Foraminal stenosis is by far the most common form of spinal stenosis. Over 72% of cases of foraminal stenosis occur at the lowest lumbar level, usually trapping the emerging nerve root of the sciatic nerve. Neural foraminal narrowing is a common result of disc degeneration.
The process of disc degeneration or bulging can cause the foraminal canal to narrow. Once the foraminal opening reaches a point of compressing the nerves inside the spinal column, pain, numbness, tingling, and muscle weakness often occur. Other possible causes of neural foraminal narrowing include rheumatoid arthritis, osteoarthritis, chronic meningitis, tumors, and neurofibromas.