Cervicothoracic ganglion

The cervicothoracic ganglion, also known as the stellate ganglion, is a sympathetic ganglion formed by the fusion of the inferior cervical ganglion and the first thoracic ganglion (T1). It is part of the sympathetic nervous system and is located at the level of the neck and upper chest. Specifically, it lies anterior to the transverse process of the seventh cervical vertebra (C7) and is situated near the first rib, just posterior to the subclavian artery and in close proximity to the apex of the lung. This ganglion plays a key role in providing sympathetic innervation to the head, neck, upper extremities, and part of the thorax.

Structure and Anatomy

Origin and Formation

The cervicothoracic ganglion, commonly referred to as the stellate ganglion, is formed by the fusion of two sympathetic ganglia: the inferior cervical ganglion and the first thoracic ganglion (T1). This fusion occurs in most individuals and results in a single, large ganglion that is part of the sympathetic trunk. The sympathetic trunk, a chain of ganglia that runs along the vertebral column, provides autonomic (sympathetic) innervation to many areas of the body.

Location

The cervicothoracic ganglion is located in the lower part of the neck and the upper part of the thoracic cavity, where the cervical and thoracic regions meet. Its specific location is:

• Anterior to the Transverse Process of C7: The ganglion lies in front of the transverse process of the seventh cervical vertebra (C7), which provides a bony landmark for its position.
• Near the First Rib: The ganglion is situated near the level of the first rib, resting above it and close to the thoracic inlet, the space through which structures pass between the thorax and neck.
• Posterior to the Subclavian Artery: The cervicothoracic ganglion is positioned just behind the subclavian artery, which arches over it as it travels from the thorax to supply blood to the upper limbs and neck. The close proximity to major vessels is an important consideration during surgical procedures or when performing stellate ganglion blocks.
• Adjacent to the Apex of the Lung: The ganglion is located near the top (apex) of the lung. This proximity is important for its clinical significance, particularly in cases where lung disease or surgical interventions may affect the ganglion.

Structure

The cervicothoracic ganglion is typically a star-shaped (stellate) structure, which gives it its name. It is larger than many other sympathetic ganglia due to the fusion of two ganglia and contains a dense cluster of sympathetic neurons. These neurons are responsible for transmitting autonomic signals to various target organs and tissues.

The ganglion is encased in a sheath of connective tissue that provides structural support and protection. It is composed primarily of preganglionic and postganglionic sympathetic fibers. Preganglionic fibers from the spinal cord synapse within the ganglion, and postganglionic fibers exit to provide innervation to the target tissues.

Relationship to Neighboring Structures

The cervicothoracic ganglion is situated in a complex area with close anatomical relationships to several important structures:

• Vertebral Column: The ganglion is located along the sympathetic trunk, which runs parallel to the vertebral column. Its proximity to the vertebrae, especially the seventh cervical vertebra, provides a structural reference for its position.
• Subclavian Artery and Vein: The ganglion lies posterior to the subclavian artery, which passes just in front of it. The subclavian vein, which drains blood from the upper limbs and neck, is also located nearby. These vessels are important landmarks and must be considered during procedures involving the ganglion.
• Brachial Plexus: The brachial plexus, a network of nerves that supplies the upper limbs, is located close to the cervicothoracic ganglion. The proximity of these structures means that the stellate ganglion can influence autonomic function in the arms and hands.
• Thoracic Inlet and Mediastinum: The ganglion is situated near the thoracic inlet, the passageway that connects the neck to the thoracic cavity. The ganglion’s location near this transition zone allows it to influence both cervical and thoracic structures.

Connections with Sympathetic Trunk and Other Nerves

The cervicothoracic ganglion is part of the larger sympathetic chain, which runs from the cervical region down to the coccyx. It forms an important relay point for sympathetic nerve fibers that travel to various target areas in the head, neck, upper extremities, and thorax.

