Prenatal imaging of posterior fossa disorders. A review

With advances in fetal imaging, prenatal diagnosis of posterior fossa anomalies has been greatly improved. Based on the anatomical approach proposed by Guibaud and Desportes in 2006, the main anomalies depicted according to the algorithm includes: (1) increased “fluid-filled” space of the posterior fossa, (2) abnormal biometry of the cerebellum, and (3) abnormal cerebellar anatomy. In this review, the spectrum of PF anomalies is covered in an attempt to update this approach in the light of both our experience, more than a decade since this algorithm was published, and the latest data in the literature.     

Postvaricella suppurative meningitis. Case reports and review of the literature.

Suppurative meningitis should be recognized as being a complication of varicella. The clinician must assiduously exclude suppurative meningitis that at times may be clinically indistinguishable from the typical postinfectious encephalomyelitis of varicella. Misdiagnosis of the cause of CNS alterations during the course of varicella is possible.     

Posterior fossa measurements II. Size of the posterior fossa in myelomeningocele

In seven myelomeningocele patients, six were operated upon while in one severe case no surgery was performed. The posterior fossa areas were measured and expressed by the posterior fossa ratio method. In two shunted patients both ratios were primarily below the lowest normal limit, but following shunt operation the ratios become normal. In five patients who were not shunted one only showed a normal ratio, two showed borderline values and in a fourth instance the ratio normalized but before two years had passed. The fifth case remained unoperated and therefore the natural course could be followed. In this case the decrease in the posterior fossa ratio explained the progress of hydrocephalus.     

Posterior fossa measurements I. The normal size of the posterior fossa

The posterior fossa area was defined as that situated below Twining's line while the one above was called the supratentorial area. A ratio has been calculated: Above 7 years this was (mean) 16.5%±2 and below 7 years 14.0%±4, with the ranges (13.2–20.2) and (9.0–19.4), respectively. When the ratio falls below 13% and 9% respectively, this implies therefore a malformation of the posterior fossa, i. e. too flat a space. Two formulas for calculation of the areas mentioned as well as two other ratios are also introduced.     

Congenital ocular motor apraxia. Case reports and literature review

Two children with congenital ocular motor apraxia (C-OMA) associated with congenital malformations of the central nervous system (CNS) are presented, and the literature is reviewed. C-OMA is an abnormality of ocular motility characterized by defective or absent voluntary horizontal gaze, associated with a characteristic head thrust. Although not rare, it is infrequently recognized. C-OMA is not a specific disease entity, but a sign. It may be associated with other static congenital CNS disorders and must be distinguished from acquired ocular motor apraxias (A-OMA) seen in progressive brain disorders and in certain serious systemic diseases. Therefore, when movements typical of C-OMA are observed, a careful systemic and neurologic examination should be performed, including immunoglobulin screening, cranial computerized tomography scanning, and adequate follow-up. Close relatives also should be examined.     

Congenital Malaria. Case reports and a brief review of literature

Two cases of congenital malaria due to Plasmodium vivax and Plasmodium falciparum respectively are reported. The children were born in S?o Paulo and Paraná to mothers from endemic area of malaria. The mothers had malaria during pregnancy. The children were admitted with severe anemia and hepatosplenomegaly. Despite congenital malaria is being considered a rare event it is a preventable disease and these cases should draw attention to the importance of adequate treatment during pregnancy. Clinical manifestations and management of congenital malaria are also discussed.     

Familial Diamond-Blackfan anemia. Case reports and a review of the related literature

We present the case of three sisters with Diamond-Blackfan anemia (DBA) from a consanguineous marriage. These sisters presented within the first 2 months of age with anemia without hepatosplenomegaly together with complete blood count and bone marrow pictures compatible with the diagnosis of DBA syndrome. They were given blood transfusions and then started on prednisolone 2 mg/kg/day in divided doses, tapering the dose to a minimum to keep Hb around 90 g/l. DBA in these three sisters from a consanguineous marriage clearly illustrates the autosomal recessive mode of inheritance. The importance of early diagnosis and management with steroid is highlighted along with the need for consideration of other modalities of treatment in those cases not responding to steroid therapy.     

