Chapter 72: Anterograde Versus Retrograde Lead Placement

INDICATIONS

The discussion for an anterograde approach versus a retrograde approach to lead placement for spinal cord stimulation (SCS) has evolved in relationship to optimal coverage for pelvic pain conditions. Early attempts to treat bladder pain focused on retrograde placement of SCS leads to the S3 foramen. Unfamiliarity of many practitioners with this technique, the more difficult technical aspects, and the variable anatomy of the sacrum have all posed challenges to this approach. Anterograde placement with lead positioning at the T10-T12 levels has shown great promise in pelvic pain structure coverage. It is now known that retrograde placement is actually a peripheral nerve stimulation performed within the spinal canal by stimulating specific sacral nerves. Whereas anterograde placement is true spinal cord stimulation giving rise to stimulation paresthesia not only in the pelvic distribution but also in the lower extremities. Anterograde stimulation produces an electrical field at the spinal cord activating all known mechanisms of action, whereas it is highly unlikely that peripheral nerve stimulation activates as many different mechanisms of action.

Indications for retrograde placement/anterograde placement include:

• Interstitial cystitis, urge incontinence, urgency/frequency

• Postoperative pelvic pain/pelvic adhesions

• Endometriosis

• Postradiation pelvic pain

• Vulvodynia

• Vaginal pain

• Coccydynia

CONTRAINDICATIONS

The basic procedural/surgical contraindications hold for a trial of retrograde or anterograde SCS. These include:

• Anticoagulation

• Thrombocytopenia

• Immunocompromised patient

• Sepsis

• Localized infection at or near insertion site

Added contraindications specific to SCS include:

• Implanted cardiac defibrillator

• Inability to use or understand the equipment

• Need for ongoing repeat MRIs

• Untreated psychiatric or addiction issues

RELEVANT ANATOMY

Pelvic Innervation

1. Sympathetic (T12-L2)

   1. Superior hypogastric plexus—largest sympathetic contribution

   2. Sympathetic chain—gray rami communicantes connect to sacral ventral primary rami

   3. Sacral splanchnic nerves—smaller contribution of sympathetics to pelvic viscera

2. Parasympathetic

   1. S2, S3, S4

      1. Inferior hypogastric plexus—preganglionic

      2. Postganglionic fibers innervate distal colon, rectum, bladder, genital organs

All pelvic viscera receive dual innervation, sympathetic and parasympathetic. Both converge at the inferior hypogastric plexus and are redistributed either directly to target organs within the plexus or via smaller subsidiary plexuses.

3. Somatic efferent and afferent innervation to the pelvis

   1. S2-S4

There is a recognized midline dorsal column pathway within the spinal cord that mediates the perception of visceral pain and if interrupted relieves visceral pelvic pain in cancer patients. Therefore, SCS systems and settings that can drive stimulation deeper into the dorsal spinal cord may respond better. Recent studies have shown higher pulse width settings drive activation of the more medial fibres and may be optimized at 900 to 1000 ms. Thus, anterograde stimulation at T11-T12 with high pulse widths may represent the best potential for achieving a bilateral pelvic analgesic response. This is in distinction to a unilateral discreet activation that may be achieved with retrograde stimulation of individual sacral nerve roots.

PREOPERATIVE ...