Definition of Stenosis



The normal neck. The spinal cord sits in a triangle of space. The floor consists of the disc and uncinate processes which are natural bony projections towards the spinal canal. The facet joints are roof structures as are the lamina.



The space available in the spinal canal in the neck is shown by the arrow. This is the space that comfortably houses the spinal cord. If this distance is too small, then pressure on the spinal cord can exist. Notice that anything on the sides of the triangle could narrow the canal.



Disc or bone spur can project into the triangle and put pressure on the spinal cord. This anterior or floor pressure is due to soft disc herniation or bone spur (osteophyte). 



The uncinate processes (natural bony projections on the floor of the spine) can enlarge with wear and tear (bones remodel along lines of mechanical stress). These processes can enlarge to the point they put pressure directly on the spinal cord, the nerve roots or both.



The canal can be narrowed due to enlargement of the facet joints (red) and/or thickening of the ligament or lamina. These are structures of the roof of the spinal canal and can put pressure from above the spinal cord and compress it against the floor.



The canal can be narrowed due to enlargement of the lamina (blue) and/or thickening of the ligament (yellow) as well as disc, or osteophyte (black) from the floor. Essentially, the spinal cord can be sandwiched between a roof and floor in which there is no room it.



The spinal canal is outlined in blue and the spinal cord outlined in red. These diagrams show the potential effects of neck motion on the spinal cord. With neck flexion (bending the neck forward). the spinal cord could be draped over a disc or bone spur on the floor of the spinal canal. With the neck extended, the spinal cord can be compressed from behind from ligament or bone spur.