Hydranenzephalie

Newborn with
hydrocephalus on prenatal ultrasound. Coronal US of the brain (above) shows only the thalamus in the midline surrounded by fluid in the supratentorial region of the brain. No discernable lateral and third ventricles are seen and no rim of cortical parenchyma could be appreciated. Sagittal US of the brain (below) shows the cerebellum to be normal in appearance.The diagnosis was hydranencephaly.
pediatricimaging.org • CC-by-nc-sa 4.0
Hydranencephaly.
The ventricles are severely dilated and fluid-filled. No intracranial haemorrhage is identified. There is minimal visualisation of the brain parenchyma secondary to large volume of fluid.
www.eurorad.org • CC by-nc-sa-4.0
Hydranencephaly.
Cranial vault expansion and protruding midline posterior sagittal suture fluid filled pulsion. Dilatation of the fourth ventricle with secondary ballooning of the entire ventricular system deformity of the tentorium, with anterior displacement of the brainstem.
www.eurorad.org • CC by-nc-sa-4.0
Hydranencephaly.
Cranial vault expansion and protruding midline posterior sagittal suture fluid filled pulsion. Dilatation of the fourth ventricle with secondary ballooning of the entire ventricular system deformity of the tentorium, with anterior displacement of the brainstem.
www.eurorad.org • CC by-nc-sa-4.0
Hydranencephaly.
Massive macrocephaly with cranial vault expansion and protruding midline posterior sagittal suture fluid-filled pulsion meningoencephalocele above lambda.
www.eurorad.org • CC by-nc-sa-4.0
Hydranencephaly.
Ballooning of the supratentorial and infratentorial compartments resulting in a secondary meningocele through the sutures, elevation of the tentorium and ballooning of the anterior and middle cranial fossa.
www.eurorad.org • CC by-nc-sa-4.0
Hydranencephaly.
Ballooning of the supratentorial and infratentorial compartments resulting in a secondary meningocele through the sutures, elevation of the tentorium and ballooning of the anterior and middle cranial fossa.
www.eurorad.org • CC by-nc-sa-4.0
Radiopaedia • CC-by-nc-sa 3.0 • de

Hydranencephaly is a rare encephalopathy that occurs in-utero. It is characterized by destruction of the cerebral hemispheres which are transformed into a membranous sac containing cerebrospinal fluid and the remnants of cortex and white matter .

Porencephaly is considered a less severe degree of the same pathology .

Epidemiology

This is a rare disorder with an incidence of 0.2% in infant autopsies . It is usually sporadic. In a minority of cases, it is the consequence of the autosomal recessive Fowler syndrome.

Clinical presentation

The condition may be diagnosed prenatally using ultrasound or fetal MRI. However, it may present in neonates with seizures, respiratory failure, flaccidity or decerebrate posturing with a vegetative state .

Associations

Pathology

There is complete absence of the cerebral hemispheres and often, the falx. They are replaced by a sac-like structure containing CSF surrounding the brainstem and basal ganglia .

The outer layer comprises leptomeninges while the inner layer of cortex and white matter is filled with CSF and necrotic material.

Porencephaly and hydranencephaly are considered different degrees of the same pathology. Porencephaly describes a more localized cerebral hemispheric defect, communicating with the ventricles or the cerebral surface; it tends to occur later in the developmental process .

Etiology

Five etiologies have been described:

  • infarction: bilateral occlusion of the supraclinoid segment of the internal carotid arteries or of the middle cerebral arteries
  • leukomalacia: an extreme form of leukomalacia formed by confluence of multiple cystic cavities
  • diffuse hypoxic-ischemic brain necrosis: fetal hypoxia due to maternal exposure to carbon monoxide or butane gas may result in massive tissue necrosis with cavitation and resorption of necrotized tissue
  • infection: necrotizing vasculitis or local destruction of the brain tissue secondary to intrauterine infection, e.g. congenital toxoplasmosis, cytomegalovirus, and herpes simplex (HSV) infections
  • thromboplastic material from a deceased co-twin
    • monochorionic twins have presented with a variety of cerebral lesions
    • lesions in the recipient twin result from emboli or thromboplastic material originating from the macerated co-twin

Radiographic features

All modalities which resolve the brain parenchyma can be used to identify the features of hydranencephaly, including ultrasound (antenatal and postnatal), MRI (antenatal and postnatal), and CT. MRI is the gold standard.

In all cases, the anatomical features are the same, although they are demonstrated to a variable degree according to the abilities of each modality:

  • essentially no remaining cortical tissue
    • often islands of residual tissue preserved at occipital poles and orbitofrontal regions
    • medial temporal tissue may be identified, as the medial temporal lobes are supplied by the basilar circulation
  • preserved thalami and posterior fossa
  • falx is usually present
  • hemicranium is filled with fluid, in which choroid can often be identified
  • antenatal ultrasound or vascular imaging demonstrate absence of middle cerebral arteries

Treatment and prognosis

Hydranencephaly is not compatible with a prolonged life after birth, with the vast majority of live births dying prior to one year of age. Termination of pregnancy is usually considered justifiable due to this reason.

Differential diagnosis

General imaging differential considerations include:

Siehe auch:
und weiter:
Assoziationen und Differentialdiagnosen zu Hydranenzephalie:
Schizenzephalie
 
Wikipedia • CC BY-SA 3.0
Verschlusshydrocephalus
 
www.eurorad.org • CC by-nc-sa-4.0