Posterior Fossa Structures Research Articles

Cerebellar Watershed Injury in Children.

Focal signal abnormalities at the depth of the cerebellar fissures in children have recently been reported to represent a novel pattern of bottom-of-fissure dysplasia. We describe a series of patients with a similar distribution and appearance of cerebellar signal abnormality attributable to watershed injury. Twenty-three children with MR imaging findings of focal T2 prolongation in the cerebellar gray matter and immediate subjacent white matter at the depth of the fissures were included. MR imaging examinations were qualitatively analyzed for the characteristics and distribution of signal abnormality within posterior fossa structures, the presence and distribution of volume loss, the presence of abnormal contrast enhancement, and the presence and pattern of supratentorial injury. T2 prolongation was observed at the depths of the cerebellar fissures bilaterally in all 23 patients, centered at the expected location of the deep cerebellar vascular borderzone. Diffusion restriction was associated with MR imaging performed during acute injury in 13/16 patients. Five of 23 patients had prior imaging, all demonstrating a normal cerebellum. The etiology of injury was hypoxic-ischemic injury in 17/23 patients, posterior reversible encephalopathy syndrome in 3/23 patients, and indeterminate in 3/23 patients. Twenty of 23 patients demonstrated an associated classic parasagittal watershed pattern of supratentorial cortical injury. Injury in the chronic phase was associated with relatively preserved gray matter volume in 8/15 patients, closely matching the published appearance of bottom-of-fissure dysplasia. In a series of patients with findings similar in appearance to the recently described bottom-of-fissure dysplasia, we have demonstrated a stereotyped pattern of injury attributable to cerebellar watershed injury.

Investigation of The Improvement Rate Regarding The Herniation of Cerebellar Tonsils Following Shunting Procedures in Patients with Chiari Malformation and Associated Hydrocephalus

Introduction and Aim: Chiari malformation is a congenital anomaly formed as the result of the herniation of posterior fossa structures through the foramen magnum toward the spinal canal. In this study, we aimed to present the improvement rate regarding the herniation in cerebellar tonsils following shunting procedures in patients with Chiari malformation and associated hydrocephalus. Method: We measured in mm the improvement rate regarding the herniation in cerebellar tonsils in postoperative cervical MRI images obtained following ventriculoperitoneal shunting procedures for hydrocephalus in adult patients with symptoms of Chiari malformation such as balance disorder, dizziness, numbness and loss of muscular strength at the hands who were diagnosed with Chiari malformation and hydrocephalus following cranial and cervical magnetic resonance imaging MRI . Results: A total of fifteen adult patients in whom the cerebellar tonsillar herniation was over 5 mm and accompanied by hydrocephalus were included in our study. The measure of herniation in the patients involved in the study was between 1.11 cm and 8 mm. The amount of improvement in herniation following the shunting procedure was between 7.76 mm and 2.2 mm. Conclusion: In patients with Chiari malformation associated with hydrocephalus, cerebellar tonsillar herniation can regress to 5 mm, which is considered as physiological, and the symptoms related to Chiari malformation can disappear. When Chiari malformation is associated with hydrocephalus, the tonsillar herniation may improve, and symptoms may disappear following the ventriculoperitoneal shunting procedure for hydrocephalus without necessitating posterior decompression for Chiari-related herniation.

The Fetal Posterior Fossa on Prenatal Ultrasound Imaging: Normal Longitudinal Development and Posterior Fossa Anomalies.

Fetal neurosonography and the assessment of the posterior fossa have gained in importance during the last 2 decades primarily due to the development of high-resolution ultrasound probes and the introduction of 3 D sonography. The anatomical development of the posterior fossa can be visualized well with the newest ultrasound technologies. This allows better knowledge of the anatomical structures and helps with understanding of the development of malformations of the posterior fossa. In this article the longitudinal development of the posterior fossa structures will be reviewed. The embryologic description will be compared with ultrasound descriptions. These embryologic and anatomic illustrations form the basis for the screening and diagnosis of malformations of the posterior fossa. During the first trimester, screening for open spina bifida as well as cystic malformations of the posterior fossa is possible. In the second and third trimester, malformations of the posterior fossa can be subdivided into 3 groups: fluid accumulation in the posterior fossa (Dandy-Walker malformation, Blake's pouch cyst, mega cisterna magna, arachnoid cyst, vermian hypoplasia), decreased cerebellar biometrics (volume) (cerebellar hypoplasia, pontocerebellar hypoplasia) and suspicious cerebellar anatomy (Arnold-Chiari malformation, rhombencephalosynapsis, Joubert syndrome). This algorithm, in combination with knowledge of normal development, facilitates the diagnostic workup of malformations of the posterior fossa.

