A stellate ganglion block (SGB) is an injection used to interrupt the transmission of signals through the sympathetic nervous system, often employed for conditions like chronic regional pain syndrome (CRPS) or post-traumatic stress disorder (PTSD). While generally considered safe when performed by trained professionals, the procedure involves injecting a local anesthetic into the neck. The SGB carries a profile of expected temporary reactions and rare, but serious, risks that warrant discussion. Understanding the mechanics and anatomical context of the SGB helps clarify why these risks exist and how they are managed.
Understanding the Stellate Ganglion Block Procedure
The stellate ganglion is a cluster of nerves located in the neck, just in front of the seventh cervical and first thoracic vertebrae. This nerve cluster is part of the sympathetic nervous system, which is responsible for regulating involuntary body functions, including the “fight or flight” response, blood flow, and sweating in the head, neck, and upper limbs. The primary goal of an SGB is to temporarily disrupt the activity of this sympathetic nerve pathway using a local anesthetic medication.
The procedure is minimally invasive and typically performed in an outpatient setting, often taking less than 30 minutes. The physician uses imaging guidance, such as ultrasound or fluoroscopy (X-ray), to precisely locate the target area and guide a thin needle to the nerve cluster. Injecting the anesthetic near the stellate ganglion effectively “resets” the nerve activity, which can help relieve pain or calm an overactive stress response.
Common and Temporary Reactions
Following a successful SGB, certain temporary physical signs are expected confirmation that the sympathetic blockade was achieved. These effects are transient, typically resolving within a few hours as the anesthetic agent wears off. They are a direct result of the intended disruption of the sympathetic nervous system pathways.
The most notable of these expected reactions is Horner’s syndrome, which presents as a triad of specific symptoms on the side of the injection. This includes a drooping of the upper eyelid (ptosis), a constriction of the pupil (miosis), redness in the eye, and nasal congestion on the same side.
Other common, short-lived effects include temporary hoarseness or a change in voice, which occurs because the anesthetic can briefly affect the recurrent laryngeal nerve. Many patients also report a feeling of warmth or tingling in the arm and hand, which is caused by the relaxation of blood vessels (vasodilation) due to the sympathetic blockade. These reactions are an indication that the block has worked and do not signify a lasting injury.
Potential Severe Complications and Risks
While the overall rate of serious complications from an SGB is very low, the procedure is not without rare but serious risks. These dangers stem from the close proximity of the injection site to several vital structures in the neck.
One of the most concerning risks is vascular puncture, where the needle accidentally pierces a major blood vessel. Structures like the carotid artery, internal jugular vein, vertebral artery, or inferior thyroid artery are located near the target site. If the anesthetic is injected directly into a vessel (intravascular injection), it can lead to a rapid spread of the medication, potentially causing a seizure or systemic toxicity. Bleeding and hematoma formation are also possible, particularly if a vessel is punctured.
Accidental puncture of the lung lining, resulting in a pneumothorax, is another rare but serious complication. While the SGB is typically performed at the C6 or C7 vertebral level to minimize this risk, the needle must be precisely controlled to avoid puncturing the lung apex, which extends into the lower neck region. Nerve injury to surrounding structures, such as the recurrent laryngeal nerve or the brachial plexus, can also occur, leading to prolonged hoarseness or temporary numbness and weakness in the arm. Furthermore, there is a minimal risk of infection at the site or an allergic reaction to the anesthetic medication used.
Patient Risk Factors and Contraindications
A thorough pre-procedure screening is necessary, as certain patient-specific factors increase the inherent risk associated with an SGB. Active infection, either at the injection site or systemic, is a contraindication because it heightens the risk of spreading bacteria into deeper tissues. The procedure must be postponed until the infection is resolved.
Patients with pre-existing bleeding disorders or those taking anticoagulant medications, commonly referred to as blood thinners, face a higher risk of bleeding and hematoma formation. These individuals require careful evaluation, and their medication regimen must often be temporarily adjusted before the SGB can be performed safely. Severe pulmonary disease, such as advanced emphysema, is another major concern because compromised lung function means that an accidental pneumothorax could be life-threatening.
Anatomical anomalies or prior neck surgery can also complicate the procedure by altering the expected location of vital structures, making precise needle placement more challenging. Individuals with a known allergy to the local anesthetic agents must be identified before the block to prevent a potentially severe allergic reaction. These patient factors underscore that safety is determined not just by the procedure itself, but by the careful assessment of the individual receiving it.