Causes of Neonatal Subarachnoid Hemorrhage
The most common causes of neonatal subarachnoid hemorrhage are birth trauma and hypoxic-ischemic events, with traumatic delivery being the predominant etiology in term newborns.
Primary Etiologies
Birth Trauma
- Mechanical forces during delivery are the leading cause of neonatal subarachnoid hemorrhage (SAH), particularly in term infants 1
- Associated with:
- Difficult or prolonged labor
- Forceps-assisted delivery
- Vacuum-assisted extraction
- Abnormal presentation
- Trauma can lead to tearing of delicate blood vessels in the subarachnoid space
Hypoxic-Ischemic Events
- Severe hypoxic-ischemic encephalopathy is the second most common cause 1
- Results in vascular injury and subsequent hemorrhage
- Often associated with perinatal asphyxia
Vascular Abnormalities
Aneurysms
- Represent 57% of SAH cases in children, though much less common in neonates 2
- Pediatric aneurysms are typically:
- Idiopathic (45%)
- Post-traumatic (20%)
- Due to abnormal vessel-wall hemodynamic stress 2
- More likely to be giant (>25mm) or fusiform in children compared to adults
Vascular Malformations
- Arteriovenous malformations (AVMs)
- Arteriovenous fistulas
- Cavernous malformations
- These account for a significant percentage of hemorrhagic strokes in children 2
Other Causes
Coagulation Disorders
- Congenital or acquired coagulopathies
- Thrombocytopenia (6% of hemorrhagic strokes in children) 2
- Vitamin K deficiency
Cerebral Venous Sinus Thrombosis
- Can lead to venous infarction with hemorrhagic transformation
- Incidence is 0.3 per 100,000 children per year, with neonates making up 43% of cases 2
Maternal and Placental Factors
- Chorioamnionitis
- Premature rupture of membranes
- Preeclampsia
- Placental insufficiency 2
Other Rare Causes
- Brain tumors (15% of hemorrhagic strokes in children) 2
- Infectious aneurysms
- Cerebral amyloid angiopathy (rare in neonates) 3
Clinical Presentation and Diagnosis
Common Presentations
- Seizures (69% of cases) - most common presentation 4
- Apnea (23% of cases) 4
- Bradycardia
- Irritability
- Lethargy
- Bulging fontanelle
Diagnostic Approach
- Unenhanced head CT is the initial imaging study of choice 2
- MRI with susceptibility-weighted imaging provides better characterization
- Ultrasound may be used in neonates with open fontanelles but has limitations in detecting SAH 2
- For suspected vascular abnormalities, MRA or catheter angiography may be required
Prognosis and Complications
Outcomes
- Mortality is significant but variable
- Among survivors, approximately 52% may be neurologically normal at follow-up 4
- Outcomes appear similar regardless of whether the etiology is hypoxic-ischemic or traumatic 4
Complications
- Post-hemorrhagic hydrocephalus (19% of survivors) 4
- May present with delayed onset beyond the neonatal period
- Seizure disorders
- Developmental delay
- Cognitive impairment
Important Considerations
- SAH in term newborns may be more serious than previously believed 4
- Close neurodevelopmental follow-up is essential
- Surveillance for hydrocephalus should continue beyond the neonatal period due to risk of delayed presentation 4
- Superficial parenchymal hemorrhages often accompany SAH, particularly in the temporal lobe near sutures 5
Neonatal SAH requires prompt recognition and management to minimize long-term neurological sequelae, with particular attention to preventing secondary injury from complications such as hydrocephalus or seizures.