An immunocytochemical study of the germinal layer vasculature in the developing fetal brain using Ulex europaeus 1 lectin

Vulnerability of the developing brain to hypoxic-ischemic damage: contribution of the cerebral vasculature to injury and repair?

As clinicians attempt to understand the underlying reasons for the vulnerability of different regions of the developing brain to injury, it is apparent that little is known as to how hypoxia-ischemia may affect the cerebrovasculature in the developing infant. Most of the research investigating the pathogenesis of perinatal brain injury following hypoxia-ischemia has focused on excitotoxicity, oxidative stress and an inflammatory response, with the response of the developing cerebrovasculature receiving less attention. This is surprising as the presentation of devastating and permanent injury such as germinal matrix-intraventricular haemorrhage (GM-IVH) and perinatal stroke are of vascular origin, and the origin of periventricular leukomalacia (PVL) may also arise from poor perfusion of the white matter. This highlights that cerebrovasculature injury following hypoxia could primarily be responsible for the injury seen in the brain of many infants diagnosed with hypoxic-ischemic encephalopathy (HIE). Interestingly the highly dynamic nature of the cerebral blood vessels in the fetus, and the fluctuations of cerebral blood flow and metabolic demand that occur following hypoxia suggest that the response of blood vessels could explain both regional protection and vulnerability in the developing brain. However, research into how blood vessels respond following hypoxia-ischemia have mostly been conducted in adult models of ischemia or stroke, further highlighting the need to investigate how the developing cerebrovasculature responds and the possible contribution to perinatal brain injury following hypoxia. This review discusses the current concepts on the pathogenesis of perinatal brain injury, the development of the fetal cerebrovasculature and the blood brain barrier (BBB), and key mediators involved with the response of cerebral blood vessels to hypoxia.

Anatomical Features of the Developing Brain Implicated in Pathogenesis of Hypoxic-Ischemic Injury

The developing nervous systems is subject to damage from lack of vital substances necessary for normal maturation and function as well as from trauma or a variety of toxins and infectious agents. By far, the most important of these is inadequate oxygen delivery to the fetus in utero, and/or during the intrapartum and/or early neonatal period. Many types of lesions have been described under the rubric of hypoxic-ischemic encephalopathy, a major proportion of which are found only in the immature nervous system and essentially are never seen later in life. Moreover, a large number are primarily hemorrhagic rather than ischemic in character. The unique character and distribution of these lesions results from a collision of the changing anatomy of the developing nervous system and pathophysiological factors afflicting the immature organism. Whereas the majority of hypoxic-ischemic lesions in the fetus/neonate fall into this group, abnormalities characteristically found in the mature nervous system are also seen. Recognition of the anatomic and physiological features peculiar to the developing nervous system will assist in diagnosis of hypoxic-ischemic damage peculiar to the fetus and neonate.