Spinal stenosis describes a condition where the spinal canal is narrowed. The spinal canal can be narrowed by disc herniations, bony overgrowth, ligamentous overgrowth (ligamentum flavum), and/or spondylolisthesis (a condition where one bone of the spine slips forward or backward in relation to the bone below). Spinal stenosis can occur centrally or in the foramen where the nerve exits. Placement of medication in close proximity to the area of narrowing provides the greatest degree of relief. Spinal stenosis may be effectively treated with intermittent injections, however if this does not provide lasting relief, surgical decompression may need to be considered; this can be performed with a minimally invasive technique in certain patients.