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Objectives: To characterise the symptomatic phenotype of Chiari-like malformation (CM), secondary syringomyelia (SM) and brachycephaly in the Cavalier King Charles Spaniel using morphometric measurements on mid-sagittal Magnetic Resonance images (MRI) of the brain and craniocervical junction., Methods: This retrospective study, based on a previous quantitative analysis in the Griffon Bruxellois (GB), used 24 measurements taken on 130 T1-weighted MRI of hindbrain and cervical region. Associated brachycephaly was estimated using 26 measurements, including rostral forebrain flattening and olfactory lobe rotation, on 72 T2-weighted MRI of the whole brain. Both study cohorts were divided into three groups; Control, CM pain and SM and their morphometries compared with each other., Results: Fourteen significant traits were identified in the hindbrain study and nine traits in the whole brain study, six of which were similar to the GB and suggest a common aetiology. The Control cohort had the most elliptical brain (p = 0.010), least olfactory bulb rotation (p = 0.003) and a protective angle (p = 0.004) compared to the other groups. The CM pain cohort had the greatest rostral forebrain flattening (p = 0.007), shortest basioccipital (p = 0.019), but a greater distance between the atlas and basioccipital (p = 0.002) which was protective for SM. The SM cohort had two conformation anomalies depending on the severity of craniocervical junction incongruities; i) the proximity of the dens (p <0.001) ii) increased airorhynchy with a smaller, more ventrally rotated olfactory bulb (p <0.001). Both generated 'concertina' flexures of the brain and craniocervical junction., Conclusion: Morphometric mapping provides a diagnostic tool for quantifying symptomatic CM, secondary SM and their relationship with brachycephaly. It is hypothesized that CM pain is associated with increased brachycephaly and SM can result from different combinations of abnormalities of the forebrain, caudal fossa and craniocervical junction which compromise the neural parenchyma and impede cerebrospinal fluid flow., Competing Interests: SPK is a post-graduate research student and CC an undergraduate at the University of Surrey where CR and RMLR are employed. ZK is employed by Montreal University. JJ, CD, AT and CR are employed by Fitzpatrick Referrals Ltd, Surrey, GU7 Q22. SG is employed by the Goddard Veterinary Group, Stone Lion Veterinary Hospital, SW19 5AU. AKM is an independent statistical consultant operating professionally as a sole trader under the company name of akm-stats and did not receive any salary or other remittance for his contribution in this investigation. The University of Surrey, Montreal University, Fitzpatrick Referrals Ltd, Goddard Veterinary Group did not play a role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript and only provided financial support in the form of authors' salaries and/or research materials. None of the authors have personal or financial relationships with other people or organizations that might inappropriately influence or bias the content of the paper. There are no patents, products in development, or marketed products to declare. This does not alter the authors' adherence to PLOS ONE policies on sharing data and materials.

Purpose: Neuroimaging techniques including structural magnetic resonance imaging (MRI) and functional positron emission tomography (PET) are useful in categorizing various midbrain-hindbrain (MHB) malformations, both in allowing diagnosis and in helping to understand the developmental processes that were disturbed. Brain imaging phenotypes of numerous malformations are characteristic features that help in guiding the genetic testing in case of direct neuroimaging-genotype correlation or, at least, to differentiate among MHB malformations entities. The present review aims to provide the reader with an update of the use of neuroimaging applications in the fine analysis of MHB malformations, using a comprehensive, recently proposed developmental and genetic classification., Methods: We have performed an extensive systematic review of the literature, from the embryology main steps of MHB development through the malformations entities, with regard to their molecular and genetic basis, conventional MRI features, and other neuroimaging characteristics., Results: We discuss disorders in which imaging features are distinctive and how these features reflect the structural and functional impairment of the brain., Conclusion: Recognition of specific MRI phenotypes, including advanced imaging features, is useful to recognize the MHB malformation entities, to suggest genetic investigations, and, eventually, to monitor the disease outcome after supportive therapies.

Purpose: To evaluate bSSFP (balanced steady state free precession) and half-Fourier RARE (rapid acceleration with relaxation enhancement) MRI sequences in their ability to demonstrate fetal anatomic landmarks, quantify the degree of cerebellar herniation in Chiari II malformations and level and length of the associated open neural tube defects, as well as evaluate interobserver reliability of these measurements., Materials and Methods: Two independent observers retrospectively reviewed MRIs of 37 fetuses with Chiari II malformations and associated open neural tube defects (mean gestational age: 27 weeks 2 days). Comparison of bSSFP and RARE included: (i) Ability to confidently identify anatomic landmarks of the posterior fossa and spine; (ii) Measurements of the foramen magnum, cerebellar tonsillar herniation length, intervertebral disc space level of tonsillar herniation, open neural tube defect length, and disc space start and end level of the open neural tube defect; (iii) Observed conspicuity of anatomic landmarks., Results: There was no significant difference in assessment of cerebellar tonsillar herniation or open neural tube defect level between bSSFP and RARE for either observer. Intervertebral discs were more conspicuous on bSSFP while cerebellar tonsils were more conspicuous on RARE (P < 0.05). Interobserver reliability was strong for both sequences in assessing the foramen magnum (r = 0.95, 0.94), tonsillar herniation length (r = 0.93, 0.95), and open neural tube defect length (r = 0.97, 0.96)., Conclusion: Despite improved conspicuity of the intervertebral discs with bSSFP and cerebellar tonsils with RARE, there is no significant difference in measurement of hindbrain herniation or open neural tube defect level; interobserver reliability is excellent for both sequences., (Copyright © 2013 Wiley Periodicals, Inc.)

