tratamiento. Tres pacientes con obstrucción del acueducto e hidrocefalia fueron tratados con derivación ventriculoperitoneal (V-P). El resto de los pacientes no ha recibido tratamiento. Sólo uno de los 20 pacientes falleció, pero no por el tumor del tronco cerebral, sino por un tumor maligno de vías ópticas del que había sido tratado 20 años antes. Conclusiones. En la NF1 los tumores del tronco cerebral son los más frecuentes en la fosa posterior y los segundos más frecuentes entre los del sistema nervioso central. El estudio por RM y en determinados pacientes por RME se ha hace necesario para un correcto diagnóstico. La mayoría de estos tumores son benignos

Objective. To describe the clinical and imaging findings of 20 patients (12 women and 8 men) with brain stem tumors associated with neurofibromatosis type 1 (NF1). Patients and methods. All patients were first time studied before 11 years old. Clinical and magnetic resonance (MR) study were made in all 20 patients, and spectroscopic MR (SMR) was performed in 7 patients. Thirteen of the 20 patients (65 %) also had optic pathway tumor. Brain stem tumor identification occurred at the same time as NF1 in the patients who were studied by MR at the time of the first consult. Results. Brain stem identification occurred at the same time as that of the NF1 in patients who were studied by MR from the beginning. Diffuse or localized medullary enlargement was the most frequent MR imaging and appeared in 13 patients (65%), followed by the tumor that involved all brain stem (pontine and medullary areas) that appeared in 6 patients (30 %). In the last group, one tumor showed extension through brain stem and medial cerebellar parts, another was located in the aqueduct and in the periaqueductal areas and showed slow progressive growth, and one third patient had a tumor with aggresive signs in the SMR study. Another patient had an aggressive tumor that involved the left optic nerve, chiasm, mesencephalon and upper right pontine areas. The histological study of the tumoral biopsic tissue of the two last patients showed astrocitoma degree 1 (benign tumor). The two aggresive tumors were treated with radiotheraphy and chemotherapy and they are still alive 4 and 7 years respectively after treatment. Three patients who had aqueductal obstruction and hydrocephalus were treated with shunt. The rest of patients did not receive treatment. Only one of the 20 patients died, although it was due to a malignant chiasmatic tumor, that had been treated twenty years before, and not by the brain stem tumor. Conclusions. In NF1, brain stem tumors are the most frequent tumors of the posterior fossa and the second most frequent of the central nervous system (CNS). MR and SMR are necessary to a correct identification of the tumor in some patients. Most of these tumors are benign

Diagnóstico diferencial en la estenosis del acueducto de Silvio en el adulto / Differential diagnosis of Sylvius aqueduct stenosis in the adult

El diagnóstico de la estenosis del acueducto de Silvio en el adulto se ha facilitado con el advenimiento de la tomografía axial computada (TAC). Los datos tomográficos son la dilatación de los ventrículos laterales y del tercer ventrículo con un IV ventrículo normal. En el presente trabajo se reporta la experiencia obtenida en el Servicio de Neurología del Hospital Universitario en Monterrey, con diez casos inicialmente diagnosticados por clínica y TAC como estenosis del acueducto. El diagnóstico definitivo se estableció en seis (concordando con el diagnóstico de ingreso), y en cuatro se demostraron otras etiologías como causa de este síndrome. Es importante la realización de TAC asociada a ventriculografía (VG) mediante microtrepano frontal lo cual nos permite definir otras posibles causas de obstrucción del acueducto. Algunas etiologías son: Cisticero en la porción distal del tercer ventrículo (caso 7) neoplásica periacueductal (caso 8) y cisticercos múltiples intraventriculares (caso 10), todos éstos sólo pudieron ser establecidos mediante la V.G. Se revisan los patrones de presentación clínica, enfatizándose la utilidad que la VG asociada a TAC proporcionan para la realización del diagnóstico definitivo de este síndrome, lo cual es importante en el manejo y pronóstico de estos pacientes