In Situ Spinal Cord Stimulator for Post Thoracotomy Pain Maunak V. Rana, M.D.*, N. Nick Knezevic, M.D., Ph.D., Andrew Germanovich, D.O.

Department of Anesthesiology, Advocate Illinois Masonic Medical Center, Chicago, IL 60657 USA *Clinical Assistant Professor of Anesthesiology, University of Illinois, Chicago, IL 60612 USA

Abstract

Introduction

Contact

DiscussionCase Description

Figure 1.

Program Area Freq (Hz)

PW (s)

Polarities Perception(mA)

Comfort (mA)

Max Tol(mA)

1 Left Lower Extremity 60 250 +-+0 0000 0000 0000

5.20 10.10 15.00

5 Left Lower Extremity 60 250 +-+0 0000 0000 0000

5.20 10.10 15.00

5 Left Lower ExtremityLeft Thoracic Region (T7-T10)

60 300 0000 00-+0000 0000

1.30 1.70 2.10

Program 1 Program 5

T7

T8

T9

T10

T11

Chronic pain after thoracic surgery is a significant problem in 25-60% of patients,1 seen after lung and coronary bypass surgeries or thoracic entities, such as slipped rib syndrome.2

The current treatments include opioid therapy or cryoanalgesia. Risks of chronic opioid therapy are sedation and respiratory depression. Cryoanalgesia on the other hand can lead to intercostal neuralgia and neuritis.3,4

A 39 year old female with Complex Regional Pain Syndrome (CRPS) I of the left lower extremity presented to our clinic with chronic 9/10 pain. The patient developed CRPS after being struck by a motor vehicle. Conservative management with opiods and popliteal/sciatic nerve blocks provided short term relief. Mutual decision was made to proceed with SCS as a long term treatment modality.

Slipping rib syndrome1 results from rib injury that may persist even without evidence of trauma. This condition is more common in females and affects ribs 8,9,10 due to cartilaginous laxity. Patients initially describe sharp pain followed by a dull, achy discomfort. Clinically, the presence of a mobile rib segment on palpation or with a “hooking” maneuver may help diagnose this entity. Treatment is conservative with rest, analgesics or rib belt, but may require surgical rib removal with persistent discomfort. Intercostal nerve blocks may provide temporary relief for persistent pain and cryoanalgesia can be used for longer pain-free intervals. The latter procedure carries a risk of neuritis and may exacerbate patient’s pain. Our patient had discomfort over the rib site that corresponded to placement of SCS lead. Trial of parameter adjustment was performed to capture the patient’s area of complaint, likely due to injury of intercostals (branches of thoracic spinal nerves) at the corresponding surgical sites. We were able to cover the lateral rib pain by use of the inferior contact points. Stimulation parameters in the inferior lead are lower than in the more midline placed portion of the lead due to the more lateral location of the electrical contacts. Summation of electrical signal may be occurring in this setting as the patient desired concurrent lower extremity and thoracic stimulation. A cycle mode5 was utilized to conserve battery life given the stimulation of both areas. This mode was also added to decrease the risk of accommodation and tachyphylaxis to the effect of stimulation.  

We present the first case of successful treatment of post thoracotomy pain following rib resection for slipped rib syndrome with the use of a spinal cord stimulator (SCS) previously implanted for another chronic pain condition. We present our approach to management and SCS parameters used to achieve lasting pain relief in our patient.

Maunak V. Rana, M.D.Department of AnesthesiologyAdvocate Illinois Masonic Medical Center 836 W. Wellington Ave., Suite 4815Chicago, IL 60657Phone: (773) 296-3741E-mail:maunakr@gmail.com

After completion of the SCS revision, the patient complained of discomfort on the left lower ribcage. It was localized to the area of previous rib trauma in the posterior thoracic region (T9/T10). Her rib discomfort continued on subsequent visits and initial SCS program settings did not alleviate her pain. The patient was noted to have hypermobile T9/T10 ribs on hooking maneuver during physical examination. She underwent local anesthetic/steroid injections of intercostal nerves with short-term relief. A CT scan did not reveal any fractures, and the patient was diagnosed with slipped rib syndrome. She eventually underwent thoracotomy with resection of 2 ribs. Following surgery the patient developed even more pain, fullness, swelling, and decreased skin sensation over the surgical site.

The stimulator setting was adjusted in attempt to recruit peripheral fibers to target the patient’s area of discomfort as the stimulator placement was off midline. A subprogram was added with 60Hz, 300 μs, 0000 00-+ with perception at 1.30mA and comfort at 1.70 with max tol of 2.10mA (Figure 2, Table 1). This adjustment provided the patient stimulation over the surgical scar site, decreased pain, without affecting tactile sensitivity. The patient’s pain has remained decreased during one year follow up and she has continued to do well with her initial presenting symptoms of CRPS of the left lower extremity.

The patient underwent successful SCS trial during which her pain level was rated as satisfactory. Patient elected to proceed with a permanent implant of a single Octrode™ with Eon Mini ™ generator at the T7 level (St. Jude Neuromodulation, Plano, Texas). Despite the initial success, this implant required revision due to lead migration following another unrelated chest wall trauma 4 weeks after SCS implantation (Figure 1). We replaced the lead at the T7 level, but were unable to get a true midline placement for anatomical reasons. Intraoperative testing revealed variation of anatomical and physiologic midline in our patient. Testing revealed parasthesia at 60 Hz, 250 μs, with +-+0 0000 with perception at 5.20 mA and max tol of 11.80mA.

Conclusion

Figure 2.

In our case an in situ SCS provided significant lasting pain relief over the surgical scar, despite decreased remaining sensitivity. While an off midline lead placement may not be ideal in every situation, a review of the effect of varying stimulation parameters allowed for coverage of the patient’s physically disparate locations of discomfort. Side effects associated with other therapies (sedation, respiratory depression, constipation) were avoided and the patient has persisted with benefit with no side effects from stimulation and able to continue with her active lifestyle.

Table 1.

References

1. Wildgaard K, et al. Eur J Cardiothorac Surg 2009;36:170-80.2. Udermann BE, et al. Lancet 1986;1:2773. Conacher ID, et al. J Cardiothor Surg 2001; 20:502-7.4. Moorjani N et al. Eur J Athl Train 2005;40:120-2.5. Nicholson CL. Acta Neurochir Suppl 2007;97:71-7.