36
W. L. Nowinski
Fig. 2.25 Deep cerebral veins
Fig. 2.26 Vascular variants of the circle of Willis: (a) double anterior communicating artery; (b)
absent left posterior communicating artery; (c) absent left P1 segment (the variants are in white)
2.4.3 Projection Tracts
The projection tracts connect the cortex with the subcortical structures in the
diencephalon, brainstem, and spinal cord. The main projection tracts are (Fig.
2.30):
• Corticospinal (pyramidal) tract
• Corticothalamic tract including the anterior, posterior (optic), and superior
thalamic radiations
• Corticobulbar tract (connecting to the brainstem)
• Corticopontine tract (projecting to the pons)
• Auditory radiations