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OBJECTIVES To provide evidence to support the hypothesis that the midline cyst-like fluid collection that is frequently observed on fetal brain ultrasound (US) imaging during the early second trimester represents a normal transient cavum veli interpositi (CVI). METHODS This was a retrospective analysis of 89 three-dimensional normal fetal brain volumes, acquired by transvaginal US imaging in 87 pregnant women between 14 and 17 gestational weeks. The midsagittal view was studied using multiplanar imaging, and the maximum length of the fluid collection located over (dorsal to) the tela choroidea of the third ventricle was measured. We calculated the correlation of the transverse cerebellar diameter (TCD) and of the maximum length of the fluid collection with gestational age according to last menstrual period. Color Doppler images were analyzed to determine the location of the internal cerebral veins with respect to the location of the fluid collection. Reports of the second-trimester anatomy scan at 22-24 weeks were also reviewed. RESULTS Interhemispheric fluid collections of various sizes were found in 55% (49/89) of the volumes (mean length, 5 (range, 3.0-7.8) mm). There was a strong correlation between TCD and gestational age (Pearson's correlation, 0.862; P

Background May-Hegglin anomaly is an autosomal dominant inherited condition, characterized by thrombocytopenia, giant platelets and Dohle-like bodies. Incidence is unknown and affected individuals can show from mild to moderate-severe haemorrhagic symptoms. The cyst of cavum veli interpositi (a virtual space filled with fluid within the third ventricle) is rarely reported in the foetal period. Furthermore, it is unclear whether isolated cavum veli interpositi cysts are a normal variant or developmental malformations. The simultaneous presence of these two anomalies was never described. Case presentation We describe a very rare case of a twin monochorionic pregnancy in a woman with the May-Hegglin anomaly, whose foetuses carried cavum veli interpositi cysts. Since childhood, our patient had shown macro-thrombocytopenia, deafness and bleeding (epistaxis and menorrhagia), but she was misdiagnosed until the age of 30 years when our Centre identified a de novo allelic variant in the gene MYH9 coding for the non-muscle myosin heavy chain IIa. Our patient bled neither during the pregnancy, nor in the peripartum period. Children are now eight-months-old and have never bled, although both inherited the MYH9 variant and have thrombocytopenia with giant platelets. Furthermore, none of them developed psychomotor disorders. Conclusions To the best of our knowledge, this is the sixth case of twin pregnancy in a woman carrying May-Hegglin anomaly and the first one with cavum veli interpositi cysts in the neonates. We speculate that MYH9 could have, at least in part, played a role in the development of both conditions, as this gene has a pleiotropic effect.

Cavum vergae, cavum septum pellucidum and cavum veli interpositi are brain midline embryological developmental cysts. They are rarely seen after trauma. Generally, they do not constitute clinical findings. These cysts sometimes become enlarged and become symptomatic. Enlarged cysts cause severe neurological dysfunction. During normal fetal development, the development of the adjacent structures of the limbic system and the septum pellucidum are synchronized. It is thought that dysgenesis in these adjacent structures may affect the lamina fusion of septum pellucidum and cause cavum septum pellucidum. Anterior one of the cavities that arise when septum pellucidum laminae do not join after birth is called "cavum septum pellucidum" (CSP). The one in the posterior is called "cavum vergae" (CV). Velum interpositum (VI) is a potential cavity below the corpus callosum splenium and sometimes presents as a cyst. Cavum veli interpositi (CVI) is located in the pineal area, below the columna fornicis and above the tela choroidea of the 3rd ventricle. Because of its rarity, the incidence of CVI cyst is uncertain. The CV obliterates from the front to the front and is seen with the cavum septum pellucidum. CSP and CV are cavities that are present in fetal life but are considered as variant intracranial defects that do not close 6 months after birth. CVI is rarely seen embryo logically in fetal life in children over 2 years and adults. These cysts are rare in adults. In this study, anatomical features and clinical reflections of CSP, CV and CVI were reviewed. WOS: 000607192100004