EP07.23: First trimester ultrasound screening of open spina bifida (OSB): comparison between two different methods

To compare two different methods in the ultrasound screening of OSB at 11–13 weeks. Single centre prospective study, including all fetuses with OSB diagnosed over a period of three years and a non-consecutive series of normal fetuses as controls. Only cases with available images of the 11-13-week scan were included. In all fetuses an evaluation of the posterior cranial fossa (PCF) structures was performed measuring the ratio between brainstem and brainstem-to-occipital-bone distance (BS/BSOB) on the midsagittal plane, and the aqueduct-to-occipital bone space (AOS) on the axial one. BS/BSOB and AOS were converted in multiple of the medians obtained from the published charts and compared between cases and controls. Overall, 26 fetuses were recruited for the study purposes, including 5 with OSB and 21 as controls. BS/BSOB was significantly increased (p < 0.001) and AOS significantly reduced (p < 0.01) in OSB group. Both parameters were predictive for OSB, with an area under the receiver operating characteristic curve of 0.990 for BS/BSOB and 0.89 for AOS. The quantitative evaluation of PCF structures at the 11-13 weeks scan has been confirmed to perform extremely well in detecting the OSB. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

First-trimester cystic posterior fossa: reference ranges, associated findings, and pregnancy outcomes

Objective To report reference ranges for fetal cerebral posterior fossa measurements and to describe the sonographic findings, karyotype results, and pregnancy outcomes in fetuses presenting with cystic posterior fossa (CPF) in the first trimester of pregnancy. Methods Two groups of patients undergoing first-trimester sonographic screening at 11–13 weeks’ gestation were studied. The first (control group) consisted of 253 consecutive fetuses with normal posterior fossa, in which the brainstem (BS), fourth ventricle, cisterna magna, and BS-occipital bone (BS−OB) diameter were prospectively measured and the BS/BS−OB diameter ratio was calculated. The second (study group) consisted of 14 fetuses in which a CPF was detected. Information on sonographic findings, prenatal karyotype results, and pregnancy outcomes was obtained by reviewing ultrasound reports and medical records. The results from the two groups were then compared. Results In the control group, the size of all posterior fossa structures increased and the BS/BS−OB diameter ratio slightly decreased as the pregnancy progressed. In the study group, the BS diameter did not differ significantly from the measurements obtained in the control group. However, the BS−OB diameter and the fourth ventricle were significantly larger (p < .05 and p < .001, respectively) in the study group than in the control group. Additionally, the cisterna magna was not identified in 13 of the 14 fetuses (93%) in the study group, in comparison to zero out of the 253 fetuses in the control group (p < .001). Finally, the BS/BS−OB diameter ratio was significantly smaller in the study group when compared with the control group (p < .05). Regarding pregnancy outcomes, 12 of the 14 (86%) affected pregnancies underwent elective termination (n = 11) or ended in an early intrauterine demise (n = 1) due to the associated chromosomal abnormalities or structural defects. The two fetuses with isolated CPF had a normal second-trimester scan and resulted in the delivery of healthy newborn infants. Conclusions The detection of a CPF in the first trimester is associated with a high rate of chromosomal and structural defects. By using normative data, early sonographic screening and detection of mildly and moderately abnormal cases is possible. Fetuses with isolated CPF require further study with a detailed second-trimester scan. This is essential in order to differentiate cases with poor and good perinatal outcomes. Finally, our data also demonstrate that the main sonographic tool when screening for CPF in the first trimester is the assessment of the fourth ventricle, which is significantly larger in abnormal cases as the result of the wide communication between the fourth ventricle and the cisterna magna.

Predictive ability of admission neutrophil to lymphocyte ratio on short-term outcome in patients with spontaneous cerebellar hemorrhage.

