Introduction

Recent advances in brain imaging have made it possible to study clinical, cognitive, and behavioural abnormalities of caudate vascular lesions. Most of the major studies on caudate vascular lesions followed the introduction and widespread use of CT scanning in the 1970s and early 1980s. There are only a few studies of the vascular lesions, either infarcts or hemorrhages, involving the caudate nucleus. Most studies included caudate lesions involving the neighbouring structures like the putamen, internal capsule, and white-matter (Damasio et al., 1982; Richfield et al., 1987; Alexander et al., 1987; Mehler, 1987; Mendez et al., 1989; Caplan et al., 1990; Cambier et al., 1979; Valenstein & Heilman, 1981; Weisberg, 1984; Stein et al., 1984; Waga et al., 1986; Pozzilli et al., 1987; Pedrazzi et al., 1990). Recently Kumral et al. studied a series of patients with caudate infarcts or hemorrhages involving the head of the caudate nucleus (confirmed by CT and MRI), and discussed the stroke etiologies, clinical profiles, and behavioural abnormalities (Kumral et al., 1999).

Anatomy of the caudate nucleus

Functional neuroanatomy: ‘parallel frontal–striatal–thalamic–frontal circuits’

According to Alexander et al.(1986) in the striatum including the caudate nucleus there are at least five parallel functionally segregated circuits that link the basal ganglia with the motor, associative, and limbic cortices. Each circuit is defined by the area of cerebral cortex projecting to specified regions of the striatum, and by the corresponding return thalamo-cortical projection to specified areas of frontal cortex. The circuits remain more or less segregated throughout the basal ganglia and thalamus and there are cross-links between them at various relays therein. Within each circuit, the basal ganglia execute a similar, common function.

Neurovascular anatomy of the pons

The anatomic distribution of the major pontine arteries was worked out by Duret (1873) and, later, Stopford (1915, 1916) and Foix and Hillemand (1925a,b). The arterial supply can be divided into three groups. (i) Paramedian arteries arising from the dorsal surface of the basilar artery penetrate the pons directly and are larger than the other penetrating vessels. They supply the medial portion of the basis pontis and the most ventral part of the tegmentum. (ii) Short circumferential arteries supply the lateral three- fifths of the pons. And (iii) long circumferential arteries nourish the lateral tegmentum and tectum. Short penetrators course more laterally and run parallel to the median arteries. Lateral penetrators arise from the long circumferential arteries, supply the lateral tegmentum, and run perpendicular to the median penetrators (Fig. 40.1).

According to a recent description of the arterial supply to the brainstem and cerebellum (Tatu et al., 1996), the pons is supplied by three groups of arteries: (i) anteromedial and anterolateral groups arising from the basilar artery, entering the foramen cecum, the basilar sulcus, and the interpeduncular fossa; (ii) lateral group arising from the AICA (entering the parenchyma in the pontomedullary sulcus and arising from the lateral pontine arteries (entering the brachium pontis); and (iii) posterior group arising from the superior cerebellar artery (medial and lateral branches).