The morphology of the cavum septi pellucidi (CSP), cavum Vergae (CV), and cavum veli interpositi (CVI) has been infrequently explored with neuroimaging. The aim of the present study was to delineate these cavities using magnetic resonance (MR) imaging. A total of 71 patients were enrolled in the present study. Following initial examinations with conventional MR sequences, constructive interference in steady-state (CISS) sequence was performed in the coronal and sagittal sections for 60 and 11 patients, respectively. The coronal CISS images at the level of the aqueduct showed two distinct morphologies of the CV roof, one formed by the fornices with varying degrees of conjugation and the other formed by the corpus callosum with completely separated fornices. Appearance of the CSP was classified into four distinct types. Furthermore, the CVI presented two distinct appearances. Typically, the CSP, CV, and CVI present with asymptomatic conditions with morphological variabilities. Visualization of the CSP, CV, and CVI using the CISS sequences may be useful when managing lesions affecting these cavities.

Los quistes intracraneales de la línea media anterior se pueden encontrar en tres formas: cavum septum pellucidum, cavum vergae y cavum velum interpositum. El cavum vergae es una extensión del cavum septum pellucidum en dirección posterior a las columna del fórnix y el foramen de Monro. Aunque no está presente en todos los fetos, cuando se observa durante la evaluación ecográfica prenatal puede ser mal diagnosticado como un quiste de la línea inter-hemisférica con pronóstico incierto. Se presenta un caso de una embarazada de 18 años quien acudió a la consulta prenatal a las 32 semanas. Durante la evaluación ecográfica se halló una lesión quística eco-negativa de 20 x 12 milímetros de diámetro, rectangular, intracraneal, presencia de cuerpo calloso y sin evidencia de hidrocefalia compresiva. El cariotipo fue normal. Se consideró el diagnóstico de quiste del cavum vergae. Se obtuvo un recién nacido normal posterior a parto vaginal espontáneo. La resonancia magnética después del parto confirmó el diagnostico.

To review and systematize literature data on the incidence of cysts of septum pellucidum, cavum vergae and cavum veli interpositi, their clinical manifestations, indications for surgical treatment and optimal surgical approach.An analysis included 72 manuscripts devoted to epidemiology, pathophysiology, clinical symptoms and results of surgical treatment of brain cysts. Case reports, series of cases, reviews and original studies were analyzed.Septum pellucidum cavity is always formed throughout an embryogenesis and persists in 20.34% of adults. Cavum vergae is observed in 2.32% of adults. Cyst of septum pellucidum is detected in 0.04% of adults. Analysis of 368 cases of cysts of septum pellucidum, cavum vergae and cavum veli interpositi has shown that clinical picture consists of headache (50% of cases), convulsive syndrome (23.6%), reduced intelligence (20.1%), behavioural disorders (15.8%), dizziness, nausea and vomiting (10.9%). Hydrocephalus occurs in 16.6% of cases. Endoscopic wall fenestration is preferred for cyst management.Brain cysts are rare and characterized by non-specific clinical manifestations. Symptomatic cyst is an indication for surgical treatment. Surgical treatment usually ensures regression of symptoms and low risk of complications.Обзор и систематизация литературных данных для определения частоты встречаемости кист прозрачной перегородки, полости Верге и промежуточного паруса, их клинических проявлений, показаний к оперативному лечению и выбора оптимальных хирургических методов.Проведен анализ 72 публикаций, характеризующих эпидемиологию, патофизиологию, клиническую картину и результаты хирургического лечения срединных ликворных кист. В анализ включены описания отдельных клинических случаев, серии наблюдений, обзоры и оригинальные исследования.Полость прозрачной перегородки всегда формируется в эмбриогенезе и сохраняется во взрослом возрасте в 20,34% случаев. Полость Верге у взрослых встречается в 2,32% случаев. Киста прозрачной перегородки выявляется у 0,04% взрослых. Анализ 368 описанных в литературе случаев кист прозрачной перегородки, полости Верге и промежуточного паруса показал, что клиническая картина складывается из головной боли — 50% случаев, судорожного синдрома — 23,6%, снижения интеллекта — 20,1%, нарушений поведения — 15,8%, эпизодов головокружения, тошноты и рвоты — 10,9%. Гидроцефалия развивается в 16,6% случаев. Оптимальным методом лечения кист является эндоскопическая фенестрация стенок.Срединные ликворные кисты встречаются редко и характеризуются неспецифическими клиническими проявлениями. Наличие симптомной кисты является показанием к хирургическому лечению. При правильном отборе пациентов оперативное лечение в большинстве случаев ведет к регрессу симптомов и сопряжено с незначительным риском осложнений.