As one of the prototypical intracranial hemorrhage (ICH), spontaneous cerebellar hemorrhage (SCH) is treated with different strategies by comparing with supratentorial hemorrhage (SH). Additionally, SCH patients usually suffer from worse prognosis than patients with other types of ICH. It is well documented that the unique anatomic structures of posterior cranial fossa lead to a higher risk for brainstem compression and/or brain edema in SCH patients. Recently, neutrophil to lymphocyte ratio (NLR) was reported to possess an excellent predictive ability for the prognosis of patients with ICH, and most of those cases are SH. Thus, the potential association between NLR and the prognosis of SCH patients remains to be elucidated. Here, we aim to assess the predictive role of admission NLR and other available inflammatory parameters for the outcomes of patients with SCH.All patients with acute SCH admitting to West China Hospital from February 2010 to October 2017 were retrospectively enrolled. According to the absolute neutrophil count, absolute lymphocyte count, white blood count and absolute monocyte count extracted from electronic medical records, NLR was calculated. The multivariable logistic regression analysis was applied to analyze the associations between disease outcome and laboratory biomarkers. The comparisons of predictive powers of each biomarker were assessed by receiver operating curves (ROCs). The spearman analyses and multiple linear analyses were also conducted to identify the independent predictors for admission NLR.Admission NLR independently associated with 30-day status (odds ratio [OR] 1.785, 95% confidence interval [CI] 1.463–2.666, P <.01) and exhibited a better predictive value (AUC 0.751, 95% CI 0.659–0.830, P <.001) with the best predictive cutoff point of 7.04 in 62 patients with unfavorable outcomes. Moreover, absolute neutrophil count, absolute lymphocyte count, presence of intraventricular hemorrhage (IVH) and Glasgow coma scale (GCS) score were also correlated with admission NLR, respectively.Admission NLR is a potential marker to independently predict the 30 days functional outcome of SCH patients. Based on our results, systemic inflammation in admission might be considered as an important player in participating the pathological process of patients with SCH.

Posterior Fossa Malformations.

This article discusses the normal anatomy of the posterior fossa structures followed by a discussion of the characteristic neuroimaging features of a variety of cerebellar and brainstem malformations. In this context, the authors classify posterior fossa malformations based on the neuroimaging pattern into (1) predominantly cerebellar, (2) cerebellar and brainstem, and (3) predominantly brainstem malformations.

Epidemiology of Symptomatic Chiari Malformation in Tatarstan: Regional and Ethnic Differences in Prevalence.

Epidemiology can assess the effect of Chiari I malformation (CM1) on the neurological health of a population and evaluate factors influencing CM1 development. To analyze the regional and ethnic differences in the prevalence of CM1. The population of the Republic of Tatarstan (RT) in the Russian Federation was evaluated for patients with CM1 symptoms over an 11-yr period. Typical symptoms of CM1 were found in 868 patients. Data from neurological examination and magnetic resonance imaging (MRI) measurement of posterior cranial fossa structures were analyzed. MRI evidence of CM1, defined as cerebellar tonsils lying at least 5 mm inferior to the foramen magnum, was found in 67% of symptomatic patients. Another 33% of symptomatic patients had 2 to 4 mm of tonsillar ectopia, which we defined as "borderline Chiari malformation type 1 (bCM1)." The period prevalence in the entire RT for symptomatic CM1 was 20:100 000; for bCM1 was 10:100 000; and for CM1 and bCM1 together was 30:100 000. Prevalence of patients with CM1 symptoms was greater in the northern than southern districts of Tatarstan, due to a high prevalence (413:100 000) of CM1 in the Baltasy region in one of the northern districts. One-third of patients with typical symptoms of CM1 had less than 5 mm of tonsillar ectopia (bCM1). Assessments of the health impact of CM1-type symptoms on a patient population should include the bCM1 patient group. A regional disease cluster of patients with Chiari malformation was found in Baltasy district of RT and needs further study.

A case with Chiari malformation 2 diagnosed with vertigo

Chiari malformations (CM) are a congenital anomally which posterior fossa structures are displaced from foroman magnum to the upper cervical spinal canal at different degrees [1]. (1) If there is accompanied by spinal dysraphism, it is defined as type 2. Symptoms occurs as a results of pressure on the cerebellum like as vertigo, ataxia, vision problems, headache. In some cases, medical therapy can be used to manage symptoms. Surgery is only treatment for decrease compression or stop progression. This malformation is frequently accompanied by syringomyelia, cystic spaces occur vertically in the spinal cord. In this article, a case with CM type 2, syringomyelia and multilacuner infarction with vertigo was discussed.

Quantification of Cerebellar Crowding in Type I Chiari Malformation.

