venerdì 18 settembre 2009
There is near complete absence of supratentorial brain parenchyma, which is replaced with CSF, with an intact falx. The brain stem and cerebellum are present and grossly normal in appearance.
- Severe hydrocephalus
Hydranencephaly - In utero destruction of cerebral parenchyma with intact falx and preservation of posterior fossa structures.
Cerebrum replaced with CSF.
Caused by in utero occlusion of bilateral supraclinoid internal carotid arteries. Etiology unclear (hereditary thrombophilic states, infection, maternal irradiation/toxin exposure, twin-twin transfusion, intrauterine anoxia).
Occurs approximately <1:10000 births, greatest incidence in teenage mothers.
Clinically, present with macrocephaly, developmental delay, irritability, hyperreflexia, seizures.
Often seen with prenatal ultrasound (anechoic cranial vault).
On CT and MR (best characterized with MR) – CSF attenuation/signal intensity replacing the supratentorial brain parenchyma with sparing of thalami, brain stem, cerebellum, and choroid plexus.
Falx is intact (distinguishes from holoprosencephaly).
No thin rim of cerebral parenchyma (distinguishes from severe hydrocephalus).
Prognosis is poor – usually death in infancy.
Treatment is supportive care, shunting to decrease head growth.