Germinal matrix-intraventricular haemorrhage

GMH-IVH is a generic term for intracranial haemorrhage in the preterm infant which does not involve the parenchyma.

Incidence With improvements in neonatal intensive care the incidence of GMH-IVH has declined over the past 20 years. Currently it is seen in 20-30% of preterm infants born weighing less than 1000g.

Aetiology The following factors are implicated in the development of GMH-IVH:

  • Vulnerable immature anatomy: the germinal matrix is a richly cellular layer surrounding the lateral ventricles and is the site of origin of neuronal and glial precursors which migrate to the developing cerebral cortex. Germinal matrix tissue is most abundant in the area overlying the head of the caudate known as the ganglionic eminence. At this point only a single layer of ependyma separates this tissue from the cerebrospinal fluid of the lateral ventricles. The germinal matrix reaches maximal volume at around 26 weeks gestation and thereafter regresses rapidly. It is a highly vascular structure with only limited supportive connective tissue and thin walled vessels and so is vulnerable to bleeding.
  • Haemodynamic instability: cerebral auto-regulation (the maintenance of constant cerebral perfusion in the presence of fluctuating arterial blood pressure) is easily disrupted in the preterm infant, particularly in response to hypoxia or acidosis. This leaves the cerebral circulation vulnerable to fluctuations in arterial blood pressure.

Rupture of vessels in the germinal matrix has the following consequences:

  • Germinal matrix haemorrhage: blood remains in the germinal matrix and gradually resolves resulting in a sub-ependymal pseudocyst.
  • Intraventricular haemorrhage: blood ruptures through the ependymal layer into the lateral ventricles.
  • Post haemorrhagic hydrocephalus: blockage of CSF flow at the level of the third ventricle (non-communicating) or CSF re-absorption at the arachnoid villi (communicating) results in progressive ventricular dilatation and hydrocephalus (ventricular dilatation > 97th centile). In 15-20% babies hydrocephalus persists requiring insertion of a ventricular-peritoneal shunt.
  • Haemorrhagic parenchymal infarction (HPI): a large IVH can obstruct the venous drainage from the cerebral cortex resulting in parenchymal venous infarction. Breakdown of the clot results in a porencephalic cyst.

Clinical features GMH-IVH may present with an acute deterioration in the babies condition with increased ventilatory requirements and hypotension. However the majority of bleeds are clinically silent and diagnosed on cranial ultrasound screening.

Diagnosis Cranial ultrasound is the ideal tool to screen for GMH-IVH. The majority of haemorrhages occur in the first 72 hours of life and so babies should be scanned at birth (to identify antenatal lesions) and at 3 days of age.

Prognosis The outcome following an uncomplicated GMH-IVH is good with the risk of handicap around 4%. 50% of babies with post haemorrhagic hydrocephalus have neurodevelopmental problems which rises to 75% if they require a shunt. Babies with a unilateral HPI have a high incidence of developing a spastic hemiplegia.