Nerve Blocks and Neurolysis

procedure

Common targets

• Sphenopalatine, occipital for headache

• Gasserian, trigeminal, mental for facial pain

• Alveolar for intraoral malignancy pain

• Glossopharyngeal for posterior tongue, hypopharynx, tonsillar CA

• Stellate ganglion for Raynauds, CPRS

• Thoracic sympathetics for phantom breast pain, hyperhidrosis

• Celiac plexus and/or splanchnics for visceral upper abdominal pain, e.g., pancreatic cancer

• Ilioinguinal, iliohypogastric for groin pain

• Medial branches for facet mediated back pain

• Superior hypogastric plexus for visceral pelvic pain, e.g., pelvic malignancy

• Ganglion impar for deep rectal pain

• Pudendals for superficial perirectal and perineal pain

• Anterior and/or lateral femoral cutaneous nerves for entrapment syndromes

• Lumbar sympathetics for vascular insufficiency LE at L2/3

Block (general)

• US, CT, and/or fluoro guidance with small gauge needle, e.g., 22 G. Nice to have patients conscious for immediate feedback such as testing with lidocaine. Reproducing the pain with needle position is also a good sign that this is the right target.

  • US works well for superficial targets such as the intercostals. Some nerves can be visualized with US such as the lateral femoral cutaneous.

  • Deeper targets tend to require CT such as the celiac plexus. Some have clear boney landmarks such as the superior hypogastric plexus, ganglion impar, or medial branches for facets and can be targeted more efficiently with fluoroscopic guidance.

• For CT and fluoro, a small amount of contrast is injected to confirm needle positioning.

• Aspirate to ensure the needle tip is NOT intravascular.

• Administer the block and remove the needle.

  • Generally an anesthetic such as lidocaine or bupivacaine plus a steroid. Kenalog should not be used around the spine because it is a particulate steroid which is embolic if inadvertently injected intravascularly. As such, dexamethasone is better choice around the spine.

  • I tend to use bupivacaine and dexamethasone for all blocks to keep it simple. The volume depends on the target, e.g., superior hypogastric plexus needs more volume so I do 10 mg (1 mL) dexamethasone in 19 mL bupivacaine. Ganglion impar is smaller target where I do 1 mL in 5 mL.

Neurolysis

• Lots of variation in approaches. Generally repeating the block but need to be more confident of positioning. For example, for the superior hypogastric plexus if done with fluoroscopic guidance I will do a cone beam CT to check the spread of contrast prior to injecting ethanol.

• Chemical vs RF vs cryoneurolysis - see above re pros and cons. I generally use ethanol for areas where I think I can do it safely and I want the treatment to spread over an area such as the superior hypogastric plexus. Other areas such as the celiac plexus or pudendals tend to be targeted better with thermal ablation.

• Celiac plexus vs splanchnics

  • Lots of variable here in terms of approaches, e.g., posterior with 2-4 needles vs anterior with one. Some only target the plexus antecrural while others also inject retrocrural which likely treats the splanchnics as well. Some will just target the splanchnics posteriorly because it’s an easier target while others use this as a plan B if targeting the celiac plexus does not provide sufficient pain relief.

  • Main risks are orthostatic hypotension and diarrhea that tend to be transient. Major complications in ~2% such as pancreatitis or nontarget nerve or vessel injury.

  • This target has the best data. Most data is on chemical neurolysis with 20-40 mL of ethanol or phenol. Ethanol is less viscous, transient pain at injection, faster onset. Phenol is more viscous, no pain at injection, slower onset requiring less volume.

  • Cryoneurolysis has gained popularity with two 8-10 min freeze cycles and 3-5 min passive thaws. It may provide better coverage of the plexus with less side effects (5% transient diarrhea vs 20% with ethanol). However, cryoneurolysis requires general anesthesia with an a-line because it can cause dramatic changes in blood pressure during the treatment. Often hypotension during the freezes, particularly the first, and hypertension during the thaw. This normalizes quickly so it’s important to not over correct in either direction and use short acting agents.

• Pudendals

  • Most data here uses thermal ablation rather than chemical. Pulsed RF is promising to target neuromodulation rather than neurolysis to preserve innervation to the pelvic floor musculature and external sphincters for continence.

  • Cryoneurolysis tends to use two 8 min freeze cycles and 3 min passive thaws. Need to warn patients of complete anesthesia to the perineum and potential issues with bladder and bowel continence due to loss of tone to external sphincter. This tends to be transient and improve with a short course of steroids if it occurs.

• Intercostals

  • Generally target at least 2 cm lateral to transverse process of vertebra. For chemical neurolysis there are rare reports of central spread and paralysis, so I only use ethanol is treating more laterally and am careful to not use too much volume, e.g., 5 mL ethanol per level.

  • Cryoneurolysis tends to use 8-3-3-3 min freeze-thaw cycles though lots of reported variation here.