Catecholamine metabolites in spinal cord injury

Previous reports of catecholamine metabolism in spinal cord injury (SCI) have found elevated levels of urinary norepinephrine metabolites. These data have been cited as evidence of a sustained increase in peripheral norepinephrine activity in this population. A study was designed to test this hypothesis and to control for the effect of affective disorders on catecholamine metabolism. Determinations were made of the level of urinary 3-methoxy-4-hydroxyphenylethylglycol (MHPG) and vanillylmandelic acid (VMA) in 30 patients with SCI. Urinary MHPG and VMA were not significantly higher than normal in the total sample. However, in spastic quadriplegia, urinary MHPG was lower than normal, and a calculated VMA:MHPG ratio was higher than normal in complete quadriplegia and spastic quadriplegia. This high ratio was due primarily to decreased MHPG. The authors suggest that these changes are due to decreased norepinephrine turnover in the damaged SC and that a VMA:MHPG ratio is the most useful measure of norepinephrine activity in SCI.