J. Anat., Lond. (1964), 98, 1, 105-116 105 With 4 plates and 3 text-figures Printed in Great Britain The blood supply of the lumbar and sacral plexuses in the human foetus* BY M. H. DAYt Department of Anatomy, Royal Free Hospital School of Medicine INTRODUCTION The existence of a blood supply to peripheral nerve is well established. Recently, a number of authors have reviewed the literature of the field, among them Blunt (1956) and Abdullah (1958), who from their own observations have confirmed that peripheral nerves are supplied by regional vessels reinforcing longitudinally arranged channels which freely anastomose with each other. There is also evidence that posterior root ganglia are particularly well supplied with blood vessels (Abdullah, 1958), but the precise distribution and arrangement of arteries to some individual nerve trunks and plexuses is still in need of investigation. The literature reveals few references to the blood supply of the lumbar and sacral plexuses. The distribution of arteries to the roots and ganglia of the sacral nerves was noted by Haller (1756), but the most important contributions in this field were those of Bartholdy (1897) and Tonkoff (1898), whose observations on the lumbar and sacral plexuses form part of a general survey of the blood supply of peripheral nerve in man. They cited the lumbar, ilio-lumbar, median and lateral sacral arteries as well as the gluteal and pudendal vessels as sources of supply, but gave no indication of the frequency of these contributions. Subsequent authors including Hovelacque (1927), dealt briefly with the distribution of the lateral sacral, median sacral, gluteal and pudendal arteries to the sacral plexus, but treated more fully the blood supply of the sciatic nerve. Although Adachi (1928), described the distribution of the intra-pelvic arteries in some detail, he made no reference to the blood supply of nerves. It appears that there is nowhere a fully documented account of the blood supply of the lumbar and sacral plexuses, and accordingly a re-assessment of the matter has been undertaken. The problem is of anatomical interest and may be of clinical significance, since ischaemic damage to nerve has been reported in obliterative vascular disease (Roberts, 1948), cryopathy (Denny-Brown, Adams, Brenner & Doherty, 1945), peripheral nerve injuries (Richards, 1954) and nerve compression syndromes (Bowden & Gutmann, 1949). MATERIALS AND METHODS Material was obtained from 18 stillborn foetuses of ages ranging from 18-40 weeks, from one neonatal autopsy, and from an adult. * The results of this investigation were presented as part ot a thesis for which the degree of Ph.D. was awarded by the University of London in May 1962. t Present address: Department of Anatomy, The Middlesex Hospital Medical School, London, W. 1. 106 M. H. DAY In 15 foetuses Neoprene rubber latex, diluted with distilled water to produce a 75 % solution, was injected through the descending thoracic aorta; in 7 cases red dye was added to the solution, and in 8 India ink. Fourteen of the foetuses were injected using a manometrically controlled injection apparatus, and one by means of a hand syringe. The injection pressures were limited to 100 mm. Hg in foetuses over the age of 20 weeks and to 80 mm. Hg under that age; the injections were judged to be complete when small skin vessels of the back and feet were filled with the injection mass. The systemic venous system of one 20-week foetus was injected through the right atrium with rubber latex and India ink at a maximum pressure of 50 mm. Hg. Following injection, the lumbar spine, sacrum and pelvis were removed en bloc and fixed in 10 % formalin for 3-4 weeks. The lumbar and sacral plexuses and their blood vessels were dissected with the aid of operating spectacles and a dissecting microscope. When the intervertebral foramina were reached lam- inectomy was performed and the contents of the intervertebral canals exposed by nibbling away the pedicles of the vertebrae. Finally, the dura mater and the arachnoid were opened to expose the spinal cord and the cauda equina. After complete dehydration in graded alcohols and chloroform the specimens injected with rubber latex and India ink were cleared in tetrahydronaphthalene (Torr, 1957), to reveal the finer vessels and obtain a three dimensional view of their distribution. The intrinsic vascular arrangements were studied histologically in one adult, and in 3 foetuses whose ages ranged from 22 to 31 weeks. Blunt's modification of Pick- worth's method (sodium nitroprusside benzidine stain), MacConaill's FALG and MG blue methods (MacConaill & Gurr, 1960), and the FALGOSE method (MacConaill, 1961), were used. RESULTS The lumbar and sacral plexuses of nerves obtain their blood supply from the nearest available vessels, all of which originate indirectly from the abdominal