Spinal Vessels

Three arteries supply the spinal cord, an anterior spinal in the median line of the anterior surface and two posterior spinal just behind the posterior spinal roots (Fig. 489). The veins are more numerous. They consist of three sets or plexuses, one on the cord in the meshes of the pia mater, another in the spinal canal between the dura mater and the bone, and the third on and around the outside of the vertebrae. The veins on the cord in the anterior and posterior median fissures communicate above with the veins of the medulla. The lateral veins empty through the radicular veins which accompany the spinal nerve roots. The veins in the spinal canal form anterior and posterior plexuses between the dura and bone and communicate with the extraspinal plexuses around the laminae and spinous processes posteriorly (dorsi-spinal veins) and the plexus around the bodies anteriorly.

Fig. 487.   Spinal cord enclosed in unopened dural sheath lying within vertebral canal; neural arches completely removed on right side, partially on left, to expose dorsal aspect of dura; first and last nerves of cervical, thoracic, lumbar. and sacral groups are indicated by Italic figures; corresponding vertebrae by Roman numerals. (Piersol).

Fig. 487. - Spinal cord enclosed in unopened dural sheath lying within vertebral canal; neural arches completely removed on right side, partially on left, to expose dorsal aspect of dura; first and last nerves of cervical, thoracic, lumbar. and sacral groups are indicated by Italic figures; corresponding vertebrae by Roman numerals. (Piersol).

Spinal Hemorrhage

Spinal hemorrhages, though sometimes caused by disease, are usually the result of injury. They frequently accompany fractures and dislocations. They may be either extradural, intradural, or in the cord - haematomyelia. They exist either coincident with the original injury or appear within a few hours.

Spinal hemorrhages are rarely large and those in the substance of the cord are the more common. They are usually venous. Extradural hemorrhage comes from the plexuses between the dura and bone and the clot may extend through the intervertebral foramina. It is usually of small extent and practically does not produce paralysis from pressure on the cord, hence operation for its relief is useless. Intradural hemorrhage comes from the vessels of the pia and may invade not only the subarachnoid but also the subdural space. It may remain localized at the site of injury or the blood may sink and fill a considerable portion of the spinal canal. Owing to the looseness of the cord in its dural sheath the hemorrhage spreads and does not usually give rise to pressure symptoms, hence operation is rarely advisable. Large hemorrhage sometimes comes down from cerebral apoplexy or injuries. Haematomyelia. - Hemorrhage into the substance of the cord may be caused by extension or accompany the contusion due to dislocation or fracture. The paralysis which follows serious injuries of the spine is usually due to hemorrhage into the gray or white matter of the cord. The gray matter being the softer is the more frequently affected, the blood penetrating it for quite a distance. Hemorrhage into the gray matter destroys it and produces an incurable paralysis. When into the white matter restoration of function through absorption may occur in from four to six weeks. In either case operation usually is of no service. The location of the hemorrhage will be revealed by the interference with the functions of the cord. The hemorrhage can occur in the form of a column of blood infiltrating the gray matter of several segments in one or both directions from the starting-point. The longer extension is usually toward the brain. It is usually limited to one side of the cord. Generally in small and sometimes in large hemorrhages the effect is mainly mechanical, but especially large hemorrhages may be surrounded by areas of softening.

Fig. 488.   Upper part of spinal cord within dural sheath, which has been opened and turned aside; ligamenta denticulata and nerve roots are shown as they pass outward to dura. (Piersol).

Fig. 488. - Upper part of spinal cord within dural sheath, which has been opened and turned aside; ligamenta denticulata and nerve-roots are shown as they pass outward to dura. (Piersol).