Tracing of Neuronal Connections in the Human Brain by Magnetic Resonance Imaging in vivo

Axon degeneration after disruption of fibre tracts in the mammalian
nervous system is accompanied by myelin breakdown which leads to
changes in its magnetic resonance properties. In two patients with
pure motor strokes due to small ischaemic lesions restricted to the
internal capsule, magnetic resonance imaging disclosed a narrow
band of pathological signal increase descending band-like into the
brain stem and ascending to the precentral gyrus, which
corresponded to the well-known path of the pyramidal tract. The
findings suggest that in man anterograde and possibly retrograde
fibre degeneration can be traced in vivo by conventional magnetic
resonance imaging techniques. Critical conditions are the presence
of small, strategically located lesions, appropriate choice of
imaging plane, and the interval between time of lesion and of
imaging. This demonstration may open a new era for functional
neuroanatomy of man.