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

impact-velocities (<20 km/h) often cause pain in the\nneck region as well as a number of other neurological\nsymptoms, most of which can be related to the nerve\npaths that pass through the cervical intervertebral\nforamina.\nWhen the neck is flexed or extended in the sagittal\nplane the length of the cervical spinal canal alters but\nthe cross-sectional area of the canal remains almost\nconstant. During flexion-extension motion of the\ncervical spine, the size of the inner volume of the\nspinal canal will change. Since the tissues inside the\ncanal can be considered incompressible, an alteration\nwill take place of either the amount of cerebro spinal\nfluid or the amount of blood in the veinplexa of the\nepidural space, or both. This requires fluid\ntransportation through the intervertebral foramina as\nwell as along the spinal canal. During a whiplash\nextension motion, the flow velocity can be expected to\nrise far above physiologically normal levels and\npressure gradients can thus be expected to occur. In turn,\nthe soft tissues inside and around the cervical spine and\nparticularly in the intervertebral foramina will sustain\nmechanical strain and stress.\nAnaesthetised pigs were exposed to a swift\nextension-flexion motion of the neck while the\npressure inside the spinal canal and the skull was\nmeasured. Pressure pulses of magnitudes up to 150\nmmHg (20 kPa) were observed during the motion. The\nmagnitude of pressure is for each moment dependent on\nthe position of the neck, the velocity and the\nacceleration of the motion.\nPlasma membrane dysfunction was indicated by the\nresults from light microscopic analyses of the cervical\nand the three upper thoracic spinal ganglia revealing\nthe staining of nerve cells and satellite cells by protein\ncomplexed to the Evans Blue dye.