Germinal Matrix Hemorrhage and Intraventricular Hemorrhage: Imaging and Diagnosis

Introduction

Germinal matrix hemorrhage (GMH) and intraventricular hemorrhage (IVH) are the intracranial complications affecting preterm babies, especially babies born before 32 weeks of pregnancy and low birth weight babies. The germinal matrix is a gelatinous, highly cellular structure that gives origin to glia and cerebral neuroblasts. It is located in the subependymal of the ventricular walls. Vascularization of the germinal matrix begins with the seven to eight weeks of gestation. Their thickness reduces from 24 weeks and almost disappears by the 36 to 37th week of gestation; hence GMH is common in preterm babies.

Germinal matrix hemorrhage occurs due to the alteration in cerebral blood flow resulting from low arterial pressure and defective cerebral autoregulation in preterm neonates. Altered cerebral blood flow results in rupture of the blood vessels, and the bleeding might be restricted within the germinal matrix or extend to the lateral ventricle. Intraventricular hemorrhage refers to the bleeding into the ventricles of the brain in premature infants.

What Are the Symptoms of Intraventricular Hemorrhage?

The common symptoms of intraventricular hemorrhage are as follows:

• Apnea (abnormally interrupted breathing).

• Altered heart rate and blood pressure.

• Decreased muscle tone.

• Lethargy.

• Excessive sleep.

• Decreased reflexes.

• Seizure (uncontrolled electrical activity in the brain cell causes abnormal body movements).

What Are the Different Types of Intraventricular Hemorrhage (IVH)?

According to the grading system of IVH, given by Burstein et al., it is classified into four types.

• Grade 1 - Grade 1 is also known as germinal matrix hemorrhage. In grade 1, there is minimal bleeding, and it extends to the germinal matrix alone.

• Garde 2 - In grade 2 also, there is minimal bleeding without dilatation. The hemorrhage extends into the lateral ventricle without causing hydrocephalus.

• Garde 3 - Grade 3 involves severe bleeding with dilatation and having less than 50 percent clot in the ventricle.

• Grade 4 - Grade 4 is also known as intraparenchymal hemorrhage. A blood clot formed during this stage blocks the cerebrospinal fluid (CSF) flow and results in hydrocephalus.

What Are the Risk Factors for Intraventricular Hemorrhage?

The risk factors for intraventricular hemorrhage are:

Prenatal (Before Birth):

• Chorioamnionitis (a bacterial infection that affects the chorion, amnion, and amniotic fluid).

• Maternal human immunodeficiency virus (HIV).

• Multiple pregnancies.

• Lack of antenatal care.

• Inherited coagulation disorders (a condition with abnormal clotting mechanism).

• Low gestational age.

Perinatal (During and Immediately After Birth):

• Low birth weight.

• Male sex.

• Fetal distress (a condition in which the fetus does not receive enough oxygen through the placenta in the womb).

• Preterm birth.

• Vaginal delivery.

• Mechanical ventilation.

Postnatal (After Birth):

• Anemia (decreased red blood cell count).

• Blood transfusion.

• Neonatal sepsis (a fatal complication of infection).

• Patent ductus arteriosus (an abnormal heart condition characterized by failure in the closure of the fetal ductus arteriosus).

• Hypercapnia (increased carbon dioxide levels in the bloodstream).

• Pneumothorax (collection of air between the lung and the chest wall).

• Hypotension (low blood pressure).

• Hyperglycemia (increased sugar level in the blood).

• Hyponatremia (low sodium level in the blood).

• Metabolic acidosis (increased acid production in the body).

• Respiratory distress syndrome (a breathing disorder that affects preterm babies due to the lack of surfactant in the lungs).

• Medication (opioids and sodium bicarbonate).

What Are the Imaging Techniques Used in the Diagnosis of Intraventricular Hemorrhage?

The imaging techniques used in the diagnosis of intraventricular hemorrhage are:

Ultrasonography:

• Ultrasonography is the first choice of imaging modality to diagnose IVH. Germinal matrix hemorrhage appears as an echogenic area near the caudothalamic groove that extends to the floor of the frontal horn of the lateral ventricle.

• Initially, IVH appears as an echogenic area, and when a large blood clot breaks in the ventricle, it appears as low echogenic and floats in the CSF. Sometimes the clot may move when the patient changes their head position. Imaging through the posterior fontanelle visualizes occipital horn clots.

• The radiologist should distinguish hemorrhage from choroid plexus as both of them looks like echogenic areas in ultrasound. The echogenicity extends anterior to the caudothalamic groove in IVH, whereas in the choroid plexus, the echogenicity ends at the groove.

• However, ultrasound cannot show smaller GMH. Pulsed wave and power Doppler ultrasound are helpful in identifying preterm babies who are at risk of IVH and GMH during their first week of life. It can detect autoregulatory fluctuation in a preterm baby's cerebral blood flow with the help of measuring the peak velocity, vascular cross-section area, and resistive index.

• According to the American academy of neurology (AAN), the preferred imaging choice for diagnosis of IVH is transcranial Doppler ultrasound in neonates less than 30 weeks gestational age. AAN suggests that the first ultrasound imaging be performed in neonates at seven to 14 days of life and repeated at 36 to 40 weeks.

• Blankenberg et al found that ultrasound has a negative predictive value (NVP) in diagnosing IVH of about 53 percent at two months follow-up and NVP of 59 percent at two-year follow-up.

Computed Tomography (CT) Scan:

• During the initial stage, IVH appears as the hyperattenuating area. After seven to 10 days, the hemorrhage becomes iso-attenuating in relation to the brain parenchyma.

• In the later stage, due to clot retraction, subependymal hematoma develops into a fluid-filled cyst. The affected parenchyma might undergo atrophy and gliosis.

• The negative predictive value for CT scans in the detection of GVM and IVH is about 50 to 60 percent at two years of life.

Magnetic Resonance Imaging (MRI) Scan:

• During the first three days of IVH, subependymal hematoma appears as isointense to mild hypointense on T1-weighted images and markedly increased hypointense on T2-weighted images.

• During the first four to seven days, the signal intensity increases on T1-weighted images.

• During the late subacute stage (seven to 14 days), the signal intensity increases on T2-weighted images.

• In the next few months, the hemorrhage appears as hypointense areas on both T1 and T2 sequences and also shows ferromagnetic effects due to the presence of hemosiderin and ferritin.

• Blankenberg et al. found that MRI has twice the sensitivity compared to ultrasound in detecting IVH and GMH.

• The negative predictive value of MRI in the detection of IVH and GMH is about 50 to 60 percent at two years of life.

Conclusion:

Ultrasound is a portable imaging tool that allows imaging in infants without any discomfort. Ultrasound has about 100 percent sensitivity and 91 percent specificity in imaging GMH larger than five millimeters. Blankenberg et al found that a CT scan shows twice the sensitivity of ultrasound in diagnosing GMH and IVH. About 50 percent of IVH occurs during the first 24 hours after birth, and up to 90 percent of cases are reported during the first 72 hours after birth. GVM and IVH affect three in 1000 live birth preterm babies and also show a 20 to 30 percent mortality rate.