Objective Cysts of the Cavum septi pellucidi (CSP), cavum vergae (CV) and cavum veli interpositi (CVI) are anterior midline intracranial findings which are typically incidental – only rarely do we encounter symptomatic cysts of this type. Only a quite small number of these cysts series have been published, controversies regarding optimal management still exist. Patients and methods This is a retrospective study of 10 patients treated at 2 clinics between 2002–2018. 9 patients underwent surgery and 1 is under long-term monitoring. Apart from demographic data, the study analyzed symptoms, cyst size and progression over time, ventricle size, complications, and treatment modality. Results CSP with CV was found in 8 cases with 1 case each of CSP and CVI. The study comprised 6 men and 4 women, including 4 children. The mean follow-up time was 43.4 months. The average cyst size was 20.4 mm in CSP and 19.8 mm in CV; the CVI was 33 mm. Headache was most commonly reported (70%) followed by behavioral disturbance (30%). Disturbance in memory, psychomotor development, school performance, visual acuity, and vomiting was variously noted in 20%. The prevailing symptom was headache in adults and behavioral and autonomic disturbance in children. Postoperatively, cysts had reduced by an average of 44.3% while the ventricles remained unchanged. Symptoms resolved in all cases with residual problems in patients presenting with memory loss. No complications were noted. Conclusion Endoscopic fenestration is the method of choice in the treatment of symptomatic midline cysts. We recommend that any further research focuses on precisely establishing their clinical presentation, particularly neuropsychological symptoms.

Familiarity with the normal brain anatomy and its age-dependent normal variation/evolution is essential for proper interpretation of neonatal head ultrasonography studies. In a preterm neonate, the brain surface is smooth, while a complex gyration and sulcation pattern is expected in term neonates. In newborns, persistent fetal fluid-filled spaces such as the cavum septum pellucidum, cavum Vergae, and cavum veli interpositi, asymmetry in size of the lateral ventricles, and variable morphology of the choroid plexus are physiological.

Objective: To investigate the incidence of associated anomalies, aneuploidy, cyst progression, need for surgery and neurodevelopmental outcome in fetuses with extra-axial supratentorial intracranial cysts. Data Sources: Medline, Embase and CINAHL databases were searched and the following outcomes analyzed: associated central nervous system (CNS) and extra-CNS anomalies detected at the scan, chromosomal anomalies, additional CNS anomalies detected only at prenatal MRI, additional CNS anomalies detected only after birth, cyst progression in utero, neurological outcome and need for surgery. Two authors reviewed all abstracts independently. Results were reported as proportions, and between-study heterogeneity was explored using the I² statistic; fixed or random effect models were used accordingly. Results: Ten studies involving 47 fetuses were included in the meta-analysis. Arachnoid cysts (n = 24) had associated CNS anomalies and extra-CNS in 73% (95% CI 56-88) and 14% (95% CI 4-29), respectively. The most common associated anomalies were ventriculomegaly and callosal abnormalities. Chromosomal abnormalities were present in 6% (95% CI 0-30), but fetuses with isolated cysts were always euploid (0/7; 95% CI 0-29). Fetal MRI and postnatal examination identified 5 additional cases (21%, 95% CI 1-57). Cavum veli interpositi (CVI) cysts had associated CNS and extra-CNS anomalies in 31% (95% CI 13-52) and 6% (95% CI 0-29), respectively. No chromosomal or callosal anomalies were found in these cases. In isolated CVI cysts, no cases of associated anomalies were detected postnatally. Intrauterine regression occurred in 23% of CVI cysts and in none of the arachnoid cysts. In children with arachnoid cyst, the occurrence of hydrocephaly and mass effect on the adjacent structures were observed in 23.9% (95% CI 8.3-4.4) and 26.8% (95% CI 4.0-60.1), respectively. None of the cases included had abnormal motor outcome or intelligence. The rate of surgery was 34.7% (95% CI 16.0-56.4). None of the children with a prenatal diagnosis of isolated CVI cyst experienced any of the adverse outcomes explored in this review. Conclusions: Extra-axial supratentorial cysts diagnosed in utero are frequently associated with other neural and extra-neural anomalies. However, this may represent the consequence of a selection bias. Interhemispheric arachnoid cysts were typically associated with callosal anomalies. Abnormal karyotypes were seen only in fetuses with multiple anomalies. Arachnoid, but not CVI, cysts frequently increased in size throughout gestation.

