Aseptic arachnoiditis in a patient treated with intrathecal morphine infusion: symptom resolution on switch to...

Since 1980, about 95,000 intrathecal (IT) drug delivery pumps have been implanted for the administration of a variety of opioid and non-opioid agents for neuropathic and nociceptive pain patients. IT granuloma in chronic opioid infusion is becoming less rare as an adverse effect of IT therapy and has been associated with many analgesic infusion agents.

After thymectomy, upper left lobectomy, and pericardial resection, our patient developed a left hemithorax nociceptive pain. An IT catheter and infusion pump were implanted, providing adequate analgesia. After eight months, the patient developed pain in the lower extremities without neurological impairment and an urge to move the legs without meningeal signs (3.2 mg morphine/day). A lumbar puncture revealed an inflammatory reaction in the cerebrospinal fluid (CSF); neuroimaging results were negative for granuloma. Reduction in morphine dose and a switch to ziconotide infusion were carried out. Nine months after the switch, CSF test values were in normal ranges. The patient described ongoing benefit in terms of pain and walking ability.

The patient reported restless legs and leg pain, causing insomnia and necessitating an increase in IT opioid dose. After the switch to ziconotide and morphine discontinuation, inflammatory reactions and symptoms in the CSF abated.

CSF analysis should be performed in patients chronically treated by IT infusion who develop a rapid increase in pain with or without neurological deficits. A switch to ziconotide can be an option in patients without neurological signs. Further studies are needed to determine the relationship between granuloma formation and CSF reaction.