A diffuse bulge of one of these discs refers to the disc bulging out from all sides (right, left, front, and back), except not the top or bottom. effacing the thecal sac means that that diffuse disc bulge is contacting the thecal sac such that being able to see that sac is obscured by the diffuse disc bulge.Thecal sac refers to the the sac which is a membrane (called dura mater) that contains the spinal cord and cerebrospinal fluid.All this statement implies is that the disc bulge is contacting the membrane that contains the spinal cord.minimal narrowing of the neuro foramina - probably you meant neural foramina.he pressure to the disc ( … disc bulge) (This tells the location on the spinal column that the bone spur has formed effacing the ventral aspect of the thecal sac is causing pressure to the spinal cord resulting in partial flattening to the cord. This is more common than formerly thought.