The presence of an interhemispheric supratentorial fluid collection requires an attentive analysis for differentiation between interhemispheric supratentorial cystlike fluid collection lesions and pathologic cystic lesions. Interhemispheric supratentorial fluid lesions are a heterogeneous group of lesions with respect to their origin, natural history, association with other anomalies, and especially prognosis. They may represent physiologic median structures without clinical importance, such as an enlarged cavum vergae or cavum veli interpositi (CVI). 1 However, the differential diagnosis of midline cystic cerebral lesions includes an enlarged third ventricle, a vein of Galen malformation, an interhemispheric cyst associated with agenesis of the corpus callosum, a suprasellar arachnoid cyst, a porencephalic cyst, a glioependimal cyst, schizencephaly, a cystic neoplasm, and intracranial hemorrhage. The clinical spectrum and prognosis of these abnormalities are difficult to delineate because of the rarity of each entity and the different associations. The cystlike structures related to median structures are considered variants of physiologic structures, whereas the other structures include pathologic processes that may be associated with neurodevelopmental delays. We report a case of prenatal diagnosis of a CVI by 2-dimensional (2D) sonography, color Doppler imaging, 3-dimensional (3D) tomographic imaging, and 3D high-definition flow. The findings were confirmed by postnatal magnetic resonance imaging (MRI).

Cavum veli interpositi is an open CSF space in the roof of the third ventricle that surrounds the internal cerebral veins, and is a forward extension of the quadrigeminal plate cistern. To the best of our knowledge, spontaneous resolution of a cavum veli interpositi has not been reported in the literature to date. Interestingly, case reports of spontaneous resolution of cystic cavum septum pellucidum in three patients and eighteen arachnoid cyst cases has been described in the literature. We describe the spontaneous resolution of a cavum veli interpositi or cyst in cavum veli interpositi in a 35-year-old man and review the literature of spontaneous resolution of cavum septum pellucidum and arachnoid cysts.

We describe the finding of cavum veli interpositi (CVI) on fetal ultrasound and MRI and the postnatal MRI and developmental follow-up in two cases. The first case was diagnosed on fetal ultrasound at 33 weeks' gestation and confirmed on fetal MRI. No abnormalities were detected on postnatal examinations and the brain MRI at 1 year of age showed no changes. At 4 years of age, his growth and development were normal.The second case was diagnosed with CVI on fetal ultrasound and MRI at 33.5 weeks' gestation. Postnatal examination showed no abnormalities, and brain MRI at 8 months of age revealed that the CVI was unchanged, but there was a dilated cavum septum pellucidum and cavum vergae. Her growth and development during the first 4 years of life were normal. CVI is a rare fetal ultrasound finding, which seems to be benign. However, further neurodevelopmental follow-up is needed to confirm this observation.