This study was focused on a semi-automated morphometric analysis of the cerebellum in the mid-sagittal plane as an alternative to tonsillar descent alone in the evaluation of Chiari malformation type 1 (CMI) patients. Morphometric analyses of posterior fossa structures were performed on mid-sagittal MRI images of 375 individuals (females, > 18years, 235 CMI and 140 healthy controls). Twenty-six parameters including linear, angular and area measurements together with non-dimensional ratios were calculated. Eighteen parameters were found to be significantly different between CMI and control subjects. Smaller posterior cranial fossa (PCF) area in CMI subjects was attributed to a smaller PCF area anterior to the brainstem. The cerebellar area was found to be larger in CMI subjects as compared to controls (15.1%), even without inclusion of the tonsillar area below the foramen magnum (FM) (8.4%). The larger cerebellar area in CMI subjects was due to cranial-caudal elongation of the cerebellum, predominately below the fastigium. The cerebrospinal fluid spaces below the FM were smaller in CMI subjects as compared to controls. Overall, greater cerebellar crowding was identified in CMI subjects relative to healthy controls. These observations may improve our understanding of the pathophysiology of CMI in adult female patients.

Practical guide to neonatal cranial ultrasound (CrUS): basics

Abstract Cranial ultrasonography is a reliable and readily available tool for neonatal brain imaging. It has become indispensable in the care of neonates as it helps to detect common congenital and acquired brain abnormalities. The use of modern ultrasound scan machines with the appropriate choice of probes, settings and acoustic windows has improved the diagnostic value of the cranial ultrasound in experienced hands. The standard acoustic window for imaging is the anterior fontanelle which is suitable for viewing the supratentorial structures. However, supplementary acoustic windows can be used for better visualisation of brain stem and posterior fossa structures. Doppler studies help to assess flow velocities in major vessels. Though cranial ultrasound has numerous advantages, it has some limitations. This article reviews the practical aspects of performing cranial ultrasound in a neonate.

RHOMBOENCEPHALOSYNAPSIS MR-SEMIOTICS AND DIFFERENTIAL DIAGNOSIS

Rombencephalosynapsys (RES) is a rare variant of anomalies of the posterior cranial fossa structures characterized by dysplastic fusion of cerebellar hemispheres and absence or hypoplasia of cerebellar vermis. Purpose: to demonstrate the possibilities of modern neuroimaging in the RES diagnosis and to identify the main markers of the differential diagnosis in posterior fossa structures (PFS) anomalies. In the department of Radiology of Russian Children’s Clinical Hospital, we observed 3 patients with RES (1 girl and 2 boys). Patients age varied from 3 months to 9 years. The studies were performed on high-field MR system GE Discovery 750 W 3 T. Results: оn MRI in patients with RES we identified the spectrum of dysplastic anomalies of the vermis, from complete absence to partial aplasia with preservation of its anterior part. Also, there were 2 case with cerebellar dysplastic features, resemling RES. The transcerebellar sulci were estimated as the a clue diagnostic marker of RES. Conclusion: High-field MRI is the preferred diagnostic tool in the definition and differentiation of the developmental anomalies of the PFC in the children, especially in patients with RES.

