What types of pain are treated by a lumbar sympathetic block?

Types of Pain Treated by Lumbar Sympathetic Block

Lumbar sympathetic blocks (LSBs) are primarily used to treat visceral pain, sympathetically maintained pain, and complex regional pain syndrome (CRPS) affecting the lower extremities. 1

Primary Indications

Visceral Pain

• Cancer-related visceral pain: LSBs are effective for visceral pain originating from abdominal and pelvic structures 1
• Pelvic pain of visceral origin: Used as an adjuvant therapy to decrease the use of oral/parenteral analgesics 1

Sympathetically Maintained Pain

• Complex Regional Pain Syndrome (CRPS): Particularly effective for CRPS type 1 affecting the lower limbs 2, 3
• Neuropathic pain: Effective for certain cases of lumbosacral radiculopathy and peripheral neuropathies 1

Vascular Conditions

• Ischemic pain: May be considered in patients with critical limb ischemia for whom revascularization is not an option 1

Mechanism and Effectiveness

LSBs work by disrupting the sympathetic nervous system's contribution to pain, which is particularly important in:

1. Visceral pain transmission: Blocking sympathetic fibers can reduce pain signals from internal organs
2. Sympathetically maintained pain: Interrupting the abnormal sympathetic activity that perpetuates pain and vasomotor changes

Duration and Considerations

• Standard LSBs with local anesthetics typically provide temporary relief (hours to days)
• Neurolytic LSBs can provide longer-lasting relief (3-6 months) but are generally reserved for patients with short life expectancy, such as those with advanced cancer 1
• Adding botulinum toxin (particularly type B) can significantly prolong the sympathetic blocking effect (median 69 days) compared to standard blocks 3

Predictors of Response

Certain clinical features may predict response to LSB:

• Negative predictors: The presence of allodynia and hypoesthesia suggests poorer outcomes 4
• Temperature differential: Contrary to common belief, neither cold nor warm type CRPS, nor the degree of temperature change after block, reliably predicts treatment success 4

Potential Side Effects

LSBs are generally safe but can cause transient side effects in up to 84% of patients, including:

• Headache, dysphagia, backache
• Transient increase in pain
• Nausea, blurred vision
• Hoarseness, hematoma at puncture site 4

Clinical Application Algorithm

1. First-line use: Consider LSB for patients with:

   • CRPS of the lower extremity not responding to standard treatments
   • Cancer-related visceral pain in the abdomen or pelvis
   • Ischemic pain in "no-option" critical limb ischemia patients

2. Technique selection:

   • For diagnostic or short-term relief: Standard LSB with local anesthetic
   • For longer-term relief in cancer patients: Consider neurolytic LSB
   • For prolonged relief in non-cancer pain: Consider LSB with botulinum toxin type B 3

3. Frequency of administration:

   • Most pain physicians perform 1-3 consecutive blocks
   • Repeat blocks are typically considered if the patient receives at least 50% pain relief lasting 1-7 days 5

Important Considerations

• LSB should be part of a comprehensive pain management strategy rather than used in isolation
• For cancer pain, LSB is an adjuvant therapy that can help reduce systemic analgesic requirements 1
• Lumbar sympathectomy (surgical or chemical) is now rarely performed and considered largely of historical interest in current clinical practice 1

Remember that patient selection is crucial for successful outcomes with LSB, and the presence of allodynia or hypoesthesia may indicate a lower likelihood of success.