SILK is a flow diverter stent used to treat complex intracranial aneurysms. It had been promoted as 'stent-only' treatment for anuerysms, however the increased incidences of delated anuerysmal ruptures have forced to manufacturers and the medical community to have a relook and now it is only recommended to be used along with coils.
The fact that flow diverters cause bleed in previously unruptured anuerysms has become well established although the exact number and percentages are unknown, and so are the probable mechanism even though few hypotheses have been floating around.
The study on SILK stent was done by a reputed group of interventional neuroradiologists in UK and found to have unacceptable complications, based on which the reommendation of using coils along with the stent has been made.
However the recent slew of publications by various authors regarding another flow diverter  -the Pipeline embolization device (PED) have been contradictory. Now the PED has been approved by the FDA wih no mention of usage of coils.
I personally believe that this has nothing to do with science but business and the so called 'authors' have vested interests in this extremely costly device.
The SILK stent trial was done by a reputed group and no doubt their results also apply to the other flow-diverter -the PED.
SILK Stent Alert