What physiologic target does a stellate ganglion block most likely target, central nervous system (CNS) sensitization, peripheral nociceptive sensitization, or autonomic dysregulation?

Stellate Ganglion Block Primarily Targets Autonomic Dysregulation

Stellate ganglion block (SGB) most directly targets autonomic dysregulation by blocking sympathetic chain activity in the cervical region, allowing the regional autonomic nervous system to "reboot" and restore sympathetic/parasympathetic balance. 1

Mechanism of Action on Autonomic Function

The stellate ganglion block achieves its therapeutic effects through selective sympathetic blockade affecting one side of the head, neck, upper extremity, and upper thorax 2. The procedure works by:

• Reversing sympathetic overdrive created by increased nerve growth factor (NGF) levels, which causes sympathetic sprouting and elevated systemic norepinephrine 3
• Reducing NGF and sympathetic sprouting through local anesthetic injection, subsequently lowering overall norepinephrine levels 3
• Decreasing cardiac vagal modulation and baroreflex sensitivity, as demonstrated by significant reductions in low-frequency and high-frequency components of heart rate variability after bilateral SGB 4

Clinical Evidence Supporting Autonomic Targets

The most compelling evidence demonstrates SGB's effects on autonomic dysfunction:

• Two Long COVID patients experienced substantial alleviation of dysautonomia symptoms following stellate ganglion block, with symptoms resembling autonomic nervous system responses to pro-inflammatory cytokines 5
• Multiple physiological and psychological disorders related to autonomic dysfunction—including dizziness, ventricular premature beats, hypotension, anxiety, and insomnia—were substantially alleviated with SGB in a patient with documented autonomic dysfunction 6
• Bilateral SGB significantly affects cardiovascular autonomic regulation, reducing heart rate variability and spontaneous baroreflex sensitivity, particularly in subjects with symptoms of vagal blockade 4

Why Not Central or Peripheral Nociceptive Sensitization?

While SGB has applications in pain management, the primary mechanism is not through direct effects on central sensitization or peripheral nociceptors:

• SGB is used for sympathetically maintained pain in conditions like complex regional pain syndrome (CRPS), but only when there is consistent improvement and increasing duration of pain relief, suggesting the target is the sympathetic component rather than central pain processing 7, 8
• The procedure provides selective sympathetic blockade rather than blocking peripheral nociceptive pathways directly 2
• Sympathetic blocks should NOT be used for long-term treatment of non-CRPS neuropathic pain, indicating the mechanism is specific to sympathetically-mediated conditions rather than general nociceptive pathways 7, 8

Clinical Applications Confirming Autonomic Target

The conditions successfully treated with SGB are predominantly autonomic in nature:

• Dysautonomia in Long COVID, with resolution of fatigue, orthostatic intolerance, and brain fog 5, 1
• Postural orthostatic tachycardia syndrome (POTS) and autonomic dysfunction 5
• Ventricular tachyarrhythmias and cardiovascular autonomic regulation 3, 4
• Impaired vascular circulation and sympathetic reflex dystrophy 2

Important Caveats

Effects may wane over time and require repeated procedures 5. The procedure should be performed cautiously, especially bilaterally, as it can significantly reduce cardiac vagal modulation and baroreflex sensitivity 4. When used for CRPS, SGB must be integrated into a multimodal rehabilitation approach and demonstrate consistent improvement with increasing duration of relief with successive blocks 7, 8.