Spinal elastance measurement in patients with spondylogenic narrowing of the spinal canal.

Spinal elastance and the time course of pressure decrease after saline injection into the lumbar subarachnoid space was measured in a control group and in a group of patients with spondylogenic narrowing of the cervical spinal canal. The elastance is higher with retroflexion of the head than with anteflexion. This is more pronounced in degenerative diseases of the spine, proving the existence of a pincers mechanism. High elastance values at high volume changes indicate a narrowing of the cervical spinal canal. With a normal spinal canal the pressure decrease shows a slow monoexponential slope (T/2 = 100.8 +/- 13.4 seconds). In patients with partial obstruction of the spinal canal, especially with retroflexion of the head, a secondary pressure increase after termination of the volume injection was observed. This secondary pressure increase decreases in a biexponential manner with a fast slope (T/2 = 37.62 +/- 15.88 seconds) followed by a slow slope. With severe obstructions a plateau remained. This easily performed and well-tolerated measurement can be of aid in the quantification of obstructions of the spinal subarachnoid space.