In its classic definition, by FranÃ§ois-Louis Ganshof (1944), feudalism describes a set of reciprocal legal and military obligations among the warrior nobility revolving around the three key concepts of lords, vassals and fiefs.
The exact cause of intracardiac echogenic foci remains unclear; however, they appear to be caused by small deposits of calcium in the papillary muscle of the fetal heart.
Neurogenic claudication is often a result of lumbar spinal stenosis, or the narrowing of the spinal canal in the lumbar region. Spinal stenosis can cause nerve compression on the spinal cord or the nerve roots and may result from several different spinal conditions.