Subependymal Cysts Research Articles

Scanning electron microscopy of transitory subependymal cysts in the developing midbrain of postnatal rats.

Transitory cystic cavities, associated with the subependymal region of the aqueduct in the midbrain of postnatal rats aged 1-15 days, were studied by light and scanning electron microscopy. The walls of these cysts, as observed in scanning electron microscopy, were lined by a dense feltwork of nerve fibres. Two types of cells were identified in the cysts: smaller glioblasts and larger amoeboid microglial cells. The glioblasts were characterized by a smoother cell body with radiating long processes. The amoeboid microglial cells showed blebs and pseudopodia on their surface. They either adhered to the walls or floated freely in the lumen. It is postulated that the formation of the subependymal cysts in the developing brain resulted following the cleavage or breakdown of the nervous tissue due to the expansion of the aqueduct and the brain as a whole. The amoeboid microglial cells in the cysts were probably derived from the extravasated blood monocytes in response to the physical damage ensuing during the formation of the cysts.

Macrocephaly Is Not Always Due to Hydrocephalus

Macrocephaly is a clinical symptom with a heterogeneous cause. Besides enlarged ventricles (hydrocephalus) it can be caused by increased brain volume, expanded extracerebral spaces, intracranial cysts, and dilated vessels. Drawing on the experience of more than 8 years using transfontanellar sonography including Doppler techniques, some typical clinical and sonographic features of several forms of macrocephaly are addressed. Besides isolated familial or sporadic megalencephaly, extracerebral fluid collections are the main explanation of macrocephaly. Subdural effusions with compression of the brain by increased intracranial pressure should be differentiated from craniocerebral disproportion without increased intracranial pressure. Subependymal and subarachnoidal cysts may cause extraodinary displacements and compression of brain structures; nevertheless, the prognosis is rather optimistic, for the brain structure itself is generally not destroyed. In some infants with complex genetic, neurocutaneous, and neurometabolic syndromes, macrocephaly is an early clinical sign. The outcome in these infants is very different and dependent on the dysfunction of the brain by the specific disease (eg, storage of neurotoxic substances, dysplasia, gliosis, vascular disturbances, or brain tumors). In infants with vascular malformations the diagnosis can be established more exactly by using Doppler techniques. I recommend some practical diagnostic procedures in cases of macrocephaly. Nevertheless, in many patients with increased head size an exact statement about the further prognosis cannot be established by one examination; therefore, a developmental evaluation in combination with regular sonographic evaluation is the most valuable method in taking care of all infants with macrocephaly.

Current Topics in Brain Ultrasonography of the Infants

In recent years brain ultrasonography has become a simple, useful and almost indispensable examina-tion for the neurological diagnosis of newborns and young infants. A pulsatility index (PI) calculated from the formula (S-D) /S for the cerebral arteries such as basilar artery (BA) or anterior cerebral artery (ACA) decreased at the stage of elevated intracranial pressure in the infants with acute encephalopathy and subdural hemorrhage. Using two-dimensional Doppler ultrasonography (color flow mapping system), the blood flow of BA or ACA was observed as a continuous line of warm color along the course of the arteries. To obtain PI of these arteries, the sampling site could be easily decided using this system. Brain ultrasonograms of 515 cases of 1-month-old infants whose birth weights were more than 2500gm. were observed at their health 1-month-examination. Subependymal cysts (SEC) were observed in 51 infants (9.9%), and choroid plexus cysts (CPC) in 31 infants (6.0%) . Since the rate of neonatal asphyxia was 15.7% in SEC, 0% in CPC and 1.9% in normal controls, SEC was correlated with neonatal asphyxia statically. SEC was suspected of subependymal hemorrhage (SEH) and the occurrence of SEH in mature neonates was indicated in this study.

Progressive postnatal subependymal necrosis in an infant with congenital cytomegalovirus infection

An infant with congenital cytomegalovirus infection developed subependymal cysts postnatally. This patient provides further support for the concept that congenitally-infected infants occasionally have postnatal progression of central nervous system lesions.

Subependymal cysts in normal neonates.

We undertook a prospective ultrasound study of subependymal cyst formation in normal neonates. Twenty five of 500 normal Chinese neonates (5%) were found to have subependymal cysts. Most of these (18 of 25) showed no obvious perinatal insult. This study suggests a rather high incidence of concealed intrauterine subependymal haemorrhage in normal term neonates.

Neurosonographic recognition of subependymal cysts in high-risk neonates.

Serial neurosonography was performed in 210 high-risk, preterm neonates. Eleven (5.8%) demonstrated small cystic formations in the subependymal lining of the lateral ventricles. These subependymal cysts were unilateral and were detected at the exact site of a previous subependymal hemorrhage in two cases. These 11 infants were not significantly different in maturity, size, or clinical parameters from our main high-risk newborn population. Ten survivors had marked motor retardation at follow-up ages of 9-13 months, and one died from neonatal sepsis.

