Germinal Matrix Bleed

= GERMINAL MATRIX–RELATED HEMORRHAGE

Risk factors:

1. Prematurity
2. Low birth weight
3. Sex (M÷F = 2÷1)
4. Multiple gestations
5. Trauma at delivery
6. Prolonged labor
7. Hyperosmolarity
8. Hypocoagulation
9. Pneumothorax
10. Patent ductus arteriosus

Etiology: hypoxia with loss of autoregulation

Pathogenesis: rupture of friable vascular bed due to

1. Fluctuating cerebral blood flow in preterm infants with respiratory distress
2. Increase in cerebral blood flow with
   1. systemic hypertension (pneumothorax, REM sleep, handling, tracheal suctioning, ligation of PDA, seizures, instillation of mydriatics)
   2. rapid volume expansion (blood, colloid, hyperosmolar glucose / sodium bicarbonate)
   3. hypercarbia (RDS, asphyxia)
3. Increase in cerebral venous pressure with labor and delivery, asphyxia (= impairment in exchange of oxygen and carbon dioxide), respiratory disturbances
4. Decrease in cerebral blood flow with systemic hypotension followed by reperfusion
5. Platelet and coagulation disturbance

Incidence: in premature neonates <32 weeks of age; in 43% of infants <1,500 g (in 65% of 500–700 g infants, in 25% of 701–1,500 g infants) ; in up to 50% without prenatal care, in 5–10% with prenatal care

Time of onset: usually during first 24 hours of life; 36% on 1^st day, 32% on 2^nd day, 18% on 3^rd day of life; by 6^th day 91% of all intracranial bleeds have occurred

Location: region of caudate nucleus and thalamostriate groove (= caudothalamic notch) remains metabolically active the longest; in 80–90% in infants <28 weeks of MA

GRADES (Papile classification):

• I: subependymal hemorrhage confined to germinal matrix (GMH) on one / both sides
• II: subependymal hemorrhage ruptured into nondilated ventricle (IVH)
• III: intraventricular hemorrhage (IVH) with ventricular enlargement: (a) mild, (b) moderate, (c) severe
• IV: extension of germinal matrix hemorrhage into brain parenchyma (intraparenchymal hemorrhage = IPH)

US (100% sensitivity + 91% specificity for lesions >5 mm; 27% sensitivity + 88% specificity for lesions ≤5 mm):

1. Germinal matrix hemorrhage (grade I)
   • well-defined ovoid area of increased echogenicity (= fibrin mesh within clot) inferolateral to floor of frontal horn ± body of lateral ventricle
   • bulbous enlargement of caudothalamic groove anterior to termination of choroid plexus
     DDx: choroid plexus (attached to inferomedial aspect of ventricular floor, tapers toward caudothalamic groove, NEVER anterior to foramen of Monro)
   • resolving bleed develops central sonolucency
   • outcome: (1) complete involution (2) thin echogenic scar (3) subependymal cyst
2. Mild intraventricular hemorrhage (grade II)
   • echogenic material filling a portion of lateral ventricles (acute phase) becoming sonolucent in a few weeks
   • clot may gravitate into occipital horns
   • vertical band of echogenicity between thalami on coronal scans (blood in 3^rd ventricle)
   • irregular bulky choroid plexus (clot layered on surface of choroid plexus)
   • temporarily increased echogenicity of ventricular wall (= subependymal white halo between 7 days and 6 weeks after hemorrhagic event)
3. Extensive intraventricular hemorrhage (grade III)
   • intraventricular cast of blood distending lateral ventricles
   • ± extension of hemorrhage into basal cisterns, cavum septi pellucidi
   • hemorrhage becomes progressively less echogenic
   • temporarily thickened echogenic walls of ventricles (“ventriculitis”)
4. Intraparenchymal hemorrhage (grade IV)
   Frequency: 5–8%
   Cause:
   1. extension of hemorrhage originating from germinal matrix (unusual)
   2. separate hemorrhage within infarcted periventricular tissue (frequent)
      = periventricular venous infarction ← thrombosis of medullary veins draining periventricular brain
   
   Location: on side of largest amount of IVH, commonly lateral to frontal horns / in parietal lobe, rare in occipital lobe + thalamus
   • unilateral triangular hemorrhage
   • homogeneous highly echogenic intraparenchymal mass with irregular margins
   • central hypoechogenicity (liquefying hematoma after 10–14 days)
   • retracted clot settles to dependent position (3–4 weeks)
   • complete resolution by 8–10 weeks results in anechoic area (= porencephalic cyst)

Serial scans: recommended in 5–10-day intervals

CT:

• hyperdense bleed only visible up to 7 days before it becomes isodense

DDx: subdural hemorrhage, cerebral parenchymal hemorrhage, posterior fossa lesion

MR (gradient-echo, susceptibility-weighted sequences):

• highest sensitivity for detecting small hemorrhages
• useful for depicting periventricular venous infarction in grade 4 germinal matrix hemorrhages

Cx:

1. Posthemorrhagic hydrocephalus (30–70%)
   • Severity of hydrocephalus directly proportional to size of original hemorrhage!
   
   Cause:
   1. temporary blockage of arachnoid villi by particulate blood clot (within days), often transient with partial / total resolution
   2. obliterative fibrosing arachnoiditis often in cisterna magna (within weeks); frequently leads to permanent progressive ventricular dilatation (50%)
   • thickened echogenic ventricular walls
   
   Time of onset: by 14 days (in 80%)
   • delayed clinical signs because of compressible premature brain parenchyma
   • ventricular dilatation, particularly affecting the occipital horns (amount of compressible immature white matter is larger posteriorly)
   
   DDx: ventriculomegaly ← periventricular cerebral atrophy (occurring slowly over several weeks)
2. Cyst formation
   1. cavitation of hemorrhage
   2. unilocular subependymal cyst
   3. unilocular porencephalic cyst
3. Mental retardation, cerebral palsy
4. Death in 25%
   • IVH is the most common cause of neonatal death!

Prognosis:

1. Grade I + II: good with normal developmental scores (12–18% risk of handicap)
2. Grade III + IV: 54% mortality; 30–40% risk of handicap (spastic diplegia, spastic quadriparesis, intellectual retardation)