Laminectomy is the term used to refer to the surgical process of removing the lamina (usually both sides). By removing the lamina, the size of the spinal canal is increased, allowing for the spinal cord or nerve roots to have more room.
This procedure, also called a spinal decompression, reduces the pressure on the nerve roots or the spinal cord, which can be caused by bony spurs or by a herniated or bulging disc. This pressure is often referred to as spinal stenosis and can cause pain and weakness. The pressure is relieved by removing the lamina as well as any other source of compression such as bone spurs, a herniated disc, or disc bulges. Decompression of the nerve roots and the spinal cord relieves pain and other symptoms.
Information from the National Institutes of Health, March, 2009