Diagnostic spinal anaesthesia in chronic spinal cord injury pain

In a double blind study, 21 patients with chronic spinal cord injury (SCI) pain underwent placement of a lumbar subarachnoid catheter and injection of placebo and lidocaine. The effects on pain intensity, distribution, altered sensations and sensory level of anaesthesia were monitored. Four patients responded briefly to placebo, while 13 demonstrated a mean reduction of pain intensity of 37.8 +/- 37% for a mean duration of 123.1 +/- 95.3 minutes in response to lidocaine. The pain response to subarachnoid lidocaine differed significantly (p less than 0.01) from placebo. Spinal anaesthesia was also associated with changes in pain distribution and altered sensation. A spinal anaesthetic-induced sensory level could not be achieved cephalad to the sensory level of neurological injury in 5 patients who presented with spinal canal obstruction. This study has demonstrated that response to diagnostic spinal anaesthesia in chronic SCI pain is complex, requiring individual interpretation in each patient and consideration of the following factors; symptomatology, etiology, pain perception, spinal canal anatomy, CSF chemistry and local anaesthetic pharmacology.