Regional Spinal Cord Blood Flow on Cord Traction:An Experimental Cat Model

Baik, Min Soo; Lee, Jae Soo; Park, Chun Kun; Jo, Tae Hoon; Kim, Moon Chan; Kang, Joon Ki; Song, Jin Un

Abstract

The tethered cord syndrome is a clinical entity manifested by progressive motor and sensory changes in the legs, incontinence, back or leg pain, and scoliosis in young children. Based on remarkable neurological improvement after release of cord tension by sectioning the filum, it might be concluded that the neurological deficit was effected by cord tethering. The main objective of this experiments was to elucidate the pathophysiology involved in the tethered cord by observing the effect of tethered cord on regional spinal cord blood flow(rSCBF) and somatosensory evoked potentials(SEPs) and define a threshold relationship between SEP and rSCBF. Thirty adult cats, weighing 2.7 to 4.2kg were used in this study. The cats were divided into three groups as follows: Control group=non-tethered(10 cats), 5g-traction group=cord traction with 5g weight(10 cats). 10g-traction group=cord traction with 10g weight(10 cats). The rSCBF and SEP measurements were performed immediately after cord traction in each animal, at 30, 60, 90, 120 minutes and the final rSCBF at 3 hours by the hydrogen clearance technique. The results obtained were as follows: 1. Traction and resulted in a reduction of flow to 30%(6.0+/-1.4ml/100g/min) of normal control spinal cord flow(18.2+/-1.6ml/100g/min) at adjacent area of traction(L1) in 5g-traction group and 18%(3.5+/-0.7ml/100g/min) of normal control flow in 10g-traction group during the cord traction for 3 hours. 2. From 30 minutes to 3 hours following the cord traction, there was a tendency toward marked reduction of the blood flow at the adjacent area(L1, T10) in 10-traction group. 3. The rostral area of spinal cord away from traction was less influenced in a reduction of blood flow following the cord traction. 4. A close correlation was found between spinal evoked potentials and flow suggesting a threshold relationship. 1) The SEP was present shortly after traction though marked by altered in shape and suppressed. 2) The SEP responses progressively decreased in latency at the adjacent distal area of the cord during traction, however less changed in shape at the rostral area of the cord. 3) The SEP suppressed in shape if the blood flow in spinal cord was below 14ml/100g/min. 4) The neuronal dysfunction caused by tethered cord could be due to impairment of blood flow. It is assumed that prolonged neuronal dysfunction may lead to structural damage of the neuron.