Definition and Overview
Stellate ganglion block (SGB) is a neuromodulatory procedure in which a local anesthetic is injected into the stellate ganglion, a cervical sympathetic ganglion, to temporarily block sympathetic nerve transmission to the head, face, neck, and upper extremities [3].
The history of stellate ganglion block dates back to the 1920s. After Leriche and Fontaine applied cervical sympathetic nerve block for the treatment of upper extremity circulatory disorders in 1934, it has been widely used in the field of pain management [3]. Its range of indications has since expanded to include complex regional pain syndrome (CRPS), headache, facial flushing, and hyperhidrosis. Since the 2000s, it has garnered renewed attention with reports of therapeutic efficacy for post-traumatic stress disorder (PTSD) [1].
Advances in ultrasound-guided techniques have greatly improved the accuracy and safety of the procedure. Compared with the conventional blind technique, ultrasound-guided procedures have significantly reduced the incidence of complications such as vascular puncture [5].
Anatomy
The stellate ganglion is a star-shaped ganglion formed by the fusion of the inferior cervical ganglion and the first thoracic ganglion. In approximately 80% of the population, these two ganglia are fused, while in the remaining 20% they exist separately [3].
The stellate ganglion is located between the anterior surface of the C7 transverse process and the neck of the first rib, anterior to the vertebral body. It lies on the longus colli muscle, with the subclavian artery and vertebral artery adjacent anteriorly [5]. Because of these anatomical relationships, precise image guidance is essential during the procedure to prevent vascular injury.
Postganglionic sympathetic fibers from the stellate ganglion are distributed to the following regions.
- Head and face: pupil dilator muscle, Müller muscle, facial blood vessels, sweat glands
- Neck: thyroid gland, carotid artery, pharynx, larynx
- Upper extremity: blood vessels and sweat glands of the arm and hand
- Heart: some of the sympathetic fibers involved in heart rate and conduction
As a result, when the stellate ganglion is blocked, extensive signs of sympathetic blockade appear, including increased blood flow to the ipsilateral face and upper extremity, decreased sweating, and pupillary constriction [3].
Indications
Stellate ganglion block is applied to various conditions involving sympathetic hyperactivity.
Pain Conditions
- Complex regional pain syndrome (CRPS): the most representative indication for SGB. Approximately 70–80% of CRPS type I patients have reported pain reduction and functional improvement following SGB [4]. Treatment response rates are higher with early intervention.
- Postherpetic neuralgia: studies suggest that early SGB during acute herpes zoster may reduce the transition to postherpetic neuralgia.
- Phantom limb pain: applied for phantom limb pain following upper extremity amputation.
- Trigeminal neuralgia and facial pain: used adjunctively for facial neuralgia unresponsive to pharmacotherapy.
Autonomic Dysfunction
- Applied for symptoms such as palpitations, sweating abnormalities, anxiety, and insomnia caused by sympathetic hyperactivity.
- Alleviates sympathetic hyperactivation through autonomic balance resetting.
Headache and Migraine
- Cluster headache: used in the acute treatment of cluster headache involving sympathetic dysregulation.
- Cervicogenic headache: applied for headaches involving cervical sympathetic hyperactivity.
Circulatory Disorders
- Raynaud phenomenon: SGB demonstrates blood flow improvement in this condition, where sympathetic hyperactivity causes vasoconstriction in the upper extremities, resulting in finger pallor and pain.
- Upper extremity thromboembolism: utilized as adjunctive treatment for acute upper extremity circulatory disorders.
Post-Traumatic Stress Disorder (PTSD)
In studies by Lipov et al., PTSD Checklist (PCL) scores decreased by an average of more than 20 points following SGB, and this effect was reported to persist for several months [1] [2]. A double-blind crossover controlled study by Hanling et al. in 2016 also showed significant PTSD symptom improvement in the SGB group compared with placebo [6]. This effect is thought to result from sympathetic blockade suppressing amygdala hyperactivity and reducing norepinephrine release [1].
