Definition of Neonatal Stroke
A stroke, in general, is defined as an event that leads to poor blood flow to a localized area of the brain. One of the difficulties in studying strokes in the neonate is that, until recently, there has not been full agreement on the definition of neonatal stroke. Recently, however, the National Institute of Child Health and Human Development and the National Institute of Neurological Disorders and Stroke provided a consensus definition of neonatal stroke as “a group of heterogeneous conditions in which there is a focal disruption of cerebral blood flow secondary to arterial or cerebral venous thrombosis or embolization between 20 weeks of fetal life through 28th post-natal day, and confirmed by neuroimaging or neuropathological studies.” Neuroimaging was defined as T2-weighted magnetic resonance imaging (MRI), magnetic resonance angiography (MRA), or diffusion-weighted imaging, as head ultrasounds can miss anterior and posterior lesions and computed tomography (CT) may not detect small or early lesions.1 However, ultrasounds and CT scans remain commonly used techniques in the evaluation of neonatal stroke. Neuropathological studies included autopsy and detailed evaluation of the placenta. Thus, the definition of neonatal stroke is currently defined by neuroimaging or neuropathologic findings, is either venous or arterial, and is either thrombotic or hemorrhagic. The location and type of stroke, as well as the neonate’s clinical status, help guide the workup.
Neonatal stroke is a common clinical event; with an estimated incidence between 1/2300 and 1/5000 live births.1 The incidence in this age category is second only to the incidence seen in elderly adults. The majority of neonatal strokes are caused by thrombosis of the arteries (70%), with a lower rate of hemorrhagic strokes (20%) and sinus venous thrombosis (10%). There is a slightly increased frequency in males compared to females and in African American infants when compared with Caucasian babies. A majority of these events occur in term infants because of their physiological hypercoagulable state near the time of delivery. As neuroimaging techniques become more sophisticated and the technology becomes more available, neonatal stroke may be more easily diagnosed, and this reported incidence may begin to rise.
Maternal Risk Factors
Pregnancy results in a relative hypercoagulable state with several plasma proteins affected and increased thrombin generation, putting both mother and baby at increased risk of thrombus.2 Several publications reported that about half (50%) of mothers of infants diagnosed with a thrombotic stroke were found to have prothrombotic abnormalities.
Chorioamnionitis has also been shown to be associated with increased risk of thrombotic strokes in neonates. A multivariate analysis of a retrospective case control study involving a total of 208 infants found that maternal fever, even in the absence of an identified infection, had a statistically significant association with perinatal arterial ischemia.3
Maternal autoimmune disorders, in particular lupus, can lead to neonatal stroke. The maternally derived ...