Chronic Pain Interventions — ESI, RFA, SCS, Sympathetic Blocks, CRPS

Steroid choice is safety-driven: particulate steroids (methylprednisolone, triamcinolone) carry the risk of catastrophic spinal cord or brainstem infarction if inadvertently injected into a radicular or vertebral artery — particles embolize.

Non-particulate dexamethasone is mandated by FDA for cervical transforaminal injections + strongly preferred for thoracic + high-lumbar transforaminal injections.

Live fluoroscopy + digital subtraction angiography to confirm absence of vascular uptake before injection.

Diagnostic medial branch blocks (lidocaine + bupivacaine onto the medial branches of the dorsal ramus innervating the joint above + below) — typically two confirmatory blocks before ablation to control for placebo response.

Radiofrequency ablation of the medial branches provides 6-12 months of relief in 60-80% of responders.

Pulsed RF (non-thermal, modulates without coagulating) used for dorsal root ganglion + selected peripheral nerves.

Sacroiliac joint RF + cooled RF for SI joint pain.

💉Traditional tonic stimulation produces paresthesia that masks pain (gate-control).

Newer paradigms: high-frequency 10 kHz (Nevro Senza) produces paresthesia-free analgesia; burst stimulation (intermittent bursts mimicking thalamic firing) similar.

DRG stimulation: leads targeting the dorsal root ganglion — superior for focal extremity pain + CRPS of foot/groin/knee, where dorsal column SCS coverage is unreliable (ACCURATE trial 2017).

💊Refill schedule + overdose risk: intrathecal overdose (refill into pocket instead of pump, programming error) presents as bradycardia + hypotension + respiratory depression + altered mental status → CSF drainage + naloxone infusion + supportive care; withdrawal from sudden pump failure is also dangerous — provide oral bridge dosing emergently.

Stellate ganglion block (C6 or C7 anterior approach with ultrasound or fluoroscopy): upper extremity CRPS, vasospastic disorders (Raynaud's), refractory ventricular arrhythmias (electrical storm — emerging indication), hot flashes, PTSD (off-label).

Confirms with Horner's syndrome on the blocked side.

Celiac plexus block + neurolysis: pancreatic cancer pain + other upper abdominal visceral pain — alcohol or phenol neurolysis for cancer pain.

Lumbar sympathetic block (L2-L3 paravertebral): lower extremity CRPS, peripheral vascular disease, phantom limb pain.

Superior hypogastric plexus block: pelvic cancer pain.

Ganglion impar block (sacrococcygeal): perineal + rectal cancer pain.

Complex regional pain syndrome diagnostic criteria (Budapest, validated 2010): continuing pain disproportionate to inciting event + at least one symptom in 3 of 4 categories + one sign in 2 of 4 categories at time of evaluation, categories being sensory, vasomotor, sudomotor/edema, motor/trophic, with no other diagnosis explaining the picture.

CRPS-I (no defined nerve injury, formerly RSD) vs CRPS-II (defined nerve injury, formerly causalgia).

Early recognition + early sympathetic blockade improve outcomes; delayed treatment risks permanent motor + trophic changes.

First-line: gabapentinoids (gabapentin 900-3600 mg/day divided TID; pregabalin 150-600 mg/day divided BID) OR SNRIs (duloxetine 60-120 mg/day, venlafaxine ER 150-225 mg/day) OR TCAs (amitriptyline/nortriptyline 10-100 mg HS — anticholinergic + cardiac side effects limit elderly use; nortriptyline better tolerated).

Second-line: topical lidocaine 5% patch (post-herpetic neuralgia, focal neuropathies — minimal systemic absorption), topical capsaicin 8% patch (PHN, painful diabetic neuropathy).

Third-line: tramadol (caution serotonin syndrome with SNRIs + TCAs; seizure risk).

Opioids are LAST line for chronic non-cancer neuropathic pain per CDC 2022 guidelines — use only when other modalities fail + with explicit risk-benefit documentation + opioid agreement + state PDMP check.