aorta. The arterial blood supply of the roots and ganglia of the lumbar and sacral nerves The first to the fourth lumbar nerves may be grouped together, as a similar pattern of supply was found at each of these segmental levels. Lumbar spinal arteries commonly arose from the posterior division of the lumbar artery, and entered the intervertebral foramen in relation to the segmental nerve. The arteries supplying the nerve roots and ganglia were derived from the lumbar spinal arteries or, much less frequently, from the corresponding lumbar arteries directly. The segmental pattern of blood supply shown for the upper four lumbar nerves was interrupted caudally at the level of the bifurcation of the aorta. Fifth lumbar arteries were present on both sides in 9 of 15 foetuses. On the left the fifth lumbar nerve roots and ganglia were supplied by the lumbar artery through its spinal branch in nine cases and by the ilio-lumbar artery in the other six. On the right side the fifth lumbar nerve roots were supplied by the fifth lumbar spinal artery, the fifth lumbar artery, the ilio-lumbar or the superior gluteal artery in the ratios of 4:2:8:1. The right fifth lumbar ganglia were supplied by the same group of vessels in the ratios of 3:2:9:1 (Table 1). Blood supply ofplexuses in human foetus 107 As in the lumbar region, the vascular supply of the sacral roots and ganglia was basically segmental (Text-fig. 1). The lateral sacral artery supplied the sacral nerve roots in 38 of 55 roots of the left, and in 37 of 62 on the right side. With regard to the other vessels involved, on both left and right sides, the superior gluteal arteries were responsible for the supply of the sacral roots (left 12/55, right 10/62); less commonly the supply to the roots came from inferior gluteal artery (left 8/55, right 3/62), the ilio-lumbar artery (left 4/55, right 3/62), the median sacral artery (left 1/55, right 7/62) and the internal iliac arteries (left 2/55, right 2/62). The sacral ganglia were supplied by the lateral sacral artery 34/56 times on the left side and 37/61 times on the right side; the superior gluteal artery supplied the ganglia (left 12/56, right 10/61), less commonly the supply came from the inferior gluteal artery (left 8/56, right 3/61), the ilio-lumbar artery (left 4/56, right 3/61, the median sacral artery (left 1/56, right 5/61) and the internal iliac artery (left 2/56, right 3/61). Text-fig. 1. The left side of the true pelvis of a full-term foetus, showing the distribution of arteries to the ventral rami forming the sacral plexus. (Drawn from an injected specimen.) When these results were combined and tabulated (Table 1), it was clear that vessels which were not segmental in origin tended to be distributed over a group of successive segments. Thus the superior gluteal artery was distributed to the roots and ganglia of the fifth lumbar to the third sacral segments (inclusive), whilst the inferior gluteal artery was distributed to the corresponding structures from the second to the fourth sacral segments. Table 1 demonstrates that the roots and ganglia between the 108 M. H. DAY fifth lumbar and the third sacral segmental level received their arteries from a variety of sources, but there appeared to be neither profusion nor poverty of blood supply to any nerve, or group of nerves, in this region. The arrangement of the lumbar and sacral spinal arteries Three principal groups of branches were derived from each spinal artery or its parent stem. These included branches to the vertebrae, the posterior root ganglia and the nerve roots. Branches to the vertebrae. At each lumbar and sacral segmental level a vertebral branch arose and passed through the intervertebral foramen anterior to the seg- mental nerve roots. This branch divided into superior and inferior subdivisions which anastomosed with vessels entering foramina both cephalic and caudal to it, as well as with vessels from the opposite side. These arteries were distributed to the vertebral bodies forming an anastomotic network on the anterior wall of the spinal canal. (Pls. 1-3). Branches to the ganglia. These arteries arose from the posterior divisions of the lumbar arteries or from lumbar spinal arteries, in a plane posterior to the vessels to the vertebrae and ran directly to the ganglia. In the sacral region, branches to the ganglia originated from vessels supplying the intra-spinal portion of the nerve roots, these latter vessels arose from the spinal branches of the sacral segmental vessels. This alteration in the basic pattern resulted from changes in the positions of the ganglia at different levels (see below). Arteries entered the ganglia by piercing their sheaths at the poles or the equatorial region; other vessels did not pierce the ganglion sheath but continued over its surface to supply the dural root sleeves and the spinal dura (Text-fig.