Brain Trust

stroke, NIHSS: stroke, NIHSSFigureFigurePART 3 IN A THREE-PART SERIES The National Institutes of Health Stroke Scale is the most widely used deficit rating scale in modern neurology, but it was not meant to be a bedside rating tool. This critical piece of the neurologic exam for any suspected stroke patient, originally developed as a research tool to measure baseline data in acute stroke clinical trials, has considerable problems that may arise in clinical practice, however. The NIHSS is used as a clinical assessment tool to evaluate the acuity of stroke patients, determine appropriate treatments, and predict patient outcomes. Several scale items require intact language, however, so it gives too much weight to deficits in patients with left versus right hemispheric strokes. A left hemispheric stroke can score up to four more points than a right hemispheric stroke of similar size. Posterior circulation strokes also suffer under the NIHSS because they receive few to no points. Important elements such as diplopia, dysphagia, gait instability, nystagmus, and dizziness receive no score, and a patient with a life-changing stroke could be completely missed if the NIHSS were the only tool considered. A good correlation is seen between NIHSS and the likelihood of finding an eligible large vessel occlusion, but no specific number seems optimal for use. (Stroke 2017;48[2]:513.) Don't fall into some of these traps; the NIHSS must be used with caution in clinical practice for rating stroke severity. Most importantly, a complete and thorough neurologic examination should be second nature and should always include anterior and posterior components. Most electronic medical records will have an NIHSS template built in, and it is widely available online, but consider other online tools such as MDCalc to help calculate a score. (www.mdcalc.com.) Noncontrast CT Neuroimaging of the patient with acute ischemic stroke is used to exclude hemorrhage, assess the degree of brain injury, and identify the vascular lesion responsible for the ischemic deficit. Noncontrast CT (NCCT) of the brain has the main advantage of widespread access and speed of acquisition. It is usually ordered to exclude or confirm hemorrhage and is highly sensitive for this indication, but it is not that sensitive for ischemia before 24 hours, and it has significantly poor sensitivity for the posterior fossa structures. (J Emerg Med 2012 May;42[5]:559.) CT angiography allows visualization of the extracranial and intracranial cerebral arteries, and CTA source images are more sensitive than NCCT scans for detecting early brain infarction. The value of CTA is to identify patients with occlusion of the major vessels within the circle of Willis or extracranial cerebral arteries, but it will still not be reliable for smaller to even medium areas of ischemia, especially in the posterior circulation territory. (Stroke 2009;40[11]:3646.) Recently, the Head Impulse, Nystagmus, Test of Skew (HINTS) exam gained attention as a series of three physical exam maneuvers to differentiate peripheral and central causes of acute vestibular syndrome. A positive HINTS exam can be 100% sensitive and 96% specific for the presence of a central lesion. It is also more sensitive than general neurologic signs: 100% vs 51%. Disclaimer ahead (and it is a big one!): The HINTS exam was tested in an outpatient setting by neuro-ophthalmologists, not emergency physicians, and may not be generalizable to an ED population. (Stroke 2009;40[11]:3504.) Use of brain MRI has significantly increased for evaluating patients with acute ischemic stroke. The rationale for MRI—diffusion-weighted imaging (DWI), in particular—is that this modality has substantially higher sensitivity (88-100%) than that of NCCT for detecting ischemia, with a specificity reported to be as high as 95%-100%. MRI also identifies acute intracranial hemorrhage with similar reliability to NCCT. As if our jobs were not hard enough, emerging evidence now shows that DWI fails to identify acute ischemic stroke in a substantial minority of patients, about seven percent. These DWI-negative stroke cases fall into three categories: posterior circulation ischemia, small strokes, particularly in the brainstem, and hyperacute ischemia (MRI done within six hours of onset). (Neurology 2017;89[3]:256.) Acute ischemic stroke remains one of the most challenging diagnoses in emergency medicine. We need to continue to rise to the challenge, using clinical judgment followed by a thorough and complete neurologic exam and appropriate imaging. Our patients can't afford for us to miss the diagnosis of acute ischemic stroke because early diagnosis can lead to improved outcome, and the neurologic exam and appropriate use of imaging are our best tools.

Focused Neuro-Otological Review of Superficial Siderosis of the Central Nervous System.

Infratentorial siderosis (iSS) is a progressive degenerative disorder targeting primarily the cerebellum and cranial nerve eighth; therefore, progressive ataxia and its neuro-otological findings are common. Toxicity from hemosiderin involves selectively vulnerable neurons and glia in these posterior fossa structures. Other neurologic findings may be present, though our focus relates to the cochlea-vestibular cerebellar involvement. Radiographic evidence of siderosis may be the result of recurrent, albeit covert bleeding in the subarachnoid space, or the consequence of an overt post-traumatic or aneurysmal subarachnoid hemorrhage (SAH). The radiographic iSS appearance is identical regardless of the SAH cause. A recent study provides compelling evidence to search and correct possible hemorrhage sources in the spinal canal. The removal of residual existing hemosiderin deposits that may potentially cause clinical symptoms remains as a major therapeutic challenge. We reviewed large data sources and identified salient papers that describe the pathogenesis, clinical and neurotologic manifestations, and the radiographic features of iSS. The epidemiology of iSS is unknown. In a recent series, clinically evident iSS was associated with recurrent SAH; by contrast, in a follow-up period ranging from weeks up to 11 years after a monophasic episode of SAH, radiographic siderosis was clinically silent. However, the post-aneurysmal or post-trauma SAH sample size in this single study was small and their observation period relatively short; moreover, the burden of intraneuronal hemosiderin is likely greater with recurrent SAH. There are a few reports of late iSS, several decades after traumatic SAH. A recent report found subjective hearing loss in aneurysmal SAH individuals with radiographic siderosis. Only in recent years, it is safe to perform magnetic resonance imaging (MRI) in post-aneurysmal SAH, because of the introduction of titanium, MRI-compatible aneurysm clips. iSS can be associated with significant neurotologic and cerebellar morbidity; the recurrent SAH variant is frequently clinically symptomatic, has a shorter latency and greater neurotologic disability. In these cases, a thorough search and management of a covert source of bleeding may stop clinical progression. The frequency and clinical course of radiographic iSS after traumatic and post-aneurysmal SAH is largely unknown. Detection of radiographic iSS after trauma or aneurysm bleeding suggests that the slower clinical course could benefit from an effective intervention if it became available. The use of cochlear implants is a valid alternative with advanced hearing impairment.

