The changes in human spinal sympathetic preganglionic neurons after spinalcord injury

We have applied conventional histochemical, immunocytochemical and morphome tric techniques to study the changes within the human spinal sympathetic pr eganglionic neurons (SPNs) after spinal cord injury. SPNs are localized wit hin the intermediolateral nucleus (IML) of the lateral horn at the thoraco- lumbar level of the spinal cord and are the major contributors to central c ardiovascular control. SPNs in different thoracic segments in the normal sp inal cord were similar in soma size. SPNs in the IML were also identified u sing immunoreactivity to choline acetyltransferase. Soma area of SPNs was 4 00.7+/-15 mu m(2) and 409.9 +/- 22 mu m(2) at the upper thoracic (T3) and m iddle thoracic (T7) segments, respectively. In the spinal cord obtained fro m a person who survived for 2 weeks following a spinal cord injury at T5, w e found a significant decrease in soma area of the SPNs in the segments bel ow the site of injury: soma area of SPNs at T8 was 272.9 +/-11 mu m(2). At T1 the soma area was 418+/-19 mu m(2) In the spinal cord obtained from a pe rson who survived 23 years after cord injury at T3, the soma area of SPNs a bove (T1) and below (T7) the site of injury was similar (416.2+/-19 and 425 .0,+/-20 mu m(2) respectively). The findings demonstrate that the SPNs in s pinal segments caudal to the level of the lesion undergo a significant decr ease of their size 2 weeks after spinal cord injury resulting in complete t ransection of the spinal cord. The impaired cardiovascular control after sp inal cord injury may be accounted for, in part, by the described changes of the SPNs. The SPNs in spinal segments caudal to the injury were of normal size in the case studied 23 years after the injury, suggesting that the atr ophy observed at 2 weeks is transient. More studies are necessary to establ ish the precise time course of these morphological changes in the spinal pr eganglionic neurons.