Ultrasonography and brain pathology of periventricular hemorrhage and subependymal cyst in the preterm neonate

Ultrasound (US) findings in 32 premature infants with intraventricular hemorrhages (IVH, 21 cases), subependymal hemorrhages (SEH, 5 cases) or subependymal cysts (SEC, 6 cases) were reviewed to determine the accuracy of US diagnosis and clarify the pathogenesis of SEC. With single US there was the possibility of false-positive or -negative SEH or IVH, but serial US showed diagnostic accuracy for SEH or IVH. Four of 6 cases with iron-negative SEC did not show an image of prior SEH and the SEC suggested focal ischemic microcirculation which may be important in the pathogenesis of the occurrence of SEH or the development from SEH to IVH.

Cysts of the subependymal germinal matrix: sonographic demonstration with pathologic correlation.

Five neonates who were born at term and who had well-defined cystic lesions in the subependymal germinal matrix demonstrated by real-time cranial ultrasonography are reported. None had evidence of subependymal or intraventricular hemorrhage. Two of the neonates had congenital viral infections, one each with rubella virus and cytomegalovirus. Two of the other three neonates died, and pathologic examination of their brains confirmed the presence of the cysts and showed no evidence of prior subependymal hemorrhage. Cranial CT examinations of three patients failed to detect the subependymal cysts. Although central liquefaction in an area of prior hemorrhage is probably the most common cause of subependymal cyst formation in neonates, other conditions such as neurotropic infection should also be considered.

Ultrasonic evaluation of neonatal intracranial hemorrhage and its complications.

High resolution, real-time ultrasound scans were obtained through the anterior fontanelle to examine the intracranial anatomy of 100 neonates. Of 43 patients with abnormalities, 26 had intracranial hemorrhage (subependymal, intraventricular, or cerebral). Of the 51 patients also studied by CT, the sensitivity of ultrasound in detecting hemorrhage was 96% and the specificity 94%. This ultrasound technique was also very useful for detecting complications such as porencephalic and subependymal cysts, ventricular septations, and hydrocephalus. In normal premature neonates (25 to 35 weeks gestation) the lateral ventricles appear as slit-like structures on the coronal scan. The midline-lateral dimension of normal lateral ventricles was 8.6 mm (range 7-11 mm) and the depth of 1.9 mm (range 1-3 mm). Follow-up scans in patients with intraventricular hemorrhage show that in mild hydrocephalus, the lateral ventricle becomes rounded rather than slit-like. This change occurs before the midline-lateral dimension of the ventricle increases.

Transitory subependymal cysts in the developing rat rhombencephalon.

A bilaterally symmetrical cystic cavity is situated in the subependymal neuropil of the rostral rhombencephalon of the rat during the perinatal period of ontogeny. These cysts are formed by the confluence of enlarged extracellular spaces in this region between E18 and E20. The cysts are present for about 2 weeks but disappear on about P15 without trace. They have a maximal volume of about 0.004 to 0.006 mm3 on P2, with a rostrocaudal extension of about 200 microm. Their shape is characterized by a medial convexity and a lateral concavity, and they have their maximal circumference at about the middle of the rostrocaudal axis. The caudal portion is juxtaposed to the subependyma, while the rostral part lies in the neuropil of the presumptive griseum centrale pontis. In the lumen and the wall of the cysts are found numerous macrophages, glioblasts and some degenerating axons and dendrites. The significance of these cysts in the context of morphogenesis and the origin of the numerous macrophages within them are both unresolved.

Cystic degeneration of the telencephalic subependymal germinal layer in newborn infants.

Cystic lesions were found in the telencephalic germinal layer of 12 newborn babies. According to their location, the cysts could be divided into three groups: anterior, middle or thalamostriate, and posterior. The histological appearance of all cysts was essentially the same, but in three cases the germinal layer had a peculiar alveolar type of microcystic degeneration. A constant feature was the presence in the cyst wall of small white granulations composed of germinal cells and/or glial tissue. Cystic degeneration of the germinal layer was usually bilateral and sometimes quite extensive. After the involution of the germinal layer, these lesions are likely to persist as subependymal cysts, characterized by their specific location and the presence of glial granulations.

Subependymal germinolysis.

Small subependymal cysts in the medioventral aspect of the caudate nucleus have been found in 30 human autopsied cases. The cysts are interpreted as a result of lysis of undifferentiated cells in the germinal matrix by various agents selectively attacking these cells while they are actively proliferating. Rubella virus and cytomegalovirus are two viruses that can cause this lesion, but other viruses or other agents yet to be discovered similarly may produce this relatively inconspicuous lesion when fetuses are exposed at a critical period in their development. The involvement of the telencephalic germinal matrix late in gestation results in imperfect development of the white matter and the supporting elements, which is a still more subtle lesion probably responsible for the striking functional subnormality.

The occurrence of subependymal cysts during the development of the human cerebellum.

The occurrence of subependymal cysts during the development of the human cerebellum.