Suitability of foramen magnum measurements in sex determination and their clinical significance.

The foramen magnum provides a transition between fossa cranii posterior and canalis vertebralis. Medulla oblongata, arteria vertebralis and nervus accessorius spinal part pass through the foramen magnum. In this study, we aimed to make the morphometric measurements of the foramen magnum on computed tomography (CT) and to determine the feasibility of sex determination based on these measurements. Besides sex determination, from a clinical aspect, it is important to know the measurements of the foramen magnum in the normal population in terms of diseases characterised by displacement of the posterior fossa structures through foramen magnum to upper cervical spinal canal such as Chiari malformations and syringomyelia. All the data for our study was obtained retrospectively from 100 patients (50 males, 50 females) who had a CT scan of the head and neck region in Adnan Menderes University Hospital, Department of Radiology. To examine the foramen magnum in each and every occipital bone, we measured the foramen magnum's anteroposterior diameter, transverse diameter, the area of the foramen magnum and its circumference. We found that men have a higher average value than women in our study. According to Student's t-test results; in all measured parameters, there is significant difference between the genders (p < 0.05). When multivariate discriminant function test is performed for all four measurements, the discrimination rate is 64% for all women, 70% for all men and 67% for both genders. As a result of our study, the metric data we obtained will be useful in cases where the skeletons' sex could not be determined by any other methods. We believe that, our study may be useful for other studies in determining of sex from foramen magnum. Our measurements could give some information of the normal ranges of the foramen magnum in normal population, so that this can contribute to the diagnosis process of some diseases by imaging. (Folia Morphol 2018; 77, 1: 99-104).

Chapter 13 - Conventional MRI

Conventional magnetic resonance imaging (MRI) allows for a detailed noninvasive visualization/examination of posterior fossa structures and represents a fundamental step in the diagnostic workup of many cerebellar disorders. In the first part of this chapter methodologic issues, like the correct choice of hardware (magnets, coils), pro and cons of the different MRI sequences, and patient management during the examination are discussed. In the second part, the MRI anatomy of the cerebellum, as noted on the various conventional MRI sequences, as well as a detailed description of cerebellar maturational processes from birth to childhood and into adulthood, are reported. Volumetric studies on the cerebellar growth based on three-dimensional MRI sequences are also presented. Moreover, we briefly discuss two main topics regarding conventional MRI of the cerebellum that have generated some debate in recent years: the differentiation between cerebellar atrophy, hypoplasia, and pontocerebellar hypoplasia, and signal changes of dentate nuclei after repetitive gadolinium-based contrast injections. The advantages and benefits of advanced neuroimaging techniques, including 1H magnetic resonance spectroscopy, diffusion-weighted imaging, diffusion tensor imaging, and perfusion-weighted imaging are discussed in the last section of the chapter.

OP07.02: The relationship between the posterior fossa structures and foramen magnum using the occipitum‐dens line (ODL) in following fetal surgery for myelomeningocele

OP07.02: The relationship between the posterior fossa structures and foramen magnum using the occipitum‐dens line (ODL) in following fetal surgery for myelomeningocele

Cerebellar Mutism Syndrome following Midline Posterior Fossa Tumor Resection in Children: An Institutional Experience.

