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Isolated Frontal Horn Paraventricular Cysts Lenticulostriate Vasculopathy Hydrocephalus
Vein of Galen Malformation Intracranial Tumour and Agenesis of the Corpus Callosum Dandy-Walker Variant
Cerebellar Hypoplasia Meningitis Polymicrogyria

Isolated Frontal Horn Paraventricular Cysts

Frontal horn cysts are an occasional finding in preterm infants having cranial ultrasound scans for routine screening for GM-IVH.

They are differentiated from periventricular leukomalacia by their position - they are generally more anterior than the lesions seen with PVLM, and lie below the lateral margin of the lateral ventricle.

Despite their impressive appearance, in isolation they are not considered to be associated with a poor long-term neurodevelopmental outcome.

Lenticulostriate Vasculopathy

Lenticulostriate vasculopathy is again an occasional finding in infants who are undergoing routine screening for GM-IVH.

The appearance is one of prominent outlining of blood vessels in the deep cerebral circulation, presumably from calcification.

The aetiology is unclear, and in most infants no clearly identifiable cause will be found.  The lesions have, however, been associated with CMV infection and with cerebral ischaemia.


These images show marked ventricular dilatation in a newborn infant.  The lateral ventricles are grossly enlarged, as is the third ventricle.  The underlying pathogenesis is due to an imbalance between CSF production and absorption, resulting in accumulation of CSF within the ventricles.  This may result from a number of causes such as obstruction of flow, excessive secretion (rare), or impaired absorption.

Congenital hydrocephalus can result from a number of causes including

  • intrauterine infection (toxoplasmosis, CMV, syphilis, and rubella)
  • congenital aqueductal stenosis (may be X-linked)
  • other congenital malformations of the CNS, such as Dandy-Walker malformation and the Arnold-Chiari malformation (associated with neural tube defects)
  • Intracranial tumours

Causes of acquired hydrocephalus include

Treatment with an external reservoir or a ventriculo-peritoneal shunt is often required.  Medical treatment in neonates is generally regarded as ineffective.



Vein of Galen Malformation

VOG Coronal 1.jpg (135832 bytes)

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VOG Coronal 3.jpg (157333 bytes)

Vein of Galen malformations involve an aneurysmal dilatation of venous structures in the area of the vein of Galen, although anatomical studies suggest that the vessel involved is actually a primitive vascular structure (the median prosencephalic vein of Markowski) that usually disappears by 11 weeks gestation.

There are usually multiple arterial connections to this structure, resulting in a large vascular mass in the central structures of the brain.  Associated complications include congestive cardiac failure (secondary to high-output cardiac failure and myocardial ischaemia, with resultant cerebral ischaemia), hydrocephalus (from compression of the aqueduct), thrombosis of the vein of Galen with haemorrhagic infarction, massive haemorrhage from rupture of the aneurysm, and atrophy secondary to compression of adjacent structures by the intracranial vascular mass.

Clinical examination usually reveals cardiac failure.  A cranial bruit is usually heard.  Despite the size of the lesion, neurological signs are unusual.

The natural history is for high mortality in the newborn period with a high rate of significant disability in survivors.  Management is a major therapeutic challenge.  Surgical approaches are difficult, and frequently the infants are in significant congestive cardiac failure.  Therefore, approaches have moved towards embolisation of the lesion to reduce flow. 

VOG Coronal colour 1.jpg (204424 bytes) VOG Midline.jpg (167172 bytes) VOG Sagittal left.jpg (156150 bytes) VOG Sagittal left colour.jpg (202623 bytes)
VOG Coronal colour 2.jpg (208025 bytes) VOG Sagittal right 1.jpg (164106 bytes) VOG Sagittal right 2.jpg (156994 bytes) VOG Sagittal right colour.jpg (207650 bytes)

Intracranial Tumour and Agenesis of the Corpus Callosum

ACC Lipoma coronal 1.jpg (173853 bytes)

ACC Lipoma coronal 2.jpg (185681 bytes)

This infant presented with an intracranial mass detected on antenatal ultrasound scan.  The mass shows up as an echogenic mass in the third ventricle, extending into both lateral ventricles.  There was an associated agenesis of the corpus callosum.

These findings and the subsequent MRI scan were felt to be consistent with a lipoma.

Lipomas are generally associated with agenesis of the corpus callosum and may be asymptomatic.  However, the most common manifestations are seizures.  Lipomas may also be found in other areas, notably the pineal region.

ACC Lipoma midline.jpg (183887 bytes) ACC Lipoma midline 2.jpg (178814 bytes) ACC Lipoma sagittal left.jpg (153216 bytes) ACC Lipoma sagittal right.jpg (176493 bytes)

Dandy-Walker Variant

DWV coronal 1.jpg (171769 bytes)

DWV coronal 2.jpg (174259 bytes)

DWV midline.jpg (183906 bytes)

The Dandy-Walker Malformation (DWM) is a developmental abnormality of closure of the roof of the neural tube.  Hydrocephalus is almost universal, and DWM account for 5-10% of causes of congenital hydrocephalus.

There are 3 major abnormalities:

  • cystic dilatation of the 4th ventricle
  • complete of partial agenesis of the cerebellar vermis
  • hydrocephalus (which may occur late)

Other developmental abnormalities of brain are common and include agenesis of the corpus callosum, neuronal heterotopia, gyral abnormalities, aqueductal stenosis, abnormalities of inferior olivary or dentate nuclei, occipital encephalocoele, or syringomyelin. 70% of infants have at least one of these associated abnormalities.