Other Indications
- Hot flashes: efficacy has been reported for menopausal or breast cancer treatment-related hot flashes.
- Hyperhidrosis: applied for excessive sweating of the upper extremities and face.
- Sudden hearing loss: has been used as adjunctive therapy to improve inner ear blood flow.
Procedure
The current standard is to perform stellate ganglion block under ultrasound guidance [5].
Pre-Procedure Preparation
- The patient lies supine with the neck slightly extended.
- The skin at the procedure site is sterilized and the ultrasound probe is positioned on the neck.
- Key structures are identified on ultrasound imaging, including the C6 or C7 transverse process, longus colli muscle, carotid artery, internal jugular vein, and thyroid gland.
Procedure Process
1. The anatomical structures and vascular courses around the stellate ganglion are confirmed in real time using ultrasound.
2. A small amount of local anesthetic is administered for skin anesthesia.
3. A 25–27 gauge needle is advanced under ultrasound guidance to the subfascial space on the surface of the longus colli muscle where the stellate ganglion is located.
4. Aspiration is performed to confirm the needle is not intravascular.
5. 0.25% bupivacaine or 1% lidocaine (5–10 mL) is slowly injected.
6. Spread of the medication around the stellate ganglion is confirmed on ultrasound imaging.
The entire procedure takes approximately 10–15 minutes, and the patient is discharged after 30 minutes to 1 hour of observation [5].
Advantages of Ultrasound Guidance
Ultrasound-guided procedures offer several advantages over the landmark-based technique used prior to the 1990s. Real-time visualization of the needle tip position significantly reduces the risk of complications such as vascular puncture, esophageal injury, and pneumothorax. According to research by Nader et al., the volume of local anesthetic required for ultrasound-guided SGB is approximately half that of conventional methods (5 mL vs. 10–20 mL), also reducing the risk of systemic toxicity [5].
Mechanism of Action
The therapeutic effects of stellate ganglion block are mediated by multilayered mechanisms.
Sympathetic Blockade and Increased Blood Flow
When the local anesthetic blocks sodium channels in the sympathetic neuronal cell bodies and nerve fibers of the stellate ganglion, vasoconstrictor signals to the innervated regions are inhibited. As a result, blood vessels in the head, face, and upper extremities dilate and blood flow increases [3]. This effect provides the treatment rationale for Raynaud phenomenon and upper extremity circulatory disorders.
Pain Inhibitory Pathways
Abnormal connections between sympathetic and sensory nerves (sympatho-afferent coupling) represent the core mechanism of sympathetically maintained pain. SGB interrupts this abnormal coupling, breaking the vicious cycle of sympathetically mediated pain [4]. This is the primary reason SGB is effective in CRPS.
Autonomic Reset Effect
Although the pharmacological blockade effect of SGB lasts only several hours, clinical symptom improvement often persists for days to weeks. This is explained by the sympathetic nervous system's hyperactive state undergoing a type of "reset," returning to normal sympathovagal balance [1]. Lipov et al. proposed this as the "sympathetic reboot" hypothesis.
Central Nervous System Effects
Recent studies have reported that SGB affects not only peripheral sympathetic nerves but also the central nervous system. Reduced amygdala hyperactivity and decreased brain norepinephrine levels have been confirmed following SGB [1]. This explains the mechanism by which SGB is effective for PTSD and suggests that peripheral sympathetic blockade also exerts bottom-up modulation effects on central autonomic regulation.
Efficacy and Evidence
Complex Regional Pain Syndrome (CRPS)
CRPS is the best-established indication for SGB. In a study by Ackerman and Zhang, a series of SGBs performed in CRPS type I patients produced significant pain reduction (50% or greater VAS reduction) in approximately 72% of patients [4]. Response rates were higher in the early treatment group who received SGB within 6 months of onset.
