Germinal Matrix - Intraventricular Haemorrhage

Germinal Matrix-Intraventricular Haemorrhage (GM-IVH) is the most common form of intracranial haemorrhage in preterm infants. It can occur in up to 20% of infants delivered at less than 32 weeks gestation.

Pathophysiology

The site of origin of GM-IVH is at the subependymal germinal matrix. This is the area of the brain where neuroblasts migrate from between 10 and 20 weeks, and becomes the source of glioblasts. It is a very vascular structure. At a microscopic level, destruction of the germinal matrix occurs when there has been a GM-IVH.

In approximately 15% of infants, there is also intraparenchymal involvement. This was previously though to represent parechymal extension of an intraventricular haemorrhage. It is associated with an ipsilateral GM-IVH in 80% of cases. However, it is now thought to represent periventricular haemorrhagic venous infarction, due to occlusion of medullary veins which return adjacent to lateral ventricle and germinal matrix.

Terminology and Classification

GM-IVH is frequently described according to where the bleed is, and how extensive. However, most neonatal units also use a grading system (Grades 1 to 4) according to extent of the haemorrhage. This is useful for audit purposes and for some prognostic categories, but is not as precise as a detailed description in this regard.

For the purposes of this website, images are presented according to their Papile grading 1. Links to the left will take you to the appropriate images.

The grading system is as follows:

Grade 1 and 2 haemorrhage make up about 75% of IVH.

Grade 1 GM-IVH

Grade 1 haemorrhage is characterised by germinal matrix haemorrhage with no or minimal intraventricular haemorrhage (<10% of ventricular area on the parasagittal view).

Approximately 35% of GM-IVH are classified as Grade 1.

The images to the right show bilateral germinal matrix haemorrhages, evident as areas of echogenicity in the germinal matrix. There is no apparent extension into the ventricles.

Grade 2 GM-IVH

The extension of germinal matrix haemorrhage into the lateral ventricle(or ventricles) is indicative of Grade 2 GM-IVH. The haemorrhage should fill less than 50% of the ventricular area - involvement of more than this would result in reclassification as a Grade 3 GM-IVH.

The images to the right show bilateral germinal matrix haemorrrhages, evident as areas of echogenicity in the germinal matrix.

A follow up scan was performed 4 days later to evaluate progression of the haemorrhage, as well as any evidence of obstruction. The images show bilateral haemorrhage resolving. There is no significant dilatation of the ventricles.

The final set of images show that the haemorrhage is resolved, but there is now evidence of periventricular leukomalacia in both periventricular areas. The ventricles are generous, which may reflect evidence of white matter loss rather than dilatation secondary to the GM-IVH.

Grade 3 GM-IVH

Grade 3 haemorrhage is characterised by intraventricular haemorrhage occupying at least 50% of the ventricle. The ventricles may appear distended or dilatation may develop secondary to posthaemorrhagic hydrocephalus. There may also be parenchymal involvement if there is venous obstruction.

The following images are from a 25 week infant delivered in good condition. He was not initially ventilated but deteriorated on the second day with pallor, acidosis, hypotension and poor handling. He was intubated and ventilated. A full blood count showed a marked reduction in haemoglobin.

Grade 4 GM-IVH

The characteristic feature of Grade 4 haemorrhage is parenchymal involvement. This traditionally was considered to be due to an extension from a ventricular bleed.

However, it is now considered to be due to periventricular haemorrhagic infarction. Deep veins pass lateral to the lateral ventricles. Following a presumed hypoperfusion-reperfusion injury, it is thought that there is haemorrhage at this site, resulting in obstruction of these veins and then venous haemorrhagic infarction. Approximately 80% of Grade 4 bleeds are associated with an ipsilateral GM-IVH. These lesions are frequently associated with neurodevelopmental sequelae. However, the severity and extent depends on size and location. Bilateral parenchymal involvement is an indicator of poor neurodevelopmental prognosis.

This series of images demonstrates the evolution of a left parenchymal bleed in the parietal region. See the image gallery for more information.

This 23 week gestation infant had significant lung disease. There was never any discussion about withdrawal of care solely because of the haemorrhage, although it was understood that some degree of neurodevelopmental problems would follow (most likely a right hemiplegia). His lung disease progressed and eventually he deteriorated to such an extent that care was withdrawn for respiratory reasons.

Posthaemorrhagic Hydrocephalus

Hydrocephalus developing following a significant Germinal Matrix haemorrhage is not uncommon and is related closely to the severity of the initial haemorrhage.

The aetiology is thought to be due to both the effects of blood clots on CSF absorption acutely and, later, obliterative arachnoiditis. Impaired CSF flow usually occurs at the outflow of the 4th ventricle as most frequently the hydrocephalus is communicating.

Although clinical signs of hydrocephalus (such as rapid head growth, bulging anterior fontanelle, and separated sutures) occur, these are usually well after imaging has demonstrated significant ventricular dilatation.

Drug therapy to prevent or treat ventricular dilatation has not been shown to be helpful. The role of serial lumbar punctures has also been disappointing, although there is still a role for this in some infants. Infants with rapid progressive ventricular dilatation or signs of raised intracranial pressure may require a ventricular reservoir or ventriculoperitoneal shunting.

Reference

1. Papile LA, Burnstein J, Burnstein R, et al. Incidence and evolution of subependymal and intraventricular hemorrhage: a study of infants with birth weights less than 1,500 gm. J Pediatr 1978; 92;529-34.