MRI of the fetal posterior fossa

MRI is a useful tool to complement US for imaging of the fetal posterior fossa (PF). In France, the discovery of a PF malformation in the fetus frequently leads to termination of pregnancy (80% in a personal series). However, despite improved accuracy in the diagnosis of PF abnormalities, prognosis remains uncertain. The first objective of this review is to document the normal MRI landmarks of the developing fetal PF. Because of their thinness, the visibility of the cerebellar fissures is dramatically delayed on MRI compared to macroscopic data. An important landmark is identification of the primary fissure of the vermis, normally seen at around 25–26 weeks gestation (WG) on the sagittal slice, separating the larger posterior lobe from the anterior lobe (volume ratio around 2:1). The prepyramidal and secondary fissures are usually only identifiable after 32 WG and the hemispheric fissures are difficult to see until the end of pregnancy. Considering the signal changes, high signal on T2-weighted (T2-W) sequences is seen from 25 WG in the posterior part of the brain stem (tegmentum and ascending sensory tracts) related to myelination. The low signal intensities seen within the cerebellum on T2-W images correspond to high cellularity of grey matter (deep nuclei), as there is no myelination within the white matter before 38 WG. The second objective is to highlight the signs highly predictive of a poor neurological prognosis. Lack of pontine curvature or vermian agenesis without a PF cyst (small volume of PF) is greatly associated with poor neurological status. The third objective is to propose a diagnostic strategy in difficult cases where prognosis is important, e.g. the Dandy Walker continuum. Analysis of the cerebellum is often impossible if a PF cyst is present (whatever its nature) as the mass effect usually blurs the foliation and even impairs evaluation of the normal ratio between the posterior and anterior lobes of the vermis. Isolated cerebellar hypoplasias raise the question of prognosis and genetic counselling. Such uncertainties require an amniocentesis and a careful search for other anomalies (cerebral and extracerebral). Unilateral abnormalities of a cerebellar hemisphere can be associated with good neurological status if they are isolated. The final objective is to discuss other rare PF fetal abnormalities, such as vascular malformations and tumours.     

Constricting bands. Manifestations of possible child abuse. Case reports and a review

Bands around extremities may be from congenital, infectious, accidental, or purposeful causes. The older child may reveal the cause of self-inflicted or caregiver-inflicted banding. Banding in a nonverbal child will challenge the diagnostic acumen of the physician. Bands of unknown cause, or bands that may have been placed purposefully by a caretaker, must be reported as possible child abuse. Failure of the caretaker to seek help for the consequences of a band may suggest that the bands were intentionally placed. This failure may also be construed as medical neglect. Four cases of banding, which were referred to a child abuse program for consultation, are described.     

Intra-operative MRI-guided approaches to the pediatric posterior fossa tumors.

INTRODUCTION: The posterior fossa in a child poses a considerable challenge to the neurosurgeon. MRI-guided surgery allows for real time interaction between imaging and the neurosurgeon, not permitted by frameless stereotaxy, and with higher resolution than ultrasound or CT. MATERIALS AND METHODS: The University of Minnesota 1.5 T Phillips interventional MRI was used. From 1997 to 2000, nine posterior fossa intraoperative magnet cases out of eleven were pediatric. The mean age was 6.4 years and the median age 7. Seven midline craniotomies were performed, of which three were re-operations. Two were burr hole placements, one for cyst aspiration and P32 instillation, and the other for tumor biopsy. RESULTS: Two tumors were predominantly in the fourth ventricle, four in the cerebellum, two in the brainstem, and one in the prepontine cystern. Four tumors were juvenile pilocytic astrocytomas, two were anaplastic astrocytomas, and one each was ependymoma, craniopharyngioma cyst, and medulloblastoma. Four patients had complete radiologic resection. Two had maximal resections limited by vital structures. P32 instillation and tumor biopsy were done in a single pass. Follow-up ranged from 3 months to 1.4 years. The cyst that was aspirated and had P32 instillation remains absent. The two mortalities were in the patients with medulloblastoma and anaplastic astrocytoma. There were no intra-operative mortalities. The other patient with anaplastic astrocytoma progressed. The remainder had stable imaging. CONCLUSION: MRI-guided surgery results in improved resection imaging and real-time needle guidance in tumor operations. Its value could lie in low-grade lesions, where maximal resection is most beneficial.     