Post-Traumatic Stress Disorder (PTSD)
Lipov et al. (2009) reported that PTSD symptom scale scores decreased by an average of 21 points (PCL-M) following SGB, with effects persisting for more than 6 months in some patients [1]. Lynch et al. (2016) confirmed significant improvement across PTSD symptom clusters (re-experiencing, hyperarousal, avoidance) following SGB in a study of 166 active-duty military personnel [7]. In a double-blind randomized controlled trial by Hanling et al. (2016), the SGB group showed significant reduction in CAPS (Clinician-Administered PTSD Scale) scores compared with placebo [6].
Onset and Duration of Effect
The sympathetic blockade effect of SGB appears within minutes of the procedure and is confirmed by the onset of Horner syndrome. The pharmacological blockade duration is 2–4 hours for lidocaine and 6–12 hours for bupivacaine, depending on the agent used. However, clinical symptom improvement has been observed to persist for days to weeks beyond the resolution of pharmacological effects, and the duration of effect tends to progressively lengthen with repeated procedures [1] [4].
Side Effects and Precautions
Normal Responses (Signs of Sympathetic Blockade)
The following signs appearing on the procedure side after SGB are normal responses indicating successful blockade.
- Horner syndrome: ipsilateral miosis (pupillary constriction), ptosis (drooping eyelid), and enophthalmos (sunken eye) appear. Observed in approximately 90–95% of SGB patients, it resolves spontaneously as the pharmacological effect wears off [3].
- Conjunctival injection: redness of the ipsilateral eye due to vascular dilation.
- Nasal congestion: due to vasodilation of the ipsilateral nasal mucosa.
- Facial anhidrosis: absence of sweating on the ipsilateral face.
- Upper extremity temperature increase: skin temperature of the ipsilateral hand rises by 1–3 degrees.
Transient Side Effects
- Voice changes (hoarseness): temporary voice changes may occur if the local anesthetic spreads to the recurrent laryngeal nerve. Most cases resolve within several hours.
- Foreign body sensation and dysphagia: if the anesthetic spreads to periphyrangeal nerves, a foreign body sensation in the throat or difficulty swallowing may occur.
- Upper extremity paresthesia: if the anesthetic partially spreads to the brachial plexus, temporary numbness or weakness of the arm may occur.
Rare Complications
- Vascular injury: puncture of adjacent vessels such as the carotid artery, internal jugular vein, or vertebral artery may occur. Under ultrasound guidance, the incidence of vascular puncture decreases to less than 1% [5].
- Pneumothorax: may occur if the needle advances to the pleura, but is extremely rare with ultrasound-guided technique.
- Epidural or subarachnoid injection: may occur if the needle advances excessively medially, prevented by real-time ultrasound confirmation of needle position.
- Local anesthetic systemic toxicity: occurs with intravascular injection, prevented by aspiration testing and appropriate dosing.
Contraindications
- Infection at the procedure site
- Anticoagulant use (increased bleeding risk)
- Recent myocardial infarction
- Bilateral simultaneous procedure (risk of respiratory distress from bilateral recurrent laryngeal nerve paralysis)
- Glaucoma (intraocular pressure changes from pupillary constriction)
Post-procedure Care
Immediately after the procedure, vital signs are monitored at rest for 30 minutes to 1 hour. The appearance of Horner syndrome is confirmed to determine successful blockade.
Recommendations for the day of the procedure are as follows.
- Be careful when eating or drinking for 2–3 hours after the procedure due to possible reduced pharyngeal sensation.
- Avoid vigorous exercise and heavy lifting.
- Refrain from alcohol consumption.
- Do not drive until symptoms in the ipsilateral eye have fully resolved.
- Bruising or swelling may appear at the procedure site and typically resolves within 2–3 days.
From the following day, patients can return to daily activities without special restrictions. Recording the treatment effect and any abnormal symptoms helps adjust the treatment plan at the next visit.
The interval between repeat procedures is determined by the condition and treatment response, and is generally performed 1–2 times per week. After 3–6 repeat procedures, the overall treatment response is evaluated to determine whether additional procedures are warranted [4].