Summary Background and purpose The aim of this study was to identify characteristic 3.0 T brain MRI findings in patients with aspartylglucosaminuria (AGU), a rare lysosomal storage disorder. Previous AGU patient material imaged at 1.0 and 1.5 T was also re-evaluated. Materials and methods Twenty-five brain MRI examinations from 20 AGU patients were included in the study. Thirteen patients underwent a prospective 3.0 T MRI (5 male, 8 female, aged 9–45 years). Twelve examinations from nine patients (4 male, 5 female, aged 8–33 years) previously imaged at 1.0 or 1.5 T were re-evaluated. Two patients were included in both the prospective and the retrospective groups. Visual analysis of the T1- and T2-weighted images was performed by two radiologists. Results The previously reported signal intensity changes in T2-weighted images were visible at all field strengths, but they were more distinct at 3.0 T than at 1.0 or 1.5 T. These included signal intensity decrease in the thalami and especially in the pulvinar nuclei, periventricular signal intensity increase and juxtacortical high signal foci. Poor differentiation between gray and white matter was found in all patients. Some degree of cerebral and/or cerebellar atrophy and mild ventricular dilatation were found in nearly all patients. This study also disclosed various unspecific findings, including a higher than normal incidence of dilated perivascular spaces, arachnoid cysts, pineal cysts and mildly dilated cavum veli interpositi. Conclusion This study revealed particular brain MRI findings in AGU, which can raise the suspicion of this rare disease in clinical practice.

Object. Frameless computerized neuronavigation has been increasingly used in intracranial endoscopic neurosurgery. However, clear indications for the application of neuronavigation in neuroendoscopy have not yet been defined. The purpose of this study was to determine in which intracranial neuroendoscopic procedures frameless neuronavigation is necessary and really beneficial compared with a free-hand endoscopic approach. Methods. A frameless infrared-based computerized neuronavigation system was used in 44 patients who underwent intracranial endoscopic procedures, including 13 third ventriculostomies, nine aqueductoplasties, eight intraventricular tumor biopsy procedures or resections, six cystocisternostomies in arachnoid cysts, five colloid cyst removals, four septostomies in multiloculated hydrocephalus, four cystoventriculostomies in intraparenchymal cysts, two aqueductal stent placements, and fenestration of one pineal cyst and one cavum veli interpositi. All interventions were successfully accomplished. In all procedures, the navigational system guided the surgeons precisely to the target. Navigational tracking was helpful in entering small ventricles, in approaching the posterior third ventricle when the foramen of Monro was narrow, and in selecting the best approach to colloid cysts. Neuronavigation was essential in some cystic lesions lacking clear landmarks, such as intraparenchymal cysts or multiloculated hydrocephalus. Neuronavigation was not necessary in standard third ventriculostomies, tumor biopsy procedures, and large sylvian arachnoid cysts, or for approaching the posterior third ventricle when the foramen of Monro was enlarged. Conclusions. Frameless neuronavigation has proven to be accurate, reliable, and extremely useful in selected intracranial neuroendoscopic procedures. Image-guided neuroendoscopy improved the accuracy of the endoscopic approach and minimized brain trauma.

Three peculiar cases with cystic dilatation of the “cavum Veli interpositi” have been observed. This structure contains a narrow subarachnoid space; dilatation of this cistern was rarely found in conditions interfering with normal drainage of the subarachnoidal pathways. We describe the clinical and MR findings due to this very uncommon condition; correlative anatomy and differential diagnosis are also discussed.

The Cavum Septi Pellucidi (CSP), Cavum Vergae (CV) and Cavum Veli Interpositi, are anatomical variants located in the midline of the brain. It is important to identify these conditions to distinguish them from other entities that may require treatment. In this paper, our purpose is to describe MR and CT findings of CSP, CV and Cavum Veli Interpositi, explaining the differential diagnosis.

Background: The cavum veli interpositi (CVI) usually is a small CSF-containing abnormality of septum pellucidum, asymptomatic and rare after the age of 3 years. When symptomatic, it is large and can be related to psychiatric disorders, syndromic association of mental retardation and seizures or to hydrocephalus. Methods: This is the first reported case of an otherwise healthy pediatric patient with a large CVI experiencing episodes of hypertonic loss of consciousness unrelated to epileptic, cardiologic or psychiatric causes without signs of chronic increase in intracranial pressure (ICP). Results: Supposing a CSF compartmentalization in the CVI as the cause of acute poussés of ICP due to block of CSF pathways and considering the severity of the symptoms, an endoscopic fenestration was performed with a reduction of cyst dimensions. Conclusion: We suggest considering the fenestration of large CVI even in otherwise asymptomatic patients to avoid the risk of CSF compartmentalization with ICP poussés.