Extradural dermoid tumours of the posterior fossa

Dermoid tumours in children usually occur in two locations: at the anterior fontanelle and on the occipital squama. An exceptional site of origin for a posterior fossa dermoid cyst is the extradural space. There are only six previous cases of this situation reported in the literature. A series of 103 subscalp and calvarial masses in children were reviewed and three children are reported with extradural dermoids of the posterior fossa, which communicated with the skin through midline occipital dermal sinuses. All three children were seen after the rapid growth or the formation of an abscess in a previously noted occipital subcutaneous mass present since birth. Although computed tomography or magnetic resonance imaging showed the dermal sinus and the intracranial tumour, these studies were unable to ascertain the intradural or extradural nature of the tumours, their exact origin only being established at operation. Histopathological study showed preclinical signs of infection in the two patients that had not yet formed an abscess. It is suggested that early neurosurgical treatment of these neoplasms should be done to prevent the development of severe intracranial infection. The previously reported simplicity of surgical removal of occipital extradural dermoids was not confirmed in this series.     

Magnetic resonance imaging of pediatric posterior fossa tumors.

MR detected abnormality in all 115 pediatric patients who subsequently had pathologically proven posterior fossa tumors. In 114, the initial magnetic resonance (MR) diagnosis was that of brain tumor. In 1, with less than 1-cm2 area of gadolinium enhancement, the significance of the initial finding was uncertain. Common posterior fossa tumor subgroups (brainstem gliomas, cerebellar astrocytomas, primitive neuroectodermal tumors, and ependymomas) have relatively consistent presentations on imaging studies. However, less common tumors mimic the MR appearance of more common ones, while common tumors may also have atypical appearances.     

Chiari II malformation and occult spinal dysraphism. Case reports and a review of the literature

We report two cases of children with occult spinal dysraphism who were also found to have many associated brain anomalies seen in the Chiari II malformation. No previous report has commented on the possible association between the Chiari II malformation and the 'closed' form of neural tube defect. One child had symptoms referable to pathology at the craniocervical junction. Neither child had cutaneous stigmata associated with occult spinal dysraphism over the caudal midline spine. These cases, although seemingly rare, lend support to the theories that the association between the Chiari II malformation and patients with myelomeningoceles is due to dysgenesis of the rostral and caudal neural tube. These cases are also important as refutation of earlier theories that link these two entities by proposing that the Chiari II malformation is due to overdrainage of cerebrospinal fluid at the site of myelomeningocele.     

Aminotransferases and muscular diseases: A disregarded lesson. Case reports and review of the literature

The aim of this study was to call the attention to the often disregarded message that hypertransaminasemia may be a marker of both liver and muscle diseases by presenting personal case reports and a systematic literature review. Three male children (mean age 5.7 years) were inappropriately addressed, during the last 12 months, to our paediatric liver unit for diagnostic work‐up of a chronic hypertransaminasemia of unknown origin. In one of them, a liver biopsy had already been performed. On admission, physical examination, evaluation of serum levels of creatine kinase, and dystrophin genetic testing finally led to a diagnosis of muscular dystrophy. One hundred fourteen similar cases, 21 with unnecessary liver biopsy, were found by Medline search. Expensive and invasive tests planned to investigate liver diseases should be postponed until alternative sources of increased serum aminotransferases, primarily myopathic injury, have been excluded.     

Ectopic cerebellum in the posterior cranial fossa

Isolated, well-differentiated ectopic cerebellar tissue is extremely rare, with only eight cases in the literature. We describe a unique case of histopathologically proven ectopic cerebellar tissue presenting as a discrete extra-axial mass in the posterior cranial fossa. We describe the clinical, CT and MRI findings, as well as the surgical and histopathological findings and review the relevant literature.