Sonographic templates of newborn perforator stroke

Abstract

Background

Many paediatric strokes occur in the perinatal period. Improvement in neuroimaging has increased detection in newborns with neurological symptoms.

Objective

To define sonographic templates of neonatal stroke in the territory of perforators of the anterior choroidal artery (AChA) and the anterior (ACA), middle (MCA) and posterior (PCA) cerebral arteries.

Materials and methods

In 24 neonates with perforator stroke, we retrospectively studied antenatal and perinatal events. Brain sonography was performed with an 8.5-MHz probe. Only hyperechoic lesions in the thalamus and/or striatum and/or centrum semiovale were included. MRI was obtained using a 1.5-T machine.

Results

We detected 28 perforator strokes in 24 infants (6 preterm): 5 MCA medial striate, 8 MCA lateral striate, 3 MCA centrum semiovale, 4 ACA Heubner’s, 5 PCA thalamic arteries, 1 AChA, and 2 hypothalamic perforators. We attributed clinical seizures to stroke in two infants only. Catheter-related embolism (certain in three, possible in six others) and birth trauma (two) were probable causes. Specific conditions were found in six others. Only one infant (in nine evaluated) had an increased prothrombotic risk (fII mutation). In describing the lesions, we focused on the templates of infarction as seen in a parasagittal US sweep. Infarcts were confirmed by MRI in 21 patients.

Conclusion

Our study showed that infarct topography can be evaluated reliably with brain sonography. This is important given the asymptomatic character of most lesions.

Appendix: anatomy of the arterial perforators

Tentative anatomical assignment relies on arterial templates of brain perfusion (Figs. 1 and 2). These are summarized from the work, in adults, of Vander Eecken [13].

The anterior choroidal artery (AChA) usually originates from the MCA at its very origin. It runs laterally and posteriorly to the optic tract, continuing underneath it to the corpora geniculata, where it divides into (a) a lateral branch entering the telediencephalic fissure of Bichat and (b) a thinner branch continuing to the lamina quadrigemina. It gives off side branches: laterally to the uncus hippocampi, the anterior part of the lower side of the hippocampus, the dentate gyrus, the amygdaloid nucleus, the curvature of the tail of caudate; medially to the optic tract, the lower part of the crus posterius and the radiatio optica, the inner segment of the globus pallidus. Several median terminal branches supply the middle third of the crus cerebri, the upper part of the substantia nigra and of the nucleus ruber, the lateral part of the subthalamic nucleus and, usually, a superficial part of the ventrolateral thalamic nucleus. The lateral terminal branch ends in the choroid plexus of the temporal horn.

Many striate perforators arise from the MCA. The lateral striate arteries are often seven to nine fine branches arising from the first part of the M1 segment. A medial group supplies the lateral segment of globus pallidus. The lateral group, or the arteriae putamino-capsulo-caudatae, supply the putamen, the upper part of the internal capsule, the corpus nuclei caudati and the upper part of the caput nuclei caudati. Some branches from these striatal arteries perfuse lateral and cranial parts of thalamus.

The basilar side branches of the anterior cerebral artery (ACA) are the arteriae striatae mediales, three or four very thin branches perforating directly the substantia perforata. One of them can be distinguished by a wider calibre: the arteria recurrens of Heubner. The level of its origin varies in relation to the anterior communicating artery. This recurrent artery runs in a lateral and dorsal direction, gives off a fine branch for the tuber olfactorium and finally penetrates into the lateral part of the anterior substantia perforata. In many cases the anterior communicating artery gives off one or two fine perforating branches, joining the arteriae striatae mediales of the ACA.

The posterior cerebral artery (PCA) runs over the oculomotor nerve, which separates it from the more posteriorly situated arteria cerebellaris superior. Then it takes a horizontal course in a wide arc around the crus cerebri, crossing it in an inferosuperior direction until it reaches the lateral mesencephalic sulcus. Here it turns in an outward and posterior direction to follow the inner border of the hippocampal gyrus, and then it divides into two branches, one following the parietooccipital and the other the calcarine sulcus. During this course around the brain stem the PCA gives off a series of side branches which can be subdivided into two groups, the branches from the crural part (of interest here), and those from the distal cortical part.

The branches from the crural part are usually deep penetrating vessels (perforating or choroidal). First, there are the arteriolae retromammilares which are divided into an anteromedial and a posteromedial group. The anteromedial (thalamostriate) group supplies the median-posterior part of the mammillary bodies; to them belong the arteriae perforantes thalami which vascularize the median anterior part of thalamus, the superior part of nucleus ruber, the median part of subthalamic nucleus, the posterior part of the hypothalamus and the superior part of the brachia conjunctiva. The posteromedial group (not indicated in Fig. 1) supplies the middle part of the crus cerebri after having perforated the intercrural substantia perforata.

The arteria quadrigemina arises close to the origin of the PCA, just medial to the point where the posterior communicating artery (PCoA) joins the latter. It forms a pericrural arc, situated between the arc of the PCA on the anterior and that of the superior cerebellar artery on the posterior side. In the transverse sulcus of the lamina quadrigemina it gives off an anterior branch for the superior colliculus and a posterior branch for the inferior colliculus. Further, during its course it gives off some branches to the anterior part of the lateral side of the crus cerebri.

The arteriae choroideae posteriores are usually double and originate separately or via a common stem. They also curve around the crus cerebri. The first, the arteria chorioidea posterior medialis, after having reached the upper side of the mesencephalon, takes a posteroanterior course towards the pineal body, to which it gives off some small branches; it diminishes in size in the choroid plexus of the third ventricle. The second, the arteria chorioidea posterior lateralis, gives two end branches. One follows the median part of the upper side of the thalamus, the superomedian part of which it irrigates. The other reaches the choroid plexus of the lateral ventricle opposite the lateral part of the pulvinar. It also vascularizes the posterior part of the caudate nucleus. During their initial ascending course, the posterior choroid arteries give off some small branches entering the median part of the pulvinar.

The arteriae thalamogeniculatae usually arise just beyond the point where the PCoA joins the PCA. There are usually five or six very thin branches penetrating into the posterior side of the thalamus. They supply the corpus geniculatum mediale, the median and posterior part of the corpus geniculatum laterale, the lower half of the nucleus lateralis thalami, the lateral part of the pulvinar and also the median part of the occipital radiation of the internal capsule.

The PCoA usually arises from the last part of the internal carotid artery. It runs in a posterior and somewhat superior direction, beneath the optic tract and above the oculomotor nerve, and joins the PCA at a small distance from the division of the basilar artery. In this way it forms a connection between the system of the internal carotid artery and that of the vertebral arteries. Five to six small arteries arise from the PoCA, also participating in the vascularization of the floor of the third ventricle (hypothalamic nuclei), and of the superoanterior part of the medial thalamic nuclei.