  The influence of microlensing in the profiles of the emission lines generated
in a biconical geometry is discussed. Microlensing amplification in this
anisotropic model is not directly related to the bicone's intrinsic size but
depends on the orientation of the bicone axis and on the cone aperture. The
orientation of the projected bicone with respect to the shear of the
magnification pattern can induce very interesting effects, like the
quasi-periodic enhancements of the red/blue part of the emission line profile
or the lack of correlation between the broad line region (BLR) and continuum
light curves of QSOs. The emission line profiles of a BLR moving in a high
caustic concentration exhibit sharp features that are well defined in
wavelength. These features (spikes) correspond to the scanning of the
kinematics of the BLR by the caustic clusters. The biconical model can
qualitatively reproduce with a transversal (with respect to the shear) movement
of the BLR, the recurrent blue-wing enhancement detected in the emission line
profile of the A image of the quasar lensed system SDSS J1004+4112. The
probability of observing this repetitive event is almost a 2% for a fraction of
matter in stars of a 5%. This result would make plausible the detection of the
spectral variability in SDSS J1004+4112 under the hypothesis of microlensing of
a bicone.