Outcomes are related to the severity of the malformation and of the associated abnormalities.

DWV sagittal left.jpg (176334 bytes) DWV sagittal right.jpg (177779 bytes)
dwvct1.jpg (48551 bytes) dwvct2.jpg (40477 bytes) dwvct4.jpg (47937 bytes) dwvct3.jpg (47653 bytes)

Cerebellar Hypoplasia

Some abnormalities of brain development or formation may be detected on antenatal imaging. Cerebellar hypoplasia has a variable clinical phenotype, with some affected individuals having normal development whilst others may have difficulties with developmental delay, hypotonia, ataxia and sometimes associated seizures or specific speech delay.

It is important, particularly if there is a significant amount of CSF in the posterior fossa, to differentiate this from a Dandy-Walker malformation (cystic dilatation of the 4th ventricle, complete or partial agenesis of the cerebellar vermis, and hydrocephalus, with elevation of the tentorium).

Another condition that can cause a large posterior fossa cystic lesion is Joubert's Syndrome (absence or underdevelopment of the cerebellar vermis with abnormalities of the brain stem), commonly associated with ataxia, hyperpnea, sleep apnea, abnormal eye and tongue movements, and hypotonia. Malformations (e.g. extra fingers and toes, cleft lip or palate, and tongue abnormalities) may also be present.  Similarly, Carbohydrate Deficient Glycoprotein Syndrome may be associated with cerebellar hypoplasia (and brain stem abnormalities).

The images to the left show two views on a postnatal ultrasound of an infant who had a large cystic space detected on an antental scan. The postnatal imaging confirmed a large cystic space containing CSF in the posterior fossa, with a degree of hypoplasia of the cerebellum.  These findings are also shown on the MRI images.  No other abnormalities were detected.


Early Scan
HUSS - Meningitis - Coronal early.jpg (52713 bytes)

HUSS - Meningitis - Sag early.jpg (54393 bytes)

This 27 week infant presented acutely unwell at 2 weeks of age with signs consistent with sepsis.  A lumbar puncture performed prior to antibiotics was normal.  However, the baby developed seizures and was extremely unwell, requiring inotropic and ventilator support, and treatment with three anticonvulsants.  He was treated with high dose antibiotics with good CSF penetration, and blood cultures grew E.coli.

The first two images were taken 2 days after presentation, and show mild ventricular dilatation.  The floor of the lateral ventricles appears a little echogenic.

The baby continued to have seizures, but no CSF could be obtained.  A repeat USS 5 days into the illness showed increasing ventricular dimensions.  The temporal horns of the lateral ventricles are not well seen.

5 days
HUSS - Meningitis - Coronal middle.jpg (49471 bytes)

HUSS - Meningitis - Sagittal midline middle.jpg (54844 bytes) HUSS - Meningitis - Sagittal left middle.jpg (54246 bytes) HUSS - Meningitis - Sagittal right middle.jpg (54247 bytes)


The final images (below) show grossly dilated lateral ventricles and the sagittal views suggest abnormality of the parenchyma.  There appear to be strands and debris in the ventricles.
A CT scan demonstrates extensive parenchymal abnormalities as well dilated ventricles

Late Scans
HUSS - Meningitis - Coronal late.jpg (52645 bytes)

HUSS - Meningitis - Sag late.jpg (58888 bytes) Meningitis CT1.jpg (230033 bytes) Meningitis CT2.jpg (250466 bytes)


PolymicrogyriaCoronal1.jpg (48798 bytes)

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PolymicrogyriaMidline1.jpg (52886 bytes)

Polymicrogyria is characterised by a large number of small folds in the cortical surface.  Histologically there are two types - nonlayered (which is felt to be a neuronal migrational disorder) and layered (which is thought to be postmigrational).
The nonlayered variety often includes other migrational defects.  The layered variety has been associated with intrauterine insults.

Zellweger cerebro-hepato-renal syndrome is the best example of a clinical syndrome associated with polymicrogyria.  Infants are extremely hypotonic, have severe seizures, and impairment or absence of responses to light, sound or other stimuli.  Other features include a distinctive appearance, hepatomegaly, multiple renal cortical cysts, and stippled calcification of the patellae.  It is due to a disorder ot perioxisomal biogenesis.

Clinical features of sporadic cases are not well defined.  Seizures are frequent and developmental problems are common.

PolymicrogyriaSagLeft1.jpg (53555 bytes) PolymicrogyriaSagLeft2.jpg (50415 bytes) PolymicrogyriaSagRight1.jpg (53120 bytes) PolymicrogyriaSagRight2.jpg (50774 bytes)
PolymicrogyriaMR1.jpg (26573 bytes) PolymicrogyriaMR2.jpg (22928 bytes) PolymicrogyriaMR3.jpg (31903 bytes) PolymicrogyriaMR4.jpg (32205 bytes)


CMV_Calcification1.jpg (31764 bytes)

CMV_Calcification2.jpg (36705 bytes)

Congenital Cytomegalovirus (CMV) infection is thought to occur in 1% of all livebirths.  Most infants are asymptomatic but some have symptoms which can include microcephaly, hepatosplenogmegaly, fulminant hepatic failure, thrombocytopenia, and petechiae.  There can be late sequelae of developmental delay and progressive hearing impairment.

Imaging may demonstrate migrational disorders with microcephaly and polymicrogyria, diminished white matter, delayed myelination, cerebellar hypoplasia, and cerebral calcifications.

The images to the left from an infant with congenital CMV demonstrate periventricular calcification, best shown in the left sagittal image as three defined areas of increased echogenicity.