Cerebrospinal fluid pressure response to upper cervical vertebral motion and displacement in the anesthetized rat

This study examined whether aligned or off-axis (subluxated) static and dynamic vertebral displacement within normal physiological ranges modulated cerebrospinal fluid pressure (CSF) as is considered to occur by some chiropractic theories.

Cerebrospinal fluid pressure pressure was measured via a subarachnoid catheter implanted at the lumbar level in 12 anesthetized adult male Wistar rats. A computer-driven manipulator was used to impose 3 motion patterns on the C2 vertebra: (i) dynamic oscillatory displacement (24 degrees peak-to-peak 1.0 and 2.0 Hz), (ii) static rotary (ramp 20 degrees at 10 degrees per second and hold for 4 minutes) displacement about both the normal and an offset axis of rotation, and (iii) a spinal manipulative thrust displacement (200 degrees per second; 12 degrees peak-to-peak).

The CSF pressure at rest for all rats ranged from 4.5 to 9.1 mm Hg, with a mean (+/- SD) of 6.3 +/- 1.4 mm Hg. Of the imposed movements, only an offset ramp and hold displacement resulted in a significant (P < .05) difference between the CSF pressure before (6.1 +/- 0.7 mm Hg) and during the imposed movement (6.6 +/- 0.7 mm Hg). None of the interventions were associated with significant changes in the powers of the principal peaks of the CSF pressure power spectrum.

The results of this study suggest that static or dynamic displacement of an upper cervical vertebra within the limits of tissue integrity do not induce physiologically important changes in absolute CSF pressure or pressure dynamics in anesthetized rats.