Dandy-Walker Phenotype with Brainstem Involvement: 2 Distinct Subgroups with Different Prognosis.

BACKGROUND AND PURPOSE: Although cardinal imaging features for the diagnostic criteria of the Dandy-Walker phenotype have been recently defined, there is a large range of unreported malformations among these patients. The brainstem, in particular, deserves careful attention because malformations in this region have potentially important implications for clinical outcomes. In this article, we offer detailed information on the association of brainstem dysgenesis in a large, multicentric cohort of patients with the Dandy-Walker phenotype, defining different subtypes of involvement and their potential clinical impact. MATERIALS AND METHODS: In this established multicenter cohort of 329 patients with the Dandy-Walker phenotype, we include and retrospectively review the MR imaging studies and clinical records of 73 subjects with additional brainstem malformations. Detailed evaluation of the different patterns of brainstem involvement and their potential clinical implications, along with comparisons between posterior fossa measurements for the diagnosis of the Dandy-Walker phenotype, was performed among the different subgroups of patients with brainstem involvement. RESULTS: There were 2 major forms of brainstem involvement in patients with Dandy-Walker phenotype including the following: 1) the mild form with anteroposterior disproportions of the brainstem structures "only" (57/73; 78%), most frequently with pontine hypoplasia (44/57; 77%), and 2) the severe form with patients with tegmental dysplasia with folding, bumps, and/or clefts (16/73; 22%). Patients with severe forms of brainstem malformation had significantly increased rates of massive ventriculomegaly, additional malformations involving the corpus callosum and gray matter, and interhemispheric cysts. Clinically, patients with the severe form had significantly increased rates of bulbar dysfunction, seizures, and mortality. CONCLUSIONS: Additional brainstem malformations in patients with the Dandy-Walker phenotype can be divided into 2 major subgroups: mild and severe. The severe form, though less prevalent, has characteristic imaging features, including tegmental folding, bumps, and clefts, and is directly associated with a more severe clinical presentation and increased mortality.

Refining the Neuroimaging Definition of the Dandy-Walker Phenotype.

BACKGROUND AND PURPOSE: The traditionally described Dandy-Walker malformation comprises a range of cerebellar and posterior fossa abnormalities with variable clinical severity. We aimed to establish updated imaging criteria for Dandy-Walker malformation on the basis of cerebellar development. MATERIALS AND METHODS: In this multicenter study, retrospective MR imaging examinations from fetuses and children previously diagnosed with Dandy-Walker malformation or vermian hypoplasia were re-evaluated, using the choroid plexus/tela choroidea location and the fastigial recess shape to differentiate Dandy-Walker malformation from vermian hypoplasia. Multiple additional measures of the posterior fossa and cerebellum were also obtained and compared between Dandy-Walker malformation and other diagnoses. RESULTS: Four hundred forty-six examinations were analyzed (174 fetal and 272 postnatal). The most common diagnoses were Dandy-Walker malformation (78%), vermian hypoplasia (14%), vermian hypoplasia with Blake pouch cyst (9%), and Blake pouch cyst (4%). Most measures were significant differentiators of Dandy-Walker malformation from non-Dandy-Walker malformation both pre- and postnatally (P < .01); the tegmentovermian and fastigial recess angles were the most significant quantitative measures. Posterior fossa perimeter and vascular injury evidence were not significant differentiators pre- or postnatally (P > .3). The superior posterior fossa angle, torcular location, and vermian height differentiated groups postnatally (P < .01), but not prenatally (P > .07). CONCLUSIONS: As confirmed by objective measures, the modern Dandy-Walker malformation phenotype is best defined by inferior predominant vermian hypoplasia, an enlarged tegmentovermian angle, inferolateral displacement of the tela choroidea/choroid plexus, an obtuse fastigial recess, and an unpaired caudal lobule. Posterior fossa size and torcular location should be eliminated from the diagnostic criteria. This refined phenotype may help guide future study of the numerous etiologies and varied clinical outcomes.

Stroke Recurrence in Children with Vertebral Artery Dissecting Aneurysm.

BACKGROUND AND PURPOSE: Pediatric vertebral artery dissecting aneurysm is a subtype of vertebral artery dissection that can be challenging to diagnose and may be associated with stroke recurrence. This study examines the presenting features, clinical outcomes, and recurrence risk in a cohort of children with vertebral artery dissection, comparing those with aneurysms with those without. MATERIALS AND METHODS: The medical records of children evaluated for vertebral artery dissection were retrospectively reviewed for neurologic presentation, treatment, stroke recurrence, and angiographic appearance of dissection. Cohort patients were categorized into 2 groups based on the presence or absence of a vertebral artery dissecting aneurysm and compared via the Fisher exact test, Student t test, and log-rank analyses. P < .05 was deemed statistically significant. RESULTS: Thirty-two patients met the inclusion criteria, including 13 with vertebral artery dissecting aneurysms. Five cases of vertebral artery dissecting aneurysm were missed on the initial evaluation and diagnosed retrospectively. All patients received antiplatelet or anticoagulation therapy at the time of diagnosis. Children in the vertebral artery dissecting aneurysm group were more likely to present with stroke (P = .059), present at a younger age (P < .001), and have recurrent stroke (P < .001) compared with the group of children with vertebral artery dissection without an aneurysm. After surgery, no patients with vertebral artery dissecting aneurysm experienced recurrent stroke (P = .02). CONCLUSIONS: Vertebral artery dissecting aneurysm is often missed on the initial diagnostic evaluation of children presenting with stroke. In children with vertebral artery dissection, the presence of an aneurysm is associated with stroke presentation at a younger age and stroke recurrence.

Congenital Nasal Pyriform Aperture Stenosis: Evidence of Premature Fusion of the Midline Palatal Suture.

