Neonatal stroke is estimated to occur in 1 per 2300 to 5000 live births.1 This estimate may be an underrepresentation of the true incidence of neonatal stroke because of the inherent challenges in diagnosing this condition. In the adult, stroke is defined as “rapidly developed signs of focal (or global) disturbance of cerebral function lasting greater than 24 hours (unless interrupted by surgery or death), with no apparent nonvascular cause.”2 In this definition, there is heavy reliance on the clinical signs of neurological dysfunction. These signs are not usually apparent in the neonate because motor dysfunction is not easily appreciated, and sophisticated repertoires of behaviors such as language or the ability to follow commands have not yet developed. In the newborn, symptoms are vague, including encephalopathy, seizures, hypotonia, poor feeding, and apnea. This list of symptoms may be present in many of the diseases treated in the neonatal intensive care unit; therefore, trying to ascertain which are caused by stroke can be immensely challenging. The correct identification of stroke, however, is paramount for many reasons, ranging from identifying potentially modifiable risk factors to acute therapeutic intervention (particularly for sinus venous thrombosis). Managing long-term outcomes, which tend to be poor, is difficult but may improve with aggressive early intervention and emerging therapies such as transcranial magnetic stimulation and constraint-induced therapy.
In neonates, a proposed definition of stroke is as follows: “A group of heterogeneous conditions in which there is a focal disruption of cerebral blood flow secondary to arterial or venous thrombosis or embolization, between 20 weeks of fetal life through the 28th post-natal day, and confirmed by neuroimaging or neuropathological studies.”3 In this definition, there is a conspicuous absence of any clinical sign or physical exam finding suggesting neurologic dysfunction caused by stroke. As in adults, stroke in neonates can be subcategorized based on the affected vascular distribution (arterial vs venous), by whether the primary mechanism is ischemic or hemorrhagic, and by the presumed timing of the event (prenatal or postnatal). In this chapter, arterial ischemic stroke is discussed first, followed by venous stroke (better known as cerebral venous sinus thrombosis, CVST), and then hemorrhagic stroke. Prenatal and perinatal ischemic events defined by the term presumed perinatal ischemic stroke (PPIS) are also discussed.
PERINATAL ARTERIAL ISCHEMIC STROKE
Arterial ischemic stroke occurs when an arterial vessel is occluded by a thrombus or an embolus, resulting in ischemic injury to the brain tissue distal to the occlusion. A thrombus is defined as a clot that is adherent to the wall of a vessel, whereas an embolus is a nonadherent thrombus. The embolus may be moving within arterial vessels or venous vessels or may become paradoxical by crossing from venous to arterial circulation. Paradoxical emboli may be more likely to occur in the neonate as right-to-left shunts are a necessary part of cardiovascular physiology during the transition ...