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Lumbar foraminal stenosis


Neurosurgery Department, University General Hospital of Alicante, Foundation for the Promotion of Health and Biomedical Research in the Valencian Region (FISABIO), Alicante, Spain

Lumbar foraminal stenosis is defined as the narrowing of the bony exit of the nerve root caused by a decrease in the height of an intervertebral disk, osteoarthritis in the facet joints, cephalad subluxation of the superior articular process of the inferior vertebra, and buckling of the ligamentum flavum or protrusion of the annulus fibrosus.

Nerve root compression was evident in twenty-one of the 100 foramina, in eight of the ten foramina in which the posterior disc height was four millimeters or less, and in four of the five foramina in which the foraminal height was fifteen millimeters or less. These critical dimensions may be indicators of lumbar foraminal stenosis. However, compression of a spinal nerve root does not always cause sciatica, and the clinical findings must always be taken into account when a diagnosis of stenosis is considered 1).


Lumbar spinal stenosis at the lumbar intervertebral foramen is the most common type of spinal stenosis.

Patients with degenerative scoliosis frequently present with foraminal stenosis and radiculopathy, the origin of which is not well understood.

A correlation between curve types and symptomatic foraminal stenosis exists. Adult scoliosis patients with sciatic nerve pain typically present with foraminal stenosis at the concavity of the caudal fractional curve. Similarly, patients with femoral nerve pain present with foraminal stenosis at the concavity of the caudal fractional curve when the main structural curve is thoracic, thoracolumbar, or lumbar (apex L2 or higher) 2).


It results from a combination of pathogenic factors, including a decrease in the area of the cauda equina, hypertrophy of ligamentum flavum, disc height loss, and lumbar facet joint degeneration


Lumbar degenerative disc disease

Bone spurs

Lumbar foraminal disc herniation


In the majority of patients, lumbar stenosis is caused by degenerative deterioration in the spine due to aging.

Clinical features

Typically, it will produce symptoms that affect one side of the body – as each vertebra has two foramina (one foramen on either side), and often, only one of those openings will be narrowed. In some cases, bilateral foraminal stenosis develops, which means both vertebral foramina are constricted and both sides of the body experience symptoms.

Because lumbar foraminal stenosis manifests in the lower back, symptoms will appear in that region, such as radial pain, or radiating pain, that travels from the lumbar region to the hips, buttocks and the back of one leg. Issues pertaining to numbness, tingling, weakness or cramping also can occur. In cases of severe foraminal stenosis, patients may experience bladder or bowel dysfunction, which could indicate a medical emergency called cauda equina syndrome.


The preoperative identification of lumbar foraminal stenosis (LSFS) is important because a lack of recognition of this clinical entity is often associated with failed back surgery syndrome.

Ohba et al., demonstrates combination of conventional imaging techniques, to improve the detection of symptomatic foraminal stenosis.

Measurement of the foraminal width and height on CT imaging of the diseased side was significantly less than that on the intact side in the LSFS group. The grading scale for facet joint arthritis on the diseased side was significantly higher than that on the intact side in the LSFS group. The prevalence of the vacuum phenomenon and stage of intervertebral disk (IVD) pathology were higher in the L5-S1 spine of the LSFS group (95.2%) compared with the lumbar spinal canal stenosis (LCS) group (21.1%). MRI study revealed that the prevalence of Type 3 Modic changes was significantly higher in the LSFS group (39.3%) compared with the LCS group (7.7%) 3).


Although magnetic resonance imaging (MRI) is widely used, and is considered by many as an appropriate tool for studying spine pathologies, there is limited data to suggest that MRI examinations are sufficiently sensitive or specific for the diagnosis of LSFS.

There is no widely used diagnostic criterion or grading system for lumbar foraminal stenosis on MRI. For clinical studies with the objective of comparing different therapeutic methods for lumbar foraminal stenosis, an adequate grading system that has good reproducibility is necessary. In addition, in daily routine practice, a grading system for lumbar foraminal stenosis is necessary for writing radiologic reports.

There have been few reports on the grading or classification of lumbar foraminal stenosis on MRI 4) 5). The grading system suggested by Wildermuth et al. 6) focused on only the degree of epidural fat obliteration. The classification of lumbar foraminal stenosis proposed by Kunogi and Hasue 7) included the anteroposterior, cephalocaudal, and circumferential types without stenosis grade. The grading system of Wildermuth et al. and the classification proposed by Kunogi and Hasue do not consider direct nerve root compression or deformity, which may be important.

Effective foraminal height, effective superior foraminal width and the effective ratio can regard as the main evaluation index for LPS in parasaggital MRI finding 8).

In patients with developmental or combined stenosis of the central spinal canal, a concomitant foraminal stenosis is likely to be present, or at least should be suspected 9).

In a T1 MRI the normal is appearance with white fat signal surrounding the exiting nerve roots.

In stenotic (narrowed), there is no fat surrounding the nerve.


The association between disc pathology and facet osteoarthrosis can cause occult foraminal stenosis. Strategies to image the spine under physiological load conditions may improve the clinical diagnosis of radicular pain 10).

Higher superior articular process area (SAPA) values were associated with a higher possibility of LFS 11).



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Pugely AJ, Ries Z, Gnanapragasam G, Gao Y, Nash R, Mendoza-Lattes SA. Curve Characteristics and Foraminal Dimensions in Patients With Adult Scoliosis and Radiculopathy. Clin Spine Surg. 2017 Mar;30(2):E111-E118. doi: 10.1097/BSD.0b013e3182aab1e3. PubMed PMID: 28207622.
Ohba T, Ebata S, Fujita K, Sato H, Devin CJ, Haro H. Characterization of symptomatic lumbar foraminal stenosis by conventional imaging. Eur Spine J. 2015 Oct;24(10):2269-75. doi: 10.1007/s00586-015-3859-4. PubMed PMID: 25772088.
4) , 6)
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Splendiani A, Ferrari F, Barile A, Masciocchi C, Gallucci M. Occult neural foraminal stenosis caused by association between disc degeneration and facet joint osteoarthritis: demonstration with dedicated upright MRI system. Radiol Med. 2014 Mar;119(3):164-74. doi: 10.1007/s11547-013-0330-7. Epub 2013 Dec 12. PubMed PMID: 24337755.
Lim TH, Choi SI, Cho HR, Kang KN, Rhyu CJ, Chae EY, Lim YS, Lee Y, Kim YU. Optimal Cut-Off Value of the Superior Articular Process Area as a Morphological Parameter to Predict Lumbar Foraminal Stenosis. Pain Res Manag. 2017;2017:7914836. doi: 10.1155/2017/7914836. PubMed PMID: 28163566; PubMed Central PMCID: PMC5253487.
lumbar_foraminal_stenosis.txt · Last modified: 2018/08/08 17:21 by administrador