Pressure Effects in the Spinal Canal During Whiplash Extension Motion - A Possible Cause of Injury to the Cervical Spinal Ganglia

Paper in proceeding, 1993

impact-velocities (<20 km/h) often cause pain in the neck region as well as a number of other neurological symptoms, most of which can be related to the nerve paths that pass through the cervical intervertebral foramina. When the neck is flexed or extended in the sagittal plane the length of the cervical spinal canal alters but the cross-sectional area of the canal remains almost constant. During flexion-extension motion of the cervical spine, the size of the inner volume of the spinal canal will change. Since the tissues inside the canal can be considered incompressible, an alteration will take place of either the amount of cerebro spinal fluid or the amount of blood in the veinplexa of the epidural space, or both. This requires fluid transportation through the intervertebral foramina as well as along the spinal canal. During a whiplash extension motion, the flow velocity can be expected to rise far above physiologically normal levels and pressure gradients can thus be expected to occur. In turn, the soft tissues inside and around the cervical spine and particularly in the intervertebral foramina will sustain mechanical strain and stress. Anaesthetised pigs were exposed to a swift extension-flexion motion of the neck while the pressure inside the spinal canal and the skull was measured. Pressure pulses of magnitudes up to 150 mmHg (20 kPa) were observed during the motion. The magnitude of pressure is for each moment dependent on the position of the neck, the velocity and the acceleration of the motion. Plasma membrane dysfunction was indicated by the results from light microscopic analyses of the cervical and the three upper thoracic spinal ganglia revealing the staining of nerve cells and satellite cells by protein complexed to the Evans Blue dye.