Aim:Cerebellar mutism (CM) syndrome is a well-known and annoying complication of posterior fossa surgery in the pediatric age group. Risk factors such as the type of tumor, size, involvement of posterior fossa structures and hydrocephalus, and postoperative cerebellar swelling for CM were investigated in this study.Materials and Methods:A consecutive series of 33 children with midline posterior fossa tumors were operated at the SMS Medical College and Hospital, Department of Neurosurgery, Jaipur India, between September 2015 and December 2016. Their speech and neuroradiological studies were systematically analyzed both preoperatively and postoperatively.Results:CM syndrome (CMS) developed in six children (18.18%) in the early postoperative period. The pre- and post-operative irritability, medulloblastoma histology, maximum size more than 45 mm, involvement of superior cerebellar peduncles, and vermian incision were significant single independent risk factors. In addition, male gender also associated with a higher risk for CMS. The latency for the development of mutism ranged from 1 to 12 days (mean 3.5 days). The speech returned to normal in all patients. All cases with CMS accompanied by cerebellar ataxia.Conclusion:The medulloblastoma, irritability, maximum size more than 45 mm, involvement of superior cerebellar peduncles, and vermian incision were significant single independent risk factors for postoperative pediatric CMS. Mutism after posterior fossa tumor resection is also accompanied with ataxia. CM usually has a self-limiting course and a favorable prognosis.

Two distinct populations of Chiari I malformation based on presence or absence of posterior fossa crowdedness on magnetic resonance imaging.

OBJECTIVE A subset of patients with Chiari I malformation demonstrate patent subarachnoid spaces around the cerebellum, indicating that reduced posterior fossa volume alone does not account for tonsillar descent. The authors distinguish two subsets of Chiari I malformation patients based on the degree of "posterior fossa crowdedness" on MRI. METHODS Two of the coauthors independently reviewed the preoperative MR images of 49 patients with Chiari I malformation and categorized the posterior fossa as "spacious" or "crowded." Volumetric analysis of posterior fossa structures was then performed using open-source DICOM software. The preoperative clinical and imaging features of the two groups were compared. RESULTS The posterior fossae of 25 patients were classified as spacious and 20 as crowded by both readers; 4 were incongruent. The volumes of the posterior fossa compartment, posterior fossa tissue, and hindbrain (posterior fossa tissue including herniated tonsils) were statistically similar between the patients with spacious and crowed subtypes (p = 0.33, p = 0.17, p = 0.20, respectively). However, patients in the spacious and crowded subtypes demonstrated significant differences in the ratios of posterior fossa tissue to compartment volumes as well as hindbrain to compartment volumes (p = 0.001 and p = 0.0004, respectively). The average age at surgery was 29.2 ± 19.3 years (mean ± SD) and 21.9 ± 14.9 years for spacious and crowded subtypes, respectively (p = 0.08). Syringomyelia was more prevalent in the crowded subtype (50% vs 28%, p = 0.11). CONCLUSIONS The authors' study identifies two subtypes of Chiari I malformation, crowded and spacious, that can be distinguished by MRI appearance without volumetric analysis. Earlier age at surgery and presence of syringomyelia are more common in the crowded subtype. The presence of the spacious subtype suggests that crowdedness alone cannot explain the pathogenesis of Chiari I malformation in many patients, supporting the need for further investigation.

Sonoembryology of the fetal posterior fossa at 11 + 3 to 13 + 6 gestational weeks on three-dimensional transvaginal ultrasound.

To describe the sonographic appearance and temporal changes of the structures of the posterior cranial fossa in fetuses at a crown-rump length (CRL) between 45 and 84 mm in transvaginal acquired three-dimensional volume blocks. This was a prospective, cross-sectional, observational study including 80 fetuses, whose mothers attended Kepler University Hospital Linz or the Ambulatorium für Fetalmedizin Feldkirch for first-trimester sonography. Three-dimensional volume blocks were acquired in a standardized way and after processing the sonographic characteristics of the brainstem, cerebellar vermis, choroid plexus, anterior membranous area (AMA) and Blake's metapore were described. Measurements of the length of the cerebellar vermis, the length of the AMA and the medulla-oblongata-pons angle (MOPA) were performed. In 20 fetuses the intra- and interobserver repeatability was calculated. The sonomorphologic characteristics of posterior fossa structures as cerebellar vermis, AMA, Blake's metapore, choroid plexus, pons and medulla oblongata were described. There is a significant correlation between CRL and vermis length, CRL and MOPA and CRL and AMA. Transvaginal three-dimensional sonography allows a detailed depiction of the structures of the posterior fossa and their temporal course in early pregnancy. © 2016 John Wiley & Sons, Ltd.