Psoas sheath chemical neurolysis for management of intractable leg pain from metastatic liposarcoma

Case Report: A 56-year-old man with widely metastatic liposarcoma, after left lower extremity amputation, complained of severe right lower extremity pain. Trials of systemic opioids had resulted in poor pain control while introducing intolerable dose-limiting side effects. Methods and Results: Initial inpatient management consisted of a lumbar epidural infusion of a dilute local anesthetic and preservative-free morphine. This provided satisfactory relief but was discontinued because of recrudescence of phantom limb pain. A lumbar epidural infusion of preservative-free morphine sulfate was associated with poor pain relief, central nervous system (CNS) side effects, and severe urinary retention resulting in acute renal failure. A repeated trial of parental opioids provided marginal pain relief with persistent CNS side effects. Chemical neurolysis of the lumbar plexus was performed with 10 ml of 10% aqueous phenol injected into the psoas muscle sheath. The pain gradually resolved over a 2-day period without apparent side effects. Motor function was preserved, pain was resolved, and as systemic opioids were reduced, cognitive function and overall well-being were improved.