• Preganglionic Fibers: Preganglionic fibers originate from the upper thoracic segments of the spinal cord (usually T1 to T4). These fibers enter the cervicothoracic ganglion through white rami communicantes, where they synapse with postganglionic neurons.
• Postganglionic Fibers: Postganglionic fibers exit the ganglion through gray rami communicantes and travel to several target areas:
  • Head and Neck: Some postganglionic fibers ascend to the superior cervical ganglion to supply sympathetic innervation to structures in the head and neck, including the eyes, salivary glands, and facial blood vessels.
  • Upper Limb: The cervicothoracic ganglion provides postganglionic sympathetic fibers to the brachial plexus, which innervates the upper limbs. These fibers influence blood vessel tone, sweat glands, and other autonomic functions in the arms and hands.
  • Thorax: Some fibers travel downward to innervate the heart, lungs, and thoracic blood vessels, contributing to the regulation of heart rate, bronchial dilation, and other thoracic autonomic functions.

Blood Supply

The cervicothoracic ganglion receives its blood supply from small branches of nearby arteries, primarily the subclavian artery and its branches. These small vessels ensure that the ganglion receives the oxygenated blood necessary to support its metabolic functions.

Venous drainage occurs through small veins that drain into the subclavian vein and other nearby venous structures.

Variability

There is some anatomical variability in the size, shape, and position of the cervicothoracic ganglion among individuals. In some cases, the ganglion may be smaller or larger than average, and its exact relationship to the first thoracic ganglion and the subclavian artery may differ slightly. Additionally, while fusion of the inferior cervical and first thoracic ganglia is common, it may not occur in all individuals, and these two ganglia may remain separate.

Function

The cervicothoracic ganglion, or stellate ganglion, plays a central role in the sympathetic nervous system, transmitting autonomic signals that regulate various functions in the head, neck, upper limbs, and thorax. Its sympathetic fibers influence smooth muscle, blood vessels, glands, and various internal organs. Below are the detailed functions of the cervicothoracic ganglion, categorized by the regions and organs it innervates.

Sympathetic Control of the Head and Neck

The cervicothoracic ganglion provides sympathetic innervation to structures in the head and neck through postganglionic fibers that ascend to the superior cervical ganglion or exit directly from the ganglion. These fibers control several autonomic functions:

• Pupillary Dilation (Mydriasis): Sympathetic fibers from the stellate ganglion innervate the dilator pupillae muscle in the eye. When activated, these fibers cause pupillary dilation, which increases the amount of light entering the eye. This function is particularly important in low-light environments or during the body’s fight-or-flight response.
• Sweating in the Face and Scalp: The ganglion sends postganglionic fibers to sweat glands in the face and scalp, regulating sweating as part of thermoregulation and emotional responses.
• Vasoconstriction of Blood Vessels in the Face: Sympathetic fibers from the cervicothoracic ganglion cause vasoconstriction of blood vessels in the skin of the face, reducing blood flow to the skin and helping maintain blood pressure during stress or physical exertion.

Sympathetic Control of the Upper Limbs

One of the primary functions of the cervicothoracic ganglion is to provide sympathetic innervation to the upper limbs. This occurs via fibers that travel through the brachial plexus to innervate the arms and hands.

• Regulation of Blood Flow in the Upper Limbs: Sympathetic fibers from the stellate ganglion cause vasoconstriction of blood vessels in the arms and hands, which helps regulate blood flow and maintain blood pressure. During stress, these fibers reduce blood flow to the skin and extremities, redirecting it to vital organs such as the heart and muscles.
• Control of Sweating in the Upper Limbs: Sympathetic fibers from the cervicothoracic ganglion innervate the sweat glands in the arms and hands, controlling the secretion of sweat for thermoregulation. This is important in maintaining body temperature during physical exertion or in hot environments.
• Piloerection (Goosebumps): The ganglion’s fibers also innervate the arrector pili muscles in the skin of the arms and hands, causing piloerection or goosebumps during cold exposure or as part of emotional responses (such as fear).

Sympathetic Innervation of the Thoracic Organs

The cervicothoracic ganglion provides important sympathetic innervation to several organs in the thorax, particularly the heart and lungs. These fibers regulate several vital functions:

• Heart Rate and Contractility: Sympathetic fibers from the stellate ganglion contribute to the regulation of heart rate and myocardial contractility. Activation of these fibers increases heart rate (positive chronotropy) and the force of heart contractions (positive inotropy), ensuring that the heart pumps more blood during periods of stress or physical activity. This function is part of the body’s fight-or-flight response, which prepares the cardiovascular system for increased demands.
• Bronchodilation: Sympathetic innervation of the bronchial smooth muscle by the cervicothoracic ganglion leads to bronchodilation, or the widening of the airways. This increases airflow to the lungs, making breathing easier during stress or physical exertion.
• Vasoconstriction in the Thorax: Sympathetic fibers from the ganglion cause vasoconstriction of blood vessels in the thoracic region, including those that supply the lungs and chest wall. This function helps maintain systemic blood pressure and directs blood flow to more critical areas during stress.