Objective The cavum veli interpositi (CVI) is a space within the double-layered tela choroidea of the third ventricle. Occasionally, this space is fluid-filled and sonographically visible as an interhemispheric anechoic cyst. Because of its rarity, the incidence of CVI cyst is undetermined and the outcome of affected individuals has been found to be variable. The aim of this study was to report our experience of the sonographic findings and outcome of fetuses affected by CVI cysts. Methods In five fetuses with a CVI cyst, we performed targeted prenatal ultrasound scans of intracranial structures and a detailed anatomical survey to rule out associated malformations. Follow-up consisted of neurological examination and neurosonography. Results The CVI cyst appeared as a well-defined anechoic lesion without adjacent mass effect. In all fetuses the cyst was single and in two cases it enlarged slightly during pregnancy. The cyst was isolated in three fetuses and associated with borderline ventriculomegaly in two. A single umbilical artery was the only associated extracranial anomaly and this was detected in only one fetus. Neurosonography confirmed the presence of CVI cysts in all cases after delivery. During postnatal follow-up (range 10–48 months), the cyst regressed in one case within 1 month after delivery while the size of the others remained stable. No infant developed psychomotor disorders. Conclusions Prenatal sonographic diagnosis of CVI cysts is feasible. Its finding in isolation is consistent with favorable postnatal outcome. Copyright © 2009 ISUOG. Published by John Wiley & Sons, Ltd.

Dear Editor, I read with interest the recent paper presented by Shane Tubbs et al. [1] where they gave comprehensive and clear description of congenital supratentorial midline fluid spaces not belonging to the ventricular system. Unfortunately, well-selected pictures received erroneous legends. Figure 1 presents in fact an axial computed tomography (CT) scan, Fig. 2 an axial magnetic resonance imaging (MRI) study, Fig. 3 a coronal MRI noting cavum septi pellucidi at the level suggesting it may be continuous with cavum Vergae and Fig. 4 an axial CT scan. In Fig. 5, which is an axial CT scan, the presence of the cavum septi pellucidi is obvious, but tortuous course and termination within the tip of tentorial notch of the walls of supposed cavum Vergae suggest rather these could be internal cerebral veins. Within the region of the velum interpositum or transverse cerebral fissure, three paired structures can be visualised in imaging studies: crura of fornices, internal cerebral veins and thalamic striae with choroid plexus of the third ventricle (Fig. 1). Very often the diverging crura of fornices under the splenium of corpus callosum are captured on the axial pictures as formation resembling reversed letter Y (Fig. 1c) and they should not be confused with cavum Vergae (Fig. 1d). Fig. 1 Axial CT scans. a A 35-year-old male with the choroid plexus of the third ventricle visible behind almost completely fused septum pellucidum. b A 44-year-old male with the internal cerebral veins joined by the basal veins visible on both sides of the ... However it is impossible to assess it from standpoint of non-native English speaker, some grammatical inconsequence in terminology can be noticed in the paper. As in the case of cavum Vergae, “Vergae” is a correct form of genetivus singularis from “Verga”, in other cases, correct forms are cavum septi pellucidi and cavum veli interpositi. Otherwise it would sound better to add the preposition “of” before septum pellucidum and velum interpositum. It would be also noteworthy to add to the discussed history of numbering the ventricles that Andrea Verga in his paper [2] recalled the old term “ventricle of Sylvius” for the cavum septi pellucidi and proposed term “aqueduct of the ventricle of Sylvius” for the channel connecting cavities located under the corpus callosum. Assuming he was the first to describe the posterior of these cavities, he proposed the terms “ventricle of fornix or sixth ventricle” as preferred by him. Crura of the fornices with their commissure used to be known also as ‘psalterium’ due to their appearance. Subsequently, cavum Vergae is also sometimes called cavum psalterii. Verga gave an interesting footnote at this point, in which he (after Sabatier and Meckel) criticised translation of Greek ‘ψαλίς’ to ‘lira’, as it should be ‘vault’ or ‘fornix’ [2]. Thus, if we try to avoid eponyms and abandon pointless terms ‘fifth’ and ‘sixth ventricle’ and poetic ‘cavum psalterii’, the discussed space should be called cavum fornicis. Yours sincerely, Maciej Ciolkowski