BACKGROUND AND PURPOSE: Various etiologies have been theorized for the development of congenital nasal pyriform aperture stenosis (CNPAS). Imaging possibly implicates abnormal fusion of the midline palatal suture and deficient lateral growth of the midface in affected neonates. MATERIALS AND METHODS: A single-center, retrospective study was performed at a tertiary care pediatric hospital involving neonates and infants between 0 and 90 days of life. Maxillofacial CT scans of patients were reviewed. Abnormality of the palatal suture and midface transverse dimensions were measured and analyzed in patients with and without CNPAS. RESULTS: A total of 109 patients between 0 and 90 days of life had maxillofacial CT scans. Thirteen patients were classified as having CNPAS, 27 patients had normal scans (control group), and 69 patients were excluded because of the presence of other craniofacial anomalies. All patients with CNPAS had evidence of abnormal fusion of the midline palatal suture. Zero patients without CNPAS had a midline palatal suture abnormality. The mean widths of the pyriform aperture were 5.7 mm (SD, 1.7) in the CNPAS group and 13.1 mm (SD, 2.7) in the control group (P < .0001). The mean distance between the superior portions of the nasolacrimal ducts was 9.1 mm (SD, 2.1) in the CNPAS group, and the mean of the control group was 13.4 mm (SD, 2.2) (P < .0001). CONCLUSIONS: Patients with CNPAS have abnormal fusion of the midline palatal suture and exhibit lateral growth restriction of the midface. This may implicate synostosis of the midline palatal suture and abnormal midface growth.

Age-Dependent Signal Intensity Changes in the Structurally Normal Pediatric Brain on Unenhanced T1-Weighted MR Imaging.

BACKGROUND AND PURPOSE: Various pathologic and nonpathologic states result in brain parenchymal signal intensity changes on unenhanced T1-weighted MR imaging. However, the absence of quantitative data to characterize typical age-related signal intensity values limits evaluation. We sought to establish a range of age-dependent brain parenchymal signal intensity values on unenhanced T1WI in a sample of individuals (18 years of age or younger) with structurally normal brains. MATERIALS AND METHODS: A single-center retrospective study was performed. Gadolinium-naïve pediatric patients with structurally normal MR brain imaging examination findings were analyzed (n = 114; 50% female; age range, 68 days to 18 years). ROI signal intensity measurements were obtained from the globus pallidus, thalamus, dentate nucleus, pons, and frontal lobe cortex and subcortical white matter. Multivariable linear regression was used to analyze the relationship between signal intensity values and age. RESULTS: Results demonstrated a statistically significant association between signal intensity values and linear age in all neuroanatomic areas tested, except the frontal gray matter, (P < .01). There were no statistically significant differences attributable to patient sex. CONCLUSIONS: Age-dependent signal intensity values were determined on unenhanced T1WI in structurally normal pediatric brains. Increased age correlated with increased signal intensity in all brain locations, except the frontal gray matter, irrespective of sex. The biologic mechanisms underlying our results remain unclear and may be related to chronologic changes in myelin density, synaptic density, and water content. Establishing age-dependent signal intensity parameters in the structurally normal pediatric brain will help clarify developmental aberrations and enhance gadolinium-deposition research by providing an improved understanding of the confounding effect of age.

Asymptomatic Interhypothalamic Adhesions in Children.

With the use of high-resolution MR imaging techniques, we have increasingly observed anomalies of the hypothalamus characterized by a band of tissue spanning the third ventricle between the hypothalami, often without associated clinical sequelae. Historically, hypothalamic anomalies are highly associated with symptoms referable to a hypothalamic hamartoma, midline congenital disorder, hypothalamic-pituitary dysfunction, or seizures, with very few asymptomatic patients reported. The interhypothalamic tissue described in our cohort was observed incidentally through the routine acquisition of high-resolution T1WI. No referable symptoms were identified in most of the study group. In the appropriate patient population in which associated symptoms are absent, the described hypothalamic anomalies may be incidental and should not be misdiagnosed as hypothalamic hamartomas.

MRI findings in children with acute flaccid paralysis and cranial nerve dysfunction occurring during the 2014 enterovirus D68 outbreak.

BACKGROUND AND PURPOSE: Enterovirus D68 was responsible for widespread outbreaks of respiratory illness throughout the United States in August and September 2014. During this time, several patients presented to our institution with acute flaccid paralysis and cranial nerve dysfunction. The purpose of this report is to describe the unique imaging findings of this neurologic syndrome occurring during an enterovirus D68 outbreak. MATERIALS AND METHODS: Patients meeting a specific case definition of acute flaccid paralysis and/or cranial nerve dysfunction and presenting to our institution during the study period were included. All patients underwent routine MR imaging of the brain and/or spinal cord, including multiplanar T1, T2, and contrast-enhanced T1-weighted imaging. RESULTS: Eleven patients met the inclusion criteria and underwent MR imaging of the brain and/or spinal cord. Nine patients presented with brain stem lesions, most commonly involving the pontine tegmentum, with bilateral facial nerve enhancement in 1 patient. Ten patients had longitudinally extensive spinal cord lesions; those imaged acutely demonstrated involvement of the entire central gray matter, and those imaged subacutely showed lesions restricted to the anterior horn cells. Ventral cauda equina nerve roots enhanced in 4 patients, and ventral cervical nerve roots enhanced in 3, both only in the subacute setting. CONCLUSIONS: Patients presenting with acute flaccid paralysis and/or cranial nerve dysfunction during the recent enterovirus D68 outbreak demonstrate unique imaging findings characterized by brain stem and gray matter spinal cord lesions, similar to the neuroimaging findings described in previous outbreaks of viral myelitis such as enterovirus 71 and poliomyelitis.