Sympathetic Modulation of Glands

The cervicothoracic ganglion plays a role in regulating the function of various glands, including sweat glands, salivary glands, and mucous glands in the respiratory tract.

• Sweat Glands: As part of the body’s thermoregulatory system, the stellate ganglion sends fibers to sweat glands in the face, neck, upper limbs, and thorax. Activation of these fibers stimulates the secretion of sweat, helping to regulate body temperature during heat exposure or physical activity.
• Salivary Glands: Sympathetic fibers originating from the cervicothoracic ganglion innervate the salivary glands, reducing saliva production during stress (this is why dry mouth occurs during stressful situations). This inhibition conserves water and diverts resources away from digestion, a characteristic feature of the fight-or-flight response.
• Mucous Glands of the Respiratory Tract: Sympathetic fibers to the respiratory tract reduce the secretion of mucus, helping to keep the airways clear during periods of physical exertion.

Role in the Fight-or-Flight Response

The cervicothoracic ganglion plays a significant role in the fight-or-flight response, a physiological reaction that occurs in response to perceived danger or stress. Through its sympathetic fibers, the stellate ganglion helps mobilize the body’s resources to respond to a threat:

• Increased Heart Rate and Blood Pressure: As part of the fight-or-flight response, the ganglion increases heart rate and blood pressure, enhancing blood flow to muscles and vital organs.
• Diversion of Blood Flow: The ganglion causes vasoconstriction in the skin, digestive organs, and other non-essential regions, diverting blood flow to more critical areas such as the brain, heart, and muscles.
• Improved Respiratory Function: By causing bronchodilation, the cervicothoracic ganglion ensures that the lungs receive more air, improving oxygen delivery to the body during times of stress or exertion.

Regulation of Blood Pressure and Vascular Tone

The cervicothoracic ganglion helps regulate systemic blood pressure through its influence on vascular tone in the head, neck, upper limbs, and thorax. By controlling the degree of vasoconstriction or vasodilation in blood vessels, the ganglion maintains vascular resistance and blood flow.

• Vasoconstriction to Maintain Blood Pressure: During stress or low blood pressure, sympathetic stimulation from the stellate ganglion causes vasoconstriction, which helps maintain blood pressure by increasing resistance in the blood vessels.
• Maintenance of Vascular Tone in Extremities: The ganglion helps maintain vascular tone in the arms and hands, balancing blood flow to these regions according to the body’s needs at any given moment.

Modulation of Autonomic Reflexes

The cervicothoracic ganglion participates in several autonomic reflexes that are important for maintaining homeostasis and responding to physiological changes:

• Baroreceptor Reflex: The ganglion plays a role in the baroreceptor reflex, which helps regulate blood pressure by adjusting heart rate and vascular tone in response to changes in blood pressure.
• Thermoregulatory Reflexes: The ganglion contributes to reflexes that control sweating and vasodilation/vasoconstriction to regulate body temperature, particularly in response to external temperature changes or physical activity.

Clinical Significance

The cervicothoracic (stellate) ganglion plays a vital role in regulating sympathetic activity in the head, neck, upper limbs, and thorax. Its dysfunction or involvement in certain conditions can lead to a variety of clinical issues. Hyperactivity of the ganglion can contribute to conditions such as Raynaud’s phenomenon, where excessive sympathetic stimulation leads to vasoconstriction in the extremities, causing pain and discoloration in the hands. Similarly, damage or compression of the ganglion, as seen in trauma or tumors, can result in Horner’s syndrome, characterized by ptosis (drooping eyelid), miosis (constricted pupil), and anhidrosis (lack of sweating) on the affected side.

Stellate ganglion block is a medical procedure used to manage chronic pain, especially in cases of complex regional pain syndrome (CRPS) affecting the arms, as well as to improve circulation in vascular disorders. It is also sometimes used for conditions like hyperhidrosis (excessive sweating) of the upper limbs.