Computed tomographic signs of the Chiari II malformation. III: Ventricles and cisterns

In patients with Chiari II malformations, the fourth ventricle is usually not visualized or appears small; the third ventricle is relatively small, typically has a large massa intermedia, and only occasionally exhibits parasellar and/or posterior third ventricular diverticula. The lateral ventricles are usually asymmetrically dilated, show medial pointing of the floor of the body near the foramen of Monro, flattening of the superolateral angles, and frequent absence of the septum pellucidum. Prior to and after shunting, the interhemispheric fissure may be either obliterated, or widely open with serrations corresponding to the interdigitated gyri of the cerebral hemispheres. Prominent confluent cisterns at the hind end of the third ventricle in patients with ventricular collapse may represent the CT equivalent of the dilated pericallosal, ambient and retropulvinaric cisterns seen in patients with hydrocephalus and poor ventricular filling at pneumography.     

Coexistent holoprosencephaly and Chiari II malformation.

Chiari II malformations and holoprosencephaly have been considered to be brain malformations that differ with respect to teratogenic insult, embryologic mechanism, and morphology. We herein describe coexistent Chiari II malformation and holoprosencephaly that occurred in a viable infant. A review of the literature regarding Chiari II malformations and holoprosencephaly suggests that a disturbance to the mesenchyme in early embryologic life may be the cause of both malformations.     

MR imaging of Chiari II malformation associated with dysgenesis of cerebellum and brain stem

Extensive cerebellar hypogenesis is rare in Chiari II malformation and, to our knowledge, has not been described in modern radiological literature. In our case near total absence of cerebellar tissue and "underdevelopment" of the brain stem were noted in a patient with several characteristic features of Chiari II malformation.     

Rhombencephalosynapsis and a Chiari II malformation

Rhombencephalosynapsis is an anomaly of the hindbrain characteristically presenting with cerebellar fusion and absence of cerebellar vermis on magnetic resonance imaging. Its association with spinal anomalies has not been reported previously. We report a unique case, a 22-year-old man with cerebellar fusion associated with a cervicothoracic meningomyelocele, diastematomyelia, tethering of the spinal cord, and dorsal dermal sinuses. In addition, cerebellar tonsillar herniation and tectal beaking similar to that seen in Chiari II malformations were present. These findings suggest that rhombencephalosynapsis can be associated with spinal malformations and, furthermore, that cases with the common features of rhombencephalosynapsis and a Chiari II malformation can exist. Such an association likely represents a new anomaly of the hindbrain and spine.     

Chiari II malformation: MR imaging evaluation

The purpose of this study was to explore the value of high-detail MR imaging in the diagnosis of the Chiari II malformation. Twenty-four patients with known Chiari II malformation as diagnosed by CT scanning were evaluated with cranial MR scans. Two patients also had spine scans. The sagittal-plane images were the most informative, and abnormalities of the telencephalon, diencephalon, mesencephalon, rhomboencephalon, upper spinal cord, and mesencephalon were shown extremely well. We found MR to be an easy and accurate method for demonstrating the abnormalities of the Chiari II malformation, and it is our procedure of choice.     

The Chiari II malformation: Part IV. The hindbrain deformity

Summary Computed tomography successfully delineates the multiple components of the Chiari II malformation at the craniocervical junction, the hindbrain, and the cervical spinal cord. These include wide foramen magnum and upper cervical spinal canal; incomplete fusions of the posterior arches of C1 and lower cervical vertebrae; cascading protrusions of vermis, fourth ventricle, medulla, and cervical cord into the spinal canal; cervicomedullary kinking; anterior displacement and sequential sagittal compression of each protrusion by the protrusions posterior to it; compression of all protrusions by the posterior lip of foramen magnum and the posterior arch of C1; and associated cervical hydromyelia, cervical diastematomyelia, and cervical arachnoid cysts.Presented in part at the CT '82, International Computer Tomography Symposium, Seefeld/Tirol, Austria, 28–30 January 1982; and presented in nearly complete form at the 10th Annual Meeting of the International Society for Paediatric Neurosurgery, Philadelphia, Pennsylvania, USA, 12–15 September 1982     

Giant vascular malformation of the kidney: Computed tomographic and angiographic appearances

Two cases of giant vascular malformation of the kidney demonstrated by computed tomography and angiography are presented. The vascular malformations form completely outside the kidney. They arise from the renal parenchyma, simulating renal cyst, and present as a renal pelvic mass causing hydronephrosis. The finding of a renal mass with a markedly and uniformly contrast enhancement demonstrated by computed tomography should suggest the possibility of a vascular malformation.     

Chiari III malformation: imaging features.

