Cervical sympathetic chain

Chain of Command - Gross Anatomy

• Location: Bilateral chain extending from the base of the skull to the neck root, lying anterior to the longus colli and capitis muscles, and posterior to the carotid sheath.
• Components: Typically consists of 3 ganglia (superior, middle, inferior).
  • Superior (SCG): Largest, at C2-C3 level.
  • Middle (MCG): Smallest, at C6 level.
  • Inferior (ICG): Fuses with the first thoracic ganglion to form the stellate ganglion in 80% of people.

⭐ A stellate ganglion block, targeting the C7 level, is used for diagnosing and treating sympathetically mediated pain in the head, neck, and upper limbs.

The Ganglia Trio - Relay Stations

• Superior Cervical Ganglion (SCG): Largest ganglion, at the C1-C4 level.
  • Targets: Structures of the head & neck (e.g., pupillary dilator, sweat glands), internal carotid artery plexus, superior cardiac nerve.
  • Lesions can produce Horner's syndrome.
• Middle Cervical Ganglion (MCG): Smallest and sometimes absent. Found at the C6 level, near the cricoid cartilage.
  • Targets: Thyroid gland, middle cardiac nerve.
• Inferior Cervical Ganglion (ICG): Fuses with the first thoracic ganglion in ~80% of individuals to form the Stellate Ganglion.
  • Location: C7 level, anterior to the neck of the 1st rib.
  • Targets: Upper limb vasculature, vertebral artery, inferior cardiac nerve.

⭐ A stellate ganglion block is used to diagnose and treat Complex Regional Pain Syndrome (CRPS) of the upper limb by interrupting sympathetic supply.

Wiring Diagram - Axon Pathways

• Preganglionic neurons: Originate from the intermediolateral (IML) nucleus of the spinal cord at levels T1-T4.
• Path to Ganglia: Axons ascend the sympathetic trunk to synapse in the superior, middle, or inferior cervical ganglia.
• Postganglionic fibers: Travel via gray rami communicantes to join cervical spinal nerves or form periarterial plexuses (e.g., carotid plexus) to reach their targets.

⭐ Horner's Syndrome: A lesion anywhere along this pathway (e.g., Pancoast tumor) causes the classic triad of ipsilateral ptosis (drooping eyelid from superior tarsal muscle paralysis), miosis (pupil constriction), and anhidrosis (decreased facial sweating).

Clinical Chaos - Horner's Syndrome

Classic triad due to sympathetic trunk lesion.

• Symptoms: Unilateral...
  • Ptosis: slight drooping of upper eyelid.
  • Miosis: constricted pupil.
  • Anhidrosis: decreased sweating on the affected side of the face.

📌 Mnemonic: PAM stops sweating!

• Localization Tests:
  • Cocaine drops: Fail to dilate the miotic pupil.
  • Apraclonidine drops: Dilate the pupil (denervation supersensitivity).

⭐ Exam Favorite: A Pancoast tumor (apical lung cancer) can compress the preganglionic sympathetic fibers, causing Horner's syndrome.

High‑Yield Points - ⚡ Biggest Takeaways

• The chain has three ganglia (superior, middle, inferior) lying anterolateral to the vertebral column.
• The inferior ganglion often fuses with T1, forming the stellate ganglion near the lung apex.
• Lesions cause Horner's syndrome: a classic triad of ptosis, miosis, and anhydrosis.
• A Pancoast tumor is a high-yield cause of stellate ganglion compression, leading to Horner's.
• It lies posterior to the carotid sheath, providing all sympathetic innervation to the head and neck.