Object Frameless computerized neuronavigation has been increasingly used in intracranial endoscopic neurosurgery. However, clear indications for the application of neuronavigation in neuroendoscopy have not yet been defined. The purpose of this study was to determine in which intracranial neuroendoscopic procedures frameless neuronavigation is necessary and really beneficial compared with a free-hand endoscopic approach. Methods A frameless infrared-based computerized neuronavi- gation system was used in 44 patients who underwent intracranial endoscopic procedures, including 13 third ventriculostomies, nine aqueductoplasties. eight intraventricular tumor biopsy procedures or resections, six cystocisternostomies in arachnoid cysts, five colloid cyst removals, four septostomies in multiloculated hydrocephalus, four cystoventriculostomies in intraparenchymal cysts, two aqueductal stent placements, and fenestration of one pineal cyst and one cavum veli interpositi. All interventions were successfully accomplished. In all procedures, the navigational system guided the surgeons precisely to the target. Navigational tracking was helpful in entering small ventricles, in approaching the posterior third ventricle when the foramen of Monro was narrow, and in selecting the best approach to colloid cysts. Neuronavigation was essential in some cystic lesions lacking clear landmarks, such as intraparenchymal cysts or multiloculated hydrocephalus. Neuronavigation was not necessary in standard third ventriculostomies, tumor biopsy procedures, and large sylvian arachnoid cysts, or for approaching the posterior third ventricle when the foramen of Monro was enlarged. Conclusions Frameless neuronavigation has proven to be accurate, reliable, and extremely useful in selected intracranial neuroendoscopic procedures. Image-guided neuroendoscopy improved the accuracy of the endoscopic approach and minimized brain trauma.

BACKGROUND The cavum veli interpositi is a not infrequent radiologic finding in both children and adults, as confirmed by computed tomography (CT) and magnetic resonance (MR). A moderate enlargement of the cavum may sometimes be observed; on the other hand, a true large cyst may be considered exceptional, with only one reported case. CASE HISTORY This 9-year-old boy with psychomotor retardation and epileptic seizures had a large CSF cyst in the region of the cavum veli interpositi, diagnosed by CT and MR. The patient was treated by endoscopic surgery, with introduction of the endoscope into the occipital horn of the right lateral ventricle and multiple fenestrations from the right ventricle to the cyst, and then from the cyst to the left lateral ventricle. The surgery resulted in decrease in the size of the cyst and reduction of the frequency of seizures. DISCUSSION AND CONCLUSIONS Children with dilated or cystic cavum veli interpositi present with a large head, mental retardation, seizures, and hydrocephalus. On CT and MR, the cyst shows a typical triangular configuration on the axial plane and lies on the roof of the third ventricle in the coronal plane. Endoscopic ventricular fenestration is the treatment of choice for these as well as all other intraventricular and intracerebral CSF cysts, because it ensures communication between the cyst and the ventricular system and avoids definitive shunting of the cyst.

Cavities formed in the interhemispheric cleavage (cavum septi pellucidi, cavum vergae, and cavum veli interpositi) develop as normal structures in the intrauterine period, and are usually developmentally obliterated during postnatal life. Remnants of these cavities are regarded as nonmalformative structures and have no clinical significance in the majority of cases. Abnormally expanded cavities that do not have free communication with the lateral ventricles or subarachnoid space are called cysts. The terms symptomatic cysts and pathological cava may be preferred for cavities that produce neurological symptoms by compressing the neighboring structures or cause hydrocephalus by obstructing the CSF pathways.1 Symptomatic or pathological cysts arising from the cava septi pellucidi, vergae, and veli interpositi are considered to be very rare.1

We accurately diagnosed two cases of cavum veli interpositi antenatally, using ultrasonography.

