Patient with past medical history of severe developmental delays without apparent neurological deterioration, and macrocephaly (HC 55 cm at 11 months old).
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Cerebral hemispheres replaced by large membranous CSF filled sac (“water bag” brain), with remnants of cortical mantle present, predominantly the occipital and temporal lobes. Thalami are at most only partially fused (third ventricle is visible), cerebellum and brain stem are intact. Choroid plexus present, tentorium cerebelli is intact, but the falx cerebri is absent.
2 case question available
This patient had an established diagnosis of substantial brain abnormality and was evaluated at an age of 11 months by a paediatric neurosurgeon who found the patient to have macrocephaly (head circumference 55 cm), severe developmental delays, open compressible anterior fontanelle, no signs of intracranial hypertension.
The MRI, in this case, is somewhat indeterminate with features both of hydranencephaly and alobar holoprosencephaly.
In favour of hydranencephaly is that the residual cortical tissue is scattered as islands, with most preserved tissue being in the posterior temporal lobes and occipital poles (posterior circulation) territory. The thalami are not completely fused (thalamic adhesion is present, but so is the third ventricle). There is no pancake cortex or horseshoe cortex as is typically seen in alobar holoprosencephaly. Nor is there evidence of facial abnormalities, commonly seen in holoprosencephaly.
In favour of holoprosencephaly is the fact that the falx appears entirely absent.
[Editors: this case has been reviewed by two paediatric neuroradiologists, both favouring alobar holoprosencephaly]
Case courtesy of Dr Guillermo Bolivar
- Kurtz, Alfred B., and Pamela T. Johnson. "Case 7: hydranencephaly." Radiology 210.2 (1999): 419-422.
- Pavone, Piero, et al. "Hydranencephaly: cerebral spinal fluid instead of cerebral mantles." Italian journal of pediatrics 40.1 (2014): 79.
- Radiology Review Manual, 7th ed. By Wolfgang Dähnert. Philadelphia, PA: Lippincott Williams & Wilkins
- Osborn, Anne G., et al. Diagnostic imaging: brain. Elsevier Health Sciences, 2015.