  Spiral waves are investigated in oscillatory media exhibiting period-doubling
bifurcations. In the period-doubled and chaotic regimes, the rotational
symmetry of the spiral wave is broken. The loss of symmetry takes the form of
synchronization defect lines where the phase of the local oscillation changes
by multiples of 2\pi. The internal structure and geometry of these
synchronization defects is studied and a discussion of the possible types of
defect lines is presented.
