Deafferentation pain exacerbated by subarachnoid lidocaine and relieved by subarachnoid morphine. Case report.
OBJECTIVE
Neuropathic pain syndromes are often resistant to traditional pharmacologic treatment. The authors describe a patient with chronic deafferentation pain of the legs associated with peripheral neuropathy that was refractory to multidisciplinary pain clinic management.


METHODS
Numerous medications had been tried, including nortriptyline, mexiletine, and oral and parenteral opioids. Spinal cord stimulation was also ineffective, despite a satisfactory pattern of stimulation-induced paresthesias. For diagnostic purposes, differential spinal anesthesia with lidocaine and morphine was performed, with evoked potential monitoring used to evaluate the intensity of spinal anesthetic block.


RESULTS
Paradoxically, lidocaine spinal anesthesia exacerbated pain, whereas subarachnoid morphine provided rapid pain relief. Long-term pain control has been maintained with an implanted spinal infusion pump.


CONCLUSIONS
Evoked potential data acquired during lidocaine spinal anesthesia and the rapid pain relief provided by subarachnoid morphine suggest that deafferentation pain may involve segmental, opioid-sensitive dorsal horn pain generators. The long-term pain relief afforded the patient demonstrates that subarachnoid opioids may be efficacious for some forms of neuropathic pain.
Iacono
R P
RP
Department of Surgery, Loma Linda University School of Medicine, California.
Boswell
M V
MV
Neumann
M
M
D000328:Adult; D000775:Anesthesia, Spinal; D018432:Drug Resistance, Multiple; D004558:Electric Stimulation; D005073:Evoked Potentials, Somatosensory / Q000187:drug effects; D005260:Female; D006801:Humans; D015918:Infusion Pumps, Implantable; D007267:Injections; D008012:Lidocaine / Q000008:administration & dosage / Q000009:adverse effects*; D009020:Morphine / Q000008:administration & dosage / Q000627:therapeutic use*; D010146:Pain / Q000188:drug therapy* / Q000503:physiopathology; D018710:Pain Clinics; D010523:Peripheral Nervous System Diseases / Q000188:drug therapy* / Q000503:physiopathology; D013116:Spinal Cord; D013346:Subarachnoid Space
D009020:Morphine; D008012:Lidocaine