Presentation
Follow-up of bilateral ventriculomegaly on the routine 20 week ultrasound.
Patient Data
There is severe dilatation of the lateral ventricles, but the 3rd and 4th ventricles are non-dilated. Aqueduct not visualized, possibly due to orientation of the brainstem on these images. Corpus callosum is severely thinned. Cerebellar vermis present, but abnormal in shape suggesting mild dysplasia.
There is ventral kinking of the brainstem at the pontomesencephalic junction, as well as exaggerated dorsal kinking at the cervico-medullary junction.
Postmortem MRI demonstrates the collapsed hemispheres surrounded by hemorrhage (note the predominantly high T1, low T2 signal in the extra-axial spaces). The thickened cortex with apparent oversulcation is noted, but the appearance is likely due to bunching of the previously stretched and now collapsed cerebral tissues, although lissencephaly certainly should be considered.
Note the normal appearance of the globes.
Case Discussion
This case demonstrates the typical finding of a kinked fetal brainstem, associated with severe ventriculomegaly and a dysplastic cerebellar vermis.
The differential for this constellation of findings includes:
- L1-CAM mutation (X-linked aqueduct stenosis)
- Tubulinopathy
- a-dystroglycanopathies (Walker-Warburg syndrome, muscle-eye-brain disease).
Genetic testing in this patient had shown L1-CAM mutation. Although the diagnosis cannot be made with certainty on imaging alone, relevant negatives in this case (which might have favored one of the other differential diagnoses) include:
- non-enlarged ganglionic eminences
- no evidence of lissencephaly or polymicrogyria (though even when present, this may be difficult to detect prenatally particularly in the setting marked ventricular distension)
- absence of globe abnormalities.
No relevant family history was available in this case, but this should be looked for (FDIU or intellectual disability in a male child of either the patient or a first degree female relative).
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