Changes of bulbocavernosus sphincter reflex in male rabbit models of sacral spinal ischemia during early stage

Abstract

Objective To explore the changes of bulbocavernosus sphincter reflex (BCR) in male rabbit models of spinal cord ischemia injury of different levels at acute stage and their values in predicting spinal cord functions, and provide theoretical basis for protecting the spinal cord function by neurophysiology examination in clinical microsurgical operation. Methods Thirty-six adult New Zealand rabbits were randomly divided into 6 groups: a control group (n=6) was used to eliminate the effects of anesthesia and surgery on BCR; rabbits in the experimental group (n=30) were randomly divided into 5 groups (n=6) according to different levels of lumbar arteries being ligatured between the left renal artery and arterial bifurcate (subgroups of one, two, three, 4 and 5 lumbar arteries being ligatured). BCR was recorded continuously within two h of ligation; rabbits in each group were subjected to double-blind Tarlov lower limb motor function scale before and 2 d after surgery; and ischemic spinal cord specimens were performed hematoxylin and eosin (HE) staining to observe pathological changes in sacral spinal cord ischemic areas after 2 days. Results There was no significant difference in BCR amplitude and latency between different time points after anesthesia (P>0.05); there was no significant difference in BCR amplitude and latency between different time points before and after operation (P>0.05). There was no significant change in the amplitude of BCR before and after one lumbar artery ligation; however, the BCR amplitude immediately changed after ligaturing two, three, 4 or 5 lumbar arteries: the latency of BCR immediately began to extend and amplitude immediately began to reduce; amplitude was stable respectively after (0.7±0.4), (0.7±0.3), (0.7±0.3) and (0.6±0.3) min of ligation. The amplitude variation of BCR was positively correlated with Tarlov lower limb motor function scale scores 2 days after ligation (r=0.791, P=0.0001). HE staining showed that the normal sacral spinal cord structure was observed in the control group, subgroups of one and two lumbar arteries being ligatured; the basically normal sacral spinal cord structure was observed in the subgroup of three lumbar arteries being ligatured; the normal sacral spinal cord structure basically disappeared in the subgroup of 5 lumbar arteries being ligatured; the spinal cord injury of subgroup of 4 lumbar arteries being ligatured was between that of subgroup of three lumbar arteries being ligatured and subgroup of 5 lumbar arteries being ligatured. Conclusion The amplitude and latency of BCR in male rabbits are sensitive to sacral cord ischemic injury, which can help find ischemic injury in the reversible phase of the sacral cord ischemia and provide theoretical basis for the prevention of occurrence of male irreversible sacral spinal cord injury during microsurgery. Key words: Bulbocavernosus sphincter reflex; Intraoperative neurophysiology monitoring; Sacral spinal ischemia injury; Reversible stage; Male rabbit