Lower limb reflex changes in segmental epidural analgesia.

Sensory changes and lower limb reflexes were observed in 35 patients receiving segmental epidural analgesia in the mid-thoracic region. Sensory blockade was confined to the thoracic and upper lumbar segments. The lower limb reflexes changed to an "upper motor neurone' pattern, with the onset and development of segmental blockade. The sequence of changes observed was hypertonic tendon reflexes, then the onset of ankle clonus, and finally the plantar response changed to a positive Babinski sign. With regression of analgesia the reflexes returned to normal in the reverse order. The significance of these findings is discussed in relation to the anatomy of the descending spinal pathways, and to the pattern of penetration of local anaesthetics into the substance of the spinal cord.