We present a case of partial rhombencephalosynapsis, diagnosed by magnetic resonance imaging (MRI), in fetus aged 27 gestational weeks, in a dizygotic twin pregnancy. The distinctive MRI features of this cerebellar malformation (segmental hypogenesis of the cerebellar vermis, partial fusion of the cerebellar hemispheres and dentate nuclei) without associated cerebral abnormalities were confirmed by 32-weeks prenatal and 3-months postnatal MRI studies. At the age of 12 months the affected twin had a slight delay in psychomotor development, mild hypotonia with normal cognitive development. To the authors' best knowledge, this is the first report of a fetal case with isolated partial rhombencephalosynapsis. Its MRI features enlarges the narrow spectrum of uncommon variants of rhombencephalosynapsis, and allow an accurate differentiation from other vermian and cerebellar anomalies with less favorable postnatal outcome.

Purpose: Foramen magnum dimensions and intracranial volume in Chiari I malformations in children were studied, and the statistical relationship between patient demographics, radiological features and foramen magnum morphometry was investigated., Methods: Linear measurements were used to calculate the intracranial volume using preoperative magnetic resonance images and computed tomogram images. The area of the foramen magnum was obtained independently using computer imaging software and a regression formula. The result of 21 pediatric patients was compared with a matched control group., Results: The area of the foramen magnum was within the range of the expected value deduced using a formula based on the intracranial volume. There was no statistical difference in the area and linear dimensions of the foramen magnum in the study and control groups. Six patients (28%) had a foramen magnum in close proximity to a spherical shape., Conclusion: The authors provide a simple, accurate and reproducible method of estimating foramen magnum area in the pediatric Chiari I group. The irregular shape of the foramen magnum is accentuated by developmental bony and soft tissue anomalies at the cranio-vertebral junction in Chiari malformation. Consequently, an individualized cross-sectional assessment of the foramen magnum in relation to the hindbrain tissue in the same plane is required to study the initiation and propagation of the Chiari I symptomatology.

Object: The goal of this study was to establish whether children with Chiari malformation Type I (CM-I) have abnormal skull base geometry., Methods: Distances and angles between skull base landmarks were measured on preoperative magnetic resonance images obtained in 30 children (age range 36-204 months) with symptomatic isolated CM-I; 16 of them (53%) had syringomyelia. Comparisons were made with 42 children of similar age who comprised the control group by using one-way analysis of variance., Results: The angle formed by the crista galli (CG), dorsum sellae (DS), and foramen magnum (FM) was larger than normal in individuals with CM-I than in those without (145 degrees in patients with CM-I but no syringomyelia and 151 degrees in those with CM-I and syringomyelia compared with 135 degrees in controls; p = 0.000). The angle formed by the left internal auditory meatus (IAM), FM, and right IAM was also larger than normal in the patients (122 degrees in patients with CM-I but no syringomyelia and 123 degrees in those with CM-I and syringomyelia compared with 110 degrees in controls; p = 0.001). The angle formed by the anterior clinoid process (ACP), CG, and right ACP was smaller than normal (29 degrees in all patients with CM-I compared with 34 degrees in controls; p = 0.000). The distance between the two IAMs was longer than normal (75 mm in patients with CM-I but no syringomyelia and 63 mm in those with CM-I and syringomyelia compared with 58 mm in controls; p = 0.000). The distance between the two ACPs was shorter than normal in the syringomyelia group (31 mm in patients with CM-I but no syringomyelia and 27 mm in those with CM-I and syrinx compared with 32 mm in controls; p = 0.001). Within the group of patients with CM-I, the DS-FM and left ACP-right ACP distances were smaller in the syringomyelia group (p = 0.009 and p = 0.037, respectively)., Conclusions: Children with CM-I have abnormal geometrical measurements of their entire skull base, not only the posterior fossa, irrespective of presence of syringomyelia. This may indicate a mesodermal defect as a possible cause of the malformation.

Objective: Some have proposed that the calvarial thickening seen in patients with rickets results in an increased rate of Chiari I malformation (CIM) in these patients. The present study measures the posterior fossa volume in children with rickets to verify previous case reports indicting a small posterior fossa as the cause for an increased rate of CIM in children with rickets., Methods: Patients were chosen by use of a computer database to search for individuals diagnosed with rickets. Nineteen patients were identified with this diagnosis. Seven patients were found from this cohort to have imaging of the head. Axial computed tomographic and magnetic resonance images were analyzed by use of the Cavalieri method to define posterior fossa volumes. These data were then compared with those from age-matched control subjects., Results: Mean volumes of the posterior fossa were significantly reduced in all patients compared with age-matched control subjects (P < 0.0001)., Conclusion: We have found that the volume of the posterior fossa is significantly smaller in children with rickets versus age-matched control subjects. Furthermore, 29% of our study group had an associated CIM. We may hope that these data will aid in the further understanding of the pathophysiology of CIM in cases of metabolic bone disease.

