A voltage has been applied to a network of multiwalled carbon nanotubes (MWCNTs) placed between two electrodes. The current flowing through the MWCNTs is found to be responsible of irreversible effects, such as the suppression of radial breathing modes (RBM) in the Raman spectra. Furthermore, we observe a significant modification of the G-band in the Raman spectra for applied voltages higher than 1 V, only if Raman analysis is performed while current is flowing. This is due to a combined effect of current flow and laser beam irradiation that induces extended structural damage in the CNT outer walls.