Axial Spinal Stenosis


When dura and Cauda Equina are compressed in a narrow vertebral canal, axial canal stenosis is present. This entity is termed axial stenosis. The latter term should not be used, because as Verbiest stated, "stenosis always reduces the periphery of an enclosed space and therefore the term central is a misnomer” (Verbiest 1990). The author prefers axial stenosis.

Canal Stenosis

Verbiest (1954, 1990) differentiated absolute and relative stenosis. Absolute stenosis was defined by a midsagittal diameter of 10 mm or less. This entity generally results in symptoms and signs as soon as the bony skeleton is mature but Schonstrom (1988) found a poor correlation in patients with symptoms and signs between the size of the dural sac and the bony dimensions of the lumbar canal. However, a significant difference was observed in the cross sectional area of the lumbar canal in these patients compared with asymptomatic subjects. Verbiest (1990) demonstrated that in nine patients with degenerative spondylolisthesis, absolute stenosis was present at adjacent levels. By classifying these patients as having only acquired stenosis, the possibility of developmental stenosis at a different level may be overlooked. Therefore, a taxonomy including a morphologic and an aetiologic classification is desirable.

axial spinal stenosis

AXIAL STENOSIS in this cased is arising from posterior vertebral bone spurs and facet joint hypertrophy but in association with bilateral lateral STENOSIS. The result is a patient in whom there was multi-level disc degeneration presenting with symtoms of AXIAL STENOSIS but in whom the major effects were arising from the bilateral lateral recess STENOSIS. Treatment at this level by endoscopic means avoided the need for widespread midline decompression by multi-level leaminectomy proposed elsewhere.

facet joint overgrowth

Facet joint overgrowth (hypertrophy) , ligamentum flavum infolding and a disc protrusion caused this patient to present with signs of AXIAL STENOSIS. Endoscopic enlargement of the foramen and removal of the protrusion endoscopically reversed all the symptoms.

Bilateral nerve root irritation

Bilateral nerve root irritation by the wide based disc protrusion caused the limbs to feel weak during exercise with a mimicry of AXIAL or so called central STENOSIS. Removal of the disc protrusion and monbilisation of the descending nerve on the predominant presenting side served to relieve these symptoms.