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 Ministry of HealthNZ Government
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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. |
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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. |
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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
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. |
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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. |
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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. |
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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:
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. |
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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
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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. |
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| 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
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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 |
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Late Scans
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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. |
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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. |
