Spinal stenosis and back pain

Spinal stenosis is a narrowing of the lumen at any level. In practice, doctors use a classification of spinal canal stenosis based on the pathogenesis and localization of the stenosis.

Congenital stenosis of the spinal canal is characterized by narrowing of its midsagittal diameter, i.e. the stenosis is central in localization. At the same time, with different variants of congenital pathology of the spinal canal, narrowing of any of its sections is possible. For acquired degenerative stenoses, most often developing with arthrosis of the intervertebral joints, narrowing of the nerve root canals is typical. The nature of acquired stenoses developing with herniated intervertebral discs depends on the zone of "prolapse" of the hernia, in accordance with which the hernia itself is designated as medial, mediolateral, lateral or foraminal.

Classification of spinal canal stenosis

	Types of stenosis
By pathogenesis	A) congenital and b) acquired, incl. associated with disc herniation associated with other pathology hyperplasia of the capsule of the facet joints, ossification of the yellow ligament, posterior longitudinal ligament other
By localization	Central stenosis, Stenosis of the nerve root canals, Foraminal stenosis (stenosis of the radicular openings)

A fairly wide range of diseases can lead to the development of spinal canal narrowing. RH Dorwart provides the following list of such pathological conditions:

Diseases accompanied by stenosis of the spinal canal (according to Dorwart R., 1981)

Types of stenosis	Diseases accompanied by stenosis
Congenital stenosis	a) idiopathic stenosis, b) achondroplasia, c) hypochondroplasia, d) mucopolysaccharidosis, d) dysplasias accompanied by weakness of the atlantoaxial joint (metatrogic epiphyseal dysplasia, spondyloepiphyseal dysplasia, Kniest disease, multiple epiphyseal dysplasia, chondrodysplasia), e) Down syndrome (C1-C2 instability), g) hypophosphatemic vitamin D-resistant rickets
Acquired stenosis
Degenerative	a) spondylosis and arthrosis, b) compression of the spinal canal by soft tissues, c) isolated lysis of the intervertebral disc, d) degenerative spondylolisthesis.
Combined	A combination of diseases causing congenital and acquired stenosis, degenerative stenosis and protrusion of the intervertebral disc
With spondylolysis	a) without spondylolisthesis, b) with spondylolisthesis
Iatrogenic	a) after laminectomy, b) after arthrodesis (spinal fusion)
Post-traumatic	a) in the acute and b) late periods of spinal trauma
For metabolic diseases	a) Paget's disease, b) epidural lipomatosis in Cushing's syndrome or long-term steroid therapy, c) acromegaly, d) fluorosis, d) pseudogout (dehydrated calcium pyrophosphate deposition disease)
Other pathological conditions	A) ankylosing spondylitis, b) calcification or ossification of the posterior longitudinal ligament (OLLP), c) diffuse idiopathic hyperostosis, d) calcification or ossification of the yellow ligament, d) single origin of the lumbosacral nerve roots (relative stenosis of the spinal canal)

The most clinically significant are stenosis of the spinal canal that develops with herniated intervertebral discs. The development of hernias is characterized by a certain stage (Bersnev V.P. et al., 1998): Stage I - protrusion or bulging of the disc, Stage II - prolapse of the nucleus pulposus and fragments of the disc into the spinal canal (hernia proper), Stage III - hidden spondylolisthesis or "slipping" disc, Stage IV - stabilization or self-healing.

Despite the repeated repetition in the text of terms characterizing various morphological variants of intervertebral disc herniations, it still seems appropriate to us to provide a definition of each of them:

• disc protrusion - displacement of the nucleus pulposus towards the spinal canal and bulging of elements of the fibrous ring
  of the intervertebral disc into the spinal canal without damaging the integrity of the latter;
• extrusion - bulging of elements of the fibrous ring and degenerated nucleus pulposus into the spinal canal;
• prolapse - the prolapse into the spinal canal through defects in the fibrous ring of fragments of the degenerated nucleus pulposus that remain connected to the disc;
• sequestration - displacement of fallen fragments of the degenerated nucleus pulposus along the spinal canal.

To compare narrowings of the spinal canal and its individual parts with different etiologies, we proposed a method for quantitatively assessing central stenosis of the spinal canal and narrowings of the dural sac in pure congenital kyphosis and kyphosis caused by tuberculous spondylitis. The relative magnitude of stenosis of the dural sac was assessed using myelo(tomography) or contrast tomography data, and the relative magnitude of stenosis of the spinal canal was assessed using CT data, transverse or midsagittal MRI sections, echospondylograms and lateral X-ray(tomography)grams of the spine. The relative magnitude of stenosis was determined using the formula

K = (a-b)/a x 100%,

Where a is the sagittal size of the subarachnoid space (spinal canal) in the neutral zone, b is the sagittal size of the subarachnoid space (spinal canal) at the level of maximum compression. When stenosis is localized at the level of physiological lumbar thickening (T10-T12), the normal size of the spinal canal (dural sac) is defined as the average between the upper and lower neutral zones. Being relative values expressed as a percentage, these indicators can be used for comparative assessment of pathological conditions of different etiology, including in different age groups. Despite their apparent uniformity and parallel changes, both indicators do not replace each other. Thus, in tuberculous spondylitis, a combination of subarachnoid space stenosis with a normal or even expanded size of the spinal canal is possible. At the same time, true stenosis of the spinal canal is characteristic of congenital deformities of the spine. In a number of cases, this sign plays a decisive role in differentiating a congenital vertebral defect, combined with a pathology of the spinal canal, from the consequences of an inflammatory process.

The study of clinical features of diseases accompanied by slowly developing compression of the spinal canal and spinal cord (congenital kyphosis, tuberculous spondylitis of the thoracic and thoracolumbar spine) allowed us to identify a clinically significant relative value of central stenosis of the dural sac (or spinal canal), in which the overwhelming majority of patients develop neurological disorders - paresis and paralysis. It has been empirically established that this value is 40-45%.

In acutely developed compression, which usually occurs with spinal injuries and herniated discs, the reserve capacity of the spinal cord is significantly more limited, and neurological disorders and back pain develop at significantly lower stenosis values.

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