This study employs ex vivo high-resolution magnetic resonance imaging (MRI) to examine anatomic structures in an intact brain of a child with Joubert's syndrome. Several of the specific hindbrain malformations associated with Joubert's syndrome are well resolved with ex vivo MRI, including the "molar tooth sign," which arises from enlarged and maloriented superior cerebellar peduncles, hypoplastic vermis, and deepening of the interpeduncular fossa. Superior resolution was achieved compared with that of in vivo MRI and included visualization of the inferior olives. One high-resolution study also showed that the decreased width of the brainstem isthmus is probably caused by failure of superior cerebellar peduncles to cross the midline at that level. The results of this study suggest that high-resolution MRI may be useful in screening the brainstem for malformations that can be studied histologically in a much more targeted fashion.

Following a high fever, a healthy woman became comatose within a few days. Severe cerebellar symptoms appeared when she regained consciousness. The brain MRIs revealed abnormal signal intensity of the cerebellar cortex and brainstem gray matter, however, no abnormalities were revealed in the cerebral hemispheres. Acute inflammation due to direct viral or autoimmune involvement of the cerebellar and brainstem gray matter was a likely explanation and thus acute cerebellitis may in fact be a rhombencephalitis. Among the previous reports of acute cerebellar ataxia, this is perhaps one of the most profoundly affected cases and appears important for the understanding of the target of this particular form of encephalitis.

The spontaneous resolution of syringomyelia has been reported infrequently. In patients with Chiari I malformations, resolution of the syringomyelia has sometimes been associated with improvement of their malformation. The authors present a case of spontaneous resolution followed by recurrence of syringomyelia and a corresponding change in the Chiari malformation. This case is of interest in light of the theories postulated to explain spontaneous resolution of syringomyelia.

A patient with Wilson's disease is reported whose brain MR imaging study disclosed enhancement of the cerebral cortex, and corticomedullary junction after administration of contrast medium, in the absence of a clinically detectable ischemic condition. It is difficult to explain such contrast enhancement. However, we would suggest that a "vasculitis" secondary to accumulation of copper in the walls of the small vessels may be the causative factor. Further studies are required to investigate the clinical and radiological significance of contrast enhancement of the cerebral cortex and corticomedullary junction on MR images in patients with Wilson's disease.

We report a series of five patients operated on for hindbrain-related syringomyelia with posterior fossa decompression and duraplasty. In all cases an early postoperative MRI was performed (24-36 h after surgery). These images have been compared with the preoperative ones and with those obtained, 1, 3 and 6 months after operation. Both before and after surgery there was not always a tight correlation between clinical and MRI pictures. In all but one patient the early postoperative MR images showed a reduction of syrinx size and were as to those obtained later. We discuss the results observed in our small series and analyze the role of early postoperative MRI studies in patients with hindbrain-related syringomyelia.

Listeria monocytogenes is a rare cause of central nervous system infection in the non-immunocomprised patient and 10% of these patients develop a rhombencephalitis. We present such a case and discuss the clinical, pathological and radiological features.

The clinical and MRI findings in two cases of rhombencephalosynapsis (RS) and two of tectocerebellar dysraphia (TCD) with an associated occipital encephalocele were studied to elucidate the clinical picture and embryogenesis of these rare anomalies. To our knowledge, only one case of TCD [1] and four of RS [2, 3] examined by MRI during life have been reported. The clinical picture in the cases of RS was rather constant and there were similarities with TCD. Consideration of the embryogenesis of the neural tube suggests a temporal proximity of the abnormalities, with TCD arising at a slightly earlier time.

Rhombencephalosynapsis is an unusual disorder characterized predominantly by agenesis/hypogenesis of the cerebellar vermis and fusion of the cerebellar hemispheres. Three cases are reported with emphasis on the MRI and clinical findings. Discussion of the relative importance of the cerebellar anomalies and associated supratentorial abnormalities is included.

Pre- and post-operative assessments are presented in 17 adult patients who have been treated with craniovertebral decompression for hindbrain herniation, 11 of whom had syringomyelia. Objective improvement in the size of the syrinx was seen in all 11 cases; contrary to expectation the hindbrain more frequently moved downwards than upwards after decompression of the tonsils and creation of an artificial cisterna magna. A method is reported for the quantitative assessment of hindbrain migration using magnetic resonance imaging (MRI). The degree of 'slump', further downward displacement of the hindbrain, was compared with the clinical outcome and the MRI appearances. Slump was more common than expected, although the severity was not usually great enough to produce symptoms. Slump was less marked where the artificial cisterna magna was generous (p less than 0.02). This quantitative method may be useful in assessing patients with unexplained post-operative symptoms and in comparing different surgical techniques.