Is sacral neuromodulation (SNM) the same as spinal cord stimulation (SCS)?

Sacral Neuromodulation vs. Spinal Cord Stimulation: Distinct Neuromodulation Techniques

No, sacral neuromodulation (SNM) and spinal cord stimulation (SCS) are not the same - they are distinct neuromodulation techniques that target different anatomical structures and are used for different primary indications.

Key Differences Between SNM and SCS

Anatomical Target

• Spinal Cord Stimulation (SCS):

  • Targets the dorsal columns of the spinal cord
  • Electrodes are placed in the epidural space of the spinal cord
  • Typically placed at thoracic or cervical levels depending on pain location 1

• Sacral Neuromodulation (SNM):

  • Targets specifically the sacral nerves (typically S3)
  • Electrodes follow the trajectory through the third sacral foramen
  • Acts on peripheral sacral nerve roots rather than the spinal cord itself 2

Primary Indications

• Spinal Cord Stimulation:

  • Primarily used for chronic neuropathic pain conditions
  • Indicated for failed back surgery syndrome, complex regional pain syndrome (CRPS)
  • Also used for peripheral neuropathic pain, peripheral vascular disease, and postherpetic neuralgia 1
  • Considered for truly refractory neuropathic pain when conservative approaches have failed 1

• Sacral Neuromodulation:

  • Primarily used for urological and pelvic disorders
  • Indicated for overactive bladder syndrome and non-obstructive urinary retention
  • Also used for fecal incontinence and certain types of pelvic pain
  • Emerging applications in neurogenic lower urinary tract dysfunction 2, 3

Mechanism of Action

• SCS: Works primarily through the gate control theory of pain, modulating pain signals as they travel up the spinal cord to the brain 4

• SNM: Acts through modulation of spinal cord reflexes and brain networks via peripheral afferents, primarily affecting bladder and bowel function 2, 5

Clinical Application Considerations

Device and Implantation Differences

• SCS:

  • Typically involves placement of leads in the thoracic or cervical epidural space
  • Multiple stimulation paradigms available: tonic, burst, and high-frequency stimulation
  • Requires psychological clearance before implantation 6

• SNM:

  • Involves a two-stage implantation technique
  • Quadripolar lead positioned through the S3 foramen under fluoroscopy
  • Can be performed under local or general anesthesia with the patient in prone position 2

Overlapping Applications

While these are distinct techniques, there is some overlap in certain applications:

• Both can be used in certain pain conditions, though SCS has more robust evidence for pain management
• SNM has shown efficacy in treating intractable pelvic pain associated with cauda equina syndrome 7
• Both techniques require a trial period before permanent implantation 1, 2

Clinical Decision Making

When deciding between these technologies:

1. Consider the primary symptom:

   • Predominant neuropathic pain → SCS
   • Predominant bladder/bowel dysfunction → SNM
   • Mixed pelvic pain with urological symptoms → Consider SNM 7

2. Evaluate anatomical location:

   • Widespread pain or pain in limbs/trunk → SCS
   • Pelvic-specific symptoms → SNM

3. Review treatment history:

   • Failed conservative pain management → SCS
   • Failed urological/bowel management → SNM

Important Considerations

• Both techniques require specialized expertise and should be performed by physicians with specific training
• Both require a trial period before permanent implantation to assess efficacy
• Neither technique should be considered first-line therapy; they are typically used after failure of more conservative approaches
• The cost and potential for mechanical complications are limiting factors for both technologies 4

In summary, while both SNM and SCS are neuromodulation techniques, they target different neural structures, have different primary indications, and should be considered distinct therapeutic options with some overlapping applications.