PURPOSE: To analyze and discuss the MR and CT features of Chiari type III malformations. PATIENTS AND METHOD: MR and CT studies in nine neonates born at term with Chiari type III malformations were retrospectively reviewed. RESULTS: High cervical/low occipital encephaloceles were present in all cases. Hypoplasia of the low and midline aspects of the parietal bones was seen in four patients. The encephaloceles contained varying amounts of brain (cerebellum and occipital lobes, six cases; cerebellum only, three cases), ventricles (fourth, six cases; lateral, three cases), cisterns, and in one case, the medulla and pons. Associated anomalies included: petrous and clivus scalloping (five cases/nine cases), cerebellar hemisphere overgrowth (two cases/nine cases), cerebellar tonsillar herniation (three cases/seven cases), deformed midbrain (nine cases), hydrocephalus (two cases/nine cases), dysgenesis of the corpus callosum (six cases/nine cases), posterior cervical vertebral agenesis (three cases/eight cases), and spinal cord syrinxes (two cases/seven cases). In four patients who underwent surgical resection and closure, aberrant deep draining veins and ectopic venous sinuses within the encephaloceles were found. Pathology examination of the encephalocele (four cases/nine cases) showed multiple anomalies (necrosis, gliosis, heterotopias, meningeal fibrosis) that were not demonstrable by either MR or CT. The marked disorganization of the tissues contained within the cephalocele may account for the lack of MR sensitivity to these abnormalities. CONCLUSION: Preoperative determination of the position of the medulla and pons is essential and is easily accomplished by MR. To avoid surgical complications, the high incidence of venous anomalies should be kept in mind.     

Small bowel rupture after blunt trauma: Computed tomographic signs and their sensitivity

The purpose of this study is to describe the characteristic computed tomographic (CT) signs of small bowel perforation after blunt abdominal trauma and to evaluate their sensitivity. Nineteen preoperative CT scans were obtained from 16 patients with surgically proven small bowel rupture secondary to blunt abdominal trauma. Only the CT findings described in the original CT reports were used. Eleven of 19 CT scans (58 %) had findings that were unequivocal for bowel rupture (i.e., extraluminal air and/or extravasation of oral contrast medium). Seven CT scans (37 %) had findings that were suggestive of severe small bowel injury (i.e., focal small bowel wall thickening and/or free peritoneal fluid without other accompanying organ injuries). In all, 95 % of cases of small bowel rupture had either pathognomonic or suggestive CT findings. One CT scan did not demonstrate small bowel wall thickening, although a hemoperitoneum was present. CT is a sensitive method for suggesting severe small bowel injury and rupture secondary to blunt abdominal trauma.     

Fetal diffusion tensor quantification of brainstem pathology in Chiari II malformation

Objectives

This prenatal MRI study evaluated the potential of diffusion tensor imaging (DTI) metrics to identify changes in the midbrain of fetuses with Chiari II malformations compared to fetuses with mild ventriculomegaly, hydrocephalus and normal CNS development.

Methods

Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were calculated from a region of interest (ROI) in the midbrain of 46 fetuses with normal CNS, 15 with Chiari II malformations, eight with hydrocephalus and 12 with mild ventriculomegaly. Fetuses with different diagnoses were compared group-wise after age-matching. Axial T2W-FSE sequences and single-shot echo planar DTI sequences (16 non-collinear diffusion gradient-encoding directions, b-values of 0 and 700 s/mm², 1.5 Tesla) were evaluated retrospectively.

Results

In Chiari II malformations, FA was significantly higher than in age-matched fetuses with a normal CNS (p?=?.003), while ADC was not significantly different. No differences in DTI metrics between normal controls and fetuses with hydrocephalus or vetriculomegaly were detected.

Conclusions

DTI can detect and quantify parenchymal alterations of the fetal midbrain in Chiari II malformations. Therefore, in cases of enlarged fetal ventricles, FA of the fetal midbrain may contribute to the differentiation between Chiari II malformation and other entities.

Key Points

? FA in the fetal midbrain is elevated in Chiari II malformations. ? FA is not elevated in hydrocephalus and mild ventriculomegaly without Chiari II. ? Measuring FA may help distinguish different causes for enlarged ventricles prenatally. ? Elevated FA may aid in the diagnosis of open neural tube defects. ? Elevated FA might contribute to stratification for prenatal surgery in Chiari II.

     

Lissencephaly: Computed tomographic diagnosis

Lissencephaly is a rare congenital condition with distinctive brain changes. Most of these changes were demonstrated on computed tomography, and include lack of cortical sulci and gyri; calcification in the region of paraphysis; wide, shallow sylvian fissures; colpocephaly; poor development of white matter; and persistent cavum septum pellucidum and cavum vergae.     

Chiari畸形的MRI表现

目的：探讨Chiari畸形的MRI表现,并评价其临床应用价值。方法：回顾性分析31例Chiari畸形患者的MRI资料与临床资料。结果：31例Chiari畸形患者小脑扁桃体疝至枕大孔平面下方3－25mm。20例合并脊髓空洞,枕大孔层面延前池前后径宽度为0－5mm,11例无脊髓空洞,延前池宽度为4．5－6mm,6例合并颅颈交界区畸形,4例合并脑积水。结论：小脑扁桃体位于枕大孔下方≥5mm即可诊断为Chiari畸形,延前池前后径宽度变窄（≤4mm）均出现脊髓空洞,而延前池宽度＞4mm则很少出现脊髓空洞,临床可根据延前池的宽度来评价预后及的手术效果。     

Spontaneous resolution of a Chiari I malformation: MR demonstration.

The MR findings in a case of a Chiari type I malformation that resolved spontaneously over a 4-year period are presented. Differential growth of the skull and spine might have accounted for the resolution of this anomaly.