Presented at the 2012 AAPM Annual Meeting « Back

Epidural Lipomatosis as a Cause for High Impedance Values During a Neuromodulation Trial

Timothy T. Davis, MD, ttdavis23@gmail.com¹, Carolyn F. Schulz, MD², (1) The Spine Institute, Santa Monica, California, (2) Physical Medicine and Rehabilitation, Los Angeles, California

Introduction: Spinal cord stimulators have been used to treat a variety of pain conditions including chronic neuropathic limb pain. A neuromodulation trial typically involves lead placement and stimulation in the lower thoracic levels without major complication or drastic changes in impedance values. However, cases have demonstrated abnormally high impedance readings due to epidural fibrosis, abnormally large canal diameters, or burrowing into the ligamentum flavum. Spinal epidural lipomatosis is a rare pathological overgrowth of adipose tissue in the extradural space that has been linked to excess exogenous cortisol use or endogenous cortisol production. To date, there is limited published literature on how spinal epidural lipomatosis may affect impedance values during a neuromodulation trial. Case Report: We present a case of a patient with a thoracic epidural lipomatosis who failed a neuromodulation trial. During lead placement, significantly higher impedance values were noted in an area dorsal to the T8 vertebral body compared to adjacent levels. Leads were then successfully placed at the level above, but the intraoperative and patient trial failed to relieve her neuropathic pain between the waist and popliteal fossa. The leads were then removed without complications. A subsequent MRI of the thoracic spine revealed T8 dorsal epidural lipomatosis that directly correlated to the high impedance levels during the neuromodulation trial. Conclusions: Spinal epidural lipomatosis causes a dramatic increase in epidural impedance values, which may, in turn, lead to neuromodulation trial failure. Epidural lipomatosis should be considered as a possible cause of abnormally high impedance during a neuromodulation trial. References: 1)Fogel GR, Cunningham PY 3rd, Esses SI. Spinal epidural lipomatosis: case reports, literature review and meta-analysis. Spine J. 2005 Mar-Apr;5(2):202-11. 2)Zhang Y, Wood MJ, Gilligan C. Spinal cord stimulation in a patient with spinal epidural lipomatosis. Pain Med. 2011 Mar;12(3):377-81. 3)Danielson KD, Harrast MA. Focal spinal epidural lipomatosis after a single epidural steroid injection. PMR. 2011 Jun;3 (6):590-3. 4)de Jongste MJ, Nagelkerke D, Hooyschuur CM, Journée HL, Meyler PW, Staal MJ,de Jonge P, Lie KI. Stimulation characteristics, complications, and efficacy of spinal cord stimulation systems in patients with refractory angina: a prospective feasibility s 5)Lang SA, Korzeniewski P, Buie D, Du Plessis S, Paterson K, Morris G. Repeated failure of epidural analgesia: an association with epidural fat? Reg Anesth Pain Med. 2002 Sep-Oct;27(5):494-500. 6)Oakley JC, Prager JP. Spinal cord stimulation: mechanisms of action. Spine(Phila Pa 1976). 2002 Nov 15;27(22):2574-83. 7)Choi KC, Kang BU, Lee CD, Lee SH. Rapid progression of spinal epidural lipomatosis. Eur Spine J. 2011 Jun 11. 8)Alo, K., Varga C., Krames E.,Prager J., Holsheimer J, Monola L., Bradley, K. Factors Affecting Impedance of Percutaneous Leads in Spinal Cord Stimulation. Neuromodulation: Technology at the Neural Interface. Volume 9, Issue 2, pages 128–135, April 2 9)López-González A, Resurrección Giner M. Idiopathic spinal epidural lipomatosis: urgent decompression in an atypical case. Eur Spine J. 2008 Sep;17 Suppl 2:S225-7. 10)Chan JY, Chang CJ, Jeng CM, Huang SH, Liu YK, Huang JS. Idiopathic spinal epidural lipomatosis-two cases report and review of literature. Chang Gung Med J. 2009 Nov-Dec;32(6):662-7.

Funding: None