A new clinical syndrome, characterized by progressive increase in head size (without intracranial hypertension), variable delay in milestones, moderate ventricular dilation, and the presence of a cavum veli interpositi is herein described. The arteriographic and venographic signs are suggestive, but not diagnostic, of the presence of a cavum veli interpositi. Pneumoencephalography, with adequate filling of the subarachnoid spaces and ventricles, is essential to confirming the diagnosis. Cerebrospinal fluid shunting appears to result in an improvement, but the results cannot as yet be considered definitive since only 10 of our 29 patients were shunted.

We report characteristic and morphometric changes of cranial computed tomography (CT) with increasing age in 56 patients with Down's syndrome aged from 0 month to 37 years. Patients were compared with 142 normal controls aged 0 to 59 years. Width of ventricles, Sylvian fissures, posterior fossa, pons and cisterna magna were measured on CT. The incidences of the cavum septi pellucidi, cavum vergae and cavum veli interpositi and high density in the basal ganglia were examined. There was high incidence (10.7%) of bilateral calcification of basal ganglia in Down's syndrome, although that of pineal body and choroid plexus calcification was similar in Down's syndrome and controls. Basal ganglia calcification is more frequently seen in young Down's syndrome and may be related to the premature aging characteristic of Down's syndrome. The CT in Down's syndrome showed relatively small posterior fossa, small cerebellum, small brain stem and relatively large Sylvian fissures in those under one year of age. There was a high frequency of midline cava and large cisterna magna. There were no significant atrophic changes on CT except after the fifth decade comparing with controls.

158 pneumoencephalographies of infants less than 2 years old were examined and 53 of them had a large cavum veli interpositi. A neuroradiological description of this cistern is given and a comparison made with injected anatomical specimens. A statistical comparison with 105 pneumoencephalographies without a cavum veli interpositi does not shown any correlation between the presence of this cistern and pathological conditions. This investigation indicates that a large cavum veli interpositi in the newborn has no relation to hydrocephalus or cerebral atrophy. The younger the child, the more frequent is the presence of this cistern, especially under eight months of age.

A case of Sotos' syndrome (cerebral gigantism) is described. Pneumencephalography, performed at the age of 15 days, revealed abnormal separation of the opercula on the right. By comparing the contours with developmental anatomical features of this area it agreed with a foetal development of 24 weeks gestational age. Bilateral carotid angiography was normal. CT showed normal development of the Sylvian area at the age of 27 months.

Elevation and dilatation of the callosal sulci accompanied by failure of filling of the lateral ventricles is a reliable pneumoencephalographic sign of obstructive hydrocephalus. Occasionally other sub-arachnoid spaces such as the ambient wing, the quadrigeminal and the superior cerebellar cisterns, the cavum veli interpositi, the cingulate, and the cerebral convexity sulci are also dilated. There is no mention of angiographic changes which might indicate the presence of a positive callosal sulcus sign. In a review of 12 patients with obstructive hydrocephalus who had pneumoencephalographic and angiographic examinations, characteristic changes in the disposition of the small horizontal rootlets emanating from the pericallosal arteries were observed on anteroposterior angiograms. These changes in position corresponded with dilatation and elevation of the callosal sulci in 9 patients. In the remaining 3 the callosal sulci were dilated but retained a horizontal position so that no change appeared in the hori...

To the Editor. —The article by Miller et al 1 concerning the cavum vergae errs in one detail: the authors use the terms cavum septum pellucidum and cavum velum interpositum for spaces properly called cavum septi pellucidi and cavum veli interpositi . If Coleridge 2 were writing about his opium dream today, his "caves of ice" would probably be just "ice caves," and the meter of Kubla Khan would limp in consequence. With regard to the cava of the brain, also, it is better to be old-fashioned, go along with the Nomina Anatomica , show oneself to be "progenitive": they should be caves of " i 's."