Anatomical configurations associated with posthemorrhagic hydrocephalus among premature infants with intraventricular hemorrhage

Abstract

OBJECTIVE Intraventricular hemorrhage (IVH) is a complication of prematurity often associated with ventricular dilation, which may resolve over time or progress to posthemorrhagic hydrocephalus (PHH). This study investigated anatomical factors that could predispose infants with IVH to PHH. METHODS The authors analyzed a cohort of premature infants diagnosed with Grade III or IV IVH between 2004 and 2014. Using existing ultrasound and MR images, the CSF obstruction pattern, skull shape, and brain/skull ratios were determined, comparing children with PHH to those with resolved ventricular dilation (RVD), and comparing both groups to a set of healthy controls. RESULTS Among 110 premature infants with Grade III or IV IVH, 65 (59%) developed PHH. Infants with PHH had more severe ventricular dilation compared with those with RVD, although ranges overlapped. Intraventricular CSF obstruction was observed in 36 (86%) of 42 infants with PHH and 0 (0%) of 18 with RVD (p < 0.001). The distribution of skull shapes in infants with PHH was similar to those with RVD, although markedly different from controls. No significant differences in supratentorial brain/skull ratio were observed; however, the mean infratentorial brain/skull ratio of infants with PHH was 5% greater (more crowded) than controls (p = 0.006), whereas the mean infratentorial brain/skull ratio of infants with RVD was 8% smaller (less crowded) than controls (p = 0.004). CONCLUSIONS Among premature infants with IVH, intraventricular obstruction and infratentorial crowding are strongly associated with PHH, further underscoring the need for brain MRI in surgical planning. Prospective studies are required to determine which factors are cause and which are consequence, and which can be used to predict the need for surgical intervention.

Keywords: CPC = choroid plexus cauterization; ETV = endoscopic third ventriculostomy; IVH = intraventricular hemorrhage; PHH = posthemorrhagic hydrocephalus; RVD = resolved ventricular dilation; intraventricular hemorrhage; posthemorrhagic hydrocephalus; prematurity.

FIG 1

Supratentorial brain/skull ratios. A: Representation of the supratentorial axial ratio, defined as the axial cross-sectional brain area (lavender) measured at closest approximation of the thalamus, divided by the axial interior skull area, measured on the same slice (blue). B: Representation of the supratentorial coronal ratio, defined as the coronal cross-sectional brain area (lavender) measured at the anterior margin of the third ventricle, on the slice with the most complete view of the basilar artery, divided by the coronal interior skull area on the same slice (blue). The overall supratentorial brain/skull ratio is equal to the mean of the axial and coronal ratios. These images are visual representations created using Microsoft drawing tools, designed to illustrate how quantification was performed. Actual quantification was performed with semiautomated imaging analysis software.

FIG 2

Infratentorial brain/skull ratios. A: Representation of the infratentorial sagittal ratio, defined as the sagittal cross-sectional cerebellar vermis area (lavender) at the midline vermis, divided by the coronal interior skull area (blue) measured on the same slice. B: Representation of the infratentorial axial ratio, defined as the axial cross-sectional cerebellar area (lavender) measured at the caudal border of the fourth ventricle divided by the axial interior skull area (blue) on the same slice. C: Representation of the infratentorial coronal ratio, defined as the coronal cross-sectional cerebellar area (lavender) measured at the straight sinus just beyond the confluence of the cerebral veins, divided by the coronal interior skull area (blue) on the same slice. These images are visual representations created using Microsoft drawing tools, designed to illustrate how quantification was performed. Actual quantification was performed with semiautomated imaging analysis software.

FIG 3

CSF obstruction pattern on MRI. A: Normal anatomy. Midsagittal T1-weighted image demonstrating normal anatomy with no CSF obstruction. B: Aqueduct obstruction. Midsagittal T1-weighted image with obstruction at the level of the aqueduct, here visible as focal T1 hyperintensity. This is accompanied by dilation of the lateral ventricles (not shown in this view) and a normal-sized fourth ventricle. C: Fourth ventricle outlets. Midsagittal fast imaging employing steady-state acquisition-C/constructive interference in steady state image demonstrating massive dilation of the fourth ventricle, with the floor of the posterior fossa occupied by stretched cerebellum. This pattern may or may not be accompanied by aqueductal obstruction. D: Posterior fossa crowding. Midsagittal T1-weighted image demonstrating tight posterior fossa with reduced size of the prepontine cistern and fourth ventricle, and protrusion of the cerebellar tonsils below the level of the foramen magnum. This infant also had primary sagittal synostosis. E: Supratentorial extraaxial space. Axial T2-weighted image showing expanded extraaxial space not explained by atrophy, with no intraventricular obstruction detected on other views. This pattern is accompanied by variable expansion of the infratentorial space, although this is less prominent than the expanded supratentorial space. F: Infratentorial extraaxial space. Midsagittal T2-weighted image demonstrating expanded extraaxial space beneath the cerebellum, with modest enlargement of the fourth ventricle, but with no evidence of fourth ventricle outlet obstruction. This pattern is accompanied by variable expansion of the supratentorial extraaxial space, although this is less prominent than the expanded infratentorial space.

FIG 4

Skull shapes in sagittal T1 (left column), axial T2 (center column), and coronal T2 (right column) MR images. A–C: Normocephalic. D–F: Brachycephalic, characterized by shortened anteroposterior diameter relative to biparietal diameter, particularly in rostral axial views. G–I: Dolichocephalic, characterized by shortened biparietal diameter relative to anteroposterior diameter. J–L: Bitemporal narrowing, characterized by narrow frontal diameter relative to occipital diameter in the axial plane. This patient also had significant posterior fossa crowding (note the cerebellar tonsils crowding the foramen magnum). M–O: Asymmetrical/irregular, characterized by marked asymmetry or irregularity.