Sympathetic Blocks & Neurolysis

Sympathetic Block Techniques

Sympathetic blocks target the paravertebral and prevertebral ganglia of the autonomic nervous system. The sympathetic chain originates from neurons at T1 through L2-L3, forming ganglia along the vertebral column that converge at the coccyx as the ganglion impar. Prevertebral ganglia exist in the preaortic celiac, superior mesenteric, and inferior mesenteric plexuses. A key anatomic advantage in the cervical and lumbar regions is that sympathetic structures are physically separated from somatic nerves, allowing selective sympathetic blockade without somatic sensory loss. This separation does not exist in the thoracic region, where the sympathetic chain lies close to somatic nerves, neuraxial structures, and the pleura.

Stellate Ganglion Block

1. Patient positioning: Supine
2. Target: Anterolateral aspect of the C6 transverse process (Chassaignac's tubercle). The needle target is C6 even though the stellate (cervicothoracic) ganglion itself lies at C7-T1 — injectate diffuses inferiorly along the longus colli fascia. C6 is preferred because it avoids the vertebral artery (which enters the C6 transverse foramen) and the apical pleura at C7
3. Imaging: Fluoroscopy or ultrasound guidance
4. Anatomy: The stellate ganglion supplies sympathetic fibers to the C7, C8, and T1 anterior rami and brachial plexus, with visceral branches to the inferior cardiac nerve and cardiac plexus
5. Indications: Sympathetically mediated conditions of the head, neck, upper chest, and upper extremities (e.g., upper extremity CRPS); also used for refractory angina, ventricular arrhythmias, and PTSD
6. Confirmation of success: Ipsilateral Horner syndrome (miosis, ptosis, and anhidrosis) indicates successful sympathetic blockade

Celiac Plexus Block

1. Patient positioning: Prone
2. Target: T12-L1 level, around the celiac artery and root of the superior mesenteric artery
3. Approach: Bilateral posterior paravertebral approach under fluoroscopy or CT; can also be performed via endoscopic ultrasound (EUS) during upper GI endoscopy
4. Anatomy: The celiac plexus is formed by the greater, lesser, and least splanchnic nerves
5. Indications: Upper abdominal visceral pain, most commonly pancreatic cancer pain; also pain from stomach, small intestine, or liver pathology
6. Post-procedure monitoring: Monitor closely for hypotension and diarrhea (parasympathetic predominance after sympathectomy); observation period of at least one hour

Lumbar Sympathetic Block

1. Patient positioning: Prone
2. Target: Anterolateral aspect of the L2-L3 vertebral bodies
3. Imaging: Fluoroscopic guidance
4. Indications: Lower extremity sympathetically mediated pain (e.g., lower extremity CRPS), vascular insufficiency, painful diabetic neuropathy
5. Confirmation: Temperature rise and vasodilation (erythema) in the affected lower extremity

Superior Hypogastric Plexus Block

1. Patient positioning: Prone
2. Target: Anterior aspect of the L5 vertebral body
3. Imaging: Fluoroscopic or CT guidance
4. Anatomy: The plexus comprises lumbar and pelvic splanchnic nerves, the abdominal aortic plexus, and the hypogastric nerves
5. Indications: Chronic pain of lower abdominal and pelvic structures, including pelvic cancer pain and endometriosis

Ganglion Impar Block

1. Patient positioning: Prone
2. Target: Sacrococcygeal junction, on the anterior surface of the sacrum
3. Imaging: Fluoroscopic guidance
4. Anatomy: The ganglion impar is the terminal convergence of the bilateral sympathetic chains
5. Indications: Pain of the lower pelvis, perineum, and coccyx (coccydynia)

Medications

• Diagnostic/therapeutic blocks: Local anesthetic (lidocaine or bupivacaine) with or without corticosteroid (betamethasone, triamcinolone, or dexamethasone); botulinum toxin has also been studied as an adjunct
• Neurolytic blocks: Phenol (most commonly used, available in viscous formulation to limit spread) or alcohol (irritant, can cause pain on injection); reserved primarily for intractable cancer pain and end-of-life care due to risk of deafferentation pain
• Radiofrequency neurotomy: Thermal RF or pulsed RF offers a middle ground between temporary LA blocks and permanent chemical neurolysis, providing sustained relief in the range of months to years

Post-Procedure Assessment

After any sympathetic block, assess for signs of successful sympathectomy:

• Vasodilation: Erythema and temperature increase in the target region within minutes
• Stellate-specific: Ipsilateral Horner syndrome (miosis, ptosis, and anhidrosis)
• Celiac-specific: Monitor blood pressure (hypotension) and GI symptoms (diarrhea)
• Pain diary: Patients should track pain relief duration to determine whether the block effect matches the expected duration of the local anesthetic used, which guides